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Official website: laplas.mephi.ru/en
Andrey P. Kuznetsov
Executive Director
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Energy-saving, high-performance laser, plasma, and radiation technologies
Innovations
Organization of effective technology transfer in cooperation with industrial partners in areas of semiconductor-, fiber- lasers, laser and plasma devices and facilities, development of advanced additive technologies.
Partners
IPG Photonics, GPI RAS, LPI RAS, Federal Institute for Materials Research and Testing (BAM) (Germany), University of Lyon (France), Fraunhofer Institute for Laser Technology ILT (Germany)
High-power lasers, extreme light fields, environment-friendly energy production by the controlled nuclear fusion
Innovations
Partners:
RFNC VNIIEF, LPI RAS, GPI RAS, NRC “Kurchatov institute”, GSI Darmstadt Germany, FZJ Uelich, Germany, NNC of Republic of Kazakhstan
Optical information processing, radiophotonics, optical, laser, and quantum metrology
Partners
VNIIFTRI, LPI RAS, JIHT RAS, PTB (Germany), MPQ (Germany), NIST (USA)
Energy-saving, high-effective industrial laser technologies
Advanced educational training program for high quality specialists in laser, plasma and energy-effective technologies – new programs
Quantum metrology:
Education - new program
Quantum metrology
Environmental energetics based on controlled thermonuclear fusion
– new programs
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Educational programs |
Level |
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Bachelor's degree programs 14.03.02 – Nuclear Physics and Technology 12.03.05 – Laser technics and laser technologies 03.03.01 – Applied mathematics and physics 22.03.01 – Materials science and materials technology Specialist's degree programs 14.05.04 – Electronics and automatization of physical facilities |
Bachelor's Degree/Specialist's Degree |
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Master's and Postgraduate's Student's degree programs 14.04.02 – Nuclear Physics and Technology 12.04.05 – Laser technics and laser technologies 03.04.01 – Applied mathematics and physics 22.04.01 – Materials science and materials technology 03.06.01 – Physics and astronomy |
Master's Degree/Postgraduate's student'sDegree |
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Russian scientists-Heads of Departments and Laboratories |
Foreign Employees of MEPhI |
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S.V. Garnov – Corresponding member of RAS, Scientific supervisor of Institute of Laser and Plasma Technologies |
Dimitry Batani (France) – University of Bordeaux |
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S.G. Garanin – Academician of RAS, Head of Dept. of Laser Thermonuclear Fusion Physics |
Antonio Bianconi (Italy) – Director of the Rome International Center of Materials Science Superstripes (RICMASS) |
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N.N. Kalachevsky – Corresponding member of RAS, Head of Dept. of Physical and Technical Problems of Metrology |
David Blashke (Poland) – University of Wroclaw |
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N.N. Evtikheev – Dr. Sci. (Phys.-Math), professor, Head of Dept. of Laser Physics |
Julien Fuchs (France) – Ecole Polytechnique |
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V.A. Kurnaev – Dr. Sci. (Phys.-Math), professor, Head of Dept. of Plasma Physics |
Sergey Krasheninnikov (USA) – University of California |
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A.P. Menushenkov – Dr. Sci. (Phys.-Math), professor, Head of Dept. of Solid State Physics and Nanosystems |
Kai Norlund (Finland) – Aatloo University |
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S.V. Popruzhenko – Dr. Sci. (Phys.-Math), professor, Head of Dept. of Theoretical Nuclear Physics |
Guido van Oost (Belgium) – Ghent University |
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V.N. Petrovsky - PhD (Phys.-Math), associate professor, Head of Laser Center of the MEPhI |
Juris Purans (Latvia) – academician, University of Latvia |
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S.M. Polosov – PhD (Phys.-Math), associate professor, Head of Lab. “Dynamics in Accelerators” |
Тetsuo Tanabe (Japan) – Kyushyu University |
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A.A. Pisarev - Dr. Sci. (Phys.-Math), senior researcher, Head of Lab. “Plasma-surface Interaction and Plasma Technology” |
Ivan Vartanyants (Germany) – DESY |
The oxygen isotope (O16/O18) effect (OIE) on the pseudogap (charge-stripe ordering) temperature T∗ is investigated for the cuprate superconductor La2-xSrxCuO4 as a function of doping x by means of x-ray absorption near edge structure studies. A strong x dependent and sign reversed OIE on T∗ is observed. The OIE exponent αT∗ systematically decreases from αT∗=-0.6(1.3) for x=0.15 to αT∗=-4.4(1.1) for x=0.06, corresponding to increasing T∗ and decreasing superconducting transition temperature Tc. Both T∗(O16) and T∗(O18) exhibit a linear doping dependence with different slopes and critical end points [where T∗(O16) and T∗(O18) fall to zero] at xc(O16)=0.201(4) and xc(O18)=0.182(3), indicating a large positive OIE of xc with an exponent of αxc=0.84(22). The remarkably large and strongly doping dependent OIE on T∗ signals a substantial involvement of the lattice in the formation of the pseudogap, consistent with a polaronic approach to cuprate superconductivity and the vibronic character of its ground state. © 2017 American Physical Society.
Optical encryption is an actively developing field of science. The majority of encryption techniques use coherent illumination and suffer from speckle noise, which severely limits their applicability. The spatially incoherent encryption technique does not have this drawback, but its effectiveness is dependent on the Fourier spectrum properties of the image to be encrypted. The application of a quick response (QR) code in the capacity of a data container solves this problem, and the embedded error correction code also enables errorless decryption. The optical encryption of digital information in the form of QR codes using spatially incoherent illumination was implemented experimentally. The encryption is based on the optical convolution of the image to be encrypted with the kinoform point spread function, which serves as an encryption key. Two liquid crystal spatial light modulators were used in the experimental setup for the QR code and the kinoform imaging, respectively. The quality of the encryption and decryption was analyzed in relation to the QR code size. Decryption was conducted digitally. The successful decryption of encrypted QR codes of up to 129 × 129 pixels was demonstrated. A comparison with the coherent QR code encryption technique showed that the proposed technique has a signal-to-noise ratio that is at least two times higher. © 2017 Astro Ltd.
We review the features of the charge density wave (CDW) conductor NbS3 (phase II) and include several additional results from transport, compositional, and structural studies. Particularly, we highlight three central results: (1) In addition to the previously reported CDW transitions at T-P1 = 360K and T-P2 = 150 K, a third CDW transition occurs at a much higher temperature T-P0 approximate to 620 - 650 K; evidence for the nonlinear conductivity of this CDW is presented. (2) We show that the CDW associated with the T-P2 transition arises from S vacancies acting as donors. Such a CDW transition has not been observed before. (3) We demonstrate the exceptional coherence of the T-P1 CDW at room temperature. The effects of uniaxial strain on the CDW transition temperature and transport are reported.
The theoretical model suggested for ITER main chamber Hα spectroscopy is applied to the high-resolution spectroscopy (HRS) data of recent JET ITER-like wall (ILW) experiments. The model is aimed at reconstructing the neutral hydrogen isotope density in the SOL, as well as the isotope ratio, by solving a multi-parametric inverse problem with allowance for (i) the strong divertor stray light (DSL) on the main-chamber lines of sight (LoS), (ii) substantial deviation of the neutral atom velocity distribution function (VDF) from a Maxwellian in the SOL, and (iii) data for the direct observation of the divertor. The JET-ILW HRS data on resolving the power at the deuterium and hydrogen spectral lines of the Balmer-alpha series is analysed, with direct observation of the divertor from the top and with observation of the inner wall along the tangential and radial LoS from the equatorial ports. This data allows the spectrum of the DSL and the signal-to-background ratio for the Balmer-alpha light emitted from the far SOL and divertor in the JET-ILW to be evaluated. The results support the expectation of the strong impact of the DSL upon the ITER main chamber Hα (and visible light) spectroscopy diagnostics. © 2016 EURATOM.
Fuelling requirements for ITER are analysed in relation to pellet fuelling and ELM pacing, and a divertor power load control consistent with the ITER pumping and fuel throughput capabilities. The plasma parameters at the separatrix and the particle sources are derived from scalings based on SOLPS simulations. Effective transport coefficients in the H-mode pedestal are derived from EPED1 + SOLPS scalings for the pedestal height and width. 1.5D transport is simulated in the ASTRA framework. The operating window for ITER DT plasmas with the required fusion performance and level of ELM, and divertor power load control compatible with ITER fuelling and pumping capabilities, is determined. It is shown that the flexibility of the ITER fuelling systems, comprising pellet and gas injection systems, enables operation with Q = 10, which was found to be marginal in previous studies following a similar approach but with different assumptions. The present assessment shows that a reduction of 〈n〉eby a factor ∼2 (from 9 to 5 × 1019 m-3) in 15 MA H-mode plasmas leads to a reduction in the required pellet fuelling rate by a factor of four. Results of the analysis of the fuelling requirements for a range of ITER scenarios are found to be similar to those obtained with the JINTRAC code that included 2D modelling of the edge plasma. © 2017 ITER.
In this paper, reduced-activation ferritic/martensitic (RAFM) steels including Eurofer (9Cr) and oxide dispersion strengthening (ODS) steels by the addition of Y2O3 particles with different amounts of Cr, namely, (9-16) Cr were exposed to low energy deuterium (D) plasma (similar to 20-200 eV per D) up to a fluence of 2.9 x 10(25) D m(-2) in the temperature range from 290 K to 700 K. The depth profile of D in steels was measured up to 8 mu m depth by nuclear reaction analysis (NRA) and the total retained amount of D in those materials was determined by thermal desorption spectroscopy (TDS). It was found that the D retention in ODS steels is higher compared to Eurofer due to the much higher density of fine dispersoids and finer grain size. This work shows that in addition to the sintering temperature and time, the type, size and concentration of the doping particles have an enormous effect on the increase in the D retention. The D retention in undamaged ODS steels strongly depends on the Cr content: ODS with 12Cr has a minimum and the D retention in the case of ODS with (14-16) Cr is higher compared to (9-12) Cr. The replacing of Ti by Al in ODS-14Cr steels reduces the D retention. The formation of nano-structure surface roughness enriched in W or Ta due to combination of preferential sputtering of light elements and radiation-induced segregation was observed at incident D ion energy of 200 eV for both Eurofer and ODS steels. Both the surface roughness and the eroded layer enhance with increasing the temperature. The surface modifications result in a reduction of the D retention near the surface due to increasing the desorption flux and can reduce the overall D retention.
The reduced-activation ferritic/martensitic (RAFM) steels including Eurofer (9Cr) and oxide dispersion strengthened (ODS) steels by the addition of Y2O3 particles investigated in Part I were pre-damaged either with 20 MeV W ions at room temperature at IPP (Garching) or with high heat flux at FZJ (Juelich) and subsequently exposed to low energy (similar to 20-200 eV per D) deuterium (D) plasma up to a fluence of 2.9 x 10(25) D m(-2) in the temperature range from 290 K to 700 K. The pre-irradiation with 20 MeV W ions at room temperature up to 1 displacement per atom (dpa) has no noticeable influence on the steel surface morphology before and after the D plasma exposure. The pre-irradiation with W ions leads to the same concentration of deuterium in all kinds of investigated steels, regardless of the presence of nanoparticles and Cr content. It was found that (i) both kinds of irradiation with W ions and high heat flux increase the D retention in steels compared to undamaged steels and (ii) the D retention in both pre-damaged and undamaged steels decreases with a formation of surface roughness under the irradiation of steels with deuterium ions with incident energy which exceeds the threshold of sputtering. The increase in the D retention in RAFM steels pre-damaged either with W ions (damage up to similar to 3 mu m) or high heat flux (damage up to similar to 10 mu m) diminishes with increasing the temperature. It is important to mention that the near surface modifications caused by either implantation of high energy ions or a high heat flux load, significantly affect the total D retention at low temperatures or low fluences but have a negligible impact on the total D retention at elevated temperatures and high fluences because, in these cases, the D retention is mainly determined by bulk diffusion.
The dynamics of transient current distributions in superconducting YBa2Cu3O7δ thin films were investigated during and immediately following an external field ramp, using high-speed (real-time) Magneto-Optical Imaging and calculation of dynamic current profiles. A number of qualitatively unique and previously unobserved features are seen in this novel analysis of the evolution of supercurrent during penetration. As magnetic field ramps up from zero, the dynamic current profile is characterized by strong peaks, the magnitude of which exceed the conventional critical current density (as determined from static current profiles). These peaks develop close to the sample edges, initially resembling screening currents but quickly growing in intensity as the external field increases. A discontinuity in field and current behaviour is newly observed, indicating a novel transition from increasing peak current toward relaxation behaviour. After this transition, the current peaks move toward the centre of the sample while reducing in intensity as magnetic vortices penetrate inward. This motion slows exponentially with time, with the current distribution in the long-time limit reducing to the expected Kim-model profile. © The Author(s) 2017.
Uniform, graded and spaced arrays of 3 μm triangular antidots in pulsed laser deposited YBa2Cu3O7 (YBCO) superconducting thin films are compared by examining the improvements in the critical current density Jc they produced. The comparison is made to establish the role of their lithographically defined (non-)uniformity and the effectiveness to control and/or enhance the critical current density. It is found that almost all types of non-uniform arrays, including graded ones enhance Jc over the broad applied magnetic field and temperature range due to the modified critical state. Whereas uniform arrays of antidots either reduce or produce no effect on Jc compared to the original (as-deposited) thin films. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA.
By analyzing profiles of experimental x-ray spectral lines of Si XIV and Al XIII, we found that both Langmuir and ion acoustic waves developed in plasmas produced via irradiation of thin Si foils by relativistic laser pulses (intensities ∼1021 W/cm2). We prove that these waves are due to the parametric decay instability (PDI). This is the first time that the PDI-induced ion acoustic turbulence was discovered by the x-ray spectroscopy in laser-produced plasmas. These conclusions are also supported by PIC simulations. Our results can be used for laboratory modeling of physical processes in astrophysical objects and a better understanding of intense laser-plasma interactions. ©2017 Optical Society of America.
Acousto-optical characteristics of double potassium tungstates are analyzed and specific directions for light modulation are found. First, an important subgroup of elasto-optic coefficients of KYb(WO4)(2) and KLu(WO4)(2) crystals are calculated with use of experimental data. It is revealed that with proper choice of ultrasound direction the acousto-optical figure-of-merit approximately 2 times exceeds the maximum value detected in previous experiments. Another unique direction is determined, which permits modulation of randomly polarized light. The elasto-optic characteristics of KYb(WO4)(2) and KLu(WO4)(2) crystals are compared to those of previously investigated materials of the same crystal group: KY(WO4)(2), KGd (WO4)(2). (C) 2016 Elsevier B.V. All rights reserved.
The poloidal current induced in the tokamak wall during fast transient events is analytically evaluated. The analysis is based on the electromagnetic relations coupled with plasma equilibrium equations. The derived formulas describe the consequences of both thermal and current quenches. In the final form, they give explicit dependence of the wall current on the plasma pressure and current. A comparison with numerical results of Villone et al. [F. Villone, G. Ramogida, G. Rubinacci, Fusion Eng. Des. 93, 57 (2015)] for IGNITOR is performed. Our analysis confirms the importance of the effects described there. The estimates show that the disruption-induced poloidal currents in the wall should be necessarily taken into account in the studies of disruptions and disruption mitigation in ITER. © 2017 Elsevier B.V.
Experimental results are presented on laser alloying of Co nanorods with Al spherical nanoparticles by laser exposure of their mixture in liquid ethanol. It is demonstrated that the initial morphology of the nanoparticles is modified upon laser exposure. The Co nanorods are transformed into Co nanospheres covered by a layer of Al. The evolution of the size distribution is studied as a function of the time of laser exposure. The average size of the nanoparticles has a maximum level with a corresponding optimal irradiation time. The results are discussed from the viewpoint of the interaction of molten nanoparticles inside a cavitation bubble filled with a liquid vapor. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.
The results of experiments studying long-living positive streamers propagating on the surface of tap water are presented; the plasma-forming gas is air at atmospheric pressure. Measurement data for the strength of the longitudinal electric field in the surface streamer, the streamer velocity versus time until it stops, and the length of the streamer versus the applied voltage are presented. It is revealed that the depth of the water in a basin influences the streamer length: the deeper the water, the longer the streamer. Besides this, restricting the transverse direction of the area in the water accessible for streamer extension suppresses streamer branching until it fully disappears. It is shown that non-branching streamers propagating in narrow water channels increase their length considerably. Placing a dielectric plate with long, narrow slits of the required configuration on the water enables one to control the trajectory of streamer propagation. Three-dimensional numerical calculations of the spatial structure of the electric field and the current inside and outside the streamer in the water basin with different depths and widths were made. It is shown numerically that the streamer length and its diameter strongly influence both the strength and spatial structure of the electric field in the air around the streamer.
Longitudinal electrostatic waves in the quantum electron–hole plasma of semiconductors are considered taking into account the degeneracy of electrons and holes and the exchange interaction. It is found in the framework of linear theory that the dispersion curve of longitudinal waves has two branches: plasmon and acoustic. An expression for the critical cutoff frequency for plasma oscillations and an expression for the speed of sound for acoustic vibrations are derived. It is shown that the plasma wave always exists in the form of a superposition of two components, characterized by different periods and wavelengths. Two nonlinear solutions are obtained within nonlinear theory: one in the form of a simple superposition of two tones and the other in the form of beats. © 2017, Pleiades Publishing, Ltd.
We show that the concept of the Lorentz-invariant mass of groups of particles can be applied to light pulses consisting of very large but finite numbers of noncollinear photons. Explicit expressions are found for the invariant mass of this manifold of photons for the case of diverging Gaussian light pulses propagating in vacuum. As the found invariant mass is finite, the light pulses propagate in vacuum with a speed somewhat smaller than the light speed. A small difference between the light speed and the beam-propagation velocity is found to be directly related to the invariant mass of a pulse. Focusing and/or defocusing light pulses is shown to strengthen the effect in which the pulse slows down while the pulse invariant mass increases. A scheme for measuring these quantities experimentally is proposed and discussed. © 2017 Astro Ltd.
For integrated modeling of equilibrium, stability and dynamics of the divertor tokamak plasma with scrape-off layer (SOL) high resolution equilibrium calculations are needed. A new version of the CAXE equilibrium code computes the tokamak equilibrium on a numerical grid adaptive to magnetic surfaces both in the plasma region with closed flux surfaces and in the SOL region with open magnetic lines. The plasma profiles can be prescribed independently in each region with nested flux surfaces, and realistic SOL profiles with very short pressure drop off length can be accurately treated. The influence of the finite current density in SOL on the connection length is studied. From the point of view of the MHD equilibrium and stability modeling, self-consistent calculations of diverted tokamak configurations with finite current density at the separatrix require taking into account plasma outside the separatrix. Calculated high resolution equilibria provide an input to new versions of the ideal MHD stability codes treating tokamak plasma with SOL. The study of the influence of the pressure gradient profile in the pedestal plasma inside and outside the separatrix on the pedestal height limit set by external kink-ballooning mode stability is presented. Another possible application of the high resolution pedestal and SOL equilibrium code is a coupling to the SOLPS code with a purpose to increase equilibrium accuracy and support self-consistent plasma flow/equilibrium modeling. © 2017 IOP Publishing Ltd.
X-ray Magnetic Circular Dichroism (XMCD) technique was used to investigate local magnetic properties of microcrystalline Nd10.4Zr4.0Fe79.2B6.4 samples, oriented along either easy or hard magnetization direction. The Nd L2,3 and Fe K edge XMCD spectra were measured at room temperature under a magnetic field of ±10 T. A very strong dependence of XMCD spectra on the sample orientation has been observed at the L2,3-edges of Nd, whereas the Fe K-edge XMCD spectra are found to be practically isotropic. This result indicates that magnetic anisotropy of NdFeB-based alloys originates from the Nd sublattice. In addition element selective magnetization curves have been recorded by measuring the intensity of XMCD signals as a function of an applied magnetic field up to ±17T. To find a correlation between local and macroscopic magnetic properties of studied samples we compared these data with magnetization curves, measured by vibrating sample magnetometer up to ±14T. Results are important for understanding the origin of high-coercivity state in NdFeB-based intermetallic compounds. © 2016 Pleiades Publishing, Inc.
The initial stage of hydrogen desorption from fully hydrogenated carbon nanotubes (3.0) and (2.2) is numerically studied by the molecular dynamics method. The temperature dependence of the desorption rate is directly determined at T = 1800–2500 K. The characteristic desorption times are determined at temperatures outside this range by extrapolation. It is shown that hydrogen desorption leads to the appearance of electronic states in the band gap. © 2017, Pleiades Publishing, Ltd.
A model is constructed allowing computer simulations of the near-wall area of a planar plasma sheet in conditions where the steady state of the plasma is supported by the production of charged particles in a region removed from the wall. Calculations have revealed variation in the energy distribution of the electrons in both time and spatially over the sheet width (cooling the electronic component) due to absorption of fast electrons at the walls bounding the plasma volume. It is shown that the plasma density profile across the sheet width has an abrupt decrease at the boundary of the region of plasma regulation. Thus the standard concepts of the potential and plasma density distributions in the sheath and presheath based on the assumption of a stable energy distribution for the electrons in the presheath yields inaccurate results for the plasma sheet where the ionization source is remote from the wall. © 2016 Elsevier Ltd
We developed a method to combine parallel superconducting HTS tapes to a current carrying element with high current and uniform current distribution among strands at ac mode. The current carrying elements are made of several parallel HTS tapes placed side-by-side on a round mandrel. The test of the small model made of five parallel 2G HTS tapes confirmed the idea. The method was implemented for 10/0.4 kV, 1 MVA power transformer. For both low and high voltage windings, we used 12 mm Amperium tapes from American Superconductor Co. For low-voltage winding 19 parallel tapes were wound on four mandrels and connected in series. High-voltage winding was wound with a single 12 mm tape. The assembled windings of each phase were tested at liquid nitrogen temperature without iron yoke. AC losses were measured in low-voltage winding at two modes: when high voltage winding was either shortened or open. In this paper, we present the details of current carrying element development and test, 1 MVA transformers winding designs and test results.
We consider a superconducting qubit coupled to the nonstationary transmission line cavity with modulated frequency taking into account energy dissipation. Previously, it was demonstrated that in the case of a single nonadiabatical modulation of a cavity frequency there are two channels of a two-level system excitation which are due to the absorption of Casimir photons and due to the counterrotating wave processes responsible for the dynamical Lamb effect. We show that the parametric periodical modulation of the resonator frequency can increase dramatically the excitation probability. Remarkably, counterrotating wave processes under such a modulation start to play an important role even in the resonant regime. Our predictions can be used to control qubit-resonator quantum states as well as to study experimentally different channels of a parametric qubit excitation. © 2016 Elsevier B.V.
It is known that in pressurized H2S, the complex electronic structure in the energy range of 200 meV near the chemical potential can be separated into two electronic components: the first characterized by steep bands with a high Fermi velocity and the second by flat bands with a vanishing Fermi velocity. Also, the phonon modes interacting with electrons at the Fermi energy can be separated into two components: hard modes with high energy around 150 meV and soft modes with energies around 60 meV. Therefore, we discuss here a multiband scenario in the standard Bardeen–Cooper–Schrieffer (BCS) approximation where the effective BCS coupling coefficient is in the range 0.1–0.32. We consider a first (second) BCS condensate in the strong (weak) coupling regime 0.32 (0.15). We discuss different scenarios segregated in different portions of the material. The results show the phenomenology of unconventional superconducting phases in this two-gap superconductivity scenario where there are two electronic components in two Fermi surface spots, and the pairing is mediated by either a soft or a hard phonon branch where the interband exchange term, also if small, plays a key role for the emergence of high-temperature superconductivity in pressurized sulfur hydride. © 2017 Springer Science+Business Media New York
The aim of this paper is to study physical and chemical properties of nano-structured multi-layered composite coating based on three-layered architecture of Ti-TiN-(ZrNbTi)N, deposited to a carbide substrate, as well as to study the mechanism of wear and failure of carbide tools with coatings under the conditions of stationary cutting. The coating obtained by the method of filtered cathodic vacuum arc deposition (FCVAD). The microstructure of carbide cubstrate with coating on transverse cross-section were investigated, as well as its hardness, strength of the adhesive bond to the substrate, chemical composition and phase composition. The studies of cutting properties of the carbide inserts with developed coating was conducted on a lathe in longitudinal turning of steel C45 (HB 200). Analysis of mechanisms of coated tool wear and failure was carried out, as well as - the study of processes of diffusion and oxidation in the surface layers of the coated substrate. © 2017 Trans Tech Publications.
The results of electromagnetic treatment (EMT) of Rusar NT aramid fibre, which increased the ultimate strength and elasticity modulus by 8-10%, are reported. The theoretical possibility of enhancing strength properties of Rusar NT fibre up to 20% by EMT is shown. The measurements were systematized by cluster analysis. It is suggested that the hydrogen bond is strengthened upon EMT, which ultimately leads to improvement in strength properties of Rusar NT fibre. © 2017 Springer Science+Business Media New York
The shape memory effect (SME) in alloys with thermoelastic martensitic transformation provides a unique possibility to create the tiny mechanical devices for NEMS / MEMS technology. SME observed in layered composite microstructors produced by FIB CVD technology, consisting of Ti2NiCu alloy layer with SME and platinum elastic layer at reducing the thickness of the active layer for at least 80 nm. In this paper the physical and technological restrictions were experimentally examined on the minimum thickness of the active layer of the composites for SME manifestation. © 2016 IEEE.
DarkSide-50 (DS-50) at Gran Sasso underground laboratory (LNGS), Italy, is a direct dark matter search experiment based on a TPC with liquid argon. DS-50 has completed its first dark matter run using atmospheric argon as target. The DS-50 detector performances and the results of the first physics run are reviewed in this proceeding. © 2015 Elsevier B.V.
Existing models for calculation of thermal conductivity of uranium dioxide are analyzed. Anomalous growth of the thermal conductivity coefficient of nuclear fuel in the high-temperature region is explained. Models of specific heat at constant volume and thermal conductivity are proposed. It is demonstrated that the contribution of degrees of freedom of charge carriers to the observed thermal conductivity coefficient of admixture-free stoichiometric UO2 can be neglected up to the melting point. © 2016, Pleiades Publishing, Ltd.
The distribution of particles inside hadronic jets produced in the decay of boosted W and Z bosons can be used to discriminate such jets from the continuum background. Given that a jet has been identified as likely resulting from the hadronic decay of a boosted W or Z boson, this paper presents a technique for further differentiating Z bosons from W bosons. The variables used are jet mass, jet charge, and a b-tagging discriminant. A likelihood tagger is constructed from these variables and tested in the simulation of Wsup′/sup→ WZ for bosons in the transverse momentum range 200 GeV < pT< 400 GeV in s= 8 TeV pp collisions with the ATLAS detector at the LHC. For Z-boson tagging efficiencies of ϵZ= 90 , 50, and 10 % , one can achieve Wsup+/sup-boson tagging rejection factors (1 / ϵW+) of 1.7, 8.3 and 1000, respectively. It is not possible to measure these efficiencies in the data due to the lack of a pure sample of high pT, hadronically decaying Z bosons. However, the modelling of the tagger inputs for boosted W bosons is studied in data using a tt¯ -enriched sample of events in 20.3 fbsup- 1/sup of data at s= 8 TeV. The inputs are well modelled within uncertainties, which builds confidence in the expected tagger performance. © 2016, CERN for the benefit of the ATLAS collaboration.
A new search signature for excited leptons is explored. Excited muons are sought in the channel pp → μμ∗→ μμ jet jet, assuming both the production and decay occur via a contact interaction. The analysis is based on 20.3 fb-1 of pp collision data at a centre-of-mass energy of s = 8 TeV taken with the ATLAS detector at the large hadron collider. No evidence of excited muons is found, and limits are set at the 95% confidence level on the cross section times branching ratio as a function of the excited-muonmass μμ∗. For μμ∗between 1.3 and 3.0 TeV, the upper limit on φB (μ∗→ μqq) is between 0.6 and 1 fb. Limits on sB are converted to lower bounds on the compositeness scale. In the limiting case L = μμ∗, excitedmuonswith amass below2.8 TeVare excluded.With the samemodel assumptions, these limits at larger μ∗masses improve upon previous limits fromtraditional searches based on the gauge-mediated decay μ∗→ μγ. © 2016 CERN for the benefit of the ATLAS Collaboration.
A search for the pair production of new light bosons, each decaying into a pair of muons, is performed with the CMS experiment at the LHC, using a dataset corresponding to an integrated luminosity of 20.7 fbsup-1/sup collected in proton-proton collisions at center-of-mass energy of √s=8 TeV. No excess is observed in the data relative to standard model background expectation and a model independent upper limit on the product of the cross section, branching fraction, and acceptance is derived. The results are compared with two benchmark models, the first one in the context of the next-to-minimal supersymmetric standard model, and the second one in scenarios containing a hidden sector, including those predicting a nonnegligible light boson lifetime. © 2015 CERN for the benefit of the CMS Collaboration.
Abstract: A search is presented for a new, light boson with a mass of about 1 GeV and decaying promptly to jets of collimated electrons and/or muons (lepton-jets). The analysis is performed with 20.3 fbsup−1/sup of data collected by the ATLAS detector at the Large Hadron Collider in proton-proton collisions at a centre-of-mass energy of 8 TeV. Events are required to contain at least two lepton-jets. This study finds no statistically significant deviation from predictions of the Standard Model and places 95% confidence-level upper limits on the contribution of new phenomena beyond the SM, incuding SUSY-portal and Higgs-portal models, on the number of events with lepton-jets.[Figure not available: see fulltext.] © 2016, The Author(s).
A search for the pair production of top squarks, each with R-parity-violating decays into two Standard Model quarks, is performed using 17.4 fb(-1) of root s = 8 TeV proton-proton collision data recorded by the ATLAS experiment at the LITC. Each top squark is assumed to decay to a b- and an 8-quark, leading to four quarks in the final state. Background discrimination is achieved with the use of b-tagging and selections on the mass and substructure of large-radius jets, providing sensitivity to top squark masses as low as 100 GeV. No evidence of an excess beyond the Standard Model background prediction is observed and top squalls decaying to bs are excluded for top squark masses in the range 100
We demonstrate that the action of physical pressure, chemical compression, or aliovalent substitution in ACo2As2 (A = Eu and Ca) has a general consequence of causing these antiferromagnetic materials to become ferromagnets. In all cases, the mixed valence triggered at the electropositive A site results in the increase of the Co 3d density of states at the Fermi level. Remarkably, the dramatic alteration of magnetic behavior results from the very minor (<0.15 electron) change in the population of the 3d orbitals. The mixed valence state of Eu observed in the high-pressure (HP) form of EuCo2As2 exhibits a remarkable stability, achieving the average oxidation state of +2.25 at 12.6 GPa. In the case of CaCo2As2, substituting even 10% of Eu or La into the Ca site causes ferromagnetic ordering of Co moments. Similar to HP-EuCo2As2, the itinerant 3d ferromagnetism emerges from electronic doping into the Co layer because of chemical compression of Eu sites in Ca0.9Eu0.1Co1.91As2 or direct electron doping in Ca0.85La0.15Co1.89As2. The results reported herein demonstrate the general possibility of amplifying minor localized electronic effects to achieve major changes in material's properties via involvement of strongly correlated electrons. © 2016 American Chemical Society.
It is shown that the surface with constant mean curvature encloses the extremal volume among all toroidal surfaces of given area. The exact solution for the corresponding variational problem is derived, and its parametric analysis is performed in the limits of high and small mean curvatures. An absence of smooth torus with constant mean curvature is proved, and the extremal surface is demonstrated to have at least one edge located on the outer side of the torus.
We discuss the gravitino problem in the context of the exotic see-saw mechanism for neutrinos and leptogenesis, UV completed by intersecting D-branes Pati-Salam models. In the exotic see-saw model, supersymmetry is broken at high scales MSUSY > 10sup9/sup GeV and this seems in contradiction with gravitino bounds from inflation and baryogenesis. However, if gravitino is the lightest stable supersymmetric particle, it will not decay into other SUSY particles, avoiding the gravitino problem and providing a good cold dark matter (CDM). Gravitini are super heavy dark particles and they can be produced by non-adiabatic expansion during inflation. Intriguingly, from bounds on the correct abundance of dark matter (DM), we also constrain the neutrino sector. We set a limit on the exotic instantonic coupling of < 10-2-10-3. This also sets constrains on the Calabi-Yau compactifications and on the string scale. This model strongly motivates very high energy DM indirect detection of neutrini and photons of 1011-1013 GeV: gravitini can decay on them in a cosmological time because of soft R-parity breaking effective operators. © 2016 World Scientific Publishing Company.
The results from experiments on measuring the rate of gasification for carbon and boron–carbon films and carbon fiber composite (CFC) exposed in oxygen–ozone mixtures are presented. The rate of gasification is 0.4–0.6 μm hsup–1/sup (at temperatures of 220–250°C, a pressure of 0.3 atm, and an ozone concentration of 0.6 at %) for carbon films; plane CFC samples; gaps 1 and 2 mm wide with walls of stainless steel; and gaps 1 mm wide with walls of CFC. It is 15 μm hsup–1/sup for plane CFC at a temperature of 250°C, a pressure of 1 atm, and an ozone concentration of 10 at %. The rate of gasification for boron–carbon films is from 3 to 30 nm hsup–1/sup for B/C ratios of 2.1 to 0.8 (at 250°C, 1 atm, and ozone concentration of 10 at %). © 2016, Allerton Press, Inc.
The roles of neutrinos and convective instability in collapsing supernovae are considered. Spherically symmetrical computations of the collapse using the Boltzmann equation for the neutrinos lead to the formation of the condition of convective instability, 0, in a narrow region of matter accretion above the neutrinosphere. If instability arises in this region, the three-dimensional solution will represent a correction to the spherically symmetrical solution for the gravitational collapse. The mean neutrino energies change only negligibly in the narrow region of accretion. Nuclear statistical equilibrium is usually assumed in the hot proto-neutron stellar core, to simplify the computations of the collapse. Neutronization with the participation of free neutrons is most efficient. However, the decay of nuclei into nucleons is hindered during the collapse, because the density grows too rapidly compared to the growth in the temperature, and an appreciable fraction of the energy is carried away by neutrinos. The entropy of the matter per nucleon is modest at the stellar center. All the energy is in degenerate electrons during the collapse. If the large energy of these degenerate electrons is taken into account, neutrons are efficiently formed, even in cool matter with reduced Y (e) (the difference between the numbers of electrons and positrons per nucleon). This process brings about an increase in the optical depth to neutrinos, the appearance of free neutrons, and an increase in the entropy per nucleon at the center. The convectively unstable region at the center increases. The development of large-scale convection is illustrated using a multi-dimensional gas-dynamical model for the evolution of a stationary, unstable state (without taking into account neutrino transport). The time for the development of convective instability (several milliseconds) does not exceed the time for the existence of the unstable region at the center (10ms). The realization of this type of instability is fundamentally different from a spherically symmetrical model. The flux of neutrinos changes and the mean energy of the neutrinos is increased, which has important implications for the detection of neutrinos from supernovae. For these same reasons, the energy absorped in the supernova envelope also changes in the transition to such a multi-dimensional model.
The tensor of the high-frequency conductivity of a plasma created via tunnel ionization of atoms in the field of linearly or circularly polarized radiation is derived. It is shown that the real part of the conductivity tensor is highly anisotropic. In the case of a toroidal velocity distribution of photoelectrons, the possibility of amplification of a weak high-frequency field polarized at a sufficiently large angle to the anisotropy axis of the initial nonequilibrium distribution is revealed. © 2016, Pleiades Publishing, Ltd.
The study is stimulated by the expected noticeable deviation of the electron velocity distribution function (eVDF) from a Maxwellian under condition of a strong auxiliary heating of electron plasmas in tokamak-reactors. The key principles of accuracy estimation of the Thomson scattering diagnostic of non-Maxwellian plasmas in tokamak-reactors are presented. The algorithm extends the conventional approach to the assessment of non-Maxwellian plasmas measurements errors for a broad class of deviations of the eVDF from a Maxwellian. The algorithm is based on solving the inverse problem many times to determine main parameters of the eVDF with allowance for all possible sources of error and statistical variation of the input parameters of the problem. The method is applied to a preliminary analysis of the advantages of the formerly suggested use of various wavelengths of probing laser radiation in the Thomson diagnostics of non- Maxwellian plasma on the example of the core plasma Thomson scattering diagnostic system which is under design for ITER tokamak. The results obtained confirm the relevance of the diversification of the probing laser radiation wavelength.
Purpose of the work is to prepare multilayer coatings corresponding to specified requirements to recovery and improvement of surface details. Requirements to coatings: providing durable and reliable adhesion base and filler materials, absence of pores, cracks, delaminations, reducing mixing metal base and cladding. We used iron-based PR-10R6M5 and tungsten carbide Hoganas 44712 powders. Experimental determination of the optimal technological mode of application of the single track, the coefficient of overlapping tracks to create a full layer, the angle of the second cladding layer, relative to the first one and, finally, the determination of the optimal additive tungsten carbide to achieve increased durability were produced to fulfill these requirements. © Published under licence by IOP Publishing Ltd.
Results of investigations of electromechanical systems with high-coercive permanent magnets from the standpoint of finding an optimal solution to reach the best energy characteristics and to ensure reliability of magnetic system design are presented.
The angular distributions and the differential branching fraction of the decay Bsup0/sup→Ksup*/sup(892)sup0/supμsup+/supμsup-/sup are studied using data corresponding to an integrated luminosity of 20.5 fbsup-1/sup collected with the CMS detector at the LHC in pp collisions at s=8 TeV. From 1430 signal decays, the forward-backward asymmetry of the muons, the Ksup*/sup(892)sup0/sup longitudinal polarization fraction, and the differential branching fraction are determined as a function of the dimuon invariant mass squared. The measurements are among the most precise to date and are in good agreement with standard model predictions. © 2015 CERN for the benefit of the CMS Collaboration.
We report the first results of elliptic (v2), triangular (v3), and quadrangular (v4) flow of charged particles in Pb-Pb collisions at a center-of-mass energy per nucleon pair of sNN=5.02 TeV with the ALICE detector at the CERN Large Hadron Collider. The measurements are performed in the central pseudorapidity region |η|<0.8 and for the transverse momentum range 0.2<pT<5 GeV/c. The anisotropic flow is measured using two-particle correlations with a pseudorapidity gap greater than one unit and with the multiparticle cumulant method. Compared to results from Pb-Pb collisions at sNN=2.76 TeV, the anisotropic flow coefficients v2, v3, and v4 are found to increase by (3.0±0.6)%, (4.3±1.4)%, and (10.2±3.8)%, respectively, in the centrality range 0%-50%. This increase can be attributed mostly to an increase of the average transverse momentum between the two energies. The measurements are found to be compatible with hydrodynamic model calculations. This comparison provides a unique opportunity to test the validity of the hydrodynamic picture and the power to further discriminate between various possibilities for the temperature dependence of shear viscosity to entropy density ratio of the produced matter in heavy-ion collisions at the highest energies. © 2016 CERN.
Morphological and fractographic features of change of FeCo-based amorphous alloy surfaces after laser treatment are studied in detail. Regimes of laser treatment that allow various degrees of crystallization of the examined alloys to be obtained, including thin (<1 ∙m) crystal layers on amorphous alloy surfaces, amorphous-crystalline composites, and completely crystalline alloys are adjusted. The Vickers hardness is estimated in zones of selective laser irradiation. The structure of the examined alloys attendant to the change of their mechanical properties is analyzed. © 2016 Springer Science+Business Media New York
The article reviews optimization of spaces of informative features and synthesis of rules for forecasting, diagnosis, and control of the state of health of a person using the theory of measurement of latent variables based on Rasch statistical models. © 2016 Springer Science+Business Media New York
Atmospheric neutrinos are produced in interactions of cosmic rays with atomic nuclei in the Earth's atmosphere. Although their flux is too low for studying in Borexino, atmospheric neutrinos act as a background for other processes. This paper presents the theoretical expected yield of atmospheric neutrinos in Borexino for three neutrino detection reactions: vp-ES, ve-ES and inverse beta-decay, as well as the status of Monte-Carlo simulation for v(12)C interaction channels. Calculations were performed based on the only currently known detailed model of atmospheric neutrinos flux at very low energies.
Portable autonomous generator of high-power RF-pulses based on the gas discharge with hollow cathode has been designed, fabricated, and tested. Input and output characteristics are the following: discharge current amplitude is 800 A, duration of generated RF-pulses is 350 ns, carrier frequency is ∼90 MHz, power in RF-pulse is 0.5 MW, pulse repetition rate is 0.5 kHz, and device efficiency is ∼25%. © 2016 Author(s).
We present measurements of the azimuthal dependence of charged jet production in central and semi-central sNN=2.76 TeV Pb-Pb collisions with respect to the second harmonic event plane, quantified as v2ch jet. Jet finding is performed employing the anti-kT algorithm with a resolution parameter R=0.2 using charged tracks from the ALICE tracking system. The contribution of the azimuthal anisotropy of the underlying event is taken into account event-by-event. The remaining (statistical) region-to-region fluctuations are removed on an ensemble basis by unfolding the jet spectra for different event plane orientations independently. Significant non-zero v2ch jet is observed in semi-central collisions (30-50% centrality) for 20pTch jet90 GeV/c. The azimuthal dependence of the charged jet production is similar to the dependence observed for jets comprising both charged and neutral fragments, and compatible with measurements of the v2 of single charged particles at high pT. Good agreement between the data and predictions from JEWEL, an event generator simulating parton shower evolution in the presence of a dense QCD medium, is found in semi-central collisions. © 2015 CERN for the benefit of the ALICE Collaboration.
In this paper we studied the non-self mode of the auto-oscillation secondary-emission discharge (ASED) in a longitudinal magnetic field with autonomous electron gun to ignite the primary beam-plasma discharge (PPD).
We report the generation of molecular hydrogen from water by laser irradiation, without any electrodes and photocatalysts. A near infrared pulsed nanosecond laser is used for exposure of colloidal solution of Au nanoparticles suspended in water. Laser exposure of the colloidal solution results in formation of breakdown plasma in liquid and emission of H2. The rate of H2 emission depends critically on the energy of laser pulses. There is a certain threshold in laser fluence in liquid (around 50 J/cmsup2/sup) below which plasma disappears and H2 emission stops. H2 emission from colloidal solution of Au nanoparticles in ethanol is higher than that from similar water colloid. It is found that formation of plasma and emission of H2 or D2 can be induced by laser exposure of pure liquids, either H2O or D2O, respectively. The results are interpreted as water molecules splitting by direct electron impact from breakdown plasma. © 2016 Elsevier B.V.
The processes of laser-assisted synthesis of Tritium nuclei and their laser-induced decay in cold plasma in the vicinity of solid targets (Au, Ti, Se, etc.) immersed into heavy water are experimentally realized at peak laser intensity of 10sup10/sup-10sup13/sup W/cmsup2/sup. Initial stages of Tritium synthesis and their laser-induced beta-decay are interpreted on the basis of non-elastic interaction of plasma electrons having kinetic energy of 5-10 eV with nuclei of Deuterium and Tritium, respectively. © Published under licence by IOP Publishing Ltd.
A classical model of the emission of radiation by relativistic electrons in a crystal has been developed using the form of the potential maximally close to its actual form. The dynamics of electrons with energies 20–25 MeV performing channeling in crystals is simulated numerically. The generation of electromagnetic radiation that accompanies this motion has been considered. It has been shown that, in the given electron energy range, this radiation corresponds to the X-ray spectral band with characteristic photon energies of up to 40 keV. The radiation yield is estimated. The requirements to the electron beam parameters are formulated based on the results of the simulation. It has been shown that numerical simulation gives results that correlate with the analytic results obtained earlier and with the experimental data. © 2016, Pleiades Publishing, Ltd.
One of the possible applications of relativistic electron radiation during channeling in crystals, i.e., the use of radiation for medical visualization, is considered.A setup scheme is proposed, the results of numerical simulation of electron dynamics in crystals and radiation generation and the results of calculations of dose loads are presented. © 2016, Allerton Press, Inc.
Results of experiments on the detection of suprathermal electron beams in the plasma of a highcurrent low-inductance vacuum spark by means of space-resolved spectral X-ray polarimetry are presented. It is shown that the observed polarization of bremsstrahlung may be caused by an ~100-keV electron beam propagating along the discharge axis from the pinching region toward the anode. The influence of the discharge initiation conditions on the parameters of the generated electron beams is analyzed. © 2016, Pleiades Publishing, Ltd.
The investigation of nonthermal electron beams in a high-current vacuum spark by Bragg polarimetry of continuous radiation from discharge plasma is reported. Movement features of electron beams inside and outside of contraction region of the discharge plasma are revealed.
Progress in the study of nuclear clustering in the relativistic B-10 and C-11 nuclei dissociation in nuclear track emulsion is presented. The contribution of the unbound Be-8 and B-9 nuclei to their structure is determined on the basis of measurements of the emission angles of relativistic He and H fragments.
This paper discusses various observations on beam-induced and cosmic-ray backgrounds in the ATLAS detector during the LHC 2012 proton-proton run. Building on published results based on 2011 data, the correlations between background and residual pressure of the beam vacuum are revisited. Ghost charge evolution over 2012 and its role for backgrounds are evaluated. New methods to monitor ghost charge with beam-gas rates are presented and observations of LHC abort gap population by ghost charge are discussed in detail. Fake jets from colliding bunches and from ghost charge are analysed with improved methods, showing that ghost charge in individual radio-frequency buckets of the LHC can be resolved. Some results of two short periods of dedicated cosmic-ray background data-taking are shown; in particular cosmic-ray muon induced fake jet rates are compared to Monte Carlo simulations and to the fake jet rates from beam background. A thorough analysis of a particular LHC fill, where abnormally high background was observed, is presented. Correlations between backgrounds and beam intensity losses in special fills with very high beta* are studied.
We report on the possibility of the beam-plasma instability development in the system with electron beam interacting with the single-component hot electron plasma without ions. As considered system, we analyse the interaction of the low-current relativistic electron beam (REB) with squeezed state in the high-current REB formed in the relativistic magnetically insulated two-section vircator drift space. The numerical analysis is provided by means of 3D electromagnetic simulation in CST Particle Studio. We have conducted an extensive study of characteristic regimes of REB dynamics determined by the beam-plasma instability development in the absence of ions. As a result, the dependencies of instability increment and wavelength on the REB current value have been obtained. The considered process brings the new mechanism of controlled microwave amplification and generation to the device with a virtual cathode. This mechanism is similar to the action of the beam-plasma amplifiers and oscillators. © 2016 AIP Publishing LLC.
The effect of the ionic Coulomb field in laser-induced above-threshold ionization is analyzed in terms of the classical mapping of the initial conditions (time of ionization and momentum transverse to the laser field) on the plane of the final momenta. This mapping brings out the Coulomb effect especially clearly because changes of the transverse momentum are only possible via the action of the Coulomb field. We formulate a model that restricts the action of the Coulomb field to a sequence of successive interactions in hard and soft recollisions and find an analytical approximation to this model. It allows us to trace the low-energy structure to the detailed behavior of the Coulomb corrections to the longitudinal and the transverse momentum and their interplay, which causes a caustic in the plane of the final momentum. © 2016 American Physical Society.
A new device is proposed for diagnostics of the SOL plasmas in tokamaks. The device allows to obtain a more detailed information on the impurity concentration, ionization state distribution, and particle fluxes, by combining the several techniques in a single device. The operation principle and the main parts of the proposed multifunctional probe are described.
Cold dark matter (DM) scenario may be cured of several problems by involving self-interaction of dark matter. Viability of the models of long-range interacting DM crucially depends on the effectiveness of recombination of the DM particles, making thereby their interaction short-range. Usually in numeric calculations, recombination is described by cross section obtained on a feasible quantum level. However in a wide range of parameter values, a classical treatment, where the particles are bound due to dipole radiation, is applicable. The cross sections, obtained in both approaches, are very different and lead to diverse consequences. Classical cross section has a steeper dependence on relative velocity, what leads to the fact that, after decoupling of DM particles from thermal background of “dark photons” (carriers of DM long-range interaction), recombination process does not “freeze out”, diminishing gradually density of unbound DM particles. Our simplified estimates show, that at the taken parameter values (the mass of DM particle is 100 GeV, interaction constant is 100sup−1/sup, and quite natural assumptions on initial conditions, from which the result is very weakly dependent) the difference in residual density reaches about 5 orders of magnitude on pre-galactic stage. This estimate takes into account thermal effects induced by dipole radiation and recombination, which resulted in the increase of both temperature and density of DM particles by a half order of magnitude. © 2016 The Author(s)
We consider model of multicomponent dark matter consisting of WIMP- and SIMP-components, possessing Coulomb-like interaction. The latter, in its term, implies an existence of thermal background of the interaction carriers. We evaluate the temperature evolution of different components for early epoch. It is shown that it can be very different depending on model parameters.
The general structure of the spherically symmetric solutions in the Weyl conformal gravity is described. The corresponding Bach equations are derived for the special type of metrics, which can be considered as the representative of the general class. The complete set of the pure vacuum solutions is found. It consists of two classes. The first one contains the solutions with constant two-dimensional curvature scalar of our specific metrics, and the representatives are the famous Robertson-Walker metrics. One of them we called the ''gravitational bubbles'', which is compact and with zero Weyl tensor. Thus, we obtained the pure vacuum curved space-times (without any material sources, including the cosmological constant) what is absolutely impossible in General Relativity. Such a phenomenon makes it easier to create the universe from ''nothing''. The second class consists of the solutions with varying curvature scalar. We found its representative as the one-parameter family. It appears that it can be conformally covered by the thee-parameter Mannheim-Kazanas solution. We also investigated the general structure of the energy-momentum tensor in the spherical conformal gravity and constructed the vectorial equation that reveals clearly some features of non-vacuum solutions. Two of them are explicitly written, namely, the metrics. © 2016 IOP Publishing Ltd and Sissa Medialab srl.
The classical Vaidya metric is transformed to the special diagonal coordinates in the case of the linear mass function allowing rather easy treatment. We find the exact analytical expressions for metric functions in these diagonal coordinates. Using these coordinates, we elaborate the maximum analytic extension of the Vaidya metric with a linear growth of the black hole mass and construct the corresponding Carter-Penrose diagrams for different specific cases. The derived global geometry is also seemingly valid for a more general behavior of the black hole mass in the Vaidya metric.
The presence of two components in the electron fluid of high-temperature superconductors and the complex charge and lattice inhomogeneity have been the hot topics of the international conference of the superstripes series, SUPERSTRIPES 2015, held in Ischia in 2015. The debate on the mechanisms for reaching room-temperature superconductors has been boosted by the discovery of superconductivity with the highest critical temperature in pressurized sulfur hydride. Different complex electronic and structural landscapes showing up in superconductors which resist to the decoherence effects of high temperature have been discussed. While low-temperature superconductors described by the BCS approximation are made of a single condensate in the weak coupling, the high-temperature superconductors are made of coexisting multiple condensates (in different spots of the k-space and the real space) some in the BCS-BEC crossover regime and others in the BCS regime. The role of “shape resonance” in the exchange interaction between these different condensates, like “the Fano-Feshbach resonance” in ultracold gasses, is emerging as a key term for high-temperature superconductivity. © 2016 Springer Science+Business Media New York
Slow oscillations (SlO) of the in-plane magnetoresistance with a frequency less than 4 T are observed in the rare-earth tritellurides and proposed as an effective tool to explore the electronic structure in various strongly anisotropic quasi-two-dimensional compounds. Contrary to the usual Shubnikov-de-Haas oscillations, SlO originate not from small Fermi-surface pockets, but from the entanglement of close frequencies due to a finite interlayer transfer integral, either between the two Te planes forming a bilayer or between two adjacent bilayers. From the observed angular dependence of the frequency and the phase of SlO we argue that they originate from the bilayer splitting rather than from the Fermi-surface warping. The SlO frequency gives the value of the interlayer transfer integral ≈1 meV for TbTe3and GdTe3. © 2016, EDP Sciences, SIF, Springer-Verlag Berlin Heidelberg.
We compare the polarization properties of cyclotron and relativistic dipole radiation of electrons moving in a magnetic field on a helix with ultrarelativistic longitudinal and nonrelativistic transverse velocity components. The applicability of these models in the case of accretion on to a neutron star is discussed. A test based on polarization observations is suggested to distinguish between a cyclotron and relativistic dipole origin of features observed in the X-ray spectra of some X-ray sources, see e.g. Santangelo et al., among which Her X-1 is the most famous (Trumper et al.).
Useful analytical approximation formulas for the sheath electric potential profile in the presence of secondary electron emission in oblique magnetic field is suggested.The potential distributions calculated with the proposed model are in good agreement with the respective simulations perfomed with a combined PIC and Monte Carlo code ELECTRAN. The influence of the magnetic field inclination angle on the angular and energy distributions of ions incident on plasma-facing components (PFC) and thus on the effective sputtering yield is analyzed. © 2016, Allerton Press, Inc.
Three-dimensional (3D) Bragg coherent x-ray diffractive imaging (CXDI) with a nanofocused beam was applied to quantitatively map the internal strain field of a single indium phosphide nanowire. The quantitative values of the strain were obtained by pre-characterization of the beam profile with transmission ptychography on a test sample. Our measurements revealed the 3D strain distribution in a region of 150 nm below the catalyst Au particle. We observed a slight gradient of the strain in the range of +/- 0.6% along the [111] growth direction of the nanowire. We also determined the spatial resolution in our measurements to be about 10 nm in the direction perpendicular to the facets of the nanowire. The CXDI measurements were compared with the finite element method simulations and show a good agreement with our experimental results. The proposed approach can become an effective tool for in operando studies of the nanowires.
We report the study of transport and magnetic properties of the YbB6-delta single crystals grown by inductive zone melting. A strong disparity in the low temperature resistivity, Seebeck and Hall coefficients is established for the samples with the different level of boron deficiency. The effective parameters of the charge transport in YbB6-delta are shown to depend on the concentration of intrinsic defects, which is estimated to range from 0.09% to 0.6%. The pronounced variation of Hall mobility mu(H) found for bulk holes is induced by the decrease of transport relaxation time from tau approximate to 7.7 fs for YbB5.994 to tau approximate to 2.2 fs for YbB5.96. An extra contribution to conductivity from electrons with mu(H) approximate to -1000 cm(2) V-1 s(-1) and the very low concentration n/n(Yb) approximate to 10(-6) discovered below 20 K for all the single crystals under investigation is suggested to arise from the surface electron states appeared in the inversion layer due to the band bending. (C) 2016 WILEY-VCH Verlag GmbH &Co. KGaA, Weinheim)
The discrete diffraction of electromagnetic waves near the interface between two different media formed by waveguide arrays is studied. One of the arrays consists of waveguides made of a positive index material; the other, of waveguides made of a negative index material. The refraction of a beam resulting from diffraction at the interface obeys an analog of Snell’s law. © 2016, Allerton Press, Inc.
The concentration of helium in tungsten fuzz-like nanostructures has been measured by means of thermal desorption spectroscopy. Fuzz was formed on the W surface under intensive plasma irradiation at 1500 K. The helium content was measured first in the as-irradiated sample, and then in a similar sample with the fuzz mechanically scraped from the sample surface. The difference gave the He content in the fuzz, which was estimated to be He/ W = (13 ± 4)%. © 2016 IAEA, Vienna.
Measurements of charged jet production as a function of centrality are presented for p–Pb collisions recorded at √sNN = 5.02 TeV with the ALICE detector. Centrality classes are determined via the energy deposit in neutron calorimeters at zero degree, close to the beam direction, to minimise dynamical biases of the selection. The corresponding number of participants or binary nucleon–nucleon collisions is determined based on the particle production in the Pb-going rapidity region. Jets have been reconstructed in the central rapidity region from charged particles with the anti-kT algorithm for resolution parameters R= 0.2 and R= 0.4 in the transverse momentum range 20 to 120 GeV/c. The reconstructed jet momentum and yields have been corrected for detector effects and underlying-event background. In the five centrality bins considered, the charged jet production in p–Pb collisions is consistent with the production expected from binary scaling from pp collisions. The ratio of jet yields reconstructed with the two different resolution parameters is also independent of the centrality selection, demonstrating the absence of major modifications of the radial jet structure in the reported centrality classes. © 2016, CERN for the benefit of the ALICE collaboration.
We report on the measurement of freeze-out radii for pairs of identical-charge pions measured in Pb-Pb collisions at root s(NN) = 2.76 TeV as a function of collision centrality and the average transverse momentum of the pair k(T). Three-dimensional sizes of the system (femtoscopic radii), as well as direction-averaged one-dimensional radii are extracted. The radii decrease with k(T), following a power-law behavior. This is qualitatively consistent with expectations from a collectively expanding system, produced in hydrodynamic calculations. The radii also scale linearly with dN(ch)/d eta (1/3). This behavior is compared to world data on femtoscopic radii in heavy-ion collisions. While the dependence is qualitatively similar to results at smaller root s(NN), a decrease in the ratio R-out/R-side is seen, which is in qualitative agreement with a specific prediction from hydrodynamic models: a change from inside-out to outside-in freeze-out configuration. The results provide further evidence for the production of a collective, strongly coupled system in heavy-ion collisions at the CERN Large Hadron Collider.
The pseudorapidity density of charged particles, dNch/dη, at midrapidity in Pb-Pb collisions has been measured at a center-of-mass energy per nucleon pair of sNN=5.02 TeV. For the 5% most central collisions, we measure a value of 1943±54. The rise in dNch/dη as a function of sNN is steeper than that observed in proton-proton collisions and follows the trend established by measurements at lower energy. The increase of dNch/dη as a function of the average number of participant nucleons, Npart, calculated in a Glauber model, is compared with the previous measurement at sNN=2.76 TeV. A constant factor of about 1.2 describes the increase in dNch/dη from sNN=2.76 to 5.02 TeV for all centrality classes, within the measured range of 0%-80% centrality. The results are also compared to models based on different mechanisms for particle production in nuclear collisions. © 2016 CERN. © 2016 CERN, for the ALICE Collaboration. Published by the American Physical Society under the terms of the »http://creativecommons.org/licenses/by/3.0/» Creative Commons Attribution 3.0 License. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.
Transverse momentum (p(T)) spectra of pions, kaons, and protons up to p(T) = 20 GeV/c have been measured in Pb-Pb collisions at root s(NN) = 2.76 TeV using the ALICE detector for six different centrality classes covering 0%-80%. The proton-to-pion and the kaon-to-pion ratios both show a distinct peak at p(T) approximate to 3 GeV/c in central Pb-Pb collisions that decreases for more peripheral collisions. For p(T) 10 GeV/c, the nuclear modification factor is found to be the same for all three particle species in each centrality interval within systematic uncertainties of 10%-20%. This suggests there is no direct interplay between the energy loss in the medium and the particle species composition in the hard core of the quenched jet. For p(T) 10 GeV/c, the data provide important constraints for models aimed at describing the transition from soft to hard physics.
The inclusive production of the ψ(2S) charmonium state was studied as a function of centrality in p-Pb collisions at the nucleon-nucleon center of mass energy √sNN = 5.02 TeV at the CERN LHC. The measurement was performed with the ALICE detector in the center of mass rapidity ranges −4.46 < ycms< −2.96 and 2.03 < ycms< 3.53, down to zero transverse momentum, by reconstructing the ψ(2S) decay to a muon pair. The ψ(2S) production cross section σψ(2S) is presented as a function of the collision centrality, which is estimated through the energy deposited in forward rapidity calorimeters. The relative strength of nuclear effects on the ψ(2S) and on the corresponding 1S charmonium state J/ψ is then studied by means of the double ratio of cross sections [σψ(2S)/σJ/ψ]pPb/[σψ(2S)/σJ/ψ]pp between p-Pb and pp collisions, and by the values of the nuclear modification factors for the two charmonium states. The results show a large suppression of ψ(2S) production relative to the J/ψ at backward (negative) rapidity, corresponding to the flight direction of the Pb-nucleus, while at forward (positive) rapidity the suppressions of the two states are comparable. Finally, comparisons to results from lower energy experiments and to available theoretical models are presented. © 2016, The Author(s).
The centrality dependence of the charged-particle pseudorapidity density measured with ALICE in Pb-Pb collisions at root s(NN) = 2.76 TeV over a broad pseudorapidity range is presented. This Letter extends the previous results reported by ALICE to more peripheral collisions. No strong change of the overall shape of charged-particle pseudorapidity density distributions with centrality is observed, and when normalised to the number of participating nucleons in the collisions, the evolution over pseudorapidity with centrality is likewise small. The broad pseudorapidity range (-3.5 eta 5) allows precise estimates of the total number of produced charged particles which we find to range from 162 +/- 22(syst.) to 17170 +/- 770(syst.) in 80-90% and 0-5% central collisions, respectively. The total charged-particle multiplicity is seen to approximately scale with the number of participating nucleons in the collision. This suggests that hard contributions to the charged-particle multiplicity are limited. The results are compared to models which describe dN(ch)/d(eta) at mid-rapidity in the most central Pb-Pb collisions and it is found that these models do not capture all features of the distributions. (C) 2016 CERN for the benefit of the ALICE Collaboration. Published by Elsevier B.V.
Prompt photon production in root S-NN = 2.76-TeV Pb + Pb collisions has been measured by the ATLAS experiment at the Large Hadron Collider using data collected in 2011 with an integrated luminosity of 0.14 nb(-1). Inclusive photon yields, scaled by the mean nuclear thickness function, are presented as a function of collision centrality and transverse momentum in two pseudorapidity intervals, vertical bar eta vertical bar 1.37 and 1.52
Charged-particle distributions are measured in proton-proton collisions at a centre-of-mass energy of 13 TeV, using a data sample of nearly 9 million events, corresponding to an integrated luminosity of 170 μbsup-1/sup, recorded by the ATLAS detector during a special Large Hadron Collider fill. The charged-particle multiplicity, its dependence on transverse momentum and pseudorapidity and the dependence of the mean transverse momentum on the charged-particle multiplicity are presented. The measurements are performed with charged particles with transverse momentum greater than 500 MeV and absolute pseudorapidity less than 2.5, in events with at least one charged particle satisfying these kinematic requirements. Additional measurements in a reduced phase space with absolute pseudorapidity less than 0.8 are also presented, in order to compare with other experiments. The results are corrected for detector effects, presented as particle-level distributions and are compared to the predictions of various Monte Carlo event generators. © 2016 CERN for the benefit of the ATLAS Collaboration.
Results of the electron density dynamics in the plasma channel of a femtosecond filament in air, nitrogen and argon from the moment of ionization up to hundreds of picoseconds after it are presented. Anisotropy of the refractive index was found, which is preceded and accompanied by ionization of the gas at the time of passage of high-intensity femtosecond laser pulse.
The detection of neutrinos emitted in the CNO reactions in the Sun is one of the ambitious goals of Borexino Phase-II. A measurement of CNO neutrinos would be a milestone in astrophysics, and would allow to solve serious issues in current solar models. A precise measurement of the rate of neutrinos from the pep reaction would allow to investigate neutrino oscillations in the MSW transition region. The pep and CNO solar neutrino physics, the measurement in Borexino Phase-I and the perspectives for the new phase are reviewed in this proceeding.
The ATLAS experiment at the CERN Large Hadron Collider has performed searches for new, heavy bosons decaying to WW, WZ and ZZ final states in multiple decay channels using 20.3 fbsup-1/sup of pp collision data at s=8 TeV. In the current study, the results of these searches are combined to provide a more stringent test of models predicting heavy resonances with couplings to vector bosons. Direct searches for a charged diboson resonance decaying to WZ in the ℓνℓsup'/supℓsup'/sup (ℓ=μ, e), ℓℓqq-, ℓνqq- and fully hadronic final states are combined and upper limits on the rate of production times branching ratio to the WZ bosons are compared with predictions of an extended gauge model with a heavy Wsup'/sup boson. In addition, direct searches for a neutral diboson resonance decaying to WW and ZZ in the ℓℓqq-, ℓνqq-, and fully hadronic final states are combined and upper limits on the rate of production times branching ratio to the WW and ZZ bosons are compared with predictions for a heavy, spin-2 graviton in an extended Randall-Sundrum model where the Standard Model fields are allowed to propagate in the bulk of the extra dimension. © 2016 CERN for the benefit of the ATLAS Collaboration.
Application of the nuclear track emulsion technique (NTE) in radioactivity and nuclear fission studies is discussed. It is suggested to use a HSP-1000 automated microscope for searching for a collinear cluster tri-partition of heavy nuclei implanted in NTE. Calibrations of cr-particles and ion ranges in a novel NTE are carried out. Surface exposures of NTE samples to a Cf-252 source started. Planar events containing fragments and long-range cr-particles as well as fragment triples only are studied. Splittings induced by thermal neutrons are studied in boron-enriched emulsion. Use of the image recognition program "ImageJ" for obtaining characteristics of individual events and for events from the large scan area is presented.
New technical capabilities have brought about the sweeping growth of the amount of data acquired by the astronomers from observations with different instruments in various parts of the electromagnetic spectrum. We consider conceptual approach to be a promising tool to efficiently deal with these data. It uses problem domain knowledge to formulate the tasks and develop problem-solving algorithms and data analysis methods in terms of domain concepts without reference to particular data sources, and thereby allows solving certain problems in general form. We demonstrate the benefits of conceptual approach by using it to solve problems related to search for secondary photometric standard candidates, determination of galaxy redshifts, creation of a binary and multiple star repository based on inhomogeneous databases, and classification of eclipsing binaries.We formulate and solve these problems over specifications of astronomical knowledge units such as photometric systems, astronomical objects, multiple stars, etc., and define them in terms of the corresponding problem domains independently of the existing data resources. © 2016, Pleiades Publishing, Ltd.
The strength and tensor structure of the Higgs boson's interactions are investigated using an effective Lagrangian, which introduces additional CP-even and CP-odd interactions that lead to changes in the kinematic properties of the Higgs boson and associated jet spectra with respect to the Standard Model. The parameters of the effective Lagrangian are probed using a fit to five differential cross sections previously measured by the ATLAS experiment in the H→γγ decay channel with an integrated luminosity of 20.3 fb-1 at √s=8 TeV. In order to perform a simultaneous fit to the five distributions, the statistical correlations between them are determined by re-analysing the H→γγ candidate events in the proton-proton collision data. No significant deviations from the Standard Model predictions are observed and limits on the effective Lagrangian parameters are derived. The statistical correlations are made publicly available to allow for future analysis of theories with non-Standard Model interactions. © 2015 CERN for the benefit of the ATLAS Collaboration.
The study considers the challenge of improving the efficiency of dry finishing and semifinishing turning of (P10-P20) steel with carbide tools with complex composition coatings by directed selection of the composition and properties of the coatings through the control of the parameters of the filtered cathodic vacuum-arc deposition (FCVAD). The conducted tests have confirmed the feasibility and effectiveness of the control of compositions, structures, and properties of complex composite coatings of Ti-TiN-TiAlN type by varying the parameters of the FCVAD process. In particular, it has been found out that the ratio of Ti/Al, which greatly affects the important properties of the coating (grain size, lattice parameter, microhardness, fracture toughness, etc.), can be changed at constant compositions of cathodes by varying such parameters of coating synthesis as titanium cathode arc current, nitrogen pressure, and substrate shear stress. It has been shown that Ti-TiN-TiAlN coating produced at different values of the parameters of synthesis significantly changes the cutting properties of carbide tool and thus allows optimizing the coating composition for a variety of machining conditions. The developed methods are also applicable for multi-component complex composite coatings. © (2016) Trans Tech Publications, Switzerland.
Features of the expansion of a pulsed laser-initiated plasma-vapor plume containing Se and Watoms in buffer gases of different chemical compositions (Ar and He) is investigated. It is found that gas pressure influences the structure and chemical state of the deposited WSex layers. The conditions for preparing coatings with low coefficients of sliding friction and high wear resistance are determined. © 2016, Allerton Press, Inc.
Abstract: The quark-gluon plasma is studied via medium-induced changes to correlations between jets and charged particles in PbPb collisions compared to pp reference data. This analysis uses data sets from PbPb and pp collisions with integrated luminosities of 166 μbsup−1/sup and 5.3 pbsup−1/sup, respectively, collected at (Formula presented.) TeV. The angular distributions of charged particles are studied as a function of relative pseudorapidity (Δη) and relative azimuthal angle (Δϕ) with respect to reconstructed jet directions. Charged particles are correlated with all jets with transverse momentum (pT) above 120 GeV, and with the leading and subleading jets (the highest and second-highest in pT, respectively) in a selection of back-to-back dijet events. Modifications in PbPb data relative to pp reference data are characterized as a function of PbPb collision centrality and charged particle pT. A centrality-dependent excess of low-pT particles is present for all jets studied, and is most pronounced in the most central events. This excess of low-pT particles follows a Gaussian-like distribution around the jet axis, and extends to large relative angles of Δη ≈ 1 and Δϕ ≈ 1.[Figure not available: see fulltext.] © 2016, The Author(s).
The paper explores quantum mechanics of half-spin particle motion in the field of Reissner-Nordstrom (RN) naked singularity. It is shown that for any quantum mechanical Dirac particle, irrespective of availability and sign of its electrical charge, the RN naked singularity is separated by an infinitely high positive potential barrier. With like charges of a particle and the source of the RN naked singularity, near the origin there exists the second completely impenetrable potential barrier. It has been proved that in the field of the RN naked singularity, bound states of half-spin particles can exist. The conditions for appearance of such states were revealed and computations were performed to find energy eigenvalues and eigenfunctions.
The paper explores quantum mechanics of half-spin particle motion in the field of Reissner-Nordstrom (RN) naked singularity. It is shown that for any quantum mechanical Dirac particle, irrespective of availability and sign of its electrical charge, the RN naked singularity is separated by an infinitely high positive potential barrier. With like charges of a particle and the source of the RN naked singularity, near the origin there exists the second completely impenetrable potential barrier. It has been proved that in the field of the RN naked singularity, bound states of half-spin particles can exist. The conditions for appearance of such states were revealed and computations were performed to find energy eigenvalues and eigenfunctions.
X-ray diffraction and X-ray absorption near edge structure (XANES) spectra have been measured at the DD3/4 K-edge and Gd L (3)-edge in GdCoO3 and Gd0.4Sr0.6CoO2.85 cobaltites. The effect of Sr substitution on the crystal structure and electronic and magnetic states of Co3+ ions in a Gd0.4Sr0.6CoO2.85 single crystal has been analyzed. The XANES measurements at the Co K-edge have not showed a noticeable shift of the absorption edge with an increase in the concentration of Sr. This indicates that the effective valence of cobalt does not change. An increase in the intensity of absorption at the Gd L (3)-edge is due to an increase in the degree of hybridization of the Gd(5d) and O(2p) states. The effect of hole doping on the magnetic properties results in the appearance of the ferromagnetic component and in a significant increase in the magnetic moment.
DarkSide-50 is a dark matter direct search experiment at LNGS, searching for rare nuclear recoils possibly induced by WIMPs. It has two nested vetoes and a dual phase liquid argon TPC as dark matter detector. Key features of this experiment are the use of underground argon as radio-pure target and of muon and neutron active vetoes to suppress the background. The first data-taking campaign was running from November 2013 to April 2015 with an atmospheric argon target and a reduced efficiency neutron veto due to internal contamination. However, an upper limit on the WIMP-nucleon cross section of 6.1×10sup-44/sup cmsup2/sup at 90% CL was obtained for a WIMP mass of 100 GeV/csup2/sup and an exposure of (1422 ± 67) kg·d. At present DarkSide-50 started a 3 years run, intended to be background-free because the neutron veto was successfully recovered and underground argon replaced the atmospheric one. Additionally calibration campaigns for both the TPC and the neutron veto were completed. Thanks to the good performance of the background rejection, the results obtained so far suggest the scalability of DarkSide-50 to a ton-scale detector, which will play a key role into the dark matter search scenario.
The deformation properties of a long lead isotopic chain up to the neutron drip line are analyzed on the basis of the energy density functional (EDF) in the FaNDFsup0/sup Fayans form. The question of whether the ground state of neutron-deficient lead isotopes can have a stable deformation is studied in detail. The prediction of this deformation is contained in the results obtained on the basis of the HFB-17 and HFB-27 Skyrme EDF versions and reported on Internet. The present analysis reveals that this is at odds with experimental data on charge radii and magnetic moments of odd lead isotopes. The Fayans EDF version predicts a spherical ground state for all light lead isotopes, but some of them (for example, sup180/supPb and sup184/supPb) prove to be very soft—that is, close to the point of a phase transition to a deformed state. Also, the results obtained in our present study are compared with the predictions of some other Skyrme EDF versions, including SKM*, SLy4, SLy6, and UNE1. By and large, their predictions are closer to the results arising upon the application of the Fayans functional. For example, the SLy4 functional predicts, in just the same way as the FaNDFsup0/sup functional, a spherical shape for all nuclei of this region. The remaining three Skyrme EDF versions lead to a deformation of some light lead isotopes, but their number is substantially smaller than that in the case of the HFB-17 and HFB-27 functionals. Moreover, the respective deformation energy is substantially lower, which gives grounds to hope for the restoration of a spherical shape upon going beyond the mean-field approximation, which we use here. Also, the deformation properties of neutron-rich lead isotopes are studied up to the neutron drip line. Here, the results obtained with the FaNDFsup0/sup functional are compared with the predictions of the HFB-17, HFB-27, SKM*, and SLy4 Skyrme EDF versions. All of the EDF versions considered here predict the existence of a region where neutron-rich lead isotopes undergo deformations, but the size of this region is substantially different for the different functionals being considered. Once again, it is maximal for the HFB-17 and HFB-27 functionals, is substantially narrower for the FaNDFsup0/sup functional, and is still narrower for the SKM* and SLy4 functionals. The two-neutron drip line proved to be Adrip sup2n/sup = 266 for all of the EDF versions considered here, with the exception of SKM*, for which it is shifted to Adrip sup2n/sup(SKM*) = 272. © 2016, Pleiades Publishing, Ltd.
High-frequency (HF) inductive magnetic sensors are the primary ITER diagnostic set for Toroidal Alfvén Eigenmodes (TAE) detection, while they also supplement low-frequency MHD and plasma equilibrium measurements. These sensors will be installed on the inner surface of ITER vacuum vessel, operated in a harsh environment with considerable neutron/nuclear radiation and high thermal load. Essential components of the HF sensor system, including inductive coil, electron cyclotron heating (ECH) shield, electrical cabling and termination load, have been designed to meet ITER measurement requirements. System performance (e.g. frequency response, thermal conduction) has been assessed. A prototyping campaign was initiated to demonstrate the manufacturability of the designed components. Prototypes have been produced according to the specifications. A series of lab tests have been performed to examine assembly issues and validate electrical and thermo-mechanical aspects of the design. In-situ microwave radiation test has been conducted in the MISTRAL test facility at IPP-Greifswald to experimentally examine the microwave shielding efficiency and structural integrity of the ECH shield. Low-power microwave attenuation measurement and scanning electron microscopic inspection were conducted to probe and examine the quality of the metal coating on the ECH shield. © 2016 ITER Organization.
Data on the thermal desorption of deuterium from beryllium irradiated with powerful pulsed plasma flows are presented. Two grades of beryllium, namely, TGP-56FW and S-65C, are investigated. Deuterium desorbs mainly in the temperature range 800–1400 K with a maximum at 1200 K. On average, the accumulation of deuterium in S-65C beryllium samples exceeds that in TGP-56FW beryllium samples by a factor of 3. © 2016, Pleiades Publishing, Ltd.
Lightweight megawatt-range power cables in electric aircraft propulsion systems will allow reducing fuel consumption by more than a half. Taking into account the low voltage limitations for onboard use, superconductivity providing high current-carrying capacity becomes an enabling technology for this application. In the frame of a preliminary study of an onboard superconducting power distribution grid, we fabricated and tested a high-temperature superconducting (HTS) Roebel cable. The work was done by a consortium of institutions and supported by Airbus Group Innovations. SuperOx provided a 400 A-class 12-mm-wide 2G HTS wire. The team at the Karlsruhe Institute of Technology prepared 5.5-mm-wide Roebel strands with a transposition length of 226 mm and assembled the strands into a 6-m-long Roebel cable. The team at the Russian Scientific Research and Development Cable Institute performed characterization of the cable. Short samples of the cable were tested to determine their critical currents, mechanical properties, and stability during thermal cycling. For a 4-m-long section of the cable, we measured the critical current, as well as the transport ac losses at frequencies in the range from 50 to 400 Hz. This paper presents the cable design and test results. The feasibility of using 2G HTS Roebel cables in electric aircraft systems is discussed. © 2002-2011 IEEE.
Application of a complex of powerful (up to 3 MW) ECR plasma heating in T-10 tokamak is pulled down with a problem of the strong plasma pollution at power input more than 2 MW. For the solution of these problems the new W and Li limiters is developed and prepared to implementation. As it is supposed, application of W as a plasma facing material will allow excluding carbon influx into vacuum chamber. An additional Li limiter arranged in a shadow of W one will be used as a Li source for plasma periphery cooling due to a reradiation on Li that will lead to decrease in power deposition on W limiters. Parameters and design of limiters are presented. Plasma facing surface of a limiter is made of capillary-porous system (CPS) with Li. Porous matrix of CPS (W felt) provides stability of liquid Li surface under MHD force effect and an opportunity of its constant renewal due to capillary forces. The necessary Li flux from a Li limiter surface is estimated for maintenance of normal operation mode of W limiters at ECRH power of 3 MW during 400 ms. It is shown, that upgrade of limiters in tokamak T-10 will allow providing of ECR plasma heating with power up to 3 MW at reasonable Li flux.
The innermost station of the ATLAS muon end-cap system will be replaced during the forthcoming Phase-I upgrade of the ATLAS detector. The small-strip Thin Gap Chambers (sTGC) are supposed to operate at harsh radiation conditions of super LHC. X-ray scanning technique for production quality control is proposed to ensure long-term reliability of these chambers. It allows to reveal different types of technological defects critical for sTGC chambers operation.
A device for gripping of microand nanoobjects (nanotweezers) with a working body made of bimetal composite (fast-quenched Ti2NiCu alloy with shape memory and platinum layer) is developed and studied. A method for manufacturing of the composite material using local ion etching and ion-stimulated deposition from gas phase is proposed. A structure of nanotweezers based on such a composite and experiments on gripping and displacement of submicron objects are presented. © 2016, Pleiades Publishing, Inc.
In this work we developed a combined approach based on the experimental investigation of corpuscular flow at the outlet of an ion source and the computer simulations of beam transport inside ion-optical system that enabled us to recover the parameters of neutron tube operation.
The production of J/psi and psi (2S) was studied with the ALICE detector in Pb-Pb collisions at the LHC. The measurement was performed at forward rapidity (2.5 y 4) down to zero transverse momentum (p(T)) in the dimuon decay channel. Inclusive J/psi yields were extracted in different centrality classes and the centrality dependence of the average p(T) is presented. The J/psi suppression, quantified with the nuclear modification factor (R-AA), was measured as a function of centrality, transverse momentum and rapidity. Comparisons with similar measurements at lower collision energy and theoretical models indicate that the J/psi production is the result of an interplay between color screening and recombination mechanisms in a deconfined partonic medium, or at its hadronization. Results on the psi(2S) suppression are provided via the ratio of psi(2S) over J/psi measured in pp and Pb-Pb collisions.
Using a micro-hole grating in a supported silver film as a laser-fabricated novel optical platform for surface-enhanced IR absoprtion/reflection spectroscopy, characteristic absorption bands of Staphylococcus aureus, in particular, its buried carotenoid fragments, were detected in FT-IR spectra with 10-fold analytical enhancement, paving the way for the spectral express-identification of pathogenic microorganisms.
A 6.8 nbsup-1/sup sample of pp collision data collected under low-luminosity conditions at s=7TeV by the ATLAS detector at the Large Hadron Collider is used to study diffractive dijet production. Events containing at least two jets with pT>20GeV are selected and analysed in terms of variables which discriminate between diffractive and non-diffractive processes. Cross sections are measured differentially in δηsupF/sup, the size of the observable forward region of pseudorapidity which is devoid of hadronic activity, and in an estimator, ξ~, of the fractional momentum loss of the proton assuming single diffractive dissociation (pp→pX). Model comparisons indicate a dominant non-diffractive contribution up to moderately large δηsupF/sup and small ξ~, with a diffractive contribution which is significant at the highest δηsupF/sup and the lowest ξ~. The rapidity-gap survival probability is estimated from comparisons of the data in this latter region with predictions based on diffractive parton distribution functions. © 2016 CERN for the benefit of the ATLAS Collaboration.
Direct photon production at mid-rapidity in Pb-Pb collisions at √sNN=2.76 TeV was studied in the transverse momentum range 0.9<pT<14 GeV/c. Photons were detected with the highly segmented electromagnetic calorimeter PHOS and via conversions in the ALICE detector material with the esup+/supesup-/sup pair reconstructed in the central tracking system. The results of the two methods were combined and direct photon spectra were measured for the 0-20%, 20-40%, and 40-80% centrality classes. For all three classes, agreement was found with perturbative QCD calculations for pT > 5 GeV/c. Direct photon spectra down to pT≈1 GeV/c could be extracted for the 20-40% and 0-20% centrality classes. The significance of the direct photon signal for 0.9<pT<2.1 GeV/c is 2.6σ for the 0-20% class. The spectrum in this pT range and centrality class can be described by an exponential with an inverse slope parameter of (297±12supstat/sup±41supsyst/sup) MeV. State-of-the-art models for photon production in heavy-ion collisions agree with the data within uncertainties. © 2016 CERN for the benefit of the ALICE Collaboration.
Article is concerned with electrode system geometry influence on high-current low-inductance vacuum spark discharge plasma development and its emissive characteristics.
Paper reports on a broadband spectrum analysis of density fluctuations in the edge plasma of the L-2M stellarator, measured using the Doppler reflectometry diagnostics. The evolution of the electron temperature-gradient (ETG) and ion temperature-gradient (ITG) instabilities in the edge plasma of the stellarator is analyzed. Two additional harmonics in the spectrum are found apart from those determined by the Doppler shift caused by poloidal rotation of plasma. The Doppler shifts of these harmonics are determined from the phase velocities of fluctuations generated by the ETG and ITG instabilities. Thus, local measurements of spectra using the Doppler reflectometry enabled us both to evaluate the poloidal rotational velocity of the plasma and describe the evolution of low-frequency plasma instabilities.
Recent experimental data on elastic scattering of high energy protons show that the critical regime has been reached at LHC energies. The approach to criticality is demonstrated by increase of the ratio of elastic to total cross sections from ISR to LHC energies. At LHC it reaches the value which can result in principal change of the character of proton interactions. The treatment of new physics of hollowed toroid-like hadrons requires usage of another branch of the unitarity condition. Its further fate is speculated and interpreted with the help of the unitarity condition in combination with present experimental data. The gedanken experiments to distinguish between different possibilities are proposed. © 2016 World Scientific Publishing Company
A kinetic treatment of geodesic acoustic modes (GAMs), taking into account ion parallel dynamics, drift and the second poloidal harmonic effects is presented. It is shown that first and second harmonics of the ion sound modes, which have respectively positive and negative radial dispersion, can be coupled due to the geodesic and drift effects. This coupling results in the drift geodesic ion sound eigenmode with a frequency below the standard GAM continuum frequency. Such eigenmode may be able to explain the split modes observed in some experiments.
Superconducting circuits provide a new platform for study of nonstationary cavity QED phenomena. An example of such a phenomenon is the dynamical Lamb effect, which is the parametric excitation of an atom due to nonadiabatic modulation of its Lamb shift. This effect was initially introduced for a natural atom in a varying cavity, while we suggest its realization in a superconducting qubit-cavity system with dynamically tunable coupling. In the present paper, we study the interplay between the dynamical Lamb effect and the energy dissipation, which is unavoidable in realistic systems. We find that despite naive expectations, this interplay can lead to unexpected dynamical regimes. One of the most striking results is that photon generation from vacuum can be strongly enhanced due to qubit relaxation, which opens another channel for such a process. We also show that dissipation in the cavity can increase the qubit excited-state population. Our results can be used for experimental observation and investigation of the dynamical Lamb effect and accompanying quantum effects. © 2016 American Physical Society..
We report a strong difference in the sliding properties of the bidirectional charge-density wave (CDW) in the two-dimensional rare-earth tritelluride ErTe3 which occurs below T-CDW1 = 265 K with a wave vector along the c axis and below T-CDW2 = 165 K with a wave vector along the a axis; the excess current carried by the motion of the CDW is 10 times less for the lower CDW compared with the value of the upper one. We tentatively explain this result by a stronger pinning of the lower temperature CDW intricated with the upper one, which inhibits its motion and may generate a phase slippage lattice.
We study the topological structure of QCD by cluster analysis. The fermionic topological charge density is constructed from low-lying modes of the overlap Dirac operator for three types of temporal boundary conditions for the fermion field. This provides the possibility of marking all three dyon constituents of Kraan-van Baal-Lee-Lu (KvBLL) calorons in the gluonic fields. The gluonic topological charge density appears in the overimproved gradient flow process stopped at the moment when it maximally matches the fermionic topological charge density. This corresponds to the smearing of gluonic fields up to the scale set by dyon size. The timelike Abelian monopoles and specific KvBLL pattern of the Polyakov line are correlated with topological clusters. © 2016 American Physical Society.
The study considers the possibility to increase the efficiency of cutting of hard-to-cut materials through the use of innovative tool materials of layer composite type with nano-scale multi-layer composite coatings and carbides with cobalt-rhenium refractory binder. The effect of the increase in the tool life was achieved through higher wear resistance of cobalt-rhenium solid carbide to thermoplastic fracture and wear at elevated temperatures. For synthesis of coatings, the process of filtered cathodic vacuum-arc deposition (FCVAD) and the control technology on its basis were used for high-performance surface preparation and application of nano-structured coatings of multi-layer complex composite architecture on WC-Co, WC-(Co/Re) carbides. During the study, the mathematical models of the FCVAD processes are developed to optimize the numerical values of the basic parameters of the deposition technology, including operating gas pressure, value of cathode current, and voltage on substrate. © 2016 Trans Tech Publications, Switzerland.
Cerium monoaluminate Ce1-x sup3+/sup Cex sup4+/sup AlO3+x/2 powders with low contents of Cesup4+/sup cations (x ∼ 0.052) were synthesized. A set of modern local structure sensitive methods of analysis, including X-ray absorption spectroscopy and Raman spectroscopy, were used to study the crystal, local, and electronic structures of the synthesized compounds. The degree of reduction and the thermal stability to oxidation of reduced powders depend not only on the reduction conditions but also on the conditions of heat pretreatment of the initial samples. It was concluded that the reaction 4CeAlO3 + O2 ↔ 4CeO2 + 2Al2O3 is reversible. © Pleiades Publishing, Ltd., 2016.
The effects of addition of ∼3% Hesup+/sup in simultaneous D-He irradiation at various D and He ion energies were studied for polycrystalline W at 300 and 500 K. Combinations of 250-750 eV/Dsup+/sup and 500-1000 eV/Hesup+/sup were used to vary the D and He ion range relative to each other. Total D and He retention were measured by thermal desorption spectroscopy up to 1473 K, and select specimens implanted at 500 K were analyzed by nuclear reaction analysis and electron recoil detection analysis. At both 300 and 500 K, D retention was reduced and trapping changed due to the addition of Hesup+/sup; however, consistent with the literature, D and He diffused well beyond the ion ranges. Furthermore, varying the ion ranges had little effect on D retention, depth profile, and trapping. D diffusion into the bulk was reduced from far beyond 7 μm to less than 2 μm with the addition of Hesup+/sup. © 2016 The Royal Swedish Academy of Sciences.
The dynamics of an electron bunch irradiated by two focused colliding super-intense laser pulses and the resulting gamma and e(-)e(+) production are studied. Due to attractors of electron dynamics in a standing wave created by colliding pulses the photon emission and pair production, in general, are more efficient with linearly polarized pulses than with circularly polarized ones. The dependence of the key parameters on the laser intensity and wavelength allows us to identify the conditions for the cascade development and gamma e(-)e(+) plasma creation.
The works dealing with the theory of e (+) e (-) pair production from vacuum under the action of highintensity laser radiation are reviewed. The following problems are discussed: pair production in a constant electric field E and time-variable homogeneous field E(t); the dependence of the number of produced pairs on the shape of a laser pulse (dynamic Schwinger effect); and a realistic three-dimensional model of a focused laser pulse, which is based on exact solution of Maxwell's equations and contains parameters such as focal spot radius R, diffraction length L, focusing parameter Delta, pulse duration tau, and pulse shape. This model is used to calculate for both a single laser pulse (n = 1) and several (n a parts per thousand yen 2) coherent pulses with a fixed total energy that simultaneously "collide" in a laser focus. It is shown that, at n a parts per thousand 1, the number of pairs increases by several orders of magnitude as compared to the case of a single pulse. The screening of a laser field by the vapors that are generated in vacuum, its "depletion," and the limiting fields to be achieved in laser experiments are considered. The relation between pair production, the problem of a quantum frequency-variable oscillator, and the theory of groups SU(1, 1) and SU(2) is discussed. The relativistic version of the imaginary time method is used in calculations. In terms of this version, a relativistic theory of tunneling is developed and the Keldysh theory is generalized to the case of ionization of relativistic bound systems, namely, atoms and ions. The ionization rate of a hydrogen-like ion with a charge 1 a parts per thousand currency sign Z a parts per thousand currency sign 92 is calculated as a function of laser radiation intensity (F and ellipticity rho.
The elliptic flow, v2, of muons from heavy-flavour hadron decays at forward rapidity (2.5<y<4) is measured in Pb-Pb collisions at sNN=2.76 TeV with the ALICE detector at the LHC. The scalar product, two- and four-particle Q cumulants and Lee-Yang zeros methods are used. The dependence of the v2 of muons from heavy-flavour hadron decays on the collision centrality, in the range 0-40%, and on transverse momentum, pT, is studied in the interval 3<pT<10 GeV/c. A positive v2 is observed with the scalar product and two-particle Q cumulants in semi-central collisions (10-20% and 20-40% centrality classes) for the pT interval from 3 to about 5 GeV/c with a significance larger than 3σ, based on the combination of statistical and systematic uncertainties. The v2 magnitude tends to decrease towards more central collisions and with increasing pT. It becomes compatible with zero in the interval 6<pT<10 GeV/c. The results are compared to models describing the interaction of heavy quarks and open heavy-flavour hadrons with the high-density medium formed in high-energy heavy-ion collisions. © 2015 CERN for the benefit of the ALICE Collaboration.
We describe a promising method for measuring the total dark matter mass near a supermassive black hole at the Galactic center based on observations of nonrelativistic precession of the orbits of fast SO stars. An analytical expression for the precession angle has been obtained under the assumption of a power-law profile of the dark matter density. The awaited weighing of the dark matter at the Galactic center provides the strong constraints on the annihilation signal from the neuralino dark matter particle candidate. The mass of the dark matter necessary for the explanation of the observed excess of gamma-radiation owing to the annihilation of the dark matter particles has been calculated with allowance for the Sommerfeld effect.
Erosion and deposition were studied in the JET divertor during the first JET ITER-like wall campaign 2011 to 2012 using marker tiles. An almost complete poloidal section consisting of tiles 0, 1, 3, 4, 6, 7, 8 was studied. The data from divertor tile surfaces were completed by the analysis of samples from remote divertor areas and from the inner wall cladding. The total mass of material deposited in the divertor decreased by a factor of 4-9 compared to the deposition of carbon during all-carbon JET operation before 2010. Deposits in 2011 to 2012 consist mainly of beryllium with 5-20 at.% of carbon and oxygen, respectively, and small amounts of Ni, Cr, Fe and W. This decrease of material deposition in the divertor is accompanied by a decrease of total deuterium retention inside the JET vessel by a factor of 10 to 20. The detailed erosion/deposition pattern in the divertor with the ITER-like wall configuration shows rigorous changes compared to the pattern with the all-carbon JET configuration. © 2016 EuroFusion.
Recent experiments in high enegry cosmic ray physics, PAMELA and AMS-02, excite a new interest to the mechanisms of generation of galactic antiparticles. In spite of the fact that global picture coincides with the predictions of the standard model, there are some black spots stimulating scientists to involve into research a particularly new physics like dark matter. In the present work, we make an attempt to estimate the impact of standard neutrino processes into the total flux of secondary antiprotons detected by contemporary experiments.
New sets of parameters (“tunes”) for the underlying-event (UE) modelling of the pythia8, pythia6 and herwig++ Monte Carlo event generators are constructed using different parton distribution functions. Combined fits to CMS UE proton–proton ( (Formula presented.) ) data at (Formula presented.) and to UE proton–antiproton ( (Formula presented.) ) data from the CDF experiment at lower (Formula presented.) , are used to study the UE models and constrain their parameters, providing thereby improved predictions for proton–proton collisions at 13 (Formula presented.). In addition, it is investigated whether the values of the parameters obtained from fits to UE observables are consistent with the values determined from fitting observables sensitive to double-parton scattering processes. Finally, comparisons are presented of the UE tunes to “minimum bias” (MB) events, multijet, and Drell–Yan ( (Formula presented.) lepton-antilepton+jets) observables at 7 and 8 (Formula presented.) , as well as predictions for MB and UE observables at 13 (Formula presented.). © 2016, CERN for the benefit of the CMS collaboration.
We report on results obtained with the event-shape engineering technique applied to Pb-Pb collisions at root s(NN) = 2.76 TeV. By selecting events in the same centrality interval, but with very different average flow, different initial-state conditions can be studied. We find the effect of the event-shape selection on the elliptic flow coefficient v(2) to be almost independent of transverse momentum p(T), which is as expected if this effect is attributable to fluctuations in the initial geometry of the system. Charged-hadron, -pion, -kaon, and -proton transverse momentum distributions are found to be harder in events with higher-than-average elliptic flow, indicating an interplay between radial and elliptic flow.
This Letter presents evidence for single top-quark production in the s-channel using proton-proton collisions at a centre-of-mass energy of 8 TeV with the ATLAS detector at the CERN Large Hadron Collider. The analysis is performed on events containing one isolated electron or muon, large missing transverse momentum and exactly two b-tagged jets in the final state. The analysed data set corresponds to an integrated luminosity of 20.3 fbsup-1/sup. The signal is extracted using a maximum-likelihood fit of a discriminant which is based on the matrix element method and optimized in order to separate single-top-quark s-channel events from the main background contributions, which are top-quark pair production and W boson production in association with heavy-flavour jets. The measurement leads to an observed signal significance of 3.2 standard deviations and a measured cross-section of σs=4.8±0.8(stat.)-1.3+1.6(syst.) pb, which is consistent with the Standard Model expectation. The expected significance for the analysis is 3.9 standard deviations. © 2016 CERN for the benefit of the ATLAS Collaboration.
We report on the first observation of high-n hollow ions (ions having no electrons in the K or L shells) produced in Si targets via pumping by ultra-intense x-ray radiation produced in intense laser-plasma interactions reaching the radiation dominant kinetics regime (RDKR). The existence of these new types of hollow ions in high-energy density plasma has been found via observation of highly resolved x-ray emission spectra of silicon plasma. This has been confirmed by plasma kinetics calculations, underscoring the ability of powerful radiation sources to fully strip electrons from the innermost shells of light atoms. Hollow-ions spectral diagnostics provide a unique opportunity to characterize powerful x-ray radiation of laboratory and astrophysical plasmas. With the use of this technique we provide evidence for the existence of the RDKR via observation of asymmetry in the observed radiation of hollow ions from the front and rear sides of the target. © EPLA, 2016.
Uranium dioxide pellets were sintered at various temperature routes and atmospheres with different oxygen content. Statistically calculated pore size distribution of the sintered pellets and distribution function was obtained. It is shown that the average pore size is almost unchanged at intermediate stage of sintering while the total number of pores reduced.
Transport of hydrogen isotopes during the various regimes of deposition of yttrium coating on zirconium in argon plasma with addition of deuterium is studied. The influence of oxygen contamination in plasma-generating gas on the processes of trapping and desorption of hydrogen isotopes is also investigated. It is shown that deposition of yttrium coating on zirconium in Ar+5%D-2 plasma enhances both hydrogen desorption from zirconium and deuterium trapping into zirconium in comparison to those under plasma exposure without deposition. Yttrium deposition in Ar+25%O-2+5%D-2 plasma, conversely, mitigates both hydrogen desorption and deuterium trapping. Hydrogen desorption from zirconium increases with the increase of energy of ions, bombarding the sample during deposition of the coating in oxygen-free plasma, but it, on the contrary, decreases in oxygen-containing plasma.
We study excitations of solitary waves the kinks in scalar models with degree eight polynomial self-interaction in (1 + 1) dimensions. We perform numerical studies of scattering of two kinks with an exponential asymptotic off each other and analyse the occurring resonance phenomena. We connect these phenomena to the energy exchange between the translational and the vibrational modes of the colliding kinks. We also point out that the interaction of two kinks with power-law asymptotic can lead to a long-range interaction between the two kinks.
Deuterium (D) interaction with vacancies in tungsten (W) was studied using thermal desorption spectroscopy (TDS). In order to obtain a TDS spectrum with a prominent peak corresponding to D release from vacancies, a special procedure comprising damaging of a recrystallized W sample by low fluences of 10 keV/D ions, its annealing, and subsequent low-energy ion implantation, was utilized. This experimental sequence was performed several times in series; the only difference was the TDS heating rate that varied in the range of 0.15-4 K/s. The sum of the D binding energy (Eb) with vacancies and the activation energy for D diffusion (ED) in W was then directly determined from the slope of the Arrhenius-like plot ln(β/Tm2) versus 1/Tm, where β - heating rate and Tm - position of the respective peak in the TDS spectrum. The determined value of Eb + ED was 1.56 ± 0.06 eV. © 2016 Elsevier B.V. All rights reserved.
The ITER baseline scenario, with 500 MW of DT fusion power and Q = 10, will rely on a Type I ELMy H-mode and will be achieved with a tungsten (W) divertor. W atoms sputtered from divertor targets during mitigated ELMs are expected to be the dominant source in ITER. W impurity concentration in the plasma core can dramatically degrade its performance and lead to potentially damaging disruptions. Understanding the physics of the target W source due to sputtering during ELMs and inter-ELMs is important and can be helped by experimental measurements with improved precision. It has been established that the ELMy target ion impact energy has a simple linear dependence with the pedestal electron temperature measured by Electron Cyclotron Emission (ECE). It has also been shown that Langmuir Probes (LP) ion flux measurements are reliable during ELMs due to the surprisingly low electron temperature. Therefore, in this paper, LP and ECE measurements in JET-ITER-Like-Wall (ILW) unseeded Type I ELMy H-mode experiments have been used to estimate the W sputtering flux from divertor targets in ELM and inter-ELM conditions. Comparison with similar estimates using W I spectroscopy measurements shows a reasonable agreement for the ELM and inter-ELM W source. The main advantage of the method involving LP measurements is the very high time resolution of the diagnostic (∼10 μs) allowing very precise description of the W sputtering source during ELMs. © 2016 EURO fusion.
The evolution of a phonon spectrum in a narrow-gap semiconductor FeSi was investigated in a wide range of temperatures (46 K
The results of T-10 experiments on the 'density pump-out' effect research, i.e. the escape of particles from the zone of on-axis electron cyclotron resonance heating (ECRH) to the plasma periphery are presented. The dependences of the pump-out on the central chord line-averaged plasma density n, total plasma current and the ECRH power were found. The influence of the gas influx intensity and the conditions of the chamber wall and limiter on the above-mentioned effect is also investigated. It is shown that this effect increases with the growth of the n up to a certain critical value nsupcr/sup, after which the escape of particles from the zone of on-axis ECRH decreases. This critical density nsupcr/sup increases with the increase of the total plasma current and the ECRH power. © 2016 IOP Publishing Ltd.
To determine the depth of the area of radiopharmaceutical accumulation a method of simultaneous recording of two lines of gamma rays of different energies and quantitative comparison of the intensity of these lines on the surface of the patient's body is provided. Since the coefficient of linear absorption of gamma radiation in the medium depends not only on the characteristics of the medium, but also on the gamma radiation energy, the intensity of gammas of different energies is attenuated differently after passing through the same absorber layer (soft tissues). Thus, the quantitative comparison of the relative intensities of gamma lines on the surface of the patient's body allows to determine the depth of area of the accumulation of the radiopharmaceutical. The result is achieved by analyzing the energy spectrum of the source, obtained with a semiconductor spectrometer, by measuring the ratio of areas of the absorption peaks of the radioisotope and defining the depth of gamma source using the calibration dependence between the areas ratio and the medium layer thickness. The most widely used medical radioisotope technetium-99m has two gamma-lines - 140 keV and 18.5keV, which allows one to apply the proposed method to search for the sentinel lymph nodes and non-palpable malignant tumors in the soft tissues.
Fayans energy density functional (EDF) FaNDF(0) has been applied to the nuclei around uranium region. Ground state characteristics of the Th, U and Pu isotopic chains, up to the two-neutron drip line, are found and compared with predictions from several Skyrme EDFs. The two-neutron drip line is found for FaNDF(0), SLy4 and SkM* EDFs for a set of elements with even proton number, from Pb up to Fm.
The electron density in the plasma channel of a femtosecond filament in air at pressures from 1 to 7 atm is measured at different instants, starting from the ionisation onset and up to several hundreds of picoseconds after it. The initial electron density is found to increase sharply in the pressure range of 3-4 atm. The plasma channel diameter is found to decrease with an increase in pressure from 3 to 7 atm. © 2016 Kvantovaya Elektronika and Turpion Ltd.
Purely azimuthal entanglement is analyzed for noncollinear frequency-degenerate biphoton states. The degree of azimuthal entanglement is found to be very high, with the Schmidt parameter K on the order of the ratio of the pump waist to its wavelength. A scheme is suggested for partial realization of this high entanglement resource in the form of a multichannel Schmidt-type decomposition. © 2016 American Physical Society.
Hydrogen recombination in the earlyUniverse in the presence of amagnetic field is studied. An equation for the recombination temperature in the presence of a magnetic field is obtained. The limiting cases of weak and strong magnetic fields are examined. A critical field above which the system being considered is in the atomic-hydrogen phase at any temperature is shown to exist. The relative shift of the recombination temperature in a magnetic field is estimated, and it is shown that this shift is small.
Boost modes (Formula presented.) are eigenfunctions of the Lorentz transformations generator in two-dimensional (2D) Minkowski space (MS). We demonstrate and discuss deep interrelation between the boost modes and the field correlators, also known as Wightman functions. In the case of a massive scalar field, the boost modes, as functions of the spectral parameter (Formula presented.), contain the Dirac delta-function singularity (Formula presented.) at the light cone. The zero boost mode coincides up to a constant factor with the Wightman function. The light cone singularity of boost modes for a fermion field is stronger. For this case, they contain the Gelfand (Formula presented.)-function of complex argument (Formula presented.), while the Wightman function components coincide with analytical continuation of the boost modes set towards the spectral values (Formula presented.). We argue that due to the discovered properties of the boost modes the so-called Unruh modes, which are at the core of the Unruh effect derivation, do not constitute a complete set in MS and thus cannot be used for quantization of neither scalar, nor fermion field. Finally, we discuss boost modes for the case of the constant electric background and rederive the well-known result for spontaneous pair creation rate. Solution of this problem in the boost modes representation reveals distinctions between the Unruh problem and the effect of pair creation by an electric field in vacuum. © 2016 World Scientific Publishing Company
Previously we have proposed simple qualitative estimates for threshold laser intensity required to observe the laser-induced self-sustained QED (or A-type) cascades. They were later brilliantly confirmed by simulation of cascades arising in a rotating purely electric field. However, in view of numerous simulations performed since then for a more realistic setup our previous criterium of arising of self-sustained cascades may now seem to be too conservative thus essentially overestimating the intensity actually required. After refining our estimates and explaining the origin of assumptions and discrepancies with some new simulation results, we present and discuss in details two particular experimental schemes for their observation. These schemes in different ways overcome a non-trivial problem of injection of seed particles into the focal region and are optimized to lower the threshold intensity value as much as possible. © Published under licence by IOP Publishing Ltd.
We have demonstrated a new description of local electronic structure in the perovskite-like bismuthates Ba1−xKxBiO3 (BKBO) based on existence of the spatially separated Fermi-Bose mixture. We have shown that two types of charge carriers: the local electron pairs (real-space bosons) and the itinerant electrons exist in metallic compound Ba1−xKxBiO3 (x ≥ 0.37). The real-space bosons are responsible for both charge transport in semiconducting BaBiO3 and superconductivity in metallic BKBO, while the fermionic subsystem is responsible for the observed metal-insulator phase transition and appearance of the Fermi-liquid state when the percolation threshold is overcome (x ≥ 0.37). Bosons and fermions occupy different types of the octahedral BiO6 complexes, so they are separated in real space. This scenario fits well into a new quantum state of pair-density wave (PDW), actively discussed for copper-based HTSC. © 2015 Springer Science+Business Media New York
The results of a comprehensive study of magnetic, magneto-transport and structural properties of nonstoichiometric MnxSi1-x (x 0.51-0.52) films grown by the Pulsed Laser Deposition (PLD) technique onto Al2O3(0001) single crystal substrates at T = 340°C are present. A highlight of used PLD method is the non-conventional ("shadow") geometry with Kr as a scattering gas during the sample growth. It is found that the films exhibit high-temperature (HT) ferromagnetism (FM) with the Curie temperature TC ∼ 370 K accompanied by positive sign anomalous Hall effect (AHE); they also reveal the polycrystalline structure with unusual distribution of grains in size and shape. It is established that HT FM order is originated from the bottom interfacial self-organizing nanocrystalline layer. The upper layer adopted columnar structure with the lateral grain size ≥50 nm, possesses low temperature (LT) type of FM order with Tc 46 K and contributes essentially to the magnetization at T ≤ 50 K. Under these conditions, AHE changes its sign from positive to negative at T ≤ 30K. We attribute observed properties to the synergy of distribution of MnxSi1-x crystallites in size and shape as well as peculiarities of defect-induced FM order in shadow geometry grown polycrystalline MnxSi1-x (x ∼ 0.5) films. © 2016 Author(s).
The dependence of magnetic moment relaxation of YBa2Cu3O7-delta films on magnetic field was studied in both partly and fully penetrated critical states. A simple approach was used to account for the influence of the demagnetizing effect on the measured moment. Field and current dependence of the activation energy for flux motion U was calculated from macroscopic electrodynamics. Field dependence of the critical current density J(c) was obtained from the analysis of U. It was shown that the critical current is suppressed by field and that the suppression takes place even in partly penetrated critical state. The observed behavior contradicts the field independence of J(c) expected in low fields for single vortex pinning in the collective pinning model.
Solar neutrinos have been pivotal to the discovery of neutrino flavour oscillations and are a unique tool to probe the reactions that keep the Sun shine. Although most of solar neutrino components have been directly measured, the neutrinos emitted by the keystone pp reaction, in which two protons fuse to make a deuteron, have so far eluded direct detection. The Borexino experiment, an ultra-pure liquid scintillator detector running at the Laboratori Nazionali del Gran Sasso in Italy, has now filled the gap, providing the first direct real time measurement of pp neutrinos and of the solar neutrino luminosity. © The Authors, published by EDP Sciences.
Infrared (IR) images of the ITER wide angle viewing system are modeled for the baseline plasma equilibrium and partially detached tungsten divertor, taking into account the three-dimensional structure of the first wall and the divertor. The modeling includes a comprehensive chain of calculations from the heat load specifications up to the synthetic, reflection-free IR images of the surface temperature, T surf. The effect of the optical blur due to finite IR detector size and diffraction/aberrations - approximated by a Gaussian filter - on the measured T surf is investigated. The optical blur characterized by σ = 0.7 pixel (approximately twice the diffraction limit) leads to underestimation of T surf,max on the inner vertical divertor target and near the upper X-point by <6% and <4%, respectively. This is within the required measurement accuracy of 10%. Larger underestimation of T surf,max (<12%) is observed on the outer vertical divertor target. The study demonstrates the importance of keeping the performance of the optical system as close as possible to the diffraction limit. © 2016 The Royal Swedish Academy of Sciences.
Complex oxides of the Ln2Hf2O7 (Ln = lanthanide) series undergo a fluorite to pyrochlore phase transformation. We have studied the whole process of the crystal and local atomic structure realignment during the crystallization and the phase transition in the series of Ln2Hf2O7 (Ln = La-Lu) samples synthesized by the coprecipitation method with the subsequent annealing of mixed hydroxides (precursors). The study employed a combination of x-ray diffraction (normal and anomalous), x-ray absorption spectroscopy, analysis of atomic pair distribution function and Raman spectroscopy. The starting and ending temperatures of the fluorite-pyrochlore phase transition for Ln2Hf2O7 compounds have been determined along the lanthanide series La-Dy. The scheme summarizing structure types (amorphous, fluorite and pyrochlore) for the whole Ln2Hf2O7 (Ln = La-Lu) series as a function of the Ln cation radius (or the rLn3+/rHf4+ ratio) and the annealing temperature has been refined. © 2016 Elsevier B.V.
The results from analyzing the yields of protons (p), deuterons (d), and tritons (t) formed in the absorption of stopped π– mesons by intranuclear clusters are presented. The contributions from cluster absorption to the production of hydrogen isotopes in stopped pion absorption reactions are determined. Phenomenological formulas are proposed for describing the mass number (A) dependences of the yields of the primary protons with ∼15% precision in the mass number range of 6 < A < 209 (and of the primary deuterons and tritons in the mass number range of 59 < A < 209). Evidence is observed of the constancy of the ratio between the elemental absorption widths for the absorption of pions by pp and pn pairs over the investigated range of mass numbers. © 2016, Allerton Press, Inc.
The possibility of obtaining new relatively inexpensive electrode materials to provide enhanced efficiency of hydrogen evolution reaction (HER) in an aqueous acid solution was investigated. For this purpose, the surface properties of cathodes made of microcrystalline graphite were modified by pulsed laser deposition of thin films of WSex. The structure, morphology, and chemical composition of the thin film coatings were varied by changing the deposition conditions and subsequent heat treatment. The compact and dense structure of the film in an amorphous and crystalline state did not result in a marked positive impact on the character of the HER process, which was investigated in 0.5 M H2SO4 solution at room temperature. Formation of thin layers consisting of nanocrystalline “petals” WSe2 caused an increase in cathodic current by more than 6 times (at a voltage of–150 mV), and the Tafel slope of the voltage vs. current curve was reduced by about 80 mV/dec. The conditions were determined to produce on the surface of the graphite cathode a high density of new catalytically active sites that formed on edges of molecular planes forming a layered structure characteristic of WSe2 nanocrystals. © 2016, Pleiades Publishing, Ltd.
Two-particle angular correlations between trigger particles in the forward pseudorapidity range (2.5 |η| 4.0) and associated particles in the central range (|η| 1.0) are measured with the ALICE detector in p-Pb collisions at a nucleon-nucleon centre-of-mass energy of 5.02 TeV. The trigger particles are reconstructed using the muon spectrometer, and the associated particles by the central barrel tracking detectors. In high-multiplicity events, the double-ridge structure, previously discovered in two-particle angular correlations at midrapidity, is found to persist to the pseudorapidity ranges studied in this Letter. The second-order Fourier coefficients for muons in high-multiplicity events are extracted after jet-like correlations from low-multiplicity events have been subtracted. The coefficients are found to have a similar transverse momentum (pT) dependence in p-going (p-Pb) and Pb-going (Pb-p) configurations, with the Pb-going coefficients larger by about 16 ± 6%, rather independent of pT within the uncertainties of the measurement. The data are compared with calculations using the AMPT model, which predicts a different pT and η dependence than observed in the data. The results are sensitive to the parent particle v2 and composition of reconstructed muon tracks, where the contribution from heavy flavour decays is expected to dominate at pT2 GeV/c. © 2015 CERN for the benefit of the ALICE Collaboration.
A measurement of the forward–backward asymmetry AFB of oppositely charged lepton pairs (μμ and ee) produced via Z / γ∗ boson exchange in pp collisions at √s = 8 TeV is presented. The data sample corresponds to an integrated luminosity of 19.7 fb-1 collected with the CMS detector at the LHC. The measurement of AFB is performed for dilepton masses between 40 GeV and 2TeV and for dilepton rapidity up to 5. The AFB measurements as a function of dilepton mass and rapidity are compared with the standard model predictions. © 2016, CERN for the benefit of the CMS collaboration.
A new nonlinear optical phenomenon-generation of surface waves by a drag current appearing at an inclined incidence of a focused femtosecond laser pulse-has been theoretically described. The generated waves have terahertz frequencies and their total energy increases with an increase in the effective frequency of electron-electron collisions and with a decrease in their density.
A new class is introduced of M2-branes solutions of d=11 supergravity that include internal fluxes obeying Englert equation in 7-dimensions. A simple criterion for the existence of Killing spinors in such backgrounds is established. Englert equation is viewed as the generalization to d=7 of Beltrami equation defined in d=3 and it is treated accordingly. All 2-brane solutions of minimal d=7 supergracity can be uplifted to d=11 and have N≥4 supersymmetry. It is shown that the simple group PSL(2, 7) is crystallographic in d=7 having an integral action on the A7 root lattice. By means of this point-group and of the T7 torus obtained quotiening R7 with the A7 root lattice we were able to construct new M2 branes with Englert fluxes and N≤4. In particular we exhibit here an N=1 solution depending on 4-parameters and admitting a large non abelian discrete symmetry, namely G21≡Z3⋉Z7⊂ PSL (2,7). The dual d=3 field theories have the same symmetries and have complicated non linear interactions. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Abstract: We study a model with a real scalar Higgs field and a scalar triplet field that allows existence of a topological defect — a domain wall. The wall breaks the global O(3) symmetry of the model, which gives rise to non-Abelian orientational degrees of freedom. We found an exact analytic solution that describes a domain wall with a localized configuration of the triplet field on it. This solution enables one to calculate contributions to the action from the orientational and translational degrees of freedom of the triplet field. We also study the linear stability of the domain wall with the triplet field switched off. We obtain that degrees of freedom localized on the wall can appear or do not appear depending on the parameters of the model. © 2016, The Author(s).
We consider a model with a real scalar field with polynomial self-interaction of the fourth degree and a coupled scalar triplet. We demonstrate that there is an exact analytic solution in the form of a domain wall with a localised configuration of the scalar triplet coupled to the wall. We study some properties of this solution.
The ATLAS (one of two general purpose detectors at the LHC) Transition Radiation Tracker (TRT) is the outermost of the three tracking subsystems of the ATLAS Inner Detector. It is a large straw-based detector and contains about 350,000 electronics channels. The performance of the TRT as tracking and particularly particle identification detector strongly depends on stability of the operation parameters with most important parameter being the gas gain which must be kept constant across the detector volume. The gas gain in the straws can vary significantly with atmospheric pressure, temperature, and gas mixture composition changes. This paper presents a concept of the gas gain stabilisation in the TRT and describes in detail the Gas Gain Stabilisation System (GGSS) integrated into the Detector Control System (DCS). Operation stability of the GGSS during Run-1 is demonstrated.
sTGC chambers are designed to operate at super-LHC conditions and will be installed in place during Phase-I upgrade of the ATLAS muon spectrometer. These chambers will provide precise coordinate measurements of the charged particle tracks and level 1 trigger for high pT muons. It is critical for the ATLAS detector to ensure a robust operation of these chambers during entire sLHC period. A quality control procedure based on X-ray scanner is being developed. Choice of the active gas for these tests is a very important issue. On one hand it should allow to find different types of chamber production defects, on the other hand one has to be sure that found problems are essential for the detector operation in future. Studies of the operation of the sTGC chamber prototype under X-ray irradiation with two gas mixtures (n-pentane/CO2 and CO2) were performed. The prototype was irradiated by X-rays with energy up to 50 keV. Particular attention was paid to the study of the "hot" chamber regions.
Quantum electrodynamic cascades in intense electromagnetic fields arise when the proper electron acceleration χ, expressed in compton units, can attain values greater than or on the order of unity. For times t < 1/ω, where ω is the carrier frequency of the field, we have derived a general formula for χ of an initially resting electron in an arbitrary electromagnetic field. Using this formula, we have found an optimal configuration of colliding laser pulses, which provides a significant reduction in the threshold intensity of occurrence of cascades up to a level of ∼10sup23/sup W cmsup-2/sup. © 2016 Kvantovaya Elektronika and Turpion Ltd.
We studied the interaction of a high-intensity laser with mass-limited Ti-wires. The laser was focused up to , with contrast of to produce relativistic electrons. High-spatial-resolution X-ray spectroscopy was used to measure isochoric heating induced by hot electrons propagating along the wire up to 1 mm depth. For the first time it was possible to distinguish surface target regions heated by mixed plasma mechanisms from those heated only by the hot electrons that generate warm dense matter with temperatures up to 50 eV. Our results are compared to simulations that highlight both the role of electron confinement inside the wire and the importance of resistive stopping powers in warm dense matter. © CopyrightEPLA, 2016.
Borexino is a liquid scintillator detector primary designed to observe solar neutrinos. Due to its low background level as well as its position in a nuclear free country, Italy, Borexino is also sensitive to geo-neutrinos. Borexino is leading this interdisciplinary field of neutrino geoscience by studying electron antineutrinos which are emitted from the decay of radioactive isotopes present in the crust and the mantle of the Earth. With 2056 days of data taken between December 2007 and March 2015, Borexino observed 77 antineutrino candidates. If we assume a chondritic Th/U mass ratio of 3.9, the number of geo-neutrino events is found to be 23.7(-5.7)(+6.5) (stat)(-0.6)(+0.9) (syst). With this measurement, Borexino alone is able to reject the null geo-neutrino signal at 5.9 a, to claim a geo-neutrino signal from the mantle at 98 % C.L. and to restrict the radiogenic heat production for U and Th between 23 and 36 TW.
The paper presents the analysis of effective potentials of Dirac equations in static Schwarzschild and Reissner-Nordstrom (RN) fields. It is shown that in all the explored cases the condition of a particle "fall" to appropriate event horizons is fulfilled. The exception is one of the solutions for the Reissner-Nordstrom extremal field, for which the existence of the stationary bound state of half-spin particles is possible inside the event horizon.
Variation of the phase of the beam transmitted through a crystalline material as a function of the rocking angle is a well-known dynamical effect in x-ray scattering. Unfortunately, it is not so easy to directly measure these phase variations in a conventional scattering experiment. It was recently suggested that the transmitted phase can be directly measured in ptychography experiments performed on nanocrystal samples. Results of such experiment for different crystal thickness, reflections, and incoming photon energies, in principle, can be fully described in the frame of dynamical theory. However, dynamical theory does not provide a simple analytical expression for the further analysis. Here we develop a quasi-kinematical theory approach that allows one to correctly describe the phase of the transmitted beam for the crystal thickness less than extinction length that is beyond applicability of the conventional kinematical theory. © 2016 American Physical Society.
We present a theory of long-range intensity correlations in phase-coherent transport of polarized light through a disordered medium. Diagrammatic calculations of the intensity correlation function are performed beyond the scalar wave approximation. The correlations between the cross-polarized fields are shown to result in the dependence of mesoscopic intensity fluctuations on the polarization of the incident light. The intensity correlation function is represented as a sum of the contributions from the scalar mode and the basic modes of circular and linear polarization. The calculations, as applied to media with large scattering inhomogeneities, are carried out for diffusive transport and for small-angle multiple scattering of light. Each polarization contribution to the variance of relative transmission fluctuations is shown not to be a self-averaging quantity and tends to a nonvanishing value as the sample thickness increases. This value is proportional to the length of polarization decay in the medium and can be measured by varying the initial polarization of light. (C) 2015 Optical Society of America
We consider the Beltrami equation for hydrodynamics and we show that its solutions can be viewed as instanton solutions of a more general system of equations. The latter are the equations of motion for an sigma model on 4-dimensional worldvolume (which is taken locally HyperKahler) with a 4-dimensional HyperKahler target space. By means of the 4D twisting procedure originally introduced by Witten for gauge theories and later generalized to 4D sigma-models by Anselmi and Fre, we show that the equations of motion describe triholomophic maps between the worldvolume and the target space. Therefore, the classification of the solutions to the 3-dimensional Beltrami equation can be performed by counting the triholomorphic maps. The counting is easily obtained by using several discrete symmetries. Finally, the similarity with holomorphic maps for sigma on Calabi-Yau space prompts us to reformulate the problem of the enumeration of triholomorphic maps in terms of a topological sigma model.
Measurements of the low masses for the pulsar PSR J0737-3039B, for the companion of PSR J1756-2251 and for the companion of PSR J0453+1559, on the one hand, and of the high masses for the pulsars PSR J1614-2230 and PSR J0348-0432, on the other, demonstrate the existence of compact stars with masses in a broad range from 1.2 to (Formula presented.). The most massive ones of these objects might be hybrid stars. To fulfill the constraint (Formula presented.) with a reserve, we exploit the stiff DD2 hadronic equation of state (EoS) without and with excluded volume (DD2vex) correction, which produce maximum neutron star masses of (Formula presented.) and (Formula presented.) , respectively. We show that the stiffness of the EoS does not preclude an explanation of the whole set of cooling data within “nuclear medium cooling” scenario for compact stars by a variation of the star masses. We select appropriate proton gap profiles from those exploited in the literature and allow for a variation of the effective pion gap controlling the efficiency of the medium modified Urca process. However, we suppress the possibility of pion condensation. In general, the stiffer the EoS the steeper a decrease with density of the effective pion gap is required. Results are compared with previously obtained ones for the HDD EoS for which (Formula presented.). The cooling of the compact star in the supernova remnant Cassiopeia A (Cas A) is explained mainly by an efficient medium modified Urca process. To explain a (Formula presented.) % decline of the cooling curve for Cas A, as motivated by an analysis of the ACIS-S instrument data, together with other cooling data exploiting the DD2 EoS a large proton gap at densities (Formula presented.) is required vanishing for (Formula presented.) , where (Formula presented.) is the saturation nuclear density. A smaller decline, as it follows from an analysis of the HRC-S instrument data, is explained with many choices of parameters. With the DD2vex EoS and using an effective pion gap steeper decreasing with the density and/or a proton gap shifted to smaller densities we are also able to reproduce both a strong decline compatible with ACIS-S data and HRC-S instrument data. The mass of Cas A is estimated as 1.6- (Formula presented.) , above the value (Formula presented.) , which we have evaluated with the softer HDD equation of state. Different mass choices for the hottest object XMMU J173203.3-344518 are discussed. We make general remarks also on hybrid star cooling and on its dependence on the stiffness of the hadronic EoS. © 2016, SIF, Springer-Verlag Berlin Heidelberg.
Fermions are considered in a multidimensional space with two extra dimensions. Fermion Lagrangian contains coupling to a metric of deformed extra space. We show that the point-like defect on a space with topology of sphere leads to fermion interaction with such defect and calculate cross section of a fermion scattering on such defect.
The process of Tb2Hf2O7 nanocrystals formation upon annealing to 1600°C was investigated by means of X-ray absorption fine structure (XAFS) spectroscopy combined with X-ray diffraction (XRD) and pair distribution function (PDF) analysis. The structure ordering and the growth of nanocrystals upon annealing were estimated independently from XRD patterns and PDF. The probable content of Tb4+ ions in Tb2Hf2O7 was estimated from XANES. All studies indicate a high disorder and a large number of local structure defects in Tb2Hf2O7 pyrochlore oxide.
We review the geoneutrino measurement with Borexino from 2056 days of data taking.
We are going to show that any conventional decaying dark matter model, providing an explanation of cosmic antiparticle excess observed by PAMELA and AMS-02, inevitably faces the contradiction with isotropic diffuse gamma-ray background, measured by FERMI/LAT.
The recent progress in designing optical lattice clocks with fractional uncertainties below 10(-17) requires unprecedented precision in estimating the role of higher-order effects of atom-lattice interactions. In this paper, we present results of systematic theoretical evaluations of the multipole, nonlinear, and anharmonic effects on the optical-lattice-based clocks of alkaline-earth-like atoms. Modifications of the model-potential approach are introduced to minimize discrepancies of theoretical evaluations from the most reliable experimental data. Dipole polarizabilities, hyperpolarizabilities, and multipolar polarizabilities for neutral Ca, Sr, Yb, Zn, Cd, and Hg atoms are calculated in the modified approach.
During the tokamak operation, variation of the stored energy can cause internal perturbations of the plasma. These perturbations may develop into large-scale vertical movement of the whole column for the vertically elongated tokamak, eventually generating the hot vertical displacement event (VDE). It will cause considerable damage to the machine. In this work, the hot VDE process due to stored energy perturbations is investigated by a mature non-linear time-evolution code DINA. The influence on the vertical instability, the displacement direction and the electromagnetic loads on in-vessel components during the hot VDE are analyzed. It is shown that a larger perturbation leads to faster development of the vertical instability. Meanwhile the variation of the Shafranov shift, due to the energy change, is related to the VDE direction. The vertical electromagnetic force on the vacuum vessel and the halo current flowing in the divertor baffle become larger in the case of VDE moving towards the X point.
In order to understand the interaction mechanisms between hydrogenic species and beryllium co-deposits, a 1D Diffusion Trapping Model of Isotopic eXchange in Be (DITMIX) is developed. Hydrogen depth profiles from DITMIX are in good agreement with those measured by sup15/supN-NRA on pre-characterised 600 nm thick Be:H layers (H/Be = 0.04), which were irradiated by D ions with a low flux of 10sup17/sup msup-2/sup ssup-1/sup and an energy of 5 keV Dsup-1/sup, for different fluences and surface temperatures. Hence DITMIX provides a qualitative understanding of the isotope exchange mechanisms, although modelled versus measured D profiles show less agreement in the bulk, casting some doubt on the processes involved. For such low fluxes, DITMIX shows that the main factors determining isotopic exchange are the irradiation fluence and the surface temperature. © 2016 Aix-Marseille Université.
The paper presents the results of investigation of gas exchange through stainless steel surface of the plasma chamber under irradiation with hydrogen atoms in oxygen atmosphere or oxygen contaminated hydrogen plasma. Dependence of this process on various irradiation parameters, such as the metal temperature, energy of irradiating ions, gas composition of plasma are studied. It is shown, that desorption from stainless steel is activated with the increase of the plasma chamber walls temperature and energy of irradiating ions. Hydrogen release occurs also under irradiation of the walls by helium and argon plasmas added with oxygen, however the amount of released hydrogen is several times lower than in the case of irradiation with oxygen contaminated deuterium plasma.
The paper presents a short revue of the study of not been investigated specific features of hydrogen trapping in graphite occurring as the results of inelastic interaction of impinging ions with carbon materials (potential trapping). The influence of potential mechanism on different regularities of hydrogen trapping are considered. Among them there is trapping dependence on irradiating ion current density, ion energy, irradiation fluence, temperature of the investigated samples and oxygen addition in the plasma.
The production of the hypertriton nuclei HΛ3 and H[U+203E]Λ-3 has been measured for the first time in Pb-Pb collisions at sNN=2.76 TeV with the ALICE experiment at LHC. The pT-integrated HΛ3 yield in one unity of rapidity, dN/dy×B.R.(HΛ3→He3,π-)=(3.86±0.77(stat.)±0.68(syst.))×10-in the 0-10% most central collisions, is consistent with the predictions from a statistical thermal model using the same temperature as for the light hadrons. The coalescence parameter B3 shows a dependence on the transverse momentum, similar to the B2 of deuterons and the B3 of sup3/supHe nuclei. The ratio of yields S3=HΛ3/(He3×Λ/p) was measured to be S3=0.60±0.13(stat.)±0.21(syst.) in 0-10% centrality events; this value is compared to different theoretical models. The measured S3 is compatible with thermal model predictions. The measured HΛ3 lifetime, τ=181-39+54(stat.)±33(syst.)ps is in agreement within 1σ with the world average value. © 2016 CERN for the benefit of the ALICE Collaboration.
This paper reports a detailed study of techniques for identifying boosted, hadronically decaying W bosons using 20.3 fb (Formula presented.) of proton–proton collision data collected by the ATLAS detector at the LHC at a centre-of-mass energy (Formula presented.). A range of techniques for optimising the signal jet mass resolution are combined with various jet substructure variables. The results of these studies in Monte Carlo simulations show that a simple pairwise combination of groomed jet mass and one substructure variable can provide a 50 % efficiency for identifying W bosons with transverse momenta larger than 200 GeV while maintaining multijet background efficiencies of 2–4 % for jets with the same transverse momentum. These signal and background efficiencies are confirmed in data for a selection of tagging techniques. © 2016, CERN for the benefit of the ATLAS collaboration.
This paper presents studies of the performance of several jet-substructure techniques, which are used to identify hadronically decaying top quarks with high transverse momentum contained in large-radius jets. The efficiency of identifying top quarks is measured using a sample of top-quark pairs and the rate of wrongly identifying jets from other quarks or gluons as top quarks is measured using multijet events collected with the ATLAS experiment in 20.3 fb−1 of 8 TeV proton-proton collisions at the Large Hadron Collider. Predictions from Monte Carlo simulations are found to provide an accurate description of the performance. The techniques are compared in terms of signal efficiency and background rejection using simulations, covering a larger range in jet transverse momenta than accessible in the dataset. Additionally, a novel technique is developed that is optimized to reconstruct top quarks in events with many jets.[Figure not available: see fulltext.] © 2016, The Author(s).
Prototype of industrial reactor antineutrino detector iDREAM is dedicated for an experiment to demonstrate the possibility of remote monitoring of PWR reactor operational modes by neutrino method in real-time in order to avoid undeclared exposure modes for nuclear fuel and unauthorized removal of isotopes. The prototype detector was started up in 2014. To test the detector elements and components of electronics distilled water has been used as a target, which enables the use of Cerenkov radiation from cosmic muons as a physical signal. Also parallel measuring of the long-term stability has been doing for samples of liquid organic scintillator doped with gadolinium and synthesized by different methods.
Two different oscillatory plasma regimes induced by seeding the plasma with high- and low-Z impurities are found for ITER-like divertor plasmas, using computer modeling with the DUSTT/UEDGE and SOLPS4.3 plasma-impurity transport codes. The oscillations are characterized by significant variations of the impurity-radiated power and of the peak heat load on the divertor targets. Qualitative analysis of the divertor plasma oscillations reveals different mechanisms driving the oscillations in the cases of high- and low-Z impurity seeding. The oscillations caused by the high-Z impurities are excited near the X-point by an impurity-related instability of the radiation-condensation type, accompanied by parallel impurity ion transport affected by the thermal and plasma friction forces. The driving mechanism of the oscillations induced by the low-Z impurities is related to the cross-field transport of the impurity atoms, causing alteration between the high and low plasma temperature regimes in the plasma recycling region near the divertor targets. The implications of the impurity-induced plasma oscillations for divertor operation in the next generation tokamaks are also discussed. © 2016 AIP Publishing LLC.
Tritium retention inside the vacuum vessel is a potentially serious constraint in the operation of large-scale fusion machines like ITER. An in situ diagnostics for first wall H/D/T retention by laser induced desorption spectroscopy (LIDS) is proposed for use between plasma discharges. The technique is based on local baking of the first wall by laser irradiation and subsequent analysis of the in-vessel gas by optical emission spectroscopy of plasma radiation. The local heating implementation, kinetics of H/D/T thermal extraction and the accuracy of optical emission spectroscopy measurements are analysed. To resolve the H/D/T lines spectroscopically, their thermal broadening should be minimized to prevent overlapping of the line shapes. A comparative performance analysis of several types of plasma sources with relatively cold ions is made including the following types of discharges: Penning, RF multipactor, laser torch and ECR. All these radiation sources require rather low power and could be used for remote in situ measurements of relative densities of the thermally extracted hydrogen isotopes. © 2016 IAEA, Vienna.
Isotope exchange was studied in-situ by Nuclear Reaction Analysis in the bulk of self-ion damaged tungsten at 600 K. Both variations of isotope exchange of H by D and of D by H were measured. The deuterium isothermal desorption was also studied and evaluated in order to be able to resolve the self-desorption from the isotope exchange at 600 K. The isotope exchange was also studied on the surface by Elastic Recoil Detection Analysis at 480 K and 380 K. The exchange mechanism was effective both on the surface and in the bulk of damaged tungsten. A simple model was introduced to describe the exchange efficiency on the surface and in the bulk obtaining the exchange cross sections on the surface and in bulk. In both cases an isotope effect was observed, where the exchange of H atoms by D atoms was more efficient than for the reverse sequence. © 2015 EURATOM. Published by Elsevier B.V. All rights reserved.
The tt- charge asymmetry is measured in proton-proton collisions at a centre-of-mass energy of 8 TeV. The data, collected with the CMS experiment at the LHC, correspond to an integrated luminosity of 19.7 fbsup-1/sup. Selected events contain an electron or a muon and four or more jets, where at least one jet is identified as originating from b-quark hadronization. The inclusive charge asymmetry is found to be 0.0010±0.0068 (stat)±0.0037 (syst). In addition, differential charge asymmetries as a function of rapidity, transverse momentum, and invariant mass of the tt- system are studied. For the first time at the LHC, the measurements are also performed in a reduced fiducial phase space of top quark pair production, with an integrated result of -0.0035±0.0072 (stat)±0.0031 (syst). All measurements are consistent within two standard deviations with zero asymmetry as well as with the predictions of the standard model. © 2016 CERN for the benefit of the CMS Collaboration.
We report on the inclusive production cross sections of (Formula presented.) , (Formula presented.) , (Formula presented.) (1S), (Formula presented.) (2S) and (Formula presented.) (3S), measured at forward rapidity with the ALICE detector in (Formula presented.) collisions at a center-of-mass energy (Formula presented.) TeV. The analysis is based on data collected at the LHC and corresponds to an integrated luminosity of 1.23 pb (Formula presented.). Quarkonia are reconstructed in the dimuon-decay channel. The differential production cross sections are measured as a function of the transverse momentum (Formula presented.) and rapidity y, over the (Formula presented.) ranges (Formula presented.) GeV/c for (Formula presented.) , (Formula presented.) GeV/c for all other resonances, and for (Formula presented.). The cross sections, integrated over (Formula presented.) and y, and assuming unpolarized quarkonia, are (Formula presented.) (Formula presented.) b, (Formula presented.) (Formula presented.) b, (Formula presented.) nb, (Formula presented.) nb and (Formula presented.) nb, where the first uncertainty is statistical and the second one is systematic. These values agree, within at most (Formula presented.) , with measurements performed by the LHCb collaboration in the same rapidity range. © 2016, CERN for the benefit of the ALICE collaboration.
The object of research is a distributed database management system Apache Cassandra and methods to improve its functionality by applying hybrid computing technologies. The encryption standard GOST 28147-89, which has a great potential for parallelization on the graphics core and can be used as the expansion module. Development was carried out in the Java language using the open source project Apache Cassandra and JCuda parallelization library for GPGPU systems. The article contains analysis of the Apache Cassandra architectural features and review of possibilities for connecting the expansion modules. The article presents a mathematical model of the proposed solution and experimental results (graphs of recording data rate to the base: in the standard mode, with using CPU encryption, with using GPU encryption). © 2016 IEEE.
We present an indirect method of estimating the strength of a shock wave, allowing on line monitoring of its reproducibility in each laser shot. This method is based on a shot-to-shot measurement of the X-ray emission from the ablated plasma by a high resolution, spatially resolved focusing spectrometer. An optical pump laser with energy of 1.0 J and pulse duration of ∼660 ps was used to irradiate solid targets or foils with various thicknesses containing Oxygen, Aluminum, Iron, and Tantalum. The high sensitivity and resolving power of the X-ray spectrometer allowed spectra to be obtained on each laser shot and to control fluctuations of the spectral intensity emitted by different plasmas with an accuracy of ∼2%, implying an accuracy in the derived electron plasma temperature of 5%-10% in pump-probe high energy density science experiments. At nano- and sub-nanosecond duration of laser pulse with relatively low laser intensities and ratio Z/A ∼ 0.5, the electron temperature follows Te ∼ Ilas sup2/3/sup. Thus, measurements of the electron plasma temperature allow indirect estimation of the laser flux on the target and control its shot-to-shot fluctuation. Knowing the laser flux intensity and its fluctuation gives us the possibility of monitoring shot-to-shot reproducibility of shock wave strength generation with high accuracy. © 2016 Author(s).
A theoretical investigation on the influence of birefringence in the modulational instability (MI) spectra of an oppositely directed coupler (ODC) with a negative index material (NIM) channel is presented. We study the effect of birefringence on MI in linear and circular birefringent ODCs for both normal and anomalous dispersion regimes. It is found that besides the instability band due to nonlinear positive index material (PIM) and negative index material (NIM) channels, new symmetric instability regions are observed as a result of birefringent effects. Also defocusing nonlinearity suppresses the NIM band in the normal dispersion regime, but in the anomalous dispersion regime the defocusing nonlinearity enhances the gain of the NIM band. In contrast to the case of linear birefringence, in terms of MI gain from circular birefringence, only two birefringent bands dominate: the inherently PIM and NIM bands. This preponderance is attributed to the fact that the cross-phase modulation effect for the case of circular birefringence is stronger, thus allowing a better coupling between the beams, which results in the enhancement of the gain. Therefore, the manipulation of MI and solitons in an ODC is better performed when the birefringence is circular rather than linear. Here we report how to generate and manipulate MI and solitons in birefringent ODCs with a particular emphasis on a NIM channel. © 2016 American Physical Society.
The influence of current density and pressure gradient profiles in the pedestal on the access to the regimes free from edge localized modes (ELMs) like quiescent H-mode in ITER is investigated. Using the simulator of MHD modes localized near plasma boundary based on the KINX code, calculations of the ELM stability were performed for the ITER plasma in scenarios 2 and 4 under variations of density and temperature profiles with the self-consistent bootstrap current in the pedestal. Low pressure gradient values at the separatrix, the same position of the density and temperature pedestals and high poloidal beta values facilitate reaching high current density in the pedestal and a potential transition into the regime with saturated large scale kink modes. New version of the localized MHD mode simulator allows one to compute the growth rates of ideal peeling-ballooning modes with different toroidal mode numbers and to determine the stability region taking into account diamagnetic stabilization. The edge stability diagrams computations and sensitivity studies of the stability limits to the value of diamagnetic frequency show that diamagnetic stabilization of the modes with high toroidal mode numbers can help to access the quiescent H-mode even with high plasma density but only with low pressure gradient values at the separatrix. The limiting pressure at the top of the pedestal increases for higher plasma density. With flat density profile the access to the quiescent H-mode is closed even with diamagnetic stabilization taken into account, while toroidal mode numbers of the most unstable peeling-ballooning mode decrease from n = 10−40 to n = 3−20. © 2016, Pleiades Publishing, Ltd.
A comparative study of the results of spark-plasma sintering (SPS) of two-types of aluminum oxide nanopowders, obtained by the method of conductor explosion and plasma synthesis. When the parameters of both powders are similar (spherical form of the particles, size, phase composition) as well as SPS modes the properties of the resulting compacts are significantly different both in mechanical properties and microstructure. The reason of differences in the properties of the obtained compacts is in technological impurities in powders, obtained by different methods. Artificial addition of impurities, contained in the nanopowder, obtained by electro explosion of conductor, into the powder, made by synthesis in plasma and not containing these impurities, allowed to reveal their effect on the formation of the microstructure and properties of the sintered by SPS method sample.
The evolution of the spin transition in LaCoO3 has been investigated with photoemission electron microscopy (PEEM) as a function of temperature. The investigated temperature range spanned from a predominantly low spin configuration (125 K) to the proposed percolation limit for metallization (413 K). The data show that the spin configuration exhibits an inhomogeneous spatial distribution that is very sensitive to the surface preparation method. In the region of the semiconductor-to-metal transition (300 to 450 K), the spatial contrast is continuously reduced, indicating a smooth transition without domain percolation. These observations support a new interpretation of the temperature evolution of the system that is in agreement with current theoretical understanding of the spin transition. © 2016 American Physical Society.
A general concept of a new interdisciplinary glossary, which includes particle accelerator terminology used in medicine, as well as relevant medical concepts, is presented. Its structure and usage rules are described. An example, illustrating the quickly searching technique of relevant information in this Glossary, is considered. A website address, where one can get an access to the Glossary, is specified. Glossary can be refined and supplemented.
Currently, high-temperature superconductor (HTS) bearings are most commonly designed with bulk REBa2Cu3O7-x (REBCO), but these HTS bulks have several drawbacks, such as brittleness and the complexity of sample preparation. An alternative for levitation systems is to use stacks of REBCO coated conductors (HTS tapes). The main advantages of HTS tapes are the simplicity of manufacturing elements in the required shape and high strength stability. For the development of HTS bearings, it is important to characterize both the levitation force along the axis connecting the magnet and the superconductor, and the stability of the system in response to lateral displacement.In this paper, we present new results of measurements of the levitation force between a permanent magnet and a stack of HTS tapes containing from 10 to 100 tapes of 12 mm × 12 mm. Measurements were conducted in zero-field cooling mode. We observed hysteresis of the levitation force in the case of lateral displacement. In addition, we have investigated the decay in the levitation force due to lateral displacement with each cycle of movement. It is shown that the decay rate tends to be constant on increasing the number of tapes in the stack. © 2016 IEEE.
Parameters of inductively coupled plasma (ICP) discharges in a mixture of gases N2, H2, and Ar at a total pressure of 1.5 × 10sup–3/sup mbar and a partial pressure ratio N2: H2: Ar = 2: 12: 1 are discussed. The plasma properties are analyzed using Langmuir probes and optical emission spectroscopy. The ICP discharge is used for the nitriding of specimens made of Russian grade 30ChGSA structural steel. The nitriding experiments are performed at different bias voltages Vb in the range of–200 V to +100 V with respect to the walls of the discharge chamber. The surface hardness of the treated specimens depends substantially on the bias voltage, being much higher than the initial value in all cases. The obtained results demonstrate the possibility of increasing the surface hardness up to 1000 HV (4–5 times the initial values) at the bias voltage equal to the floating potential. © 2016, Allerton Press, Inc.
The particle–hole dispersive optical model, developed recently, is applied to study properties of high-energy isoscalar monopole excitations in medium-heavy mass spherical nuclei. The energy-averaged strength functions of the isoscalar giant monopole resonance and its overtone in 208Pb are analyzed. In particular, we analyze the energy-averaged isoscalar monopole double transition density, the key quantity in the description of the hadron–nucleus inelastic scattering, and studied the validity of the factorization approximation using semi classical and microscopic one body transition densities, respectively, in calculating the cross sections for the excitation of isoscalar giant resonances by inelastic alpha scattering. © 2016 Elsevier B.V.
We consider static, spherically symmetric configurations of electrically charged dust in Einstein-Maxwell-dilaton gravity where the Lagrangian contains the interaction term P(χ)FμνFsupμν/sup with an arbitrary function P(χ). Unlike previous studies, we assume that the scalar field χ (which can be canonical or phantom) does not have a charge of its own and exists only due to this interaction. We discuss possible solutions to the field equations, in particular, those describing black holes (BHs) and quasi-black holes (QBHs). The latter are globally regular configurations whose size is very close to that of a BH of the same mass and which therefore are almost indistinguishable from BHs for a distant observer. Some general features are revealed, a family of explicitly integrable models is found, and some explicit examples are presented. © 2016, Pleiades Publishing, Ltd.
While 203 K high temperature superconductivity in H 3 S has been interpreted by BCS theory in the dirty limit here we focus on the effects of hydrogen zero-point-motion and the multiband electronic structure relevant for multigap superconductivity near Lifshitz transitions. We describe how the topology of the Fermi surfaces evolves with pressure giving different Lifshitz-transitions. A neck-disrupting Lifshitz-transition (type 2) occurs where the van Hove singularity, vHs, crosses the chemical potential at 210 GPa and new small 2D Fermi surface portions appear with slow Fermi velocity where the Migdal-approximation becomes questionable. We show that the neglected hydrogen zero-point motion ZPM, plays a key role at Lifshitz transitions. It induces an energy shift of about 600 meV of the vHs. The other Lifshitz-transition (of type 1) for the appearing of a new Fermi surface occurs at 130 GPa where new Fermi surfaces appear at the Γ point of the Brillouin zone here the Migdal-approximation breaks down and the zero-point-motion induces large fluctuations. The maximum Tc = 203 K occurs at 160 GPa where EF/ω0 = 1 in the small Fermi surface pocket at Γ. A Feshbach-like resonance between a possible BEC-BCS condensate at Γ and the BCS condensate in different k-space spots is proposed.
The motion of classical spinning test particles in the equatorial plane of a Kerr black hole is considered for the case where the particle spin is perpendicular to the equatorial plane.We review some results of our recent research of the innermost stable circular orbits (ISCO) [1] and present some new calculations. The ISCO radius, total angular momentum, energy, and orbital angular frequency are considered. We calculate the ISCO parameters numerically for different values of the Kerr parameter a and investigate their dependence on both black hole and test particle spins. Then we describe in detail how to calculate analytically small-spin corrections to the ISCO parameters for an arbitrary values of a. The cases of Schwarzschild, slowly rotating Kerr and extreme Kerr black holes are considered. The use of the orbital angular momentum is discussed. We also consider the ISCO binding energy. It is shown that the efficiency of accretion onto an extreme Kerr black hole can be larger than the maximum known efficiency (42%) if the test body has a spin. © 2016, Pleiades Publishing, Ltd.
We have found the time dependence of the ablation depth of aluminium irradiated by a femtosecond laser pulse. It is shown to what extent an increase in the radiation energy flux density leads to an increase in the quasi-stationary value of the ablation depth. By reducing the aluminium film thickness down to one hundred nanometres and less, the ablation depth significantly increases. At the same time, the quasi-stationary value of the ablation depth of a thin film is obtained due to the removal of heat from the focal spot region. © 2016 Kvantovaya Elektronika and Turpion Ltd.
The spectral and total electron densities of states in two-dimensional FeAs clusters, which simulate iron-based superconductors, have been calculated using the generalized quantum Monte Carlo algorithm within the full two-orbital model. Spectra have been reconstructed by solving the integral equation relating the Matsubara Green’s function and spectral density by the method combining the gradient descent and Monte Carlo algorithms. The calculations have been performed for clusters with dimensions up to 10 × 10 FeAs cells. The profiles of the Fermi surface for the entire Brillouin zone have been presented in the quasiparticle approximation. Data for the total density of states near the Fermi level have been obtained. The effect of the interaction parameter, size of the cluster, and temperature on the spectrum of excitations has been studied. © 2016, Pleiades Publishing, Inc.
We consider the coupled electromagnetic waves propagating in a nonlinear coupler and in nonlinear waveguide array, which consists of alternating waveguides of positive and negative refraction indexes. The forward wave and backward wave interaction is realized in these devices. Gap solitons in a nonlinear oppositely directional coupler with one channel or both channels fabricated from nonlinear medium having negative refraction index are discussed. Generalization of the usually waveguide array is zigzag array. Due to zigzag configuration there are interactions between both nearest and next nearest neighboring waveguides exist. The system of evolution equations for coupled waves has the steady state solution describing the electromagnetic pulse running in the array. Numerical simulation demonstrates robustness of these solitary waves. © Springer Science+Business Media Dordrecht 2016.
The overview of the main problems and methods of cosmoparticle physics, studying fundamental relationship of micro- and macro-worlds, is accompanied by the demonstration of the facility of Virtual Institute of Astroparticle physics (VIA) activity as a well proven platform for scientific collaborative work and education at distance.
A research of radiation spectra of a low inductance vacuum spark in visible and ultraviolet regions was realized. Time dependences for hydrogen atom lines, and so for iron atom lines and iron ion lines were obtained. Temperature of an external plasma cover was determined.
An equation of state of cold nuclear matter with an arbitrary isotopic composition is studied within a relativistic mean-field approach with hadron masses and coupling constants depending self-consistently on the scalar mean-field. All hadron masses decrease universally with the scalar field growth, whereas meson-nucleon coupling constants can vary differently. More specifically we focus on two modifications of the KVOR model studied previously. One extension of the model (KVORcut) demonstrates that the equation of state stiffens if the increase of the scalar-field magnitude with the density is bounded from above at some value for baryon densities above the saturation nuclear density. This can be realized if the nucleon vector-meson coupling constant changes rapidly as a function of the scalar field slightly above the desired value. The other version of the model (MKVOR) utilizes a smaller value of the nucleon effective mass at the nuclear saturation density and a saturation of the scalar field in the isospin asymmetric matter induced by a strong variation of the nucleon isovector-meson coupling constant as function of the scalar field. A possibility of hyperonization of the matter in neutron star interiors is incorporated. Our equations of state fulfill majority of known empirical constraints including the pressure-density constraint from heavy-ion collisions, direct Urca constraint, gravitational-baryon mass constraint for the pulsar J0737-3039B, and the constraint on the maximum mass of the neutron stars. © 2016 Elsevier B.V.
The equation of state of cold baryonic matter is studied within a relativistic mean-field model with hadron masses and coupling constants depending on a scalar field. We demonstrate that if the effective nucleon mass stops to decrease with a density increase at densities n n(*) no, where no is the nuclear saturation density, the equation of state stiffens for these densities and the limiting neutron star mass increases. The stabilization of the nucleon mass can be realised if in the equation of motion for the scalar mean-field there appear a term sharply varying in a narrow vicinity of the field value corresponding to the density n,. We show several possible realizations of this mechanism getting sufficiently stiff equations of state. The appearance of hyperons in dense neutron star interiors is accounted for. The obtained equations of state remain sufficiently stiff if the reduction of the phi meson mass is incorporated. Thereby, the hyperon puzzle can be resolved.
Within the particle-hole dispersive optical model it is shown that the spreading effect determines a significant part of the anomalously large excitation energy of deep-hole states in the Zr-90 and Pb-208 parent nuclei.
Regime with the plasma detached from the divertor targets (detached divertor regime) is a natural continuation of the high recycling conditions to higher density and stronger impurity radiation loss. Both the theoretical considerations and experimental data show clearly that the increase of the impurity radiation loss and volumetric plasma recombination causes the rollover of the plasma flux to the target when the density increases, which is the manifestation of detachment. Plasma-neutral friction (neutral viscosity effects), although important for the sustainment of high density/pressure plasma upstream and providing the conditions for efficient recombination and power loss, is not directly involved in the reduction of the plasma flux to the targets. The stability of detachment is also discussed. © 2016 Author(s).
We seek wormholes among rotating cylindrically symmetric configurations in general relativity. Exact wormhole solutions are presented with such sources of gravity as a massless scalar field, a cosmological constant, and a scalar field with an exponential potential. However, none of these solutions are asymptotically flat, which excludes the existence of wormhole entrances as local objects in our Universe. To overcome this difficulty, we try to build configurations with flat asymptotic regions using the cut-and-paste procedure: on both sides of the throat, a wormhole solution is matched to a properly chosen region of flat space-time at some surfaces ∑- and ∑+. It is shown, however, that if the source of gravity in the throat region is a scalar field with an arbitrary potential, then one or both thin shells appearing on ∑- and ∑+ inevitably violate the null energy condition. Thus, although rotating wormhole solutions are easily found without exotic matter, such matter is still necessary for obtaining asymptotic flatness. © 2016 World Scientific Publishing Company.
We investigate the electronic structure of the two-dimensional t–J model in a transverse external static magnetic field with canted long-range magnetic order using cluster perturbation theory. The distribution of the spectral weight in the whole range of fields from zero to ferromagnetic saturation is explored. We demonstrate the possibility of a sharp change in a distribution of spectral weight at the Fermi level associated with the magnetic correlations when varying magnetic field. © 2016, Pleiades Publishing, Inc.
This paper presents the testing results of the neutral particles converter device "Aries-L" for the "Luna-Resurs" project of the Space Research Institute (RAS).
This paper deals with the influence of laser plasma on the structure of the radiation field of a powerful Nd-glass laser with pulse energy up to 30 J and with the diameter of the output beam 45 mm. Laser plasma is generated by focusing the laser radiation on a low-density target such as nylon mesh and teflon or mylar films. Temporal profile of the laser pulse with a total duration of 25 ns consists of a several short pulse train. Duration of each pulse is about 2 ns. Notable smoothing of spatially non-uniform radiation structure was observed in the middle of the laser pulse.
Properties of corona discharge near metallic surface were researched. Electrical oscillations in discharge plasma of 1 kHz - 100 MHz rate were registered. Spectrum of electrical oscillations in this range was obtained. Possible plasma waves for observed electronic oscillations explanation are discussed.
Spatial distributions of charged particle concentration, electron temperature, and DC potential in an electrode microwave discharge in nitrogen at a pressure of 1 Torr have been measured using the double electric probe method. It has been shown that, near the electrode/antenna, the charged particle concentration exceeds a critical value. The concentration and heterogeneity of the discharge increase with increasing microwave power. © 2016, Pleiades Publishing, Ltd.
Calculation of the total dielectronic recombination (DR) rates was done in the frame of a statistical model of atoms. The model is based on the idea of collective excitations of atomic electrons with the local plasma frequency, which depends on atomic electrons density distribution. The electron density is described in a frame of the Thomas-Fermi model of atoms. Simple scaling laws for temperature Te and nuclear charge Z dependences follow from the statistical model of DR. Results of the statistical model were compared with other numerical data following detailed level-by-level computations for different multielectron ions. The specific attention is paid to Ni-like ion sequences of different chemical elements in order to check the Z -dependence of DR rates. A comparison with numerical data of Flexible Atomic Code (FAC) is presented for tungsten ions. The reasonable correspondence between the statistical model and the detailed numerical data is demonstrated. The application of the statistical model provides very simple and fast calculations of the DR rates useful in modern plasma modelling. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Acollective, macroscopic signature to detect radiation friction in laser-plasma experiments is proposed. In the interaction of superintense circularly polarized laser pulses with high density targets, the effective dissipation due to radiative losses allows the absorption of electromagnetic angular momentum, which in turn leads to the generation of a quasistatic axial magnetic field. This peculiar inverse Faraday effect is investigated by analytical modeling and three-dimensional simulations, showing thatmulti-gigagaussmagnetic fieldsmay be generated at laser intensities < 10sup23/sup W cmsup-2/sup. © 2016 IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.
The local crystal structure of superconducting powders of iron chalcogenides FeTe (x) Se1-x (x = 0.1, 0.22, 0.49, 0.8, 0.9) prepared by dry synthesis (without mineralizer) has been studied by EXAFS spectroscopy above the K Se and K Fe absorption edges in the temperature range of 80-300 K. The dependences of Se-Fe, Fe-Te, and Fe-Fe interatomic bond lengths and degrees of their local disordering (Debye-Waller factors) on the tellurium content and temperature have been obtained. Einstein temperatures characterizing the stiffness of each bond have been determined. The correlation of the Se-Fe bond stiffness with the dependence of the critical temperature of the superconducting transition T (c) on the composition of the samples under study have been established, which indicates the specific role of the Se-Fe bond in the superconducting state formation in iron chalcogenides FeTe (x) Se1-x .
Post-mortem studies with ion beam analysis, thermal desorption, and secondary ion mass spectrometry have been applied for investigating the long-term fuel retention in the JET ITERlike wall components. The retention takes place via implantation and co-deposition, and the highest retention values were found to correlate with the thickness of the deposited impurity layers. From the total amount of retained D fuel over half was detected in the divertor region. The majority of the retained D is on the top surface of the inner divertor, whereas the least retention was measured in the main chamber on the mid-plane of the inner wall limiter. The recessed areas of the inner wall showed significant contribution to the main chamber total retention. Thermal desorption spectroscopy analysis revealed the energetic T from DD reactions being implanted in the divertor. The total T inventory was assessed to be >0.3 mg. © 2016 The Royal Swedish Academy of Sciences.
For large volume neutrino and antineutrino detectors it is crucial to have an efficient data acquisition system capable of digitizing data from thousands of detection channels. Here we present a flexible DAQ system architecture consisting of a large number of fast waveform digitizers and configurable FPGA-based trigger logic. The current implementation of the system is functioning in the Borexino neutrino detector providing zero dead time spectroscopy data in the energy range from 1 up to 100 MeV. Acquisition complex in combination with our custom analysis software is successfully being used for registration of geoneutrinos, as well as search for neutrino signal from GRBs, solar netrino spectroscopy and other applications.
The results of the study of magnetization of Y1−xCaxBa2Cu3O7−δ HTS films deposited on the metallic substrate are presented. The magnetization measurements were carried out in a wide temperature range 4–77 K and magnetic fields up to 14 T. Based on critical state model, the analysis of the influence of calcium concentration on the critical current was performed. It was found that the change in Ca concentration causes the decrease in value of critical current density jc. The increase in temperature leads to enhancement of the observed effect. At T = 4.2 K and in the magnetic fields higher than 8 T, the jc reduction was found to be insignificant. This fact may indicate the possibility of jc growth in strong magnetic fields due to increase in carrier concentration caused by replacing Y3+ by Ca2+. © 2015 Springer Science+Business Media New York
In this paper, we present the results of the measurements of HTS tape stack magnetization and magnetic levitation forces between the permanent-magnet NdFeB and the stacks composed of n = 5-100 tapes of ReBCO (with the size of 12 mm x 12 mm) in the field cooling and zero-field cooling modes in a crossed magnetic field. The alternating magnetic field parallel to the surface of the tapes was produced by a copper coil with the amplitude up to 80-Oe frequency was varied in the range from 50 to 400 Hz. Measurements were carried out in liquid nitrogen. The dependencies of the magnetization of the stacks and the levitation force on the magnitude and frequency of the alternating magnetic field were obtained. The suppression of the levitation force and magnetization in a crossed field for the stacks of various thicknesses was shown. The results were compared with the characteristics of the bulk superconductors.
The magnetization of a layered high-temperature superconductor with different anisotropy parameters has been calculated using the Monte Carlo method in the framework of a modified three-dimensional Lawrence–Doniach model with actual boundary conditions. The penetration of a magnetic flux into a bulk sample from the boundary has been simulated, and the curves of magnetization reversal of a high-temperature superconductor by an external magnetic field have been calculated for different anisotropy parameters γ and types of defects in the sample. It has been found that there are significant differences in the magnetization curves and transport properties of superconductors with different anisotropy parameters γ. The influence of tilted columnar defects on the critical current has been analyzed. A decreasing dependence of the critical current on the tilt angle of defects with respect to the c axis has been obtained. It has been shown that, as the anisotropy parameter increases, this dependence weakens and, for a specific value of γ, disappears. An explanation of the mechanism responsible for the disappearance of the dependence has been proposed. © 2016, Pleiades Publishing, Ltd.
Polycrystalline tungsten (W) specimens were pre-irradiated with self-ions to create identical samples with high density of defects up to ∼2.5 μm near the surface. Then, W specimens were exposed to either thermal atomic deuterium (D) beam with an incident energy of ∼0.2 eV or low energy D plasma with the incident energy varied between 5 and 200 eV at different sample temperatures. Each sample was exposed once at certain temperature and fluence. The D migration and accumulation in W were studied post-mortem by nuclear reaction method. It was shown that the rate of the D to occupy radiation-induced defects increases with increasing the incident energy, ion flux, and temperature. Experimental investigation was accompanied by modelling using the rate-equation model. Moreover, the analytical model was developed and benchmarked against numerical model. The calculations of the deuterium diffusion with trapping at radiation-induced defects in tungsten by analytical model are consistent with numerical calculations using rate-equation model. The data of reflection and penetration of atomic and low-energy D were taking from calculations using molecular dynamics (MD) with Juslin interatomic potentials and a binary collision code TRIM. MD calculations show an agreement with a binary collision code TRIM only in a very narrow range of deuterium energies between 1 and 20 eV. Incorporation of the data of reflection and penetration of deuterium in the macroscopic modelling has been done to verify the range of validity of calculations using MD and binary collision code TRIM by comparison of modelling results with experimental data. Modelling results are consistent with experiments using reflection and penetration data of D obtained from TRIM code for incident ion energy above 1 eV. Otherwise, the parameters obtained from MD should be incorporated in the rate-equation model to have a good agreement with the experiments. © 2016 AIP Publishing LLC.
The operation of a nuclear fusion reactor has been simulated within a model based on experimental results obtained at the TEXTOR-94 tokamak and other facilities in which quasistationary regimes were achieved with long confinement times, high densities, and absence of the edge-localized mode. The radiative improved mode of confinement studied in detail at the TEXTOR-94 tokamak is the most interesting such regime. One of the most important problems of modern tokamaks is the problem of a very high thermal load on a divertor (or a limiter). This problem is quite easily solved in the radiative improved mode. Since a significant fraction of the thermal energy is reemitted by an impurity, the thermal loading is significantly reduced. As the energy confinement time τE at high densities in the indicated mode is significantly larger than the time predicted by the scaling of ITERH-98P(y, 2), ignition can be achieved in a facility much smaller than the ITER facility at plasma temperatures below 20 keV. The revealed decrease in the degradation of the confinement time τE with an increase in the introduced power has been analyzed. © 2016, Pleiades Publishing, Inc.
We report on the first measurement of an excess in the yield of J/ψ at very low transverse momentum (pT0.3 GeV/c) in peripheral hadronic Pb-Pb collisions at sNN
The production of D*sup±/sup, Dsup±/sup and Ds sup±/sup charmed mesons has been measured with the ATLAS detector in pp collisions at s=7 TeV at the LHC, using data corresponding to an integrated luminosity of 280 nbsup-1/sup. The charmed mesons have been reconstructed in the range of transverse momentum 3.5<pT(D)<100 GeV and pseudorapidity |η(D)|<2.1. The differential cross sections as a function of transverse momentum and pseudorapidity were measured for D*sup±/sup and Dsup±/sup production. The next-to-leading-order QCD predictions are consistent with the data in the visible kinematic region within the large theoretical uncertainties. Using the visible D cross sections and an extrapolation to the full kinematic phase space, the strangeness-suppression factor in charm fragmentation, the fraction of charged non-strange D mesons produced in a vector state, and the total cross section of charm production at s√=7 TeV were derived. © 2016 The Authors.
Integrated fiducial cross sections for the production of four leptons via the H → 4ℓ decays (ℓ = e, μ) are measured in pp collisions at (Formula presented.) and 8TeV. Measurements are performed with data corresponding to integrated luminosities of 5.1 fbsup−1/sup at 7TeV, and 19.7 fbsup−1/sup at 8 TeV, collected with the CMS experiment at the LHC. Differential cross sections are measured using the 8 TeV data, and are determined as functions of the transverse momentum and rapidity of the four-lepton system, accompanying jet multiplicity, transverse momentum of the leading jet, and difference in rapidity between the Higgs boson candidate and the leading jet. A measurement of the Z → 4ℓ cross section, and its ratio to the H → 4ℓ cross section is also performed. All cross sections are measured within a fiducial phase space defined by the requirements on lepton kinematics and event topology. The integrated H → 4ℓ fiducial cross section is measured to be 0. 56− 0.44 sup+ 0.67/sup(stat)− 0.06 sup+ 0.21/sup(syst) fb at 7 TeV, and 1. 11− 0.35 sup+ 0.41/sup(stat)− 0.10 sup+ 0.14/sup(syst) fb at 8 TeV. The measurements are found to be compatible with theoretical calculations based on the standard model. © 2016, The Author(s).
A measurement is presented of differential cross sections for Higgs boson (H) production in pp collisions at √s = 8TeV. The analysis exploits the H→γγ decay in data corresponding to an integrated luminosity of 19.7fbsup-1/sup collected by the CMS experiment at the LHC. The cross section is measured as a function of the kinematic properties of the diphoton system and of the associated jets. Results corrected for detector effects are compared with predictions at next-to-leading order and next-to-next-to-leading order in perturbative quantum chromodynamics, as well as with predictions beyond the standard model. For isolated photons with pseudorapidities |η|<2.5, and with the photon of largest and next-to-largest transverse momentum (pT supγ/sup) divided by the diphoton mass mγγ satisfying the respective conditions of pT supγ/sup/mγγ>1/3 and >1/4, the total fiducial cross section is 32±10fb. © 2016, CERN for the benefit of the CMS collaboration.
The production of prompt Ds sup+/sup mesons was measured for the first time in collisions of heavy nuclei with the ALICE detector at the LHC. The analysis was performed on a data sample of Pb-Pb collisions at a centre-of-mass energy per nucleon pair, (Formula presented.) , of 2.76 TeV in two different centrality classes, namely 0–10% and 20–50%. Ds sup+/sup mesons and their antiparticles were reconstructed at mid-rapidity from their hadronic decay channel Ds sup+/sup → ϕπsup+/sup, with ϕ → Ksup−/supKsup+/sup, in the transverse momentum intervals 4 < pT < 12GeV/c and 6 < pT < 12 GeV/c for the 0–10% and 20–50% centrality classes, respectively. The nuclear modification factor RAA was computed by comparing the pT-differential production yields in Pb-Pb collisions to those in proton-proton (pp) collisions at the same energy. This pp reference was obtained using the cross section measured at (Formula presented.) TeV and scaled to (Formula presented.) TeV. The RAA of Ds sup+/sup mesons was compared to that of non-strange D mesons in the 10% most central Pb-Pb collisions. At high pT (8 < pT < 12 GeV/c) a suppression of the Ds sup+/sup-meson yield by a factor of about three, compatible within uncertainties with that of non-strange D mesons, is observed. At lower pT (4 < pT < 8 GeV/c) the values of the Ds sup+/sup-meson RAA are larger than those of non-strange D mesons, although compatible within uncertainties. The production ratios Ds sup+/sup/Dsup0/sup and Ds sup+/sup/Dsup+/sup were also measured in Pb-Pb collisions and compared to their values in proton-proton collisions. © 2016, The Author(s).
The production of electrons from heavy-flavour hadron decays was measured as a function of transverse momentum (pT) in minimum-bias p-Pb collisions at sNN=5.02 TeV using the ALICE detector at the LHC. The measurement covers the pT interval 0.5<pT<12 GeV/c and the rapidity range -1.065<ycms<0.135 in the centre-of-mass reference frame. The contribution of electrons from background sources was subtracted using an invariant mass approach. The nuclear modification factor RpPb was calculated by comparing the pT-differential invariant cross section in p-Pb collisions to a pp reference at the same centre-of-mass energy, which was obtained by interpolating measurements at s=2.76 TeV and s=7 TeV. The RpPb is consistent with unity within uncertainties of about 25%, which become larger for pT below 1 GeV/c. The measurement shows that heavy-flavour production is consistent with binary scaling, so that a suppression in the high-pT yield in Pb-Pb collisions has to be attributed to effects induced by the hot medium produced in the final state. The data in p-Pb collisions are described by recent model calculations that include cold nuclear matter effects. © 2015 CERN for the benefit of the ALICE Collaboration.
Event-shape observables measured using charged particles in inclusive Z-boson events are presented, using the electron and muon decay modes of the Z bosons. The measurements are based on an integrated luminosity of 1.1fb-1 of proton–proton collisions recorded by the ATLAS detector at the LHC at a centre-of-mass energy s=7 TeV. Charged-particle distributions, excluding the lepton–antilepton pair from the Z-boson decay, are measured in different ranges of transverse momentum of the Z boson. Distributions include multiplicity, scalar sum of transverse momenta, beam thrust, transverse thrust, spherocity, and F-parameter, which are in particular sensitive to properties of the underlying event at small values of the Z-boson transverse momentum. The measured observables are compared with predictions from Pythia 8, Sherpa, and Herwig 7. Typically, all three Monte Carlo generators provide predictions that are in better agreement with the data at high Z-boson transverse momenta than at low Z-boson transverse momenta, and for the observables that are less sensitive to the number of charged particles in the event. © 2016, CERN for the benefit of the ATLAS collaboration.
The momentum-weighted sum of the charges of tracks associated to a jet is sensitive to the charge of the initiating quark or gluon. This paper presents a measurement of the distribution of momentum-weighted sums, called jet charge, in dijet events using 20.3 fb(-1) of data recorded with the ATLAS detector at root s = 8 TeV in pp collisions at the LHC. The jet charge distribution is unfolded to remove distortions from detector effects and the resulting particle-level distribution is compared with several models. The p(T) dependence of the jet charge distribution average and standard deviation are compared to predictions obtained with several leading-order and next-to-leading-order parton distribution functions. The data are also compared to different Monte Carlo simulations of QCD dijet production using various settings of the free parameters within these models. The chosen value of the strong coupling constant used to calculate gluon radiation is found to have a significant impact on the predicted jet charge. There is evidence for a pT dependence of the jet charge distribution for a given jet flavor. In agreement with perturbative QCD predictions, the data show that the average jet charge of quark-initiated jets decreases in magnitude as the energy of the jet increases.
Results on two-particle angular correlations for charged particles produced in pp collisions at a center-of- mass energy of 13 TeV are presented. The data were taken with the CMS detector at the LHC and correspond to an integrated luminosity of about 270 nb(-1). The correlations are studied over a broad range of pseudorapidity (vertical bar eta vertical bar 2.4) and over the full azimuth (phi) as a function of charged particle multiplicity and transverse momentum (p(T)). In high-multiplicity events, a long-range (vertical bar Delta eta vertical bar 2.0), near-side (Delta phi approximate to 0) structure emerges in the two-particle Delta eta-Delta phi correlation functions. The magnitude of the correlation exhibits a pronounced maximum in the range 1.0 p(T) 2.0 GeV/c and an approximately linear increase with the charged particle multiplicity, with an overall correlation strength similar to that found in earlier pp data at root s
Measurement of the Solar pp-neutrino flux completed the measurement of Solar neutrino fluxes from the pp-chain of reactions in Borexino experiment. The result is in agreement with the prediction of the Standard Solar Model and the MSW/LMA oscillation scenario. A comparison of the total neutrino flux from the Sun with Solar luminosity in photons provides a test of the stability of the Sun on the 105 years time scale, and sets a strong limit on the power production by the unknown energy sources in the Sun.
The consistency of the spin correlation strength in top quark pair production with the standard model (SM) prediction is tested in the muon+jets final state. The events are selected from pp collisions, collected by the CMS detector, at a centre-of-mass energy of 8 TeV, corresponding to an integrated luminosity of 19.7 fbsup-1/sup. The data are compared with the expectation for the spin correlation predicted by the SM and with the expectation of no correlation. Using a template fit method, the fraction of events that show SM spin correlations is measured to be 0.72±0.08(stat)sup+0.15/sup -0.13(syst), representing the most precise measurement of this quantity in the muon+jets final state to date. © 2016 The Author.
The centrality dependence of the mean charged-particle multiplicity as a function of pseudorapidity is measured in approximately 1 (Formula presented.) b (Formula presented.) of proton–lead collisions at a nucleon–nucleon centre-of-mass energy of (Formula presented.) (Formula presented.) using the ATLAS detector at the Large Hadron Collider. Charged particles with absolute pseudorapidity less than 2.7 are reconstructed using the ATLAS pixel detector. The p + Pb collision centrality is characterised by the total transverse energy measured in the Pb-going direction of the forward calorimeter. The charged-particle pseudorapidity distributions are found to vary strongly with centrality, with an increasing asymmetry between the proton-going and Pb-going directions as the collisions become more central. Three different estimations of the number of nucleons participating in the p + Pb collision have been carried out using the Glauber model as well as two Glauber–Gribov inspired extensions to the Glauber model. Charged-particle multiplicities per participant pair are found to vary differently for these three models, highlighting the importance of including colour fluctuations in nucleon–nucleon collisions in the modelling of the initial state of p + Pb collisions. © 2016, The Author(s).
In the pp→tt process the angular distributions of top and anti-top quarks are expected to present a subtle difference, which could be enhanced by processes not included in the Standard Model. This Letter presents a measurement of the charge asymmetry in events where the top-quark pair is produced with a large invariant mass. The analysis is performed on 20.3 fbsup-1/sup of pp collision data at √s=8TeV collected by the ATLAS experiment at the LHC, using reconstruction techniques specifically designed for the decay topology of highly boosted top quarks. The charge asymmetry in a fiducial region with large invariant mass of the top-quark pair (mtt>0.75 TeV) and an absolute rapidity difference of the top and anti-top quark candidates within -2<|yt|-|yt|<2 is measured to be 4.2±3.2%, in agreement with the Standard Model prediction at next-to-leading order. A differential measurement in three tt- mass bins is also presented. © 2016 CERN for the benefit of the ATLAS Collaboration.
The charge asymmetry in the production of top quark and antiquark pairs is measured in proton-proton collisions at a center-of-mass energy of 8 TeV. The data, corresponding to an integrated luminosity of 19.6 fb(-1), were collected by the CMS experiment at the LHC. Events with a single isolated electron or muon, and four or more jets, at least one of which is likely to have originated from hadronization of a bottom quark, are selected. A template technique is used to measure the asymmetry in the distribution of differences in the top quark and antiquark absolute rapidities. The measured asymmetry is A(c)(y) = [0.33 +/- 0.26(stat) +/- 0.33(syst)]%, which is the most precise result to date. The results are compared to calculations based on the standard model and on several beyond-the-standard-model scenarios.
This paper reports inclusive and differential measurements of the t (t) over bar charge asymmetry A(C) in 20.3 fb(-1) of root s = 8 TeV pp collisions recorded by the ATLAS experiment at the Large Hadron Collider at CERN. Three differential measurements are performed as a function of the invariant mass, transverse momentum and longitudinal boost of the t (t) over bar system. The t (t) over bar pairs are selected in the single-lepton channels (e or mu) with at least four jets, and a likelihood fit is used to reconstruct the t (t) over bar event kinematics. A Bayesian unfolding procedure is performed to infer the asymmetry at parton level from the observed data distribution. The inclusive t (t) over bar charge asymmetry is measured to be A(C) = 0.009 +/- 0.005 (stat. + syst.). The inclusive and differential measurements are compatible with the values predicted by the Standard Model.
The number of charged particles inside jets is a widely used discriminant for identifying the quark or gluon nature of the initiating parton and is sensitive to both the perturbative and non-perturbative components of fragmentation. This paper presents a measurement of the average number of charged particles with >500 pT> 500 MeV MeV inside high-momentum jets in dijet events using 20.3 fb-1 of data recorded with the ATLAS detector in pp collisions at √s = 8 TeV collisions at the LHC. The jets considered have transverse momenta from 50 GeV up to and beyond 1.5 TeV. The reconstructed charged-particle track multiplicity distribution is unfolded to remove distortions from detector effects and the resulting charged-particle multiplicity is compared to several models. Furthermore, quark and gluon jet fractions are used to extract the average charged-particle multiplicity for quark and gluon jets separately. © 2016, CERN for the benefit of the ATLAS collaboration.
A measurement of the correlations between the polar angles of leptons from the decay of pair-produced t and (t) over bar quarks in the helicity basis is reported, using proton-proton collision data collected by the ATLAS detector at the LHC. The dataset corresponds to an integrated luminosity of 4.6 fb(-1) at a center-of-mass energy of root s = 7 TeV collected during 2011. Candidate events are selected in the dilepton topology with large missing transverse momentum and at least two jets. The angles theta(1) and theta(2) between the charged leptons and the direction of motion of the parent quarks in the t (t) over bar rest frame are sensitive to the spin information, and the distribution of cos theta(1).cos theta(2) is sensitive to the spin correlation between the t and (t) over bar quarks. The distribution is unfolded to parton level and compared to the next-to-leading order prediction. A good agreement is observed.
The CP-violating weak phase φs of the Bs0 meson and the decay width difference δΓs of the Bs0 light and heavy mass eigenstates are measured with the CMS detector at the LHC using a data sample of Bs0→J/ψφ(1020)→μ+μ-K+K- decays. The analysed data set corresponds to an integrated luminosity of 19.7fbsup-1/sup collected in pp collisions at a centre-of-mass energy of 8TeV. A total of 49 200 reconstructed Bs0 decays are used to extract the values of φs and δΓs by performing a time-dependent and flavour-tagged angular analysis of the μsup+/supμsup-/supKsup+/supKsup-/sup final state. The weak phase is measured to be φs=-0.075±0.097(stat)±0.031(syst) rad, and the decay width difference is δΓs=0.095±0.013(stat)±0.007(syst) pssup-1/sup. © 2016 CERN for the benefit of the CMS Collaboration.
The relationship between jet production in the central region and the underlying-event activity in a pseudorapidity-separated region is studied in 4.0 pbsup-1/sup of s=2.76 TeV pp collision data recorded with the ATLAS detector at the LHC. The underlying event is characterised through measurements of the average value of the sum of the transverse energy at large pseudorapidity downstream of one of the protons, which are reported here as a function of hard-scattering kinematic variables. The hard scattering is characterised by the average transverse momentum and pseudorapidity of the two highest transverse momentum jets in the event. The dijet kinematics are used to estimate, on an event-by-event basis, the scaled longitudinal momenta of the hard-scattered partons in the target and projectile beam-protons moving toward and away from the region measuring transverse energy, respectively. Transverse energy production at large pseudorapidity is observed to decrease with a linear dependence on the longitudinal momentum fraction in the target proton and to depend only weakly on that in the projectile proton. The results are compared to the predictions of various Monte Carlo event generators, which qualitatively reproduce the trends observed in data but generally underpredict the overall level of transverse energy at forward pseudorapidity. © 2016 CERN for the benefit of the ATLAS Collaboration.
The differential cross-section for pair production of top quarks with high transverse momentum is measured in 20.3 fb-1 of proton-proton collisions at a center-of-mass energy of 8 TeV. The measurement is performed for tt¯ events in the lepton+jets channel. The cross-section is reported as a function of the hadronically decaying top quark transverse momentum for values above 300 GeV. The hadronically decaying top quark is reconstructed as an anti-kt jet with radius parameter R=1.0 and identified with jet substructure techniques. The observed yield is corrected for detector effects to obtain a cross-section at particle level in a fiducial region close to the event selection. A parton-level cross-section extrapolated to the full phase space is also reported for top quarks with transverse momentum above 300 GeV. The predictions of a majority of next-to-leading-order and leading-order matrix-element Monte Carlo generators are found to agree with the measured cross-sections. © 2016 CERN.
The production rates of prompt and non-prompt J/psi and psi(2S) mesons in their dimuon decay modes are measured using 2.1 and 11.4 fb(-1) of data collected with the ATLAS experiment at the Large Hadron Collider, in proton-proton collisions at root s = 7 and 8 respectively. Production cross-sections for prompt as well as non-prompt sources, ratios of psi(2S) to J/psi production, and the fractions of non-prompt production for J/psi and psi(2S) are measured as a function of meson transverse momentum and rapidity. The measurements are compared to theoretical predictions.
The NEMO-3 experiment at the Modane Underground Laboratory investigates the double-beta decay of Ca-48. Using 5.25 yr of data recorded with a 6.99 g sample of Ca-48, approximately 150 double-beta decay candidate events are selected with a signal-to-background ratio greater than 3. The half-life for the two-neutrino double-beta decay of Ca-48 is measured to be T-1/2(2v) = [6.4(-0.6)(+0.7)(stat)(-0.6)(+0.7)(syst)] x 10(19) yr. A search for neutrinoless double-beta decay of Ca-48 yields a null result, and a corresponding lower limit on the half-life is found to be T-1/2(0v) 2.0 x 10(22) yr at 90% confidence level, translating into an upper limit on the effective Majorana neutrino mass of m(beta beta) 6.0-26 eV, with the range reflecting different nuclear matrix element calculations. Limits are also set on models involving Majoron emission and right-handed currents.
The double-differential inclusive jet cross section is measured as a function of jet transverse momentum pT and absolute rapidity |y|, using proton-proton collision data collected with the CMS experiment at the LHC, at a center-of-mass energy of √s = 2.76 TeV and corresponding to an integrated luminosity of 5.43 pb-1. Jets are reconstructed within the pT range of 74 to 592 GeV and the rapidity range |y|<3.0. The reconstructed jet spectrum is corrected for detector resolution. The measurements are compared to the theoretical prediction at next-to-leading-order QCD using different sets of parton distribution functions. This inclusive cross section measurement explores a new kinematic region and is consistent with QCD predictions. © 2016, CERN for the benefit of the CMS collaboration.
The inelastic hadronic cross section in proton–lead collisions at a centre-of-mass energy per nucleon pair of 5.02 TeV is measured with the CMS detector at the LHC. The data sample, corresponding to an integrated luminosity of L=12.6±0.4 nb−1, has been collected with an unbiased trigger for inclusive particle production. The cross section is obtained from the measured number of proton–lead collisions with hadronic activity produced in the pseudorapidity ranges 3<η<5 and/or −5<η<−3, corrected for photon-induced contributions, experimental acceptance, and other instrumental effects. The inelastic cross section is measured to be σinel(pPb)=2061±3(stat)±34(syst)±72(lumi) mb. Various Monte Carlo generators, commonly used in heavy ion and cosmic ray physics, are found to reproduce the data within uncertainties. The value of σinel(pPb) is compatible with that expected from the proton–proton cross section at 5.02 TeV scaled up within a simple Glauber approach to account for multiple scatterings in the lead nucleus, indicating that further net nuclear corrections are small. © 2016 The Author
The cross-section for the production of a single top quark in association with a W boson in proton-proton collisions at √s = 8TeV is measured. The dataset corresponds to an integrated luminosity of 20.3 fbsup−1/sup, collected by the ATLAS detector in 2012 at the Large Hadron Collider at CERN. Events containing two leptons and one central b-jet are selected. The W t signal is separated from the backgrounds using boosted decision trees, each of which combines a number of discriminating variables into one classifier. Production of W t events is observed with a significance of 7.7σ. The cross-section is extracted in a profile likelihood fit to the classifier output distributions. The W t cross-section, inclusive of decay modes, is measured to be 23.0 ± 1.3(stat.)− 3.5 sup+ 3.2/sup(syst.)±1.1(lumi.) pb. The measured cross-section is used to extract a value for the CKM matrix element |Vtb| of 1.01 ± 0.10 and a lower limit of 0.80 at the 95% confidence level. The cross-section for the production of a top quark and a W boson is also measured in a fiducial acceptance requiring two leptons with pT> 25 GeV and |η| < 2.5, one jet with pT> 20 GeV and |η| < 2.5, and ET supmiss/sup > 20 GeV, including both W t and top-quark pair events as signal. The measured value of the fiducial cross-section is 0.85 ± 0.01(stat.)− 0.07 sup+ 0.07/sup(syst.)±0.03(lumi.) pb. © 2016, The Author(s).
A measurement of the ratio of the branching fractions of the Bs0 meson to J/ψf0(980) and to J/ψφ(1020) is presented. The J/ψ, f0(980), and φ(1020) are observed through their decays to μsup+/supμsup-/sup, πsup+/supπsup-/sup, and Ksup+/supKsup-/sup, respectively. The f0 and the φ are identified by requiring |Mπ+π--974 MeV|<50 MeV and |MK+K--1020 MeV|<10 MeV. The analysis is based on a data sample of pp collisions at a centre-of-mass energy of 7 TeV, collected by the CMS experiment at the LHC, corresponding to an integrated luminosity of 5.3 fbsup-1/sup. The measured ratio is B(Bs sup0/sup→J/ψf0)B(f0→πsup+/supπsup-/sup)/B(Bs sup0/sup→J/ψφ)B(φ→Ksup+/supKsup-/sup) = 0.140±0.008(stat) ± 0.023(syst), where the first uncertainty is statistical and the second is systematic. © 2016 CERN for the benefit of the CMS Collaboration.
Abstract: This paper presents the measurement of the relative width difference ΔΓd/Γd of the B0‐ B¯ 0 system using the data collected by the ATLAS experiment at the LHC in pp collisions at s=7 TeV and s=8 TeV and corresponding to an integrated luminosity of 25.2 fb−1. The value of ΔΓd/Γd is obtained by comparing the decay-time distributions of B0 → J/ψKS and B0 → J/ψK*0(892) decays. The result is ΔΓd/Γd = (−0.1±1.1 (stat.)± 0.9 (syst.)) × 10−2. Currently, this is the most precise single measurement of ΔΓd/Γd. It agrees with the Standard Model prediction and the measurements by other experiments.[Figure not available: see fulltext.] © 2016, The Author(s).
A new set of measurements of the top quark mass are presented, based on the proton-proton data recorded by the CMS experiment at the LHC at root s = 8 TeV corresponding to a luminosity of 19.7 fb(-1). The top quark mass is measured using the lepton + jets, all-jets and dilepton decay channels, giving values of 172.35 +/- 0.16(stat) +/- 0.48(syst) GeV, 172.32 +/- 0.25(stat) +/- 0.59(syst) GeV, and 172.82 +/- 0.19(stat) +/- 1.22(syst) GeV, respectively. When combined with the published CMS results at s = 7 TeV, they provide a top quark mass measurement of 172.44 +/- 0.13(stat) +/- 0.47(syst) GeV. The top quark mass is also studied as a function of the event kinematical properties in the lepton + jets decay channel. No indications of a kinematic bias are observed and the collision data are consistent with a range of predictions from current theoretical models of t (t) over bar production.
The top quark pair production cross section is measured for the first time in proton-proton collisions at root s = 13 TeV by the CMS experiment at the CERN LHC, using data corresponding to an integrated luminosity of 43 pb(-1). The measurement is performed by analyzing events with at least one electron and one muon of opposite charge, and at least two jets. The measured cross section is 746 +/- 58(stat) +/- 53(syst) +/- 36(lumi) pb, in agreement with the expectation from the standard model.
Distributions of transverse momentum p(T)(ll) and the related angular variable phi(eta)*. of Drell-Yan lepton pairs are measured in 20.3 fb(-1) of proton-proton collisions at root s = 8 TeV with the ATLAS detector at the LHC. Measurements in electron-pair and muon-pair final states are corrected for detector effects and combined. Compared to previous measurements in proton-proton collisions at root s = 7 TeV, these new measurements benefit from a larger data sample and improved control of systematic uncertainties. Measurements are performed in bins of lepton-pair mass above, around and below the Z-boson mass peak. The data are compared to predictions from perturbative and resummed QCD calculations. For values of phi(eta)*. 1 the predictions from the Monte Carlo generator ResBos are generally consistent with the data within the theoretical uncertainties. However, at larger values of phi(eta)*. this is not the case. Monte Carlo generators based on the parton-shower approach are unable to describe the data over the full range of p(T)(ll) while the fixed-order prediction of Dynnlo falls below the data at high values of p(T)(ll). ResBos and the parton-shower Monte Carlo generators provide a much better description of the evolution of the phi(eta)*. and p(T)(ll) distributions as a function of lepton-pair mass and rapidity than the basic shape of the data.
The cross section for (Formula presented.) production in the all-jets final state is measured in pp collisions at a centre-of-mass energy of 8 (Formula presented.) at the LHC with the CMS detector, in data corresponding to an integrated luminosity of 18.4 (Formula presented.). The inclusive cross section is found to be (Formula presented.) (Formula presented.). The normalized differential cross sections are measured as a function of the top quark transverse momenta, (Formula presented.) , and compared to predictions from quantum chromodynamics. The results are reported at detector, parton, and particle levels. In all cases, the measured top quark (Formula presented.) spectra are significantly softer than theoretical predictions. © 2016, CERN for the benefit of the CMS collaboration.
The ZZ production cross section in proton-proton collisions at 13 TeV center-of-mass energy is measured using 3.2 fb(-1) of data recorded with the ATLAS detector at the Large Hadron Collider. The considered Z boson candidates decay to an electron or muon pair of mass 66-116 GeV. The cross section is measured in a fiducial phase space reflecting the detector acceptance. It is also extrapolated to a total phase space for Z bosons in the same mass range and of all decay modes, giving 16.7(-2.0)(+2.2) (stat)(-0.7)(+0.9) (syst)(-0.7)(+1.0) (lumi) pb. The results agree with standard model predictions.
A first measurement of the top quark spin asymmetry, sensitive to the top quark polarisation, in t-channel single top quark production is presented. It is based on a sample of pp collisions at a centre-of-mass energy of 8 TeV corresponding to an integrated luminosity of 19.7 fbsup−1/sup. A high-purity sample of t-channel single top quark events with an isolated muon is selected. Signal and background components are estimated using a fit to data. A differential cross section measurement, corrected for detector effects, of an angular observable sensitive to the top quark polarisation is performed. The differential distribution is used to extract a top quark spin asymmetry of 0.26 ± 0.03(stat) ± 0.10(syst), which is compatible with a p-value of 4.6% with the standard model prediction of 0.44. © 2016, The Author(s).
Abstract: An analysis of dijet events in PbPb and pp collisions is performed to explore the properties of energy loss by partons traveling in a quark-gluon plasma. Data are collected at a nucleon-nucleon center-of-mass energy of 2.76 TeV at the LHC. The distribution of transverse momentum (pT) surrounding dijet systems is measured by selecting charged particles in different ranges of pT and at different angular cones of pseudorapidity and azimuth. The measurement is performed as a function of centrality of the PbPb collisions, the pT asymmetry of the jets in the dijet pair, and the distance parameter R used in the anti-kT jet clustering algorithm. In events with unbalanced dijets, PbPb collisions show an enhanced multiplicity in the hemisphere of the subleading jet, with the pT imbalance compensated by an excess of low-pT particles at large angles from the jet axes. © 2016, The Author(s).
Fiducial cross-sections for tt¯ production with one or two additional b-jets are reported, using an integrated luminosity of 20.3 fb-1 of proton–proton collisions at a centre-of-mass energy of 8 TeV at the Large Hadron Collider, collected with the ATLAS detector. The cross-section times branching ratio for tt¯ events with at least one additional b-jet is measured to be 950 ± 70 (stat.) -190 +240 (syst.) fb in the lepton-plus-jets channel and 50 ± 10 (stat.) -10 +15 (syst.) fb in the eμ channel. The cross-section times branching ratio for events with at least two additional b-jets is measured to be 19.3 ± 3.5 (stat.) ± 5.7 (syst.) fb in the dilepton channel (eμ, μμ, and ee) using a method based on tight selection criteria, and 13.5 ± 3.3 (stat.) ± 3.6 (syst.) fb using a looser selection that allows the background normalisation to be extracted from data. The latter method also measures a value of 1.30 ± 0.33 (stat.) ± 0.28 (syst.)% for the ratio of tt¯ production with two additional b-jets to tt¯ production with any two additional jets. All measurements are in good agreement with recent theory predictions. © 2016, CERN for the benefit of the ATLAS collaboration.
The four-lepton (4ℓ, ℓ=e, μ) production cross section is measured in the mass range from 80 to 1000 GeV using 20.3 fb-1 of data in pp collisions at s=8 TeV collected with the ATLAS detector at the LHC. The 4ℓ events are produced in the decays of resonant Z and Higgs bosons and the non-resonant ZZ continuum originating from qq-, gg, and qg initial states. A total of 476 signal candidate events are observed with a background expectation of 26.2±3.6 events, enabling the measurement of the integrated cross section and the differential cross section as a function of the invariant mass and transverse momentum of the four-lepton system. In the mass range above 180 GeV, assuming the theoretical constraint on the qq- production cross section calculated with perturbative NNLO QCD and NLO electroweak corrections, the signal strength of the gluon-fusion component relative to its leading-order prediction is determined to be μgg=2.4±1.0 (stat.)±0.5 (syst.)±0.8 (theory). © 2015 CERN for the benefit of the ATLAS Collaboration.
Measurements of the top quark-antiquark (t (t) over bar) spin correlations and the top quark polarization are presented for t (t) over bar pairs produced in pp collisions at root s = 8 TeV. The data correspond to an integrated luminosity of 19.5 fb(-1) collected with the CMS detector at the LHC. The measurements are performed using events with two oppositely charged leptons (electrons or muons) and two or more jets, where at least one of the jets is identified as originating from a bottom quark. The spin correlations and polarization are measured from the angular distributions of the two selected leptons, both inclusively and differentially, with respect to the invariant mass, rapidity, and transverse momentum of the t (t) over bar system. The measurements are unfolded to the parton level and found to be in agreement with predictions of the standard model. A search for new physics in the form of anomalous top quark chromo moments is performed. No evidence of new physics is observed, and exclusion limits on the real part of the chromo-magnetic dipole moment and the imaginary part of the chromo-electric dipole moment are evaluated.
Combined analyses of the Higgs boson production and decay rates as well as its coupling strengths to vector bosons and fermions are presented. The combinations include the results of the analyses of the H → γγ, ZZ∗, WW∗, Zγ, bb, ττ and μμ decay modes, and the constraints on the associated production with a pair of top quarks and on the off-shell coupling strengths of the Higgs boson. The results are based on the LHC proton-proton collision datasets, with integrated luminosities of up to 4.7 fb-1 at √S =7 TeV and 20.3 fb-1 at √S = 8 TeV, recorded by the ATLAS detector in 2011 and 2012. Combining all production modes and decay channels, the measured signal yield, normalised to the Standard Model expectation, is 1.18+0.15 -0.14. The observed Higgs boson production and decay rates are interpreted in a leading-order coupling framework, exploring a wide range of benchmark coupling models both with and without assumptions on the Higgs boson width and on the Standard Model particle content in loop processes. The data are found to be compatible with the Standard Model expectations for a Higgs boson at a mass of 125.36 GeV for all models considered. © 2015, The Author(s).
The charge asymmetry in tt‾ events is measured using dilepton final states produced in pp collisions at the LHC at s=8TeV. The data sample, collected with the CMS detector, corresponds to an integrated luminosity of 19.5fb−1. The measurements are performed using events with two oppositely charged leptons (electrons or muons) and two or more jets, where at least one of the jets is identified as originating from a bottom quark. The charge asymmetry is measured from differences in kinematic distributions, unfolded to the parton level, of positively and negatively charged top quarks and leptons. The tt‾ and leptonic inclusive charge asymmetries are found to be 0.011±0.011(stat)±0.007(syst) and 0.003±0.006(stat)±0.003(syst), respectively. These results, as well as charge asymmetry measurements made as a function of the invariant mass, rapidity, and transverse momentum of the tt‾ system, are in agreement with predictions of the standard model. © 2016 The Author(s)
This paper presents measurements of W(+/-)Z production in pp collisions at a center-of-mass energy of 8 TeV. The gauge bosons are reconstructed using their leptonic decay modes into electrons and muons. The data were collected in 2012 by the ATLAS experiment at the Large Hadron Collider and correspond to an integrated luminosity of 20.3 fb(-1). The measured inclusive cross section in the detector fiducial region is sigma W(+/-)Z - l'nu ll = 35.1 +/- 0.9(stat) +/- 0.8(sys) +/- 0.8(lumi) fb, for one leptonic decay channel. In comparison, the next-to-leading-order Standard Model expectation is 30.0 +/- 2.1 fb. Cross sections for W(+)Z and W(-)Z production and their ratio are presented as well as differential cross sections for several kinematic observables. Limits on anomalous triple gauge boson couplings are derived from the transverse mass spectrum of the W(+/-)Z system. From the analysis of events with a W and a Z boson associated with two or more forward jets an upper limit at 95% confidence level on the W(+/-)Z scattering cross section of 0.63 fb, for each leptonic decay channel, is established, while the Standard Model prediction at next-to-leading order is 0.13 +/- 0.01 fb. Limits on anomalous quartic gauge boson couplings are also extracted.
The production of Z bosons with one or two isolated high-energy photons is studied using pp collisions at root s = 8 TeV. The analyses use a data sample with an integrated luminosity of 20.3 fb(-1) collected by the ATLAS detector during the 2012 LHC data taking. The Z gamma and Z gamma gamma production cross sections are measured with leptonic (e(+) e(-), mu(+) mu(-), nu(nu) over bar) decays of the Z boson, in extended fiducial regions defined in terms of the lepton and photon acceptance. They are then compared to cross-section predictions from the Standard Model, where the sources of the photons are radiation off initial-state quarks and radiative Z-boson decay to charged leptons, and from fragmentation of final-state quarks and gluons into photons. The yields of events with photon transverse energy E-T 250 GeV from l(+) l(-) gamma events and with E-T 400 GeV from nu(nu) over bar gamma events are used to search for anomalous triple gauge-boson couplings ZZ gamma and Z gamma gamma. The yields of events with diphoton invariant mass m(gamma gamma) 200 GeV from l(+) l(-) gamma gamma events and with m(gamma gamma) 300 GeV from nu(nu) over bar gamma gamma events are used to search for anomalous quartic gauge-boson couplings ZZ gamma gamma and Z gamma gamma gamma. No deviations from Standard Model predictions are observed and limits are placed on parameters used to describe anomalous triple and quartic gauge-boson couplings.
Fusion research is driven by the applied goal of energy production from fusion reactions. There is, however, a wealth of fundamental physics to be discovered and studied along the way. This Commentary discusses selected developments in diagnostics and present-day research topics in high-temperature plasma physics.
Nanostructure evolution during ion irradiation of two thermally aged binary Fee22Cr alloys has been investigated using atom probe tomography. Specimens aged at 500 °C for 50 and 200 h were irradiated by 5.6 MeV Fe ions at room temperature up to fluences of 0.3 × 10sup15/sup ions/cmsup2/sup and 1 × 10sup15/sup ions/cmsup2/sup. The effect of irradiation on the material nanostructure was examined at a depth of 1 μm from the irradiated surface. The analysis of Cr radial concentration functions reveals that dense α′-phase precipitates in the 200 h aged alloy become diffuse and thereby larger when subjected to irradiation. On the other hand, less Cr-enriched precipitates in the alloy aged for 50 h are less affected. The CreCr pair correlation function analysis shows that matrix inhomogeneity decreases under irradiation. Irradiation leads to a decrease in the number density of diffuse clusters, whereas in the case of well-developed precipitates it remains unchanged. © 2016 Published by Elsevier B.V.
We introduce an approach toward the synthesis of micro- and nanostructures under nonequilibrium microwave discharges within metal-dielectric powder mixtures induced by powerful microwave gyrotron radiation. A new plasma-chemical reactor capable of sustaining a discharge regime with an afterglow phase of an order of magnitude longer than the gyrotron pulse duration was constructed for these experiments. In the nonequilibrium conditions of such a discharge, plasma-induced exothermic chemical reactions leading to the synthesis of various compounds were initiated. The synthesized structures were deposited on the reactor walls and on the impurity particles within the reactor. This method was tested under gyrotron-initiated discharges within various metal-dielectric powder mixtures of titanium-boron, molybdenum-boron, titanium-silicon-boron, molybdenum-boron nitride, molybdenum-tungsten-boron nitride, and so on. Depending on the powder mixture composition, reactor atmosphere, and other parameters, micro- and nanosized particles of boron nitride, titanium diboride, molybdenum boride, titanium boride, molybdenum, and molybdenum oxide, were synthesized, detected, and analyzed. © 2015 Society of Photo-Optical Instrumentation Engineers (SPIE).
A theory of above-threshold ionization of atoms by a strong laser field is formulated. Two versions of the strong-field approximation (SFA) are considered, the direct SFA and the improved SFA, which do not and do, respectively, take into account rescattering of the freed electron off the parent ion. The atomic bound state is included in two different ways: as an expansion in terms of Slater-type orbitals or as an asymptotic wave function. Even though we are using the single-active-electron approximation, multielectron effects are taken into account in twoways: by a proper choice of the ground state and by an adequate definition of the ionization rate. For the case of the asymptotic bound-state wave functions, using the saddle-point method, a simple expression for the T-matrix element is derived for both the direct and the improved SFA. The theory is applied to ionization by a bicircular field, which consists of two coplanar counterrotating circularly polarized components with frequencies that are integer multiples of a fundamental frequency omega. Special emphasis is on the omega-2 omega case. In this case, the threefold rotational symmetry of the field carries over to the velocity map of the liberated electrons, for both the direct and the improved SFA. The results obtained are analyzed in detail using the quantum-orbit formalism, which gives good physical insight into the above-threshold ionization process. For this purpose, a specific classification of the saddle-point solutions is introduced for both the backward-scattered and the forward-scattered electrons. The high-energy backward-scattering quantum orbits are similar to those discovered for high-order harmonic generation. The short forward-scattering quantum orbits for a bicircular field are similar to those of a linearly polarized field. The conclusion is that these orbits are universal, i.e., they do not depend much on the shape of the laser field.
Trapped field magnets are usually constructed on the base of bulk YBCO superconductors. However, recent achievements in the production of long-size coated conductors have opened the opportunity of using a tape stack for these applications. Better thermal conductivity, mechanical stability in high fields, and high critical current densities make such systems favorable. Moreover, the tape form of the conductor allows for organizing different spatial structures and optimizing device design. Trapped field was measured on the stack of high-temperature superconducting tapes in this work. An industrially stabilized (with copper shield) tape, which was produced by SuperOx company with GdBa2Cu3O7-x superconductor inside, was used in experiments. The stack was made of 12-mm-diameter disk-shaped tapes, and the height was 20 layers. Magnetization was carried out by an 8-T superconducting magnet on the temperature of 77 K. To calculate the trapped field of a stack, field dependence and angular field dependence of critical current were measured on these tapes. The finite-element method was used for numerical simulations. It is shown that taking into account the magnetic field orientation in different areas of the stack leads to better agreement with the experimental measured trapped field values.
The miniature gamma counter based on a cylindrical LaBr3(Ce) crystal (5 mm diameter and 10 mm length) and SensL FC30035 silicon photomultiplier (SiPM) is introduced. The main counter characteristics such as relative efficiency, LaBr3(Ce) self-radioactivity and energy resolution are presented. Capability of using such detector for gamma spectrometry applications is discussed.
Abstract: In this paper we study some properties of the newly found Arnold-Beltrami flux-brane solutions to the minimal D = 7 supergravity. To this end we first single out the appropriate Free Differential Algebra containing both a gauge 3-form Bsup[3]/sup and a gauge 2-form Bsup[2]/sup: then we present the complete rheonomic parametrization of all the generalized curvatures. This allows us to identify two-brane configurations with Arnold-Beltrami fluxes in the transverse space with exact solutions of supergravity and to analyze the Killing spinor equation in their background. We find that there is no preserved supersymmetry if there are no additional translational Killing vectors. Guided by this principle we explicitly construct Arnold-Beltrami flux two-branes that preserve 0, 18 and 14 of the original supersymmetry. Two-branes without fluxes are instead BPS states and preserve 12 supersymmetry. For each two-brane solution we carefully study its discrete symmetry that is always given by some appropriate crystallographic group Γ. Such symmetry groups Γ are transmitted to the D = 3 gauge theories on the brane world-volume that would occur in the gauge/gravity correspondence. Furthermore we illustrate the intriguing relation between gauge fluxes in two-brane solutions and hyperinstantons in D = 4 topological sigma-models. © 2016, The Author(s).
It was noted earlier [1] that high performance regimes of many tokamaks were achieved in the condition of plasma heating power P H limited from above. The exceeding of this limit usually ended as a plasma collapse. The analysis of the high performance regimes of well known tokamaks which operated during the last 50 years has shown that the values of such 'permissible' P H grow approximately linearly with the area S of the first wall surface facing to the plasma. The paper attempts to explain the existence the P H/S limit for high performance tokamak regimes as a consequence of the vacuum breakdown of the plasma sheath in the area of a plasma contact with the vessel wall and unipolar arcs which followed it. © 2016 IOP Publishing Ltd.
V. D. Shafranov was a key person in the fusion program. The paper presents the recollections of one of his close colleagues about Shafranov's impact on the early days of tokamak research.
Quantum-electrodynamic cascade generation is numerically simulated for the case of the oblique collision of a beam of ultrarelativistic electrons with the field of two counterpropagating, focused, circularly polarised laser pulses. It is shown that although the 'collapse and revival' effect is observed at any value of the collision angle, the multiplicity of the cascade essentially depends on this angle and is maximal in the configuration, when the electron beam hits the focus perpendicularly to the optical axis of the laser pulses. © 2016 Kvantovaya Elektronika and Turpion Ltd.
Physical models of specific heat at constant volume and thermal conductivity of uranium dioxide are developed based on phonon spectrum data. It is explained an abnormal growth of thermal conductivity coefficient of oxide nuclear fuel in high temperature region. It is shown that the contribution from charge carrier's degrees of freedom into observed thermal conductivity coefficient of uranium dioxide can be neglected up to melting point. Developed models of thermophysical properties do not contain fitting parameters.
A theoretical investigation of the modulation instability (MI) in the three core triangular oppositely directed coupler with negative index material channel is presented. This class of couplers have an effective feedback mechanism due to the opposite directionality of the phase velocities in the negative and positive index channels. It is found that the MI in the nonlinear three core triangular oppositely directed coupler is significantly influenced by the ratio of the forward- to backward-propagating wave power and nonlinearity. Also, in the case of the normal dispersion regime a threshold-like behavior is observed, whereas this behavior is not identified in the anomalous dispersion regime. For the asymmetric case (h ≠1), two pairs of instability bands are observed for both the nonlinear NIM and PIM channels, while a single pair of instability bands is noted for the symmetric case (h = 1). In the normal dispersion regime, the defocusing nonlinearity is found to suppress the MI by reducing both the gain and width of the instability band, whereas the MI is enhanced in the anomalous dispersion regime due to the defocusing nonlinearity. Thus we report new ways to generate and manipulate the MI and solitons in threecore triangular oppositely directed couplers with a particular emphasis on a negative-index material (NIM) channel. © 2016 IOP Publishing Ltd Printed in the UK.
Strong discontinuities in solutions of the gas dynamic equations under isentropic conditions, i.e., with continuity of entropy at the discontinuity, are examined. Solutions for a standard shock wave with continuity of energy at the discontinuity are compared with those for an isentropic "shock wave." It is shown that numerical simulation of astrophysical problems in which high-amplitude shock waves are encountered (supernova explosions, modelling of jets) with conservation of entropy, rather than of energy, leads to large errors in the shock calculations. The isentropic equations of gas dynamics can be used only when there are no strong discontinuities in the solution or when the intensity of the shocks is not high and they do not significantly affect the flow.
The multi-strange baryon yields in PbPb collisions have been shown to exhibit an enhancement relative to pp reactions. In this work, Ξ and Ω production rates have been measured with the ALICE experiment as a function of transverse momentum, pT, in pPb collisions at a centre-of-mass energy of sNN=5.02 TeV. The results cover the kinematic ranges 0.6 GeV/c<pT<7.2 GeV/c and 0.8 GeV/c<pT<5 GeV/c, for Ξ and Ω respectively, in the common rapidity interval -0.5<yCMS<0. Multi-strange baryons have been identified by reconstructing their weak decays into charged particles. The pT spectra are analysed as a function of event charged-particle multiplicity, which in pPb collisions ranges over one order of magnitude and lies between those observed in pp and PbPb collisions. The measured pT distributions are compared to the expectations from a Blast-Wave model. The parameters which describe the production of lighter hadron species also describe the hyperon spectra in high multiplicity pPb collisions. The yield of hyperons relative to charged pions is studied and compared with results from pp and PbPb collisions. A continuous increase in the yield ratios as a function of multiplicity is observed in pPb data, the values of which range from those measured in minimum bias pp to the ones in PbPb collisions. A statistical model qualitatively describes this multiplicity dependence using a canonical suppression mechanism, in which the small volume causes a relative reduction of hadron production dependent on the strangeness content of the hyperon. © 2016 The Author(s).
Three- and four-pionBose-Einstein correlations are presented in pp, p-Pb, and Pb-Pb collisions at the LHC. We compare our measured four-pion correlations to the expectation derived from two-and three-pion measurements. Such a comparison provides a method to search for coherent pion emission. We also present mixed-charge correlations in order to demonstrate the effectiveness of several analysis procedures such as Coulomb corrections. Same-charge four-pion correlations in pp and p-Pb appear consistent with the expectations from three-pion measurements. However, the presence of non-negligible background correlations in both systems prevent a conclusive statement. In Pb-Pb collisions, we observe a significant suppression of three-and four-pion Bose-Einstein correlations compared to expectations from two-pionmeasurements. There appears to be no centrality dependence of the suppression within the 0%-50% centrality interval. The origin of the suppression is not clear. However, by postulating either coherent pion emission or large multibody Coulomb effects, the suppression may be explained.
We report on two-particle charge-dependent correlations in pp, p-Pb, and Pb-Pb collisions as a function of the pseudorapidity and azimuthal angle difference, Delta eta and Delta phi respectively. These correlations are studied using the balance function that probes the charge creation time and the development of collectivity in the produced system. The dependence of the balance function on the event multiplicity as well as on the trigger and associated particle transversemomentum (p(T)) in pp, p-Pb, and Pb-Pb collisions at root s(NN) = 7, 5.02, and 2.76 TeV, respectively, are presented. In the low transverse momentum region, for 0.2 p(T) 2.0 GeV/c, the balance function becomes narrower in both Delta eta and Delta phi directions in all three systems for events with higher multiplicity. The experimental findings favor models that either incorporate some collective behavior (e.g. AMPT) or different mechanisms that lead to effects that resemble collective behavior (e.g. PYTHIA8 with color reconnection). For higher values of transverse momenta the balance function becomes even narrower but exhibits no multiplicity dependence, indicating that the observed narrowing with increasing multiplicity at low pT is a feature of bulk particle production.
The production of charged pions, kaons and (anti)protons has been measured at mid-rapidity (−0.5<y<0) in p–Pb collisions at sNN=5.02 TeV using the ALICE detector at the LHC. Exploiting particle identification capabilities at high transverse momentum (pT), the previously published pT spectra have been extended to include measurements up to 20 GeV/c for seven event multiplicity classes. The pT spectra for pp collisions at s=7 TeV, needed to interpolate a pp reference spectrum, have also been extended up to 20 GeV/c to measure the nuclear modification factor (RpPb) in non-single diffractive p–Pb collisions. At intermediate transverse momentum (2<pT<10 GeV/c) the proton-to-pion ratio increases with multiplicity in p–Pb collisions, a similar effect is not present in the kaon-to-pion ratio. The pT dependent structure of such increase is qualitatively similar to those observed in pp and heavy-ion collisions. At high pT (>10 GeV/c), the particle ratios are consistent with those reported for pp and Pb–Pb collisions at the LHC energies. At intermediate pT the (anti)proton RpPb shows a Cronin-like enhancement, while pions and kaons show little or no nuclear modification. At high pT the charged pion, kaon and (anti)proton RpPb are consistent with unity within statistical and systematic uncertainties. © 2016 The Author
This article documents the performance of the ATLAS muon identification and reconstruction using the LHC dataset recorded at root s = 13 TeVin 2015. Using a large sample of J/.psi - mu mu and Z - mu mu decays from 3.2 fb(-1) of pp collision data, measurements of the reconstruction efficiency, as well as of the momentum scale and resolution, are presented and compared to Monte Carlo simulations. The reconstruction efficiency is measured to be close to 99 % over most of the covered phase space (vertical bar eta vertical bar 2.5 and 5 p(T) 100 GeV). The isolation efficiency varies between 93 and 100 % depending on the selection applied and on the momentum of the muon. Both efficiencies are well reproduced in simulation. In the central region of the detector, the momentum resolution is measured to be 1.7 % (2.3 %) for muons from J/psi - mu mu(Z - mu mu) decays, and the momentum scale is known with an uncertainty of 0.05 %. In the region vertical bar eta vertical bar 2.2, the p(T) resolution for muons from Z - mu decays is 2.9 % while the precision of the momentum scale for low-p(T) muons from J/psi - mu mu decays is about 0.2 %.
Excellent mechanical properties of ODS steels are directly related to the high density of homogeneously distributed, well-formed oxide particles (such as Y2O3, or Y-Ti-O). However, atom probe tomography study of ODS steels revealed that in addition they contain almost a hundred times more nanoclusters enriched in Y, O and V/Ti (if present in the alloy composition) than larger oxide particles.In this work, we carried out atom probe tomography (APT) and transmission electron microscopy (TEM) studies of three different ODS steels produced by mechanical alloying: ODS Eurofer, 13.5Cr ODS and 13.5Cr-0.3Ti ODS. These materials were investigated after irradiation with Fe (5.6MeV) or Ti (4.8MeV) ions up to 10sup15/sup ion/cmsup2/sup and part of them up to 3×10sup15/sup ion/cmsup2/sup. In all cases, areas for TEM investigation were cut at a depth of ∼ 1.3μm from the irradiated surface corresponding to the peak of the radiation damage dose. It was shown that after irradiation at RT and at 300°S the number density of oxide particles in all the samples grew up. Meanwhile, the fraction of small particles in the size distribution has increased. APT revealed an essential increase in nanoclusters number and a change of their chemical composition at the same depth. The nanostructure was the most stable in 13.5Cr-0.3Ti ODS irradiated at 300°S: the increase of the fraction of small oxides was minimal and no change of nanocluster chemical composition was detected. © 2016.
We propose an intracavity plasmon absorption spectroscopy method based on graphene active plasmonics. It is shown that the plasmonic cavity contribution to the sensitivity is proportional to the quality factor Q of the graphene plasmonic cavity and reaches two orders of magnitude. The addition of gain medium into the cavity increases the sensitivity of method. Maximum sensitivity is reached in the vicinity of the plasmon generation threshold. The gain contribution to the sensitivity is proportional to Q1/2. The giant amplification of sensitivity in the graphene plasmon generator is associated with a huge path length, limited only by the decoherence processes. An analytical estimation of the sensitivity to loss caused by analyzed particles (molecules, nanoparticles, etc.) normalized by the single pass plasmon scheme is derived. Usage of graphene nanoflakes as plasmonic cavity allows a high spatial resolution to be reached, in addition to high sensitivity. © 2016 Elsevier B.V.
In a previous study, we have shown that spectral and anisotropy properties of IceCube astrophysical neutrino signals reveal evidence for a sizeable Galactic contribution to the neutrino flux in the Southern Hemisphere. We check if the Galactic contribution is detectable in the astrophysical muon neutrino flux observed from a low positive declinations region of the Northern sky. Estimating the Galactic neutrino flux in this part of the sky from gamma-ray and Southern sky neutrino data, we find that the Northern sky astrophysical muon neutrino signal shows an excess over the Galactic flux. This points to the presence of an additional hard spectrum (extragalactic or large-scale Galactic halo) component of the astrophysical neutrino flux. We show that the Galactic flux component should still be detectable in the muon neutrino data in a decade-long IceCube exposure.
Neutron generation in a vacuum plasma diode with accelerating voltage to 280 kV and laser source of deuterons in the anode was investigated. The maximum neutron yield in a regime with magnetic insulation of the electrons in the reaction D(d, n)3 He is Qdd = 5·107 per count, which is 10 times higher than the value without a magnetic field. A hollow cylindrical NdFeB magnet, which is placed inside the vacuum volume of the diode and is also the diode’s cathode, is used to create a magnetic field. The conversion on the basis of numerical modeling showed that the neutron yield in the reaction T(d, n)4 He can reach 5·109 per count. © 2016 Springer Science+Business Media New York
A method is suggested for interpreting the data from the Balmer-alpha high-resolution spectroscopy diagnostics of the edge plasma in the tokamak main chamber, which additionally uses the data from direct observation of the divertor. Such an extension of the diagnostics is motivated by the fact that in a tokamak-reactor with the metal first wall, like ITER tokamak, a significant role of the divertor stray light (DSL), which is emitted by the plasma in the divertor in the same spectral line and reflected from the first wall of the vacuum chamber to a spectrometer in the main chamber, is expected. The results of the first applications of the developed model to interpret the data from the JET-ILW tokamak experiments, which simulate the conditions of occurrence of the DSL in ITER, are discussed.
We explore systematically a new class of two-phase equations of state (EoS) for hybrid stars that is characterized by three main features: 1) stiffening of the nuclear EoS at supersaturation densities due to quark exchange effects (Pauli blocking) between hadrons, modelled by an excluded volume correction; 2) stiffening of the quark matter EoS at high densities due to multiquark interactions; and 3) possibility for a strong first-order phase transition with an early onset and large density jump. The third feature results from a Maxwell construction for the possible transition from the nuclear to a quark matter phase and its properties depend on the two parameters used for 1) and 2), respectively. Varying these two parameters, one obtains a class of hybrid EoS that yields solutions of the Tolman-Oppenheimer-Volkoff (TOV) equations for sequences of hadronic and hybrid stars in the mass-radius diagram which cover the full range of patterns according to the Alford-Han-Prakash classification following which a hybrid star branch can be either absent, connected or disconnected with the hadronic one. The latter case often includes a tiny connected branch. The disconnected hybrid star branch, also called "third family", corresponds to high-mass twin stars characterized by the same gravitational mass but different radii. We perform a Bayesian analysis and demonstrate that the observation of such a pair of high-mass twin stars would have a sufficient discriminating power to favor hybrid EoS with a strong first-order phase transition over alternative EoS.
Background: The search for new opportunities to investigate the low-energy level in the Th229 nucleus, which is nowadays intensively studied experimentally, has motivated us to theoretical studies of the magnetic hyperfine (MHF) structure of the 5/2∗ (0.0 eV) ground state and the low-lying 3/2∗ (7.8 eV) isomeric state in highly charged Th89∗229 and Th87∗229 ions. Purpose: The aim is to calculate, with the maximal precision presently achievable, the energy of levels of the hyperfine structure of the Th229 ground-state doublet in highly charged ions and the probability of radiative transitions between these levels. Methods: The distribution of the nuclear magnetization (the Bohr-Weisskopf effect) is accounted for in the framework of the collective nuclear model with Nilsson model wave functions for the unpaired neutron. Numerical calculations using precise atomic density functional theory methods, with full account of the electron self-consistent field, have been performed for the electron structure inside and outside the nuclear region. Results: The deviations of the MHF structure for the ground and isomeric states from their values in a model of a pointlike nuclear magnetic dipole are calculated. The influence of the mixing of the states with the same quantum number F on the energy of sublevels is studied. Taking into account the mixing of states, the probabilities of the transitions between the components of the MHF structure are calculated. Conclusions: Our findings are relevant for experiments with highly ionized Th229 ions in a storage ring at an accelerator facility. © 2016 American Physical Society.
The results of the study of the output laser beam spatial characteristics of the Nd:Gd3Ga5O12 (Nd:GGG) disk laser with multipoint spatially periodic diode-pumping are presented. The presence of the optical coupling between the TEM00 lasing channels is demonstrated. The phase-locking of channels was realized due to partial overlapping of laser beams inside the pumped areas of the active element disk. © 2016 Astro Ltd.
A second-power yield of resonantly enhanced third harmonic and three-photon luminescence of 744 nm femtosecond laser pump pulses, weakly focused onto a layer of silver nanorolls on a silica substrate, was spectrally detected in the fluence range of 4-20 mJ cm(-2), saturating at higher fluences. The third-harmonic yield and its saturation were explored in terms of ultrafast carrier dynamics, based on direct three-photon or cascade one-and two-photon transitions balanced by Auger recombination (and the final band-filling effect) which limited the radiative recombination output in the form of the third harmonic and three-photon luminescence.
The effect of suppression of the anomalous transmission of X rays due to the destruction of the system of weakly and strongly absorbing Bloch waves under ultrasound has been proposed to separate the radiation of high-intensity pulsed X-ray sources. The switching speed from the anomalous transmission mode to the zero transmission state is actually determined by only the X-ray frequency, which suggests that the switching time is several tens of nanoseconds. © 2016, Pleiades Publishing, Inc.
Nonlinear effects accompanying the propagation of high-intensity beams of X-ray free-electron lasers are considered. It is shown that the X-ray wave field in the crystal significantly changes due to the formation of “hollow” atomic shells as a result of the photoelectric effect. © 2016, Pleiades Publishing, Inc.
Cold and hot vertical displacement events (VDEs) are frequently related to the disruption of vertically-elongated tokamaks. The weak poloidal magnetic field around the null-points of a snowflake divertor configuration may influence the vertical displacement process. In this paper, the major disruption with a cold VDE and the vertical disruption in the HL-2M tokamak are investigated by the DINA code. In order to better illustrate the effect from the weak poloidal field, a double-null snowflake configuration is compared with the standard divertor (SD) configuration under the same plasma parameters. Computational results show that the weak poloidal magnetic field can be partly beneficial for mitigating the vertical instability of the plasma under small perturbations. For major disruption, the peak poloidal halo current fraction is almost the same between the snowflake and the SD configurations. However, this fraction becomes much larger for the snowflake in the event of a hot VDE. Furthermore, during the disruption for a snowflake configuration, the distribution of electromagnetic force on a vacuum vessel gets more non-uniform during the current quench. © 2016 IOP Publishing Ltd.
ATLAS has measured two-particle correlations as a function of the relative azimuthal angle, Delta phi, and pseudorapidity, Delta eta, in root s = 13 and 2.76 TeV pp collisions at the LHC using charged particles measured in the pseudorapidity interval vertical bar eta vertical bar 2.5. The correlation functions evaluated in different intervals of measured charged-particle multiplicity show a multiplicity-dependent enhancement at Delta phi similar to 0 that extends over a wide range of Delta eta, which has been referred to as the "ridge." Per-trigger-particle yields, Y(Delta phi) are measured over 2 vertical bar Delta eta vertical bar 5. For both collision energies, the Y(Delta phi) distribution in all multiplicity intervals is found to be consistent with a linear combination of the per-trigger-particle yields measured in collisions with less than 2 phi reconstructed tracks, and a constant combinatoric contribution modulated by cos (2 Delta phi). The fitted Fourier coefficient, nu(2,2), exhibits factorization, suggesting that the ridge results from per-event cos (2 phi) modulation of the single-particle distribution with Fourier coefficients nu(2). The nu(2) values are presented as a function of multiplicity and transverse momentum. They are found to be approximately constant as a function of multiplicity and to have a p(T) dependence similar to that measured in p + Pb and Pb + Pb collisions. The nu(2) values in the 13 and 2.76 TeV data are consistent within uncertainties. These results suggest that the ridge in pp collisions arises from the same or similar underlying physics as observed in p + Pb collisions, and that the dynamics responsible for the ridge has no strong root s dependence.
Measurements of the cross sections for top quark pairs produced in association with a W or Z boson are presented, using 8 TeV pp collision data corresponding to an integrated luminosity of 19.5 fb(-1), collected by the CMS experiment at the LHC. Final states are selected in which the associated W boson decays to a charged lepton and a neutrino or the Z boson decays to two charged leptons. Signal events are identified by matching reconstructed objects in the detector to specific final state particles from t (t) over barW or t (t) over barZ decays. The t (t) over barW cross section is measured to be 382(-102)(+117) fb with a significance of 4.8 standard deviations from the background-only hypothesis. The t (t) over barZ cross section is measured to be 242(-55)(+65) fb with a significance of 6.4 standard deviations from the background-only hypothesis. These measurements are used to set bounds on five anomalous dimension-six operators that would affect the t (t) over barW and t (t) over barZ cross sections.
A method of detecting a weak radiation of the Balmer lines from the hydrogen isotopes in the edge plasma of a tokamak (SOL) on the strong optical background formed by reflection of the light emitted from the divertor plasma is proposed. The method is based on a parallel registration of the radiation from the optical dump and from the wall near the dump. Calibration of the attenuation of the stray light radiation by the optical dump is being performed in the course of the measurements, using the intensity of the high-frequency pulsations that are not correlated with the edge plasma emission. Statistical estimates show that a 20-fold attenuation of the light by the dump allows registration of the weak edge plasma radiation making down to 0.5% of the background intensity.
As we are going to show, some self-interacting dark matter models may provide an intriguing solution to the "cosmic antiparticle excess vs. isotropic diffuse gamma-ray background" problem (an overproduction of diffuse gamma rays, arising in any reasonable decaying or annihilating dark matter model explaining high-energy charged cosmic antiparticles anomalous abundance).
The interaction between deuterium and radiation-induced point defects in tungsten and the stages of their transformation and annealing are investigated by means of thermal-desorption spectroscopy. Primary defects, mainly vacancies, are created using 10-keV D+ ions at room temperature. In investigating the evolution of radiation-induced defects, irradiated samples are annealed at temperatures of 550–1400 K and the subsequent filling of defects is carried out by deuterium after sample irradiation with D3 + ions with an energy of 0.67 keV/deuteron at room temperature. The characteristic positions of thermal desorption peaks, as well as the temperatures of vacancy clusterization and annealing of defects, are determined. © 2016, Pleiades Publishing, Ltd.
It is proposed to consider the scalings of anomalous transport (superdiffusion), determined experimentally in turbulent plasma of the Earth’s magnetosphere and laboratory plasma of thermonuclear facilities and processed using modern statistical cascade models of strong turbulence with intermittency, also within the approach of physical kinetics to the theory of plasma turbulence. © 2016, Allerton Press, Inc.
Dynamics of disordering of graphene upon heating has been studied by computer simulation. The mechanism governing the formation of seeds for a three-dimensional grid of entangled carbon chains into which graphene is transformed upon melting has been analyzed in detail. It has been shown that the emergence of these seeds is preceded by the disruption of several interatomic bonds, accompanied with the formation of large rings or groups of adjacent rings and the formation of penta- and heptagons of their C-C bonds. The results of this work on the whole agree with the Lindemann-Lozovik criterion. The melting temperature is estimated as T (m) similar to 5100 K.
The structural and optical properties of Cu2ZnSnS4 thin-film layers formed by reactive pulsed laser deposition in a H2S atmosphere at room temperature with the use of a Cu metal target and a Zn–Sn alloy target are studied in relation to the parameters of annealing in a N2 atmosphere. © 2016, Pleiades Publishing, Ltd.
Fundamental properties of warm dense matter are described by the dielectric function, which gives access to the frequency-dependent electrical conductivity; absorption, emission, and scattering of radiation; charged particles stopping; and further macroscopic properties. Different approaches to the dielectric function and the related dynamical collision frequency are compared in a wide frequency range. The high-frequency limit describing inverse bremsstrahlung and the low-frequency limit of the dc conductivity are considered. Sum rules and Kramers-Kronig relation are checked for the generalized linear response theory and the standard approach following kinetic theory. The results are discussed in application to aluminum, xenon, and argon plasmas. © 2016 American Physical Society.
Knowledge of antineutrino interaction cross-sections is an important and necessary ingredient in many measurements. With the advent of new precision experiments, the demands on better understanding of neutrino interactions is becoming even greater. The purpose of this report is to survey our current knowledge of the inverse beta decay cross-sections and to do a comparison the theoretical analysis with experimental data.
The Borexino experiment is running at the Laboratori del Gran Sasso in Italy since 2007. Its technical distinctive feature is the unprecedented ultralow background of the inner scintillating core, which is the basis of the outstanding achievements accumulated by the experiment. In this talk, after recalling the main features of the detector, the impressive solar data gathered so far by the experiment will be summarized, with special emphasis to the most recent and prominent result concerning the detection of the fundamental pp solar neutrino flux, which is the direct probe of the engine mechanism powering our star. Such a milestone measurement puts Borexino in the unique situation of being the only experiment able to do solar neutrino spectroscopy over the entire solar spectrum; the counterpart of this peculiar status in the oscillation interpretation of the data is the capability of Borexino alone to perform the full validation across the solar energy range of the MSW-LMA paradigm. The talk will be concluded highlighting the perspectives for the final stage of the solar program of the experiment, centered on the goal to fully complete the solar spectroscopy with the missing piece of the CNO neutrinos. If successful, such a measurement would represent the final crowning of the long quest of Borexino to unravel all the properties of the neutrinos from the Sun.
Counter-propagating and suitably polarized light (laser) beams can provide conditions for pair production. Here, we consider in more detail the following two situations: (i) in the homogeneity regions of anti-nodes of linearly polarized ultra-high intensity laser beams, the Schwinger process is dynamically assisted by a second high-frequency field, e.g. by an XFEL beam; and (ii) a high-energy probe photon beam colliding with a superposition of co-propagating intense laser and XFEL beams gives rise to the laser-assisted Breit-Wheeler process. The prospects of such bi-frequent field constellations with respect to the feasibility of conversion of light into matter are discussed. © 2016 Cambridge University Press.
We present a Bayesian approach to particle identification (PID) within the ALICE experiment. The aim is to more effectively combine the particle identification capabilities of its various detectors. After a brief explanation of the adopted methodology and formalism, the performance of the Bayesian PID approach for charged pions, kaons and protons in the central barrel of ALICE is studied. PID is performed via measurements of specific energy loss (dE/dx) and time of flight. PID efficiencies and misidentification probabilities are extracted and compared with Monte Carlo simulations using high-purity samples of identified particles in the decay channels K-S(0) - pi(-)pi(+), phi - K-K+, and A - p pi(-) in p-Pb collisions at root sNN = 5.02 TeV. In order to thoroughly assess the validity of the Bayesian approach, this methodology was used to obtain corrected p(T) spectra of pions, kaons, protons, and D-0 mesons in pp collisions at root s = 7TeV. In all cases, the results using Bayesian PID were found to be consistent with previous measurements performed by ALICE using a standard PID approach. For the measurement of D-0 - K-pi(+), it was found that a Bayesian PID approach gave a higher signal-to-background ratio and a similar or larger statistical significance when compared with standard PID selections, despite a reduced identification efficiency. Finally, we present an exploratory study of the measurement of A(c)(+) - pK(-)pi(+) in pp collisions at root s = 7TeV, using the Bayesian approach for the identification of its decay products.
The identification of jets containing b hadrons is important for the physics programme of the ATLAS experiment at the Large Hadron Collider. Several algorithms to identify jets containing b hadrons are described, ranging from those based on the reconstruction of an inclusive secondary vertex or the presence of tracks with large impact parameters to combined tagging algorithms making use of multi-variate discriminants. An independent b-tagging algorithm based on the reconstruction of muons inside jets as well as the b-tagging algorithm used in the online trigger are also presented. The b-jet tagging efficiency, the c-jet tagging efficiency and the mistag rate for light flavour jets in data have been measured with a number of complementary methods. The calibration results are presented as scale factors defined as the ratio of the efficiency (or mistag rate) in data to that in simulation. In the case of b jets, where more than one calibration method exists, the results from the various analyses have been combined taking into account the statistical correlation as well as the correlation of the sources of systematic uncertainty. © CERN 2016 for the benefit of the ATLAS collaboration, published under the terms of the Creative Commons Attribution 3.0 License by IOP Publishing Ltd and Sissa Medialab srl.
A method is developed to consider the particle–phonon coupling (PC) effects in the problem of finding odd–even double mass differences (DMD) of magic nuclei within the approach starting from the free NN potential. Three PC effects are taken into account, the phonon induced interaction, the renormalization of the “ends” due to the Z-factors and the change of the single-particle energies. We use the perturbation theory in gL sup2/sup, where gL is the vertex of the L-phonon creation. PC corrections to single-particle energies are found selfconsistently. In addition to the usual pole diagram, the phonon “tadpole” diagram is taken into account approximately. Results for double-magic sup132/supSn and sup208/supPb nuclei show that the PC corrections make agreement with the experimental data better. © 2016, Pleiades Publishing, Inc.
This work is devoted to the study of two new synthetic bacteriochlorins with four and eight cationic substitutes as the photosensitizers in the photodynamic process. The spectral and antibacterial properties of these photosensitizers in saline solution were investigated. It is shown, that the aggregation ability decreases and the antibacterial efficiency grows as the cationic substitute number increases. © Published under licence by IOP Publishing Ltd.
It is shown that phagraphene, a recently predicted planar allotropic form of graphene with Dirac fermions, is unstable or, at least, almost unstable with respect to transverse atomic displacements in the monolayer. This result is obtained by numerical calculations in the framework of both the tight-binding model and the density functional theory. A nonplanar atomic configuration of phagraphene has a wavy shape and is nearly degenerate in energy with respect to the planar configuration. The main types of possible structural defects in phagraphene are determined. The temperature dependence of characteristic times of their formation is found.
The theory of turbulent heating in the mode of hot deuterium ions and cold tritium ions is developed for plasma with equal deuterium and tritium ion concentrations. The possibility of heating electrons and deuterium ions by thousands of times is shown.
Progressive advance in technology of second-generation (2G) high-temperature superconducting (HTS) superconductors leads to the continuous rise of their critical-current density. Critical current of 200 A at 4-mm tapes and ∼600 A at 12-mm tapes is already state of the art. One problem is that critical currents of HTS tapes have sounding anisotropy. Moreover, it was found that in external magnetic field, the Lorentz force direction is affecting the critical currents of 2G HTS tapes. Two hypotheses were suggested as a reason for this phenomenon. This is the result of the properties of crystal lattice in a 2G HTS tape or of spatial inhomogeneity of critical currents across the width of HTS tapes. In this paper, the verification of hypotheses was done by the cutting of wide 2G HTS tapes into narrow tapes and measuring of critical-current anisotropy in narrowed tapes. We present the experimental results and their discussion. We concluded that the spatial inhomogeneity of critical-current density in the cross section of a tape is the reason for the Lorentz force direction influence on the anisotropy of 2G HTS tape critical currents. © 2002-2011 IEEE.
We report the high-pressure XANES study of the electronic phase transition from 4f7 to 4f 6 configuration of europium in the rare-earth compound EuCu2Ge2. The hydrostatic pressure dependence of the europium valence was obtained in a wide pressure range (1-30 GPa) at room temperature. It was found that upon the pressure increase above 20 GPa the europium valence does not reach the integer value +3 but stabilizes at 2.87. The experimental results were supported by the band structure calculations in the framework of DFT, which allowed us to discuss the features of 3d-4f hybridization in this system. The study also compares the mechanisms of external and "chemical" pressure by the Si substitution in Ge site in series EuCu2(SixGe1-x)2.
In this paper, we present a detailed analysis of the results of the magneto-optical measurements of the field's topography in the coated conductor (CC) tapes at various temperatures in order to study the distribution of the field and develop a simple method for determining the critical current density. It is shown that the fitting of calculated field profiles to the results of the magneto-optical measurements gives a satisfactory agreement between the model and the experiment. In addition, we proposed a method for the determination of the critical current density from measurements of the topography of the transverse field that is insensitive to the precise form of the current lines. Furthermore, it is shown that the experimentally observed asymmetry of the field profile is probably due to a slight misalignment between the MOI film and the CC tape, which is possibly due to the presence of a small transverse curvature of actual CC tapes. © 2016 IEEE.
This article presents the sensitivity of the ATLAS experiment to the lepton-flavour-violating decays of tau - 3 mu. A method utilising the production of t leptons via W - tau nu decays is used. This method is applied to the sample of 20.3 fb(-1) of pp collision data at a centre-of-mass energy of 8 TeV collected by the ATLAS experiment at the LHC in 2012. No event is observed passing the selection criteria, and the observed (expected) upper limit on the tau lepton branching fraction into three muons, Br(tau - 3 mu), is 3.76 x 10(-7) (3.94 x 10(-7)) at 90 % confidence level.
The production of (anti-)deuteron and (anti-)He3 nuclei in Pb-Pb collisions at sNN=2.76 TeV has been studied using the ALICE detector at the LHC. The spectra exhibit a significant hardening with increasing centrality. Combined blast-wave fits of several particles support the interpretation that this behavior is caused by an increase of radial flow. The integrated particle yields are discussed in the context of coalescence and thermal-statistical model expectations. The particle ratios, He3/d and He3/p, in Pb-Pb collisions are found to be in agreement with a common chemical freeze-out temperature of Tchem≈156 MeV. These ratios do not vary with centrality which is in agreement with the thermal-statistical model. In a coalescence approach, it excludes models in which nucleus production is proportional to the particle multiplicity and favors those in which it is proportional to the particle density instead. In addition, the observation of 31 anti-tritons in Pb-Pb collisions is reported. For comparison, the deuteron spectrum in pp collisions at s=7 TeV is also presented. While the p/π ratio is similar in pp and Pb-Pb collisions, the d/p ratio in pp collisions is found to be lower by a factor of 2.2 than in Pb-Pb collisions. © 2016 CERN. ©2016 CERN, for the ALICE Collaboration. Published by the American Physical Society under the terms of the Creative Commons Attribution 3.0 License. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.
The particle-hole dispersive optical model developed recently is applied to describe properties of high-energy isoscalar monopole excitations in Pb-208. We consider, in particular, the double transition density averaged over the energy of the isoscalar monopole excitations in a wide energy interval, which includes the isoscalar giant monopole resonance and its overtone. The energy-averaged strength functions of these resonances are also analyzed. Some corrections to the calculation scheme are formulated to restore the model unitarity.
The pseudorapidity (η) and transverse-momentum (pT) distributions of charged particles produced in proton-proton collisions are measured at the centre-of-mass energy √s=13 TeV. The pseudorapidity distribution in |η|<1.8 is reported for inelastic events and for events with at least one charged particle in |η|<1. The pseudorapidity density of charged particles produced in the pseudorapidity region |η|<0.5 is 5.31±0.18 and 6.46±0.19 for the two event classes, respectively. The transverse-momentum distribution of charged particles is measured in the range 0.15<pT<20 GeV/c and |η|<0.8 for events with at least one charged particle in |η| < 1. The evolution of the transverse momentum spectra of charged particles is also investigated as a function of event multiplicity. The results are compared with calculations from PYTHIA and EPOS Monte Carlo generators. © 2015 CERN for the benefit of the ALICE Collaboration.
This paper presents results of a study of the x-ray emission and the composition of the material ejected from the inter-electrode gap of a high-current, low-inductance vacuum spark. Pairs of electrodes made of different materials (Fe, Cu, Mo, W, Pb) were used. The most stable reproducibility of x-ray radiation emission is found to be with the Fe and Mo cathodes.
Application of the nuclear track emulsion technique (NTE) in radioactivity and nuclear fission studies is discussed. It is suggested to use a HSP-1000 automated microscope for searching for a collinear cluster tri-partition of heavy nuclei implanted in NTE. Calibrations of α-particles and ion ranges in a novel NTE are carried out. Surface exposures of NTE samples to a Cf-252 source started. Planar events containing fragments and long-range α-particles as well as fragment triples only are studied. NTE samples are calibrated by ions Kr and Xe of energy of 1.2 and 3 A MeV. Use of the image recognition program "ImageJ" for obtaining characteristics of individual events and for events from the large scan area is presented. © Owned by the authors, published by EDP Sciences-SIF, 2016.
The Borexino detector was built starting from 1996 in the underground hall C of Gran Sasso National Laboratory (LNGS) in Italy under about 1400 m of rock (3800 m.w.e) and it is mostly aimed to the study in real-time of the low-energy solar neutrinos. Since the beginning of data taking, in May 2007, the unprecedented detector radio-purity made the performances of the detector unique: a milestone has been very recently achieved with the measurement of solar pp neutrino flux, providing the first direct observation in real time of the key fusion reaction powering the Sun. In this contribution the most important Borexino achievements to the fields of solar, geo-neutrino and particle physics are reviewed and the future perspectives discussed, emphasizing in particular the unique possibility of Borexino to cover at the end of its program the entire solar neutrino spectrum and to exploit the possible existence of a fourth sterile neutrino (SOX project). © 2015 Elsevier B.V.
This paper describes the algorithms used by the CMS experiment to reconstruct and identify tau - hadrons + nu(tau) decays during Run 1 of the LHC. The performance of the algorithms is studied in proton-proton collisions recorded at a centre-of-mass energy of 8 TeV, corresponding to an integrated luminosity of 19.7 fb(-1). The algorithms achieve an identification efficiency of 50-60%, with misidentification rates for quark and gluon jets, electrons, and muons between per mille and per cent levels.
This paper presents a new method of reconstructing the individual charged and neutral hadrons in tau decays with the ATLAS detector. The reconstructed hadrons are used to classify the decay mode and to calculate the visible four-momentum of reconstructed tau candidates, significantly improving the resolution with respect to the calibration in the existing tau reconstruction. The performance of the reconstruction algorithm is optimised and evaluated using simulation and validated using samples of Z→ ττ and Z(→ μμ) +jets events selected from proton–proton collisions at a centre-of-mass energy s=8TeV, corresponding to an integrated luminosity of 5 fb - 1. © 2016, The Author(s).
We review the Effective Field Theory (EFT) to make projections on physics beyond the Standard Model in the Higgs sector. We provide relations between the non-Standard Model couplings of the Strongly-Interacting Light Higgs (SILH) effective Lagrangian implemented in the eHDecay package and the corresponding terms of the spin-0 Higgs Characterisation model's effective Lagrangian used with the aMC@NLO Monte Carlo generator. Constraints on BSM couplings are determined on the basis of existing experimental limits on Higgs boson width and branching ratios.
Nowadays, magnetic bearings are used to design motors, generators, separating platforms, and flywheel energy storage systems. High-temperature superconducting (HTS) magnetic bearing construction is based on YBa2Cu3O7-x (YBCO) bulks through its ability to capture and hold significant magnetic field for a long time. However, that material requires external mechanical reinforcement and has low thermal conductivity, which provides additional restrictions on practical application. Modern HTS tapes do not have such disadvantages. Its structure provides better rigidity and thermal stability in comparison with HTS bulk. One more significant advantage of tapes is simplicity of cutting to required form. In order to construct magnetic bearings from stacks of HTS tapes, it is necessary to have data about stability of system stack magnet under different dynamic processes. In this work, relaxation of levitation force was researched in both static and vibration modes with vertical oscillation frequencies of 15, 20, and 30 Hz. The measurements were performed for stacks with different amounts of 12 mm × 12 mm REBCO tapes in a stack (n=1, 5, 10, 15, 20) at temperature T=77 K. Stacks were placed over permanent magnet with a minimal gap of 4 mm. FC cooling method was realized. All static and dynamic relaxation measurements were carried out at 11.6-mm gap. © 2016 IEEE.
How black holes accrete surrounding matter is a fundamental yet unsolved question in astrophysics. It is generally believed that matter is absorbed into black holes via accretion disks, the state of which depends primarily on the mass-accretion rate. When this rate approaches the critical rate (the Eddington limit), thermal instability is supposed to occur in the inner disk, causing repetitive patterns of large-amplitude X-ray variability (oscillations) on timescales of minutes to hours(1). In fact, such oscillations have been observed only in sources with a high mass-accretion rate, such as GRS 1915+105 (refs 2, 3). These large-amplitude, relatively slow timescale, phenomena are thought to have physical origins distinct from those of X-ray or optical variations with small amplitudes and fast timescales (less than about 10 seconds) often observed in other black-hole binaries-for example, XTE J1118+480 (ref. 4) and GX 339-4 (ref. 5). Here we report an extensive multi-colour optical photometric data set of V404 Cygni, an X-ray transient source(6) containing a black hole of nine solar masses(7) (and a companion star) at a distance of 2.4 kiloparsecs (ref. 8). Our data show that optical oscillations on timescales of 100 seconds to 2.5 hours can occur at mass-accretion rates more than ten times lower than previously thought(1). This suggests that the accretion rate is not the critical parameter for inducing inner-disk instabilities. Instead, we propose that a long orbital period is a key condition for these large-amplitude oscillations, because the outer part of the large disk in binaries with long orbital periods will have surface densities too low to maintain sustained mass accretion to the inner part of the disk. The lack of sustained accretion-not the actual rate-would then be the critical factor causing large-amplitude oscillations in long-period systems.
The magnetic-field dependencies of the longitudinal and Hall resistance of the electron-doped compounds Nd2-xCexCuO4+δ in underdoped region with x = 0.14 and with varying degrees of disorder (δ) were investigated. It was established experimentally that the correlation between the longitudinal electrical resistivity and the Hall resistivity can be analyzed on the basis of scaling relationships: ρxy(B) ∼ [ρxx(B)]supβ/sup. For the totality of the investigated single-crystal films of Nd2-xCexCuO4+δ/SrTiO3 the values of β from 0.8 to 1.55 is found. The observed feature in the electron-doped two-dimensional systems can be associated both with a displaying of anisotropic s - wave or d - wave pairing symmetry and with a pinning due to an essential degree of disorder in the samples under study. © 2016 Published by Elsevier B.V.
Liquid argon is a bright scintillator with potent particle identification properties, making it an attractive target for direct-detection dark matter searches. The DarkSide-50 dark matter search here reports the first WIMP search results obtained using a target of low-radioactivity argon. DarkSide-50 is a dark matter detector, using a two-phase liquid argon time projection chamber, located at the Laboratori Nazionali del Gran Sasso. The underground argon is shown to contain Ar39 at a level reduced by a factor (1.4±0.2)×103 relative to atmospheric argon. We report a background-free null result from (2616±43) kg d of data, accumulated over 70.9 live days. When combined with our previous search using an atmospheric argon, the 90% C.L. upper limit on the WIMP-nucleon spin-independent cross section, based on zero events found in the WIMP search regions, is 2.0×10-44 cm2 (8.6×10-44 cm2, 8.0×10-43 cm2) for a WIMP mass of 100 GeV/c2 (1 TeV/c2, 10 TeV/c2). © 2016 American Physical Society.
The Russian Scientific R&D Cable Institute was obliged to produce and to deliver 20% toroidal field (TF) conductors and 20% poloidal field (PF) cables for the ITER magnet system. The task has been completed in October 2015. This work was a great technological challenge in the development of tricky technologies. Development of manufacturing processes was accompanied by extensive scientific studies directed to an improvement of technologies and a search of causes resulting in change of cables and conductors properties during manufacturing and testing. In this paper, we present the extended review and summary of results obtained for Russian superconductors that permitted improving technologies and finding out the reasons of changes of properties of cables and conductors during manufacturing and testing. The study of rotation and untwisting of TF cables during insertions into jackets allowed developing the model describing the rotation process and suggesting the device which keeps untwisting within demanded levels. Analyses of mandatory SULTAN high-field electromagnetic tests of PF and TF conductors from Russia confirmed good quality and adequacy of manufacturing processes. Micrographic studies of Nb3Sn strands before and after SULTAN tests permitted qualitatively understanding the reason for the stability of RF TF conductor behavior during multiple electromagnetic and thermal cycling. Statistical studies of residual resistance ratio (RRR) of Nb3Sn and NbTi strands permitted tracking of its degradation during manufacturing processes and SULTAN tests. The optimal heat treatment process for Nb3Sn conductors has been confirmed after RRR statistical study. The hydraulic performance has been measured in the short samples of TF conductor. By using the parameters obtained, it is possible to predict hydraulic performance of helium flow in a conductor at any temperature. These results led to deeper understanding and to improving manufacturing processes and quality of TF and PF conductors for the ITER magnet system and could be useful for suppliers of superconducting cables and conductors using ITER-like technologies.
We review some properties of black hole structures appearing in gravity with a massless scalar field, with both minimal and nonminimal coupling. The main properties of the resulting cold black holes are described. The study of black holes in scalar-gravity systems is extended to (Formula presented.)-essence theories, and some examples are explicitly worked out. In these cases, even while the existence of horizons is possible, the metric regularity requirement on the horizon implies either a cold black type structure or a singular behavior of the scalar field. © 2016 World Scientific Publishing Company
We study the properties of possible static, spherically symmetric configurations in k-essence theories with the Lagrangian functions of the form F(X), X ≡ ϕ,αϕ,supα/sup. A no-go theorem has been proved, claiming that a possible black-hole-like Killing horizon of finite radius cannot exist if the function F(X) is required to have a finite derivative dF/dX. Two exact solutions are obtained for special cases of kessence: one for F(X) = F0Xsup1/3/sup, another for F(X) = F0|X|sup1/2/sup − 2Λ, where F0 and Λ are constants. Both solutions contain horizons, are not asymptotically flat, and provide illustrations for the obtained nogo theorem. The first solution may be interpreted as describing a black hole in an asymptotically singular space-time, while in the second solution two horizons of infinite area are connected by a wormhole. © 2016, Pleiades Publishing, Ltd.
The dusty-gas model has been extended to the case of nanoporous media, in which the action of surface forces must be taken into account. A basic set of transport equations underlying the model has been derived proceeding from a set of kinetic equations for an ordinary gas and dust particles. In the kinetic equations, the interaction between the gas and dust particles is represented as a sum of a long-range (analog of surface forces) and short-range components. The contribution of the long-range component has been taken into account in the self-consistent approximation, while the short-range component has been considered in the standard manner. Allowance for the surface forces has been shown to result in a substantial modification of the equation for gas transport through porous bodies, with this modification being most pronounced at nonuniform temperatures.
New solution for two interpenetrating universes is found. Higher derivative gravity acting in 6-dimensional space is the basis of the study that allows to obtain stable solution without introducing matter of any sort. Stability of the solution is maintained by a difference between asymptotic behavior at spacial infinities. For an external observer such a funnel looks similar to a spherical wormhole. © 2016 The Author(s)
The way to solve the hierarchy problem based on multidimensional gravity is discussed. Various metrics of deformed extra space are produced at the Planck scale. It is shown that the Higgs vacuum value depends on a metric of extra space and hence their different numerical values are realized in various universes. An interval of the Higgs vacuum values is proved include zero value. Our universe belongs to a set of universes the vacuum values of which are close to zero
We have performed a numerical analysis of the magnetic response of a single piece of a higherature superconducting (HTS) tape and the stacks of rectangular pieces of HTS tapes. The number of tapes in the stacks was varied from N=1 to 100. We have carried out the simulation in the framework of the critical state model, taking into account the double-exponential dependence of the critical current density on the external applied field that was proposed by the authors earlier. The results of the calculation of the magnetization of rectangular packages of HTS tapes are presented and discussed. We found that the value of the magnetization per one tape is reduced as the number of tapes in the stack is increased. The decrease in the normalized magnetization was shown to be due to mutual screening among tapes in the stack. We have compared the calculated magnetization with the experimental data and found a good agreement between both results. The novel method of calculations of the magnetic properties of HTS tapes can be successfully used for the calculation of the magnetization of HTS tapes and stacks with arbitrary shape. © 2016 IEEE.
An effective, reliable and time saving numerical method with use of the Pruefer transformation is proposed to calculate eigenvalues of Chandrasekhar–Page angular equations. © 2016 World Scientific Publishing Company
Results are presented from experimental and analytical studies of the processes resulting in the excitation of microplasma discharges (MPDs) on a metal surface partially covered with a thin dielectric film under the action of an external plasma flow in vacuum. It is shown experimentally that MPDs are excited at the interface between the open metal surface and the region covered by the dielectric film. The probability of MPD excitation is investigated as a function of the thickness of the dielectric film deposited on the metal. It is found that, for a film thickness of 1 μm, the probability of MPD excitation is close to unity. As the film thickness decreases below ~10 nm or increases above ~10 μm, the probability of MPD excitation is reduced by more than two orders of magnitude. A two-dimensional kinetic numerical code is developed that allows one to model the processes of Debye sheath formation and generation of a strong electric field near the edge of a finite-thickness dielectric film on a metal surface in a plasma flow for different configurations of the film edge. It is shown that the maximum value of the tangential component of the electric field is reached at the film edge and amounts to Emax ≈ |φ0|/2d (where φ0 < 0 is the electric potential applied to the metal and d is the film thickness), which for typical conditions of experiments on the excitation of MPDs on metal surfaces (φ0 ≈–400 V, d ≈ 1 μm) yields Emax ≈ 2 MV/cm. The results of kinetic simulations confirm the qualitative idea about the mechanism of the formation of a strong electric field resulting in the excitation of MPDs at the edge of a dielectric film on a metal surface in a plasma flow and agree with experimental data. © 2016, Pleiades Publishing, Ltd.
An original 2D3V (two-dimensional in coordinate space and three-dimensional in velocity space) particle-in-cell code has been developed for simulation of multipactor discharge on a dielectric in a parallelplate metal waveguide with allowance for secondary electron emission (SEE) from the dielectric surface and waveguide walls, finite temperature of secondary electrons, electron space charge, and elastic and inelastic scattering of electrons from the dielectric and metal surfaces. The code allows one to simulate all stages of the multipactor discharge, from the onset of the electron avalanche to saturation. It is shown that the threshold for the excitation of a single-surface multipactor on a dielectric placed in a low-profile waveguide with absorbing walls increases as compared to that in the case of an unbounded dielectric surface due to escape of electrons onto the waveguide walls. It is found that, depending on the microwave field amplitude and the SEE characteristics of the waveguide walls, the multipactor may operate in two modes. In the first mode, which takes place at relatively low microwave amplitudes, a single-surface multipactor develops only on the dielectric, the surface of which acquires a positively potential with respect to the waveguide walls. In the second mode, which occurs at sufficiently high microwave intensities, a single-surface multipactor on the dielectric and a two-surface multipactor between the waveguide walls operate simultaneously. In this case, both the dielectric surface and the interwall space acquire a negative potential. It is shown that electron scattering from the dielectric surface and waveguide walls results in the appearance of high-energy tails in the electron distribution function. © 2016, Pleiades Publishing, Ltd.
This paper presents evaluation of the plasma pressure in a high current, low inductance vacuum spark on the cathode surface (the electrode material is steel). Calculations are provided for the first half period of the discharge, wherein the cathode surface is subjected to the most severe impacts (micropinches are created resulting in high-energy plasma beams). The evaluations were made using the experimental data obtained on the Pion device. The data of electrical measurements of the discharge current, the average plasma flow values obtained with the multi-grid probe and the data from a cathode macrostructure study were used. The results are given for different values of the discharge current.
The theoretical and experimental investigation of physical processes in strong fields of different nature (electromagnetic, gravitational, etc.) is one of the important directions of modern physics. Particular interest is devoted to the area of extremely strong fields, in which qualitatively new effects become important due to the restructuring of the physical vacuum which accompanies the creation of matter from the vacuum at modern laser facilities. Such kind of time-dependent strong field vacuum effects can be appropriately described within a kinetic theory approach as an effective instrument of theoretical investigations. A short review of recent achievements in the direction of the dynamical Schwinger effect is given in this contribution. © Published under licence by IOP Publishing Ltd.
A wide class of non-stationary superdiffusive transport on a uniform background with a power-law decay at large distances of the step-length probability distribution function (PDF) is shown to possess an approximate automodel solution. The solution for the Green's function is constructed using the scaling laws for the propagation front (relevant-to-superdiffusion average displacement) and asymptotic solutions far beyond and far in advance of the propagation front. These scaling laws are determined essentially by the long-free-path carriers (Levy flights). The validity of the suggested automodel solution is proved by its comparison with numerical solutions in the one-dimensional (1D) case of the transport equation with a simple long-tailed PDF with various power-law exponents and in the 3D case of the Biberman-Holstein equation of the resonance radiation transfer for various (Doppler, Lorentz, Voigt and Holtsmark) spectral line shapes.
A search is described for a Higgs boson decaying into two photons, one of which has an internal conversion to a muon or an electron pair (ℓℓγ). The analysis is performed using proton-proton collision data recorded with the CMS detector at the LHC at a centre-of-mass energy of 8 TeV, corresponding to an integrated luminosity of 19.7 fb-1. The events selected have an opposite-sign muon or electron pair and a high transverse momentum photon. No excess above background has been found in the three-body invariant mass range 120mℓℓγ150 GeV, and limits have been derived for the Higgs boson production cross section times branching fraction for the decay H→γ*γ→ℓℓγ, where the dilepton invariant mass is less than 20 GeV. For a Higgs boson with mH
Abstract: A search for a high-mass Higgs boson H is performed in the H → WW → ℓνℓν and H → WW → ℓνqq decay channels using pp collision data corresponding to an integrated luminosity of 20.3 fbsup−1/sup collected at s=8(Formula presented.) TeV by the ATLAS detector at the Large Hadron Collider. No evidence of a high-mass Higgs boson is found. Limits on σH × BR(H → WW) as a function of the Higgs boson mass mH are determined in three different scenarios: one in which the heavy Higgs boson has a narrow width compared to the experimental resolution, one for a width increasing with the boson mass and modeled by the complex-pole scheme following the same behavior as in the Standard Model, and one for intermediate widths. The upper range of the search is mH = 1500 GeV for the narrow-width scenario and mH = 1000 GeV for the other two scenarios. The lower edge of the search range is 200–300 GeV and depends on the analysis channel and search scenario. For each signal interpretation, individual and combined limits from the two WW decay channels are presented. At mH = 1500 GeV, the highest-mass point tested, σH × BR(H → WW) for a narrow-width Higgs boson is constrained to be less than 22 fb and 6.6 fb at 95% CL for the gluon fusion and vector-boson fusion production modes, respectively.[Figure not available: see fulltext.] © 2016, The Author(s).
A search is reported for a light pseudoscalar Higgs boson decaying to a pair of τ leptons, produced in association with a bb pair, in the context of two-Higgs-doublet models. The results are based on pp collision data at a centre-of-mass energy of 8 TeV collected by the CMS experiment at the LHC and corresponding to an integrated luminosity of 19.7 fbsup-1/sup. Pseudoscalar boson masses between 25 and 80 GeV are probed. No evidence for a pseudoscalar boson is found and upper limits are set on the product of cross section and branching fraction to τ pairs between 7 and 39 pb at the 95% confidence level. This excludes pseudoscalar A bosons with masses between 25 and 80 GeV, with SM-like Higgs boson negative couplings to down-type fermions, produced in association with bb pairs, in Type II, two-Higgs-doublet models. © 2016 The Author(s).
A search for a very light Higgs boson decaying into a pair of τ leptons is presented within the framework of the next-to-minimal supersymmetric standard model. This search is based on a data set corresponding to an integrated luminosity of 19.7 fbsup−1/sup of proton-proton collisions collected by the CMS experiment at a centre-of-mass energy of 8 TeV. The signal is defined by the production of either of the two lightest scalars, h1 or h2, via gluon-gluon fusion and subsequent decay into a pair of the lightest Higgs bosons, a1 or h1. The h1 or h2 boson is identified with the observed state at a mass of 125 GeV. The analysis searches for decays of the a1 (h1) states into pairs of τ leptons and covers a mass range for the a1 (h1) boson of 4 to 8 GeV. The search reveals no significant excess in data above standard model background expectations, and an upper limit is set on the signal production cross section times branching fraction as a function of the a1 (h1) boson mass. The 95% confidence level limit ranges from 4.5 pb at ma1(mh1) = 8 GeV to 10.3 pb at ma1(mh1)=5 GeV. © 2016, The Author(s).
A search is presented for a high-mass Higgs boson in the , , , and decay modes using the ATLAS detector at the CERN Large Hadron Collider. The search uses proton-proton collision data at a centre-of-mass energy of 8 TeV corresponding to an integrated luminosity of 20.3 fb. The results of the search are interpreted in the scenario of a heavy Higgs boson with a width that is small compared with the experimental mass resolution. The Higgs boson mass range considered extends up to for all four decay modes and down to as low as 140 , depending on the decay mode. No significant excess of events over the Standard Model prediction is found. A simultaneous fit to the four decay modes yields upper limits on the production cross-section of a heavy Higgs boson times the branching ratio to boson pairs. 95 % confidence level upper limits range from 0.53 pb at GeV to 0.008 pb at GeV for the gluon-fusion production mode and from 0.31 pb at GeV to 0.009 pb at GeV for the vector-boson-fusion production mode. The results are also interpreted in the context of Type-I and Type-II two-Higgs-doublet models.
Abstract: The electroweak production and subsequent decay of single top quarks is determined by the properties of the Wtb vertex. This vertex can be described by the complex parameters of an effective Lagrangian. An analysis of angular distributions of the decay products of single top quarks produced in the t -channel constrains these parameters simultaneously. The analysis described in this paper uses 4.6 fbsup−1/sup of proton-proton collision data at (Formula presented.) TeV collected with the ATLAS detector at the LHC. Two parameters are measured simultaneously in this analysis. The fraction f1 of decays containing transversely polarised W bosons is measured to be 0.37 ± 0.07 (stat.⊕syst.). The phase δ− between amplitudes for transversely and longitudinally polarised W bosons recoiling against left-handed b-quarks is measured to be −0.014π ± 0.036π (stat.⊕syst.). The correlation in the measurement of these parameters is 0.15. These values result in two-dimensional limits at the 95% confidence level on the ratio of the complex coupling parameters gR and VL, yielding Re[gR/VL] ∈ [−0.36, 0.10] and Im[gR/VL] ∈ [−0.17, 0.23] with a correlation of 0.11. The results are in good agreement with the predictions of the Standard Model.[Figure not available: see fulltext.] © 2016, The Author(s).
The result of a search for flavor changing neutral currents (FCNC) through single top quark production in association with a photon is presented. The study is based on proton-proton collisions at a center-of-mass energy of 8 TeV using data collected with the CMS detector at the LHC, corresponding to an integrated luminosity of 19.8 fbsup−1/sup. The search for tγ events where t → Wb and W → μν is conducted in final states with a muon, a photon, at least one hadronic jet with at most one being consistent with originating from a bottom quark, and missing transverse momentum. No evidence of single top quark production in association with a photon through a FCNC is observed. Upper limits at the 95% confidence level are set on the tuγ and tcγ anomalous couplings and translated into upper limits on the branching fraction of the FCNC top quark decays: ℬ(t → uγ) < 1.3 × 10sup− 4/sup and ℬ(t → cγ) < 1.7 × 10sup− 3/sup. Upper limits are also set on the cross section of associated tγ production in a restricted phase-space region. These are the most stringent limits currently available. © 2016, The Author(s).
Charged Higgs bosons heavier than the top quark and decaying via Hsup±/sup → tb are searched for in proton-proton collisions measured with the ATLAS experiment at (Formula presented.) TeV corresponding to an integrated luminosity of 20.3fbsup−1/sup. The production of a charged Higgs boson in association with a top quark, gb → tHsup±/sup, is explored in the mass range 200 to 600 GeV using multi-jet final states with one electron or muon. In order to separate the signal from the Standard Model background, analysis techniques combining several kinematic variables are employed. An excess of events above the background-only hypothesis is observed across a wide mass range, amounting to up to 2.4 standard deviations. Upper limits are set on the gb → tHsup±/sup production cross section times the branching fraction BR(Hsup±/sup → tb). Additionally, the complementary s-channel production, qqsup′/sup → Hsup±/sup, is investigated through a reinterpretation of Wsup′/sup → tb searches in ATLAS. Final states with one electron or muon are relevant for Hsup±/sup masses from 0.4 to 2.0 TeV, whereas the all-hadronic final state covers the range 1.5 to 3.0 TeV. In these search channels, no significant excesses from the predictions of the Standard Model are observed, and upper limits are placed on the qqsup′/sup → Hsup±/sup production cross section times the branching fraction BR(Hsup±/sup → tb). © 2016, The Author(s).
Charged Higgs bosons produced in association with a single top quark and decaying via Hsup±/sup→τν are searched for with the ATLAS experiment at the LHC, using proton–proton collision data at s=13 TeV corresponding to an integrated luminosity of 3.2 fbsup−1/sup. The final state is characterised by the presence of a hadronic τ decay and missing transverse momentum, as well as a hadronically decaying top quark, resulting in the absence of high-transverse-momentum electrons and muons. The data are found to be consistent with the expected background from Standard Model processes. A statistical analysis leads to 95% confidence-level upper limits on the production cross section times branching fraction, σ(pp→[b]tHsup±/sup)×BR(Hsup±/sup→τν), between 1.9 pb and 15 fb, for charged Higgs boson masses ranging from 200 to 2000 GeV. The exclusion limits for this search surpass those obtained with the proton–proton collision data recorded at s=8 TeV. © 2016 The Author(s)
A search for evidence of particle dark matter (DM) and unparticle production at the LHC has been performed using events containing two charged leptons, consistent with the decay of a Z boson, and large missing transverse momentum. This study is based on data collected with the CMS detector corresponding to an integrated luminosity of 19.7 fb(-1) of pp collisions at the LHC at a center-of-mass energy of 8 TeV. No significant excess of events is observed above the number expected from the standard model contributions. The results are interpreted in terms of 90% confidence level limits on the DM-nucleon scattering cross section, as a function of the DM particle mass, for both spin-dependent and spin-independent scenarios. Limits are set on the effective cutoff scale., and on the annihilation rate for DM particles, assuming that their branching fraction to quarks is 100%. Additionally, the most stringent 95% confidence level limits to date on the unparticle model parameters are obtained.
This article reports on a search for dark matter pair production in association with a Higgs boson decaying to a pair of bottom quarks, using data from 20.3 fb-1 of pp collisions at a center-of-mass energy of 8 TeV collected by the ATLAS detector at the LHC. The decay of the Higgs boson is reconstructed as a high-momentum bb system with either a pair of small-radius jets, or a single large-radius jet with substructure. The observed data are found to be consistent with the expected Standard Model backgrounds. Model-independent upper limits are placed on the visible cross sections for events with a Higgs boson decaying into bb and large missing transverse momentum with thresholds ranging from 150 to 400 GeV. Results are interpreted using a simplified model with a Z′ gauge boson decaying into different Higgs bosons predicted in a two-Higgs-doublet model, of which the heavy pseudoscalar Higgs decays into a pair of dark matter particles. Exclusion limits are also presented for the mass scales of various effective field theory operators that describe the interaction between dark matter particles and the Higgs boson. © 2016 CERN, for the ATLAS Collaboration.
Results: are reported from a search for the top squark t ˜ 1, the lighter of the two supersymmetric partners of the top quark. The data sample corresponds to 19.7 fb−1 of proton-proton collisions at s=8 TeV collected with the CMS detector at the LHC. The search targets t˜1→bχ˜1± and t˜1→t(∗)χ˜10 decay modes, where χ˜1± and χ˜10 are the lightest chargino and neutralino, respectively. The reconstructed final state consists of jets, b jets, missing transverse energy, and either one or two leptons. Leading backgrounds are determined from data. No significant excess in data is observed above the expectation from standard model processes. The results exclude a region of the two-dimensional plane of possible t ˜ 1 and χ˜10 masses. The highest excluded t ˜ 1 and χ˜10 masses are about 700 GeV and 250 GeV, respectively.[Figure not available: see fulltext.] © 2016, The Author(s).
A search for direct pair production of the supersymmetric partner of the top quark, decaying via a scalar tau to a nearly massless gravitino, has been performed using 20 fb (Formula presented.) of proton–proton collision data at (Formula presented.). The data were collected by the ATLAS experiment at the LHC in 2012. Top squark candidates are searched for in events with either two hadronically decaying tau leptons, one hadronically decaying tau and one light lepton, or two light leptons. No significant excess over the Standard Model expectation is found. Exclusion limits at (Formula presented.) confidence level are set as a function of the top squark and scalar tau masses. Depending on the scalar tau mass, ranging from the (Formula presented.) LEP limit to the top squark mass, lower limits between 490 and (Formula presented.) are placed on the top squark mass within the model considered. © 2016, CERN for the benefit of the ATLAS collaboration.
A search for compositeness of electrons and muons is presented using a data sample of proton-proton collisions at a center-of-mass energy of (Formula presented.) TeV collected with the CMS detector at the LHC and corresponding to an integrated luminosity of 19.7 fbsup−1/sup. Excited leptons (ℓsup*/sup) produced via contact interactions in conjunction with a standard model lepton are considered, and a search is made for their gauge decay modes. The decays considered are ℓsup*/sup → ℓγ and ℓsup*/sup → ℓZ, which give final states of two leptons and a photon or, depending on the Z-boson decay mode, four leptons or two leptons and two jets. The number of events observed in data is consistent with the standard model prediction. Exclusion limits are set on the excited lepton mass, and the compositeness scale Λ. For the case Mℓ* = Λ the existence of excited electrons (muons) is excluded up to masses of 2.45 (2.47) TeV at 95% confidence level. Neutral current decays of excited leptons are considered for the first time, and limits are extended to include the possibility that the weight factors f and f′, which determine the couplings between standard model leptons and excited leptons via gauge mediated interactions, have opposite sign. © 2016, The Author(s).
The analysis of 2-dimentional Dalitz' diagram, measured in C-14(pi(-), pd)X reaction, allowed to distinguish the pion absorption by (3)p intranuclear cluster and to obtain an indication on the existence of (3)p + Li-11 configuration in C-14 nucleus. Highly excited states of Be-12,Be-13 isotopes were found with the energy of E-x approximate to 30 MeV for the first time. It was shown that these states decay as follows Be-12* - p + Li-11 and Be-13* - d + Li-11.
A search is presented for exotic decays of a Higgs boson into undetectable particles and one or two isolated photons in pp collisions at a center-of-mass energy of 8 TeV. The data correspond to an integrated luminosity of up to 19.4 fb-1 collected with the CMS detector at the LHC. Higgs bosons produced in gluon-gluon fusion and in association with a Z boson are investigated, using models in which the Higgs boson decays into a gravitino and a neutralino or a pair of neutralinos, followed by the decay of the neutralino to a gravitino and a photon. The selected events are consistent with the background-only hypothesis, and limits are placed on the product of cross sections and branching fractions. Assuming a standard model Higgs boson production cross section, a 95% confidence level upper limit is set on the branching fraction of a 125 GeV Higgs boson decaying into undetectable particles and one or two isolated photons as a function of the neutralino mass. For this class of models and neutralino masses from 1 to 120 GeV an upper limit in the range of 7 to 13% is obtained. Further results are given as a function of the neutralino lifetime, and also for a range of Higgs boson masses. © 2015 CERN for the benefit of the CMS Collaboration.
A search for the flavour-changing neutral-current decay is presented. Data collected by the ATLAS detector during 2012 from proton-proton collisions at the Large Hadron Collider at a centre-of-mass energy of root s = 8 TeV, corresponding to an integrated luminosity of 20.3 fb(-1), are analysed. Top-quark pair-production events with one top quark decaying through the t - qZ (q = u,c) channel and the other through the dominant Standard Model mode t - bW are considered as signal. Only the decays of the Z boson to charged leptons and leptonic W boson decays are used. No evidence for a signal is found and an observed (expected) upper limit on the t - qZ branching ratio of 7 x 10(-4) (8 x 10(-4)) is set at the 95 % confidence level.
A search for a Higgs boson produced via vector-boson fusion and decaying into invisible particles is presented, using 20.3 fbsup−1/sup of proton-proton collision data at a centre-of-mass energy of 8 TeV recorded by the ATLAS detector at the LHC. For a Higgs boson with a mass of 125 GeV, assuming the Standard Model production cross section, an upper bound of 0.28 is set on the branching fraction of H → invisible at 95% confidence level, where the expected upper limit is 0.31. The results are interpreted in models of Higgs-portal dark matter where the branching fraction limit is converted into upper bounds on the dark-matter-nucleon scattering cross section as a function of the dark-matter particle mass, and compared to results from the direct dark-matter detection experiments. © 2016, The Author(s).
Search for isobar-analog states (IAS) of superheavy hydrogen isotopes H5-7 was performed among the high-excited states of helium isotopes He5-7. The excited spectra were measured in stopped pion absorption by light nuclei. The experiment was performed at low energy pion channel of LANL with two-arm multilayer semiconductor spectrometer. Excited states of He5-7 were observed in three-body reaction channels on B-10,B-11 nuclei. Several excited levels were observed for the first time. He-6 excited state with E-x = 27.0(8) MeV observed in B-10(pi(-), pt)X channel is an IAS candidate for H-6 with E-r similar to 5.5 MeV. He-7 excited state with E-x = 24.8(4) MeV observed in B-10(pi(-),pd)X, B-11(pi(-),pt)X and B-11(pi(-),dd)X channels is an IAS candidate for H-7 with E-r similar to 3 MeV.
A search for highly ionizing particles produced in proton-proton collisions at 8 TeV center-of-mass energy is performed by the ATLAS Collaboration at the CERN Large Hadron Collider. The data set used corresponds to an integrated luminosity of 7.0 fb(-1). A customized trigger significantly increases the sensitivity, permitting a search for such particles with charges and energies beyond what was previously accessible. No events were found in the signal region, leading to production cross section upper limits in the mass range 200-2500 GeV for magnetic monopoles with magnetic charge in the range 0.5g(D) vertical bar g vertical bar 2.0g(D), where g(D) is the Dirac charge, and for stable particles with electric charge in the range 10 vertical bar z vertical bar 60. Model-dependent limits are presented in given pair-production scenarios, and model-independent limits are presented in fiducial regions of particle energy and pseudorapidity.
A search for a massive resonance W sup′/supdecaying into a W and a Higgs boson in the ℓνb b ¯ (ℓ= e , μ) final state is presented. Results are based on data corresponding to an integrated luminosity of 19.7fb sup- 1/sup of proton–proton collisions at s= 8 TeV , collected using the CMS detector at the LHC. For a high-mass (≳ 1TeV) resonance, the two bottom quarks coming from the Higgs boson decay are reconstructed as a single jet, which can be tagged by placing requirements on its substructure and flavour. Exclusion limits at 95 % confidence level are set on the production cross section of a narrow resonance decaying into WH, as a function of its mass. In the context of a little Higgs model, a lower limit on the W sup′/sup mass of 1.4TeV is set. In a heavy vector triplet model that mimics the properties of composite Higgs models, a lower limit on the W sup′/sup mass of 1.5TeV is set. In the context of this model, the results are combined with related searches to obtain a lower limit on the W sup′/sup mass of 1.8TeV , the most restrictive to date for decays to a pair of standard model bosons. © 2016, CERN for the benefit of the CMS collaboration.
This paper presents a search for massive charged long-lived particles produced in pp collisions at root s = 13 TeV at the LHC using the ATLAS experiment. The data set used corresponds to an integrated luminosity of 3.2 fb(-1). Many extensions of the Standard Model predict the existence of massive charged long-lived particles, such as R-hadrons. These massive particles are expected to be produced with a velocity significantly below the speed of light, and therefore to have a specific ionization higher than any Standard Model particle of unit charge at high momenta. The Pixel subsystem of the ATLAS detector is used to measure the ionization energy loss of reconstructed charged particles and to search for such highly ionizing particles. The search presented here has much greater sensitivity than a similar search performed using the ATLAS detector in the root s = 8 TeV data set, thanks to the increase in expected signal cross section due to the higher center-of-mass energy of collisions, to an upgraded detector with a new silicon layer close to the interaction point, and to analysis improvements. No significant deviation from Standard Model background expectations is observed, and lifetime-dependent upper limits on R-hadron production cross sections and masses are set. Gluino R-hadrons with lifetimes above 0.4 ns and decaying to q (q) over bar plus a 100 GeV neutralino are excluded at the 95% confidence level, with lower mass limit ranging between 740 and 1590 GeV. In the case of stable R-hadrons the lower mass limit at the 95% confidence level is 1570 GeV.
A search for narrow resonances in proton-proton collisions at root s = 13 TeV is presented. The invariant mass distribution of the two leading jets is measured with the CMS detector using a data set corresponding to an integrated luminosity of 2.4 fb(-1). The highest observed dijet mass is 6.1 TeV. The distribution is smooth and no evidence for resonant particles is observed. Upper limits at 95% confidence level are set on the production cross section for narrow resonances with masses above 1.5 TeV. When interpreted in the context of specific models, the limits exclude string resonances with masses below 7.0 TeV, scalar diquarks below 6.0 TeV, axigluons and colorons below 5.1 TeV, excited quarks below 5.0 TeV, color-octet scalars below 3.1 TeV, and W' bosons below 2.6 TeV. These results significantly extend previously published limits.
A search for narrow resonances decaying into dijet final states is performed on data from proton-proton collisions at a center-of-mass energy of 8 TeV, corresponding to an integrated luminosity of 18.8 fb(-1). The data were collected with the CMS detector using a novel technique called data scouting, in which the information associated with these selected events is much reduced, permitting collection of larger data samples. This technique enables CMS to record events containing jets at a rate of 1 kHz, by collecting the data from the high-level-trigger system. In this way, the sensitivity to low-mass resonances is increased significantly, allowing previously inaccessible couplings of new resonances to quarks and gluons to be probed. The resulting dijet mass distribution yields no evidence of narrow resonances. Upper limits are presented on the resonance cross sections as a function of mass, and compared with a variety of models predicting narrow resonances. The limits are translated into upper limits on the coupling of a leptophobic resonance Z'(B) to quarks, improving on the results obtained by previous experiments for the mass range from 500 to 800 GeV.
A search for neutral Higgs bosons predicted in the minimal supersymmetric standard model (MSSM) for μ+μ- decay channels is presented. The analysis uses data collected by the CMS experiment at the LHC in proton-proton collisions at centre-of-mass energies of 7 and 8 TeV, corresponding to integrated luminosities of 5.1 and 19.3 fb-1, respectively. The search is sensitive to Higgs bosons produced either through the gluon fusion process or in association with a bb quark pair. No statistically significant excess is observed in the μ+μ- mass spectrum. Results are interpreted in the framework of several benchmark scenarios, and the data are used to set an upper limit on the MSSM parameter tanβ as a function of the mass of the pseudoscalar A boson in the range from 115 to 300 GeV. Model independent upper limits are given for the product of the cross section and branching fraction for gluon fusion and b quark associated production at s=8 TeV. They are the most stringent limits obtained to date in this channel. © 2015 The Authors.
A search is performed for a new resonance decaying into a lighter resonance and a Z boson. Two channels are studied, targeting the decay of the lighter resonance into either a pair of oppositely charged τ leptons or a bb pair. The Z boson is identified via its decays to electrons or muons. The search exploits data collected by the CMS experiment at a centre-of-mass energy of 8 TeV, corresponding to an integrated luminosity of 19.8 fb-1. No significant deviations are observed from the standard model expectation and limits are set on production cross sections and parameters of two-Higgs-doublet models. © 2016 The Author.
This Letter describes a model-agnostic search for pairs of jets (dijets) produced by resonant and non-resonant phenomena beyond the Standard Model in 3.6 fbsup-1/sup of proton-proton collisions with a centre-of-mass energy of s=13 TeV recorded by the ATLAS detector at the Large Hadron Collider. The distribution of the invariant mass of the two leading jets is examined for local excesses above a data-derived estimate of the smoothly falling prediction of the Standard Model. The data are also compared to a Monte Carlo simulation of Standard Model angular distributions derived from the rapidity of the two jets. No evidence of anomalous phenomena is observed in the data, which are used to exclude, at 95% CL, quantum black holes with threshold masses below 8.3 TeV, 8.1 TeV, or 5.1 TeV in three different benchmark scenarios; resonance masses below 5.2 TeV for excited quarks, 2.6 TeV in a Wsup'/sup model, a range of masses starting from mZ'=1.5 TeV and couplings from gq=0.2 in a Zsup'/sup model; and contact interactions with a compositeness scale below 12.0 TeV and 17.5 TeV respectively for destructive and constructive interference between the new interaction and QCD processes. These results significantly extend the ATLAS limits obtained from 8 TeV data. Gaussian-shaped contributions to the mass distribution are also excluded if the effective cross-section exceeds values ranging from approximately 50-300 fb for masses below 2 TeV to 2-20 fb for masses above 4 TeV. © 2016 CERN for the benefit of the ATLAS Collaboration.
Results of a search for new phenomena in events with an energetic photon and large missing transverse momentum with the ATLAS experiment at the Large Hadron Collider are reported. The data were collected in proton-proton collisions at a centre-of-mass energy of 13 TeV and correspond to an integrated luminosity of 3.2 fbsup−1/sup. The observed data are in agreement with the Standard Model expectations. Exclusion limits are presented in models of new phenomena including pair production of dark matter candidates or large extra spatial dimensions. In a simplified model of dark matter and an axial-vector mediator, the search excludes mediator masses below 710 GeV for dark matter candidate masses below 150 GeV. In an effective theory of dark matter production, values of the suppression scale M∗ up to 570 GeV are excluded and the effect of truncation for various coupling values is reported. For the ADD large extra spatial dimension model the search places more stringent limits than earlier searches in the same event topology, excluding MD up to about 2.3 (2.8) TeV for two (six) additional spatial dimensions; the limits are reduced by 20-40% depending on the number of additional spatial dimensions when applying a truncation procedure. © 2016, The Author(s).
Results of a search for new phenomena in events with at least three photons are reported. Data from proton–proton collisions at a centre-of-mass energy of 8 TeV, corresponding to an integrated luminosity of 20.3 fb (Formula presented.) , were collected with the ATLAS detector at the LHC. The observed data are well described by the Standard Model. Limits at the 95 % confidence level on new phenomena are presented based on the rate of events in an inclusive signal region and a restricted signal region targeting the rare decay (Formula presented.) , as well as di-photon and tri-photon resonance searches. For a Standard Model Higgs boson decaying to four photons via a pair of intermediate pseudoscalar particles (a), limits are found to be (Formula presented.) for 10 GeV (Formula presented.) 62 GeV. Limits are also presented for Higgs boson-like scalars (H) for (Formula presented.) 125 GeV, and for a (Formula presented.) decaying to three photons via (Formula presented.). Additionally, the observed limit on the branching ratio of the Z boson decay to three photons is found to be BR (Formula presented.) , a result five times stronger than the previous result from LEP. © 2016, CERN for the benefit of the ATLAS collaboration.
Results are reported of a search for new phenomena, such as supersymmetric particle production, that could be observed in high-energy proton-proton collisions. Events with large numbers of jets, together with missing transverse momentum from unobserved particles, are selected. The data analysed were recorded by the ATLAS experiment during 2015 using the 13 TeV centre-of-mass proton-proton collisions at the Large Hadron Collider, and correspond to an integrated luminosity of 3.2 fbsup-1/sup. The search selected events with various jet multiplicities from ≥7 to ≥10 jets, and with various b-jet multiplicity requirements to enhance sensitivity. No excess above Standard Model expectations is observed. The results are interpreted within two supersymmetry models, where gluino masses up to 1400 GeV are excluded at 95% confidence level, significantly extending previous limits. © 2016 CERN for the benefit of the ATLAS Collaboration.
Abstract: A search is performed for the production of high-mass resonances decaying into a photon and a jet in 3.2 fbsup−1/sup of proton-proton collisions at a centre-of-mass energy of (Formula presented.) TeV collected by the ATLAS detector at the Large Hadron Collider. Selected events have an isolated photon and a jet, each with transverse momentum above 150 GeV. No significant deviation of the γ+jet invariant mass distribution from the background-only hypothesis is found. Limits are set at 95% confidence level on the cross sections of generic Gaussian-shaped signals and of a few benchmark phenomena beyond the Standard Model: excited quarks with vector-like couplings to the Standard Model particles, and non-thermal quantum black holes in two models of extra spatial dimensions. The minimum excluded visible cross sections for Gaussian-shaped resonances with width-to-mass ratios of 2% decrease from about 6 fb for a mass of 1.5 TeV to about 0.8 fb for a mass of 5 TeV. The minimum excluded visible cross sections for Gaussian-shaped resonances with width-to-mass ratios of 15% decrease from about 50 fb for a mass of 1.5 TeV to about 1.0 fb for a mass of 5 TeV. Excited quarks are excluded below masses of 4.4 TeV, and non-thermal quantum black holes are excluded below masses of 3.8 (6.2) TeV for Randall-Sundrum (Arkani-Hamed-Dimopoulous-Dvali) models with one (six) extra dimensions.[Figure not available: see fulltext.] © 2016, The Author(s).
A search for pair production of first and second generation leptoquarks is performed in final states containing either two charged leptons and two jets, or one charged lepton, one neutrino and two jets, using proton-proton collision data at root s = 8 TeV. The data, corresponding to an integrated luminosity of 19.7 fb(-1), were recorded with the CMS detector at the LHC. First-generation scalar leptoquarks with masses less than 1010 (850) GeV are excluded for beta = 1.0 (0.5), where beta is the branching fraction of a leptoquark decaying to a charged lepton and a quark. Similarly, second-generation scalar leptoquarks with masses less than 1080 (760) GeV are excluded for beta = 1.0 (0.5). Mass limits are also set for vector leptoquark production scenarios with anomalous vector couplings, and for R-parity violating supersymmetric scenarios of top squark pair production resulting in similar final-state signatures. These are the most stringent limits placed on the masses of vector leptoquarks and RPV top squarks to date.
A search for the production of a heavy B quark, having electric charge -1/3 and vector couplings to W, Z, and H bosons, is carried out using proton-proton collision data recorded at the CERN LHC by the CMS experiment, corresponding to an integrated luminosity of 19.7 fb(-1). The B quark is assumed to be pair produced and to decay in one of three ways: to tW, bZ, or bH. The search is carried out in final states with one, two, and more than two charged leptons, as well as in fully hadronic final states. Each of the channels in the exclusive final-state topologies is designed to be sensitive to specific combinations of the B quark-antiquark pair decays. The observed event yields are found to be consistent with the standard model expectations in all the final states studied. A statistical combination of these results is performed, and upper limits are set on the cross section of the strongly produced B quark-antiquark pairs as a function of the B quark mass. Lower limits on the B quark mass between 740 and 900 GeVare set at a 95% confidence level, depending on the values of the branching fractions of the B quark to tW, bZ, and bH. Overall, these limits are the most stringent to date.
The results of a search for a supersymmetric partner of the top quark (top squark), pair-produced in proton–proton collisions at s=8 TeV, are presented. The search, which focuses on R-parity violating, chargino-mediated decays of the top squark, is performed in final states with low missing transverse momentum, two oppositely charged electrons or muons, and at least five jets. The analysis uses a data sample corresponding to an integrated luminosity of 19.7 fbsup−1/sup collected with the CMS detector at the LHC in 2012. The data are found to be in agreement with the standard model expectation, and upper limits are placed on the top squark pair production cross section at 95% confidence level. Assuming a 100% branching fraction for the top squark decay chain, t˜→tχ˜1 sup±/sup,χ˜1 sup±/sup→ℓsup±/sup+jj, top squark masses less than 890 (1000) GeV for the electron (muon) channel are excluded for the first time in models with a single nonzero R-parity violating coupling λijk sup′/sup (i,j,k≤2), where i,j,k correspond to the three generations. © 2016 The Author(s)
A search is performed for the production of heavy resonances decaying into top-antitop quark pairs in proton-proton collisions at root s = 8 TeV. Data used for the analyses were collected with the CMS detector and correspond to an integrated luminosity of 19.7 fb(-1). The search is performed using events with three different final states, defined by the number of leptons (electrons and muons) from the t (t) over bar. WbWb decay. The analyses are optimized for reconstruction of top quarks with high Lorentz boosts, where jet substructure techniques are used to enhance the sensitivity. Results are presented for all channels and a combination is performed. No significant excess of events relative to the expected yield from standard model processes is observed. Upper limits on the production cross section of heavy resonances decaying to t (t) over bar are calculated. A narrow leptophobic topcolor Z' resonance with a mass below 2.4 TeV is excluded at 95% confidence level. Limits are also derived for a broad Z' resonance with a 10% width relative to the resonance mass, and a Kaluza-Klein excitation of the gluon in the Randall-Sundrum model. These are the most stringent limits to date on heavy resonances decaying into top-antitop quark pairs.
A search is performed for the process pp→G*→BHb-/B-Hb→Hbb-→bb-bb-, predicted in composite Higgs scenarios, where Gsup*/sup is a heavy colour octet vector resonance and BH a vector-like quark of charge -1/3. The data were obtained from pp collisions at a centre-of-mass energy of 8 TeV corresponding to an integrated luminosity of 19.5 fbsup-1/sup, recorded by the ATLAS detector at the LHC. The largest background, multijet production, is estimated using a data-driven method. No significant excess of events with respect to Standard Model predictions is observed, and upper limits on the production cross section times branching ratio are set. Comparisons to the predictions from a specific benchmark model are made, resulting in lower mass limits in the two-dimensional mass plane of mG* vs. mBH. © 2016 The Author.
A search is presented for the production of both first- and second-generation scalar leptoquarks with a final state of either two electrons and one jet or two muons and one jet. The search is based on a data sample of proton-proton collisions at center-of-mass energy root s = 8 TeV recorded with the CMS detector and corresponding to an integrated luminosity of 19.6 fb(-1). Upper limits are set on both the first- and second-generation leptoquark production cross sections as functions of the leptoquark mass and the leptoquark couplings to a lepton and a quark. Results are compared with theoretical predictions to obtain lower limits on the leptoquark mass. At 95% confidence level, single production of first- generation leptoquarks with a coupling and branching fraction of 1.0 is excluded for masses below 1730 GeV, and second-generation leptoquarks with a coupling and branching fraction of 1.0 is excluded for masses below 530 GeV. These are the best overall limits on the production of first-generation leptoquarks to date.
A search for single top-quark production via flavour-changing neutral current processes from gluon plus up- or charm-quark initial states in proton-proton collisions at the LHC is presented. Data collected with the ATLAS detector in 2012 at a centre-of-mass energy of 8TeV and corresponding to an integrated luminosity of 20.3 fb(-1) are used. Candidate events for a top quark decaying into a lepton, a neutrino and a jet are selected and classified into signal- and background-like candidates using a neural network. No signal is observed and an upper limit on the production cross-section multiplied by the t - Wb branching fraction is set. The observed 95% CL limit is sigma(qg - t) x B(t - Wb) 3.4 pb and the expected 95% CL limit is sigma(qg - t) x B(t - Wb) 2.9 pb. The observed limit can be interpreted as upper limits on the coupling constants of the flavour-changing neutral current interactions divided by the scale of new physics kappa(ugt)/Lambda 5.8 x 10(-3) TeV-1 and kappa(cgt)/Lambda 13x10(-3) TeV and on the branching fractions B(t - ug) 4.0 x 10(-5) and B(t - cg) 20 x 10(-5).
A search for squarks and gluinos in final states containing hadronic jets, missing transverse momentum but no electrons or muons is presented. The data were recorded in 2015 by the ATLAS experiment in √s= 13 TeV proton–proton collisions at the Large Hadron Collider. No excess above the Standard Model background expectation was observed in 3.2 fb-1 of analyzed data. Results are interpreted within simplified models that assume R-parity is conserved and the neutralino is the lightest supersymmetric particle. An exclusion limit at the 95 % confidence level on the mass of the gluino is set at 1.51 TeV for a simplified model incorporating only a gluino octet and the lightest neutralino, assuming the lightest neutralino is massless. For a simplified model involving the strong production of mass-degenerate first- and second-generation squarks, squark masses below 1.03 TeV are excluded for a massless lightest neutralino. These limits substantially extend the region of supersymmetric parameter space excluded by previous measurements with the ATLAS detector. © 2016, CERN for the benefit of the ATLAS collaboration.
In the recent years, the Borexino detector has proven its outstanding performances in detecting neutrinos and antineutrinos in the low energy regime. Consequently, it is an ideal tool to investigate the existence of sterile neutrinos, whose presence has been suggested by several anomalies over the past two decades. The SOX (Short distance neutrino Oscillations with boreXino) project will investigate the presence of sterile neutrinos placing a neutrino and an antineutrino sources in a location under the detector foreseen for this purpose since the construction of Borexino. Interacting in the detector active volume, each beam would create a well detectable spatial wave pattern in case of oscillation of neutrino or antineutrino in a sterile state. Otherwise, the experiment will set a very stringent limit on the existence of a sterile state.
Abstract: A search is conducted for new physics in multijet final states using 3.6 inverse femtobarns of data from proton-proton collisions at (Formula presented.) TeV taken at the CERN Large Hadron Collider with the ATLAS detector. Events are selected containing at least three jets with scalar sum of jet transverse momenta (HT) greater than 1 TeV. No excess is seen at large HT and limits are presented on new physics: models which produce final states containing at least three jets and having cross sections larger than 1.6 fb with HT> 5.8 TeV are excluded. Limits are also given in terms of new physics models of strong gravity that hypothesize additional space-time dimensions.[Figure not available: see fulltext.] © 2016, The Author(s).
A search for strongly produced supersymmetric particles is conducted using signatures involving multiple energetic jets and either two isolated leptons (e or μ) with the same electric charge or at least three isolated leptons. The search also utilises b-tagged jets, missing transverse momentum and other observables to extend its sensitivity. The analysis uses a data sample of proton–proton collisions at √s= 13 TeV recorded with the ATLAS detector at the Large Hadron Collider in 2015 corresponding to a total integrated luminosity of 3.2 fbsup-1/sup. No significant excess over the Standard Model expectation is observed. The results are interpreted in several simplified supersymmetric models and extend the exclusion limits from previous searches. In the context of exclusive production and simplified decay modes, gluino masses are excluded at 95 % confidence level up to 1.1–1.3 TeV for light neutralinos (depending on the decay channel), and bottom squark masses are also excluded up to 540 GeV. In the former scenarios, neutralino masses are also excluded up to 550–850 GeV for gluino masses around 1 TeV. © 2016, CERN for the benefit of the ATLAS collaboration.
Results are reported from a search for supersymmetry with gauge-mediated supersymmetry breaking in electroweak production. Final states with photons and large missing transverse energy ( ET supmiss/sup) were examined. The data sample was collected in pp collisions at √s=8TeV with the CMS detector at the LHC and corresponds to 7.4fbsup-1/sup. The analysis focuses on scenarios in which the lightest neutralino has bino- or wino-like components, resulting in decays to photons and gravitinos, where the gravitinos escape undetected. The data were obtained using a specially designed trigger with dedicated low thresholds, providing good sensitivity to signatures with photons, ET supmiss/sup, and low hadronic energy. No excess of events over the standard model expectation is observed. The results are interpreted using the model of general gauge mediation. With the wino mass fixed at 10GeV above that of the bino, wino masses below 710GeV are excluded at 95% confidence level. Constraints are also set in the context of two simplified models, for which the analysis sets the lowest cross section limits on the electroweak production of supersymmetric particles. © 2016 The Author.
A search for supersymmetry involving events with at least one photon, one electron or muon, and large missing transverse momentum has been performed by the CMS experiment. The data sample corresponds to an integrated luminosity of 19.7 fbsup-1/sup of pp collisions at s=8 TeV, produced at the CERN LHC. No excess of events is observed beyond expectations from standard model processes. The result of the search is interpreted in the context of a general model of gauge-mediated supersymmetry breaking, where the charged and neutral winos are the next-to-lightest supersymmetric particles. Within this model, winos with a mass up to 360 GeV are excluded at the 95% confidence level. Two simplified models inspired by gauge-mediated supersymmetry breaking are also examined, and used to derive upper limits on the production cross sections of specific supersymmetric processes. © 2016 CERN for the benefit of the CMS Collaboration.
Results are presented from a search for supersymmetric particles in scenarios with small mass splittings. The data sample corresponds to 19.7 fbsup-1/sup of proton-proton collisions recorded by the CMS experiment at s=8 TeV. The search targets top squark (t~) pair production in scenarios with mass differences δm=m(t~)-m(χ~10) below the W-boson mass and with top-squark decays in the four-body mode (t~→bℓνχ~10), where the neutralino (χ~10) is assumed to be the lightest supersymmetric particle (LSP). The signature includes a high transverse momentum (pT) jet associated with initial-state radiation, one or two low-pT leptons, and significant missing transverse energy. The event yields observed in data are consistent with the expected background contributions from standard model processes. Limits are set on the cross section for top squark pair production as a function of the t~ and LSP masses. Assuming a 100% branching fraction for the four-body decay mode, top-squark masses below 316 GeV are excluded for δm=25 GeV at 95% CL. The dilepton data are also interpreted under the assumption of chargino-neutralino production, with subsequent decays to sleptons or sneutrinos. Assuming a difference between the common χ~1+/χ~20 mass and the LSP mass of 20 GeV and a τ-enriched decay scenario, masses in the range m(χ~1+)<307 GeV are excluded at 95% CL. © 2016 The Author.
A search for supersymmetry in hadronic final states with highly boosted W bosons and b jets is presented, focusing on compressed scenarios. The search is performed using proton-proton collision data at a center-of-mass energy of 8 TeV, collected by the CMS experiment at the LHC, corresponding to an integrated luminosity of 19.7 fb(-1). Events containing candidates for hadronic decays of boosted W bosons are identified using jet substructure techniques, and are analyzed using the razor variables M-R and R-2, which characterize a possible signal as a peak on a smoothly falling background. The observed event yields in the signal regions are found to be consistent with the expected contributions from standard model processes, which are predicted using control samples in the data. The results are interpreted in terms of gluino-pair production followed by their exclusive decay into top squarks and top quarks. The analysis excludes gluino masses up to 1.1 TeV for light top squarks decaying solely to a charm quark and a neutralino, and up to 700 GeV for heavier top squarks decaying solely to a top quark and a neutralino.
A search for new physics is performed based on all-hadronic events with large missing transverse momentum produced in proton-proton collisions at s=13 TeV. The data sample, corresponding to an integrated luminosity of 2.3 fbsup-1/sup, was collected with the CMS detector at the CERN LHC in 2015. The data are examined in search regions of jet multiplicity, tagged bottom quark jet multiplicity, missing transverse momentum, and the scalar sum of jet transverse momenta. The observed numbers of events in all search regions are found to be consistent with the expectations from standard model processes. Exclusion limits are presented for simplified supersymmetric models of gluino pair production. Depending on the assumed gluino decay mechanism, and for a massless, weakly interacting, lightest neutralino, lower limits on the gluino mass from 1440 to 1600 GeV are obtained, significantly extending previous limits. © 2016 The Author.
Abstract: This paper presents the search for the production of a Higgs boson in association with a single top quark (tHq), using data collected in proton-proton collisions at a center-of-mass energy of 8 TeV corresponding to an integrated luminosity of 19.7 fb−1. The search exploits a variety of Higgs boson decay modes resulting in final states with photons, bottom quarks, and multiple charged leptons, including tau leptons, and employs a variety of multivariate techniques to maximize sensitivity to the signal. The analysis is optimized for the opposite sign of the Yukawa coupling to that in the standard model, corresponding to a large enhancement of the signal cross section. In the absence of an excess of candidate signal events over the background predictions, 95% confidence level observed (expected) upper limits on anomalous tHq production are set, ranging between 600 (450) fb and 1000 (700) fb depending on the assumed diphoton branching fraction of the Higgs boson. This is the first time that results on anomalous tHq production have been reported.[Figure not available: see fulltext.] © 2016, The Author(s).
The ATLAS experiment has performed extensive searches for the electroweak production of charginos, neutralinos, and staus. This article summarizes and extends the search for electroweak supersymmetry with new analyses targeting scenarios not covered by previously published searches. New searches use vector-boson fusion production, initial-state radiation jets, and low-momentum lepton final states, as well as multivariate analysis techniques to improve the sensitivity to scenarios with small mass splittings and low-production cross sections. Results are based on 20 fbsup-1/sup of proton-proton collision data at √s = 8 TeV recorded with the ATLAS experiment at the Large Hadron Collider. No significant excess beyond Standard Model expectations is observed. The new and existing searches are combined and interpreted in terms of 95% confidence-level exclusion limits in simplified models, where a single production process and decay mode is assumed, as well as within phenomenological supersymmetric models. © 2016 CERN, for the ATLAS Collaboration. Published by the American Physical Society under the terms of the "http://creativecommons.org/licenses/by/3.0/" Creative Commons Attribution 3.0 License. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.
A search is presented for a singly produced excited bottom quark (bsup*/sup) decaying to a top quark and a W boson in the all-hadronic, lepton+jets, and dilepton final states in proton-proton collisions at s=8(Formula Presented.)TeV recorded by the CMS experiment at the CERN LHC. Data corresponding to an integrated luminosity of 19.7 fbsup−1/sup are used. No significant excess of events is observed with respect to standard model expectations. We set limits at 95% confidence on the product of the bsup*/sup quark production cross section and its branching fraction to tW. The cross section limits are interpreted for scenarios including left-handed, right-handed, and vector-like couplings of the bsup*/sup quark and are presented in the two-dimensional coupling plane based on the production and decay coupling constants. The masses of the left-handed, right-handed, and vector-like bsup*/sup quark states are excluded at 95% confidence below 1390, 1430, and 1530 GeV, respectively, for benchmark couplings. This analysis gives the most stringent limits on the mass of the bsup∗/sup quark to date.[Figure not available: see fulltext.] © 2016, The Author(s).
A search for vector-like quarks and excited quarks in events containing a top quark and a W boson in the final state is reported here. The search is based on 20.3 fbsup−1/sup of proton-proton collision data taken at the LHC at a centre-of-mass energy of 8 TeV recorded by the ATLAS detector. Events with one or two leptons, and one, two or three jets are selected with the additional requirement that at least one jet contains a b-quark. Single-lepton events are also required to contain at least one large-radius jet from the hadronic decay of a high-pTW boson or a top quark. No significant excess over the expected background is observed and upper limits on the cross-section times branching ratio for different vector-like quark and excited-quark model masses are derived. For the excited-quark production and decay to Wt with unit couplings, quarks with masses below 1500 GeV are excluded and coupling-dependent limits are set. © 2016, The Author(s).
A search for Higgs boson production in association with a pair of top quarks (tt¯ H) is performed, where the Higgs boson decays to bb¯, and both top quarks decay hadronically. The data used correspond to an integrated luminosity of 20.3 fb−1 of pp collisions at √s = 8 TeV collected with the ATLAS detector at the Large Hadron Collider. The search selects events with at least six energetic jets and uses a boosted decision tree algorithm to discriminate between signal and Standard Model background. The dominant multijet background is estimated using a dedicated data-driven technique. For a Higgs boson mass of 125 GeV, an upper limit of 6.4 (5.4) times the Standard Model cross section is observed (expected) at 95% confidence level. The best-fit value for the signal strength is μ = 1.6 ± 2.6 times the Standard Model expectation for mH = 125 GeV. Combining all tt¯ H searches carried out by ATLAS at √s = 8 and 7 TeV, an observed (expected) upper limit of 3.1 (1.4) times the Standard Model expectation is obtained at 95% confidence level, with a signal strength μ = 1.7 ± 0.8. © 2016, The Author(s).
A search for the standard model Higgs boson produced in association with a vector boson with the decay H - tau tau is presented. The data correspond to 20.3 fb(-1) of integrated luminosity from proton-proton collisions at root s = 8 TeV recorded by the ATLAS experiment at the LHC during 2012. The data agree with the background expectation, and 95% confidence-level upper limits are placed on the cross section of this process. The observed (expected) limit, expressed in terms of the signal strength mu= sigma/sigma(SM) for m(H) = 125 GeV, is mu 5.6 (3.7). The measured value of the signal strength is mu
A search for fermionic top quark partners T of charge 2/3 is presented. The search is carried out in proton-proton collisions corresponding to an integrated luminosity of 19.7 fb(-1) collected at a center-of-mass energy of root s = 8 TeV with the CMS detector at the LHC. The T quarks are assumed to be produced strongly in pairs and can decay into tH, tZ, and bW. The search is performed in five exclusive channels: a single-lepton channel, a multilepton channel, two all-hadronic channels optimized either for the bW or the tH decay, and one channel in which the Higgs boson decays into two photons. The results are found to be compatible with the standard model expectations in all the investigated final states. A statistical combination of these results is performed and lower limits on the T quark mass are set. Depending on the branching fractions, lower mass limits between 720 and 920 GeV at 95% confidence level are found. These are among the strongest limits on vectorlike T quarks obtained to date.
A search is performed for the production of a massive W' boson decaying to a top and a bottom quark. The data analysed correspond to an integrated luminosity of 19.71 fb(-1) collected with the CMS detector at the LHC in proton-proton collisions at root s = 8 TeV. The hadronic decay products of the top quark with high Lorentz boost from the W' boson decay are detected as a single top flavoured jet. The use of jet substructure algorithms allows the top quark jet to be distinguished from standard model QCD background. Limits on the production cross section of a right-handed W' boson are obtained, together with constraints on the left-handed and right-handed couplings of the W' boson to quarks. The production of a right-handed W' boson with a mass below 2.02 TeV decaying to a hadronic final state is excluded at 95% confidence level. This mass limit increases to 2.15 TeV when both hadronic and leptonic decays are considered, and is the most stringent lower mass limit to date in the tb decay mode.
The first search for a heavy charged vector boson in the final state with a tau lepton and a neutrino is reported, using 19.7 fb-1 of LHC data at s=8 TeV. A signal would appear as an excess of events with high transverse mass, where the standard model background is low. No excess is observed. Limits are set on a model in which the W' decays preferentially to fermions of the third generation. These results substantially extend previous constraints on this model. Masses below 2.0 to 2.7 TeV are excluded, depending on the model parameters. In addition, the existence of a W' boson with universal fermion couplings is excluded at 95% confidence level, for W' masses below 2.7 TeV. For further reinterpretation a model-independent limit on potential signals for various transverse mass thresholds is also presented. © 2016 CERN for the benefit of the CMS Collaboration.
We present results of a search for two hypothetical strange dibaryon states, i.e. the H-dibaryon and the possible Λn bound state. The search is performed with the ALICE detector in central (0-10%) Pb-Pb collisions at sNN=2.76 TeV, by invariant mass analysis in the decay modes Λn→dπ+ and H-dibaryon →Λpπ-. No evidence for these bound states is observed. Upper limits are determined at 99% confidence level for a wide range of lifetimes and for the full range of branching ratios. The results are compared to thermal, coalescence and hybrid UrQMD model expectations, which describe correctly the production of other loosely bound states, like the deuteron and the hypertriton. © 2015 The Authors.
A search for a heavy scalar boson H decaying into a pair of lighter standard-model-like 125 GeV Higgs bosons hh and a search for a heavy pseudoscalar boson A decaying into a Z and an h boson are presented. The searches are performed on a data set corresponding to an integrated luminosity of 19.7 fbsup-1/sup of pp collision data at a centre-of-mass energy of 8 TeV, collected by CMS in 2012. A final state consisting of two τ leptons and two b jets is used to search for the H→hh decay. A final state consisting of two τ leptons from the h boson decay, and two additional leptons from the Z boson decay, is used to search for the decay A→Zh. The results are interpreted in the context of two-Higgs-doublet models. No excess is found above the standard model expectation and upper limits are set on the heavy boson production cross sections in the mass ranges 260<mH<350 GeV and 220<mA<350 GeV. © 2016 CERN for the benefit of the CMS Collaboration.
Searches for pair-produced scalar leptoquarks are performed using 20 fb$$-1$$-1 of proton–proton collision data provided by the LHC and recorded by the ATLAS detector at $$=8$$s=8 TeV. Events with two electrons (muons) and two or more jets in the final state are used to search for first (second)-generation leptoquarks. The results from two previously published ATLAS analyses are interpreted in terms of third-generation leptoquarks decaying to $$b_tau barbbarnu _tau $$b??b???? and $$t_tau bartbarnu _tau $$t??t???? final states. No statistically significant excess above the Standard Model expectation is observed in any channel and scalar leptoquarks are excluded at 95 % CL with masses up to $$m_mathrm LQ1$$mLQ1 1050 GeV for first-generation leptoquarks, $$m_mathrm LQ2$$mLQ2 1000 GeV for second-generation leptoquarks, $$m_mathrm LQ3$$mLQ3 625 GeV for third-generation leptoquarks in the $$b_tau barbbarnu _tau $$b??b???? channel, and 200 $$ m_mathrm LQ3 $$mLQ3 640 GeV in the $$t_tau bartbarnu _tau $$t??t???? channel. © 2015, CERN for the benefit of the ATLAS collaboration.
Analysis of the two-dimensional Dalitz plot measured in the reaction 14C(π–, pd)X allows us to follow the absorption of pions by cluster 3p and identify signs of the configuration 3p + 11Li in the 14C nucleus. The highly excited state of 12,13Be beryllium isotopes with excitation energies E* ≈ 30 MeV and which decay with the emission of hydrogen isotopes is observed for the first time: 12Be* → p + 11Li and 13Be* → d + 11Li. © 2016, Allerton Press, Inc.
We report the results of Swift and Chandra observations of an ultraluminous X-ray source, ULX-1 in M101. We show strong observational evidence that M101 ULX-1 undergoes spectral transitions from the low/hard state to the high/soft state during these observations. The spectra of M101 ULX-1 are well fitted by the so-called bulk motion Comptonization (BMC) model for all spectral states. We have established the photon index (Γ) saturation level, Γsat = 2.8 ± 0.1, in the Γ versus mass accretion rate (M) correlation. This Γ-M correlation allows us to evaluate black hole (BH) mass in M101 ULX-1 to be MBH ∼ (3.2-4.3) × 104 M⊙, assuming the spread in distance to M101 (from 6.4 ± 0.5 Mpc to 7.4 ± 0.6 Mpc). For this BH mass estimate we apply the scaling method, using Galactic BHs XTE J1550-564, H 1743-322 and 4U 1630-472 as reference sources. The Γ vs. M correlation revealed in M101 ULX-1 is similar to that in a number of Galactic BHs and clearly exhibits the correlation along with the strong Γ saturation at ≈ 2.8. This is robust observational evidence for the presence of a BH in M101 ULX-1. We also find that the seed (disk) photon temperatures are low, on the order of 40-100 eV, which is consistent with high BH mass in M101 ULX-1. Thus, we suggest that the central object in M101 ULX-1 has intermediate BH mass on the order of 104 solar masses. © ESO, 2015.
We present a theoretical study of light transmission through a disordered medium with large (compared to the light wavelength) inhomogeneities. Both numerical integration and analytic treatments of the radiative transfer equation are performed. An effect of the single-scattering phase function on the total transmittance is found in a sub diffusion thickness range. The effect reveals itself at grazing angles of incidence and originates from small-angle multiple scattering of light. A simple analytic formula for the total transmittance is derived. Our results are in good agreement with data of independent numerical calculations. (C) 2016 Optical Society of America
The Borexino detector has convincingly shown its outstanding performances in the low energy, sub-MeV regime through its unprecedented accomplishments in the solar and geo-neutrinos detection. These performances make it the ideal tool to accomplish a state-of-the-art experiment able to test unambiguously the long-standing issue of the existence of a sterile neutrino, as suggested by the several anomalous results accumulated over the past two decades, i.e. the outputs of the LSND and Miniboone experiments, the results of the source calibration of the two Gallium solar neutrino experiments, and the recently hinted reactor anomaly. The SOX project will exploit two sources, based on Chromium and Cerium, respectively, which deployed under the experiment, in a location foreseen on purpose at the time of the construction of the detector, will emit two intense beams of neutrinos (Cr) and anti-neutrinos (Ce). Interacting in the active volume of the liquid scintillator, each beam would create an unmistakable spatial wave pattern in case of oscillation of the νe (or νÌ. e) into the sterile state: such a pattern would be the smoking gun proving the existence of the new sterile member of the neutrino family. Otherwise, its absence will allow setting a very stringent limit on its existence. © The Authors, published by EDP Sciences.
The ATLAS experiment at the Large Hadron Collider measures charged hadron spectra in Pb+Pb and p+Pb collisions. The results are compared to the pp spectra of charged hadrons at the same centre-of-mass energy. Charged hadron distributions from Pb+Pb are compared to charged particle cross-sections in pp collisions at root s = 2.76 TeV, reference crosssection for p+Pb at root s(NN) = 5.02 TeV is reconstructed using root s = 2.76 TeV and 7 TeV pp results. These allow for a detailed comparison of the collision systems in a wide transverse momentum and rapidity ranges in different centrality intervals. The nuclear modification factors RAA and Rppb are presented as a function of centrality, P-T, eta. The charged particle R-AA is found to vary significantly as a function of transverse momentum, and shows a pronounced minimum at about 7 GeV. Above 60 GeV, R-AA is consistent with a flat, centrality-dependent, value within the uncertainties. R-pPb results show strong rapidity dependence in the region of so-called Cronin peak at about 2 GeV and above pr of 10 GeV show anomalous enhancement.
The passage of current through the electrodes of a plasma focus chamber is analyzed taking into account the skin effect; the thermal load on the elliptical shaped electrodes is studied in the interaction with the current-plasma sheath, calculated within the two-dimensional ideal magnetohydrodynamic model. The heating of the anode of the plasma focus chamber by the discharge current is assessed under the limit modes of operation. Signs of the thermal action of plasma particles on the electrode surface are demonstrated. © 2016, Pleiades Publishing, Ltd.
For the purposes of the experiments on heavy ions deceleration in ionized matter a plasma target based on a linear electric discharge in hydrogen has been designed. The two-imensional hydrodynamic code was used for numeric simulation of the main stage of discharge. Estimated distribution of electron density and the degree of plasma ionization along the discharge tube axis of the target at the time of maximum discharge current corresponds to the experimental measurements of time dynamic of linear electron density and degree of plasma ionization in the target.
The slow oscillations of intralayer magnetoresistance in the quasi-2D metallic compounds TbTe(Formula presented.) and GdTe(Formula presented.) have been observed for the first time. These oscillations do not originate from small Fermi-surface pockets, as revealed usually by Shubnikov–de Haas oscillations, but from the entanglement of close frequencies due to a finite interlayer transfer integral (Formula presented.), either between the two Te planes forming a bilayer or between two adjacent bilayers, which allows to estimate its values. For TbTe(Formula presented.) and GdTe(Formula presented.), we obtain the estimate (Formula presented.) meV. © 2016 Springer Science+Business Media New York
A number of electron beam vacuum devices such as small radiofrequency (RF) linear accelerators (linacs) and microwave traveling wave tubes (TWTs) utilize slow wave structures which are usually rather complicated in production and may require multi-step brazing and time consuming tuning. Fabrication of these devices becomes challenging at centimeter wavelengths, at large number of cells, and when a series or mass production of such structures is required. A hybrid, metal-dielectric, periodic structure for low gradient, low beam current applications is introduced here as a modification of Andreev's disk-and-washer (DaW) structure. Compensated type of coupling between even and odd TE01 modes in the novel structure results in negative group velocity with absolute values as high as 0.1c-0.2c demonstrated in simulations. Sensitivity to material imperfections and electrodynamic parameters of the disk-and-ring (DaR) structure are considered numerically using a single cell model. © 2016 Elsevier B.V. All rights reserved.
The problem of choosing the cluster or a cluster node for task execution is important for the overall performance of a distributed system. This paper presents a complex approach to the planning of computations on heterogeneous distributed systems - a set of clusters and NoSQL storage systems. Dynamic scheduling algorithm depends on: the inter-cluster network parameters, characteristics of cluster interconnect, compute nodes utilization, co-processors computing capabilities, etc. In this work Hadoop YARN, CUDA technology and NoSQL-system Apache Cassandra has been used as the experimental platform. © 2016 IEEE.
The Borexino detector has convincingly shown its outstanding performances in the low energy regime through its accomplishments in the observation and study of the solar and geo neutrinos. It is then an ideal tool to perform a state of the art source-based experiment for testing the longstanding hypothesis of a fourth sterile neutrino with ∼ eVsup2/sup mass, as suggested by several anomalies accumulated over the past three decades in source, reactor, and accelerator-based experiments. The SOX project aims at successively deploying two intense radioactive sources, made of Cerium (antineutrino) and Chromium (neutrino), respectively, in a dedicated pit located beneath the detector. The existence of such an ∼ eVsup2/sup sterile neutrino would then show up as an unambiguous spatial and energy distortion in the count rate of neutrinos interacting within the active detector volume. This article reports on the latest developments about the first phase of the SOX experiment, namely CeSOX, and gives a realistic projection of CeSOX sensitivity to light sterile neutrinos in a simple (3+1) model.
The Borexino detector has convincingly shown its outstanding performance in the in the sub-MeV regime through its unprecedented accomplishments in the solar and geo-neutrinos detection, which make it the ideal tool to unambiguously test the long-standing issue of the existence of a sterile neutrino, as suggested by several anomalies: the outputs of the LSND and Miniboone experiments, the results of the source calibration of the two Gallium solar ν experiments, and the recently hinted reactor anomaly. The SOX project will exploit two sources, based on chromium and cerium, which deployed under the experiment will emit two intense beams of νe (Cr) and νe (Ce). Interacting in the active volume of the liquid scintillator, each beam would create a spatial wave pattern in case of oscillation of the νe (or νe) into the sterile state, which would be the smoking gun proving the existence of the new sterile member of the neutrino family. Otherwise, its absence will allow setting very stringent limit on its existence. © 2015.
The problem of digital holographic imaging of optically transparent objects in arbitrary spectral intervals is discussed. An optical scheme based on Mach-Zehnder interferometer with acousto-optic filtration of broadband light is proposed, and an experimental setup is described. Digital holograms of test patterns and real biological objects are presented.
The paper describes a new laboratory stand constructed for film deposition and for testing of deposited films and materials under pulsed and continuous heat load, ion and electron irradiation. The films are formed on substrates by atoms of target materials as a result of their sputtering by ions of argon plasma. The ion energy and ion flux can be varied independently. This enables the deposition of coatings with variable composition over thickness or of multi-layer coatings. Testing of materials is carried out in plasma under ion or electron irradiation by biasing the tested sample negatively or positively, respectively. The energies of ions or electrons can be varied up to 25 keV. The applied power can reach 4000 W (40 MW/msup2/sup power density in the case of a 1-cmsup2/sup sample) in both continuous and pulsed regimes. In pulsed regime, pulses of 1 - 99% duty cycle at 0 - 500 Hz can be applied to the sample. The pulsed particle load can be combined with a continuous load. The size of the tested sample must not exceed 100 mm in diameter. The heat flux can irradiate the whole sample or be focused at its center (minimum spot of ∼ 4mmsup2/sup). Heating of the samples up to 2800 K is possible. At the same time, the backside of the tested sample could be actively cooled. This paper presents the results of deposition and testing of a B4C coating on tungsten and tungsten testing. © Published under licence by IOP Publishing Ltd.
The structure and thermophysical properties of materials formed in the system Dy2O3–HfO2 (molar ratio 1 : 3 to 3 : 1) as a result of isothermal firing of x-ray amorphous mixed hydroxides at temperature to 1600°C are investigated. It is shown that for ratios 1 : 3 to 1 : 1 the crystallization process results in the formation of single-phase solid solutions with the structure of defective fluorite and marked nonequivalence of the parameters of the local environment of the Dy and Hf atoms. It is determined that the ceramic based on dysprosium hafnate (Dy2O3: HfO2 = 1 : 1) possesses low, practically temperature independent (to 800°C), thermal conductivity about 1.4 W/(m · K). © 2016 Springer Science+Business Media New York
The introduction of molybdenum nanoparticles in MoSex thin films formed by pulsed laser deposition led to changes in the film structure. The base planes of the layered atomic packing of the MoSeх matrix around Mo nanoparticles rotated; as a consequence, the edge sites that formed during the “breaking” of the Se–Mo–Se layered atomic packing came out to the film surface. At high nanoparticle concentrations, this effect led to high density of edge sites possessing increased catalytic activity (compared with that of the base planes) for initiating the electrochemical evolution of hydrogen in a 0.5 M H2SO4 solution. Voltammetric measurements at room temperature showed that when the carbon cathode was coated with MoSex thin films under optimum conditions, the hydrogen overvoltage considerably decreased, and the cathodic current increased. The results indicate that developments in the field of preparation of nanostructured electrodes based on layered transition metal dichalcogenides show promise as an alternative to expensive electrodes based on platinum group metals for electrocatalysts of hydrogen evolution. © 2016, Pleiades Publishing, Ltd.
Magnetic resonance at the F (g) = 1 F (e) = 1 transition of the D (1) line in Rb-87 has been studied with pumping and detection by linearly polarized radiation and detection at the double frequency of the radiofrequency field. The intervals of allowed values of the static and alternating magnetic fields in which magnetic resonance has a single maximum have been found. The structure appearing beyond these intervals has been explained. It has been shown that the quadratic Zeeman shift is responsible for the three-peak structure of resonance; the radiofrequency shift results in the appearance of additional extrema in resonance, which can be used to determine the relaxation constant I"(2). The possibility of application in magnetometry has been discussed.
Defining the limits of the existence of the nuclear structure is one of fundamental problems of natural science, requiring the advancement of studies towards the sites of maximum neutron- and proton-excess nuclei, to the borders of nuclear stability, and further, to the regions of nuclear instability. In such regions, nuclear systems exist only as resonant states in continuous spectra with characteristic 'nuclear' lifetimes. This work is done most effectively with experimental setups providing radioactive ion beams (RIBs). This review discusses the approaches in this field of research developed during the last 20 years at the ACCULINNA fragment separator in the Flerov Laboratory of Nuclear Reactions (FLNR) of the Joint Institute for Nuclear Research (JINR). The methodology developed is based on the comprehensive study of correlations among the reaction fragments emitted in the decays of nuclear-unstable systems which are populated in direct reactions induced by RIBs with intermediate (20 - 60 MeV per nucleon) energies. This allows us to acquire detailed knowledge about exotic nuclear systems close to and beyond nuclear drip lines. We discuss exotic forms of nuclear dynamics appearing in the vicinity of nuclear drip lines and relevant results of their theoretical analysis. Also discussed are existing facilities and prospective projects aimed at nuclear structure studies with RIBs at JINR. © 2016 Uspekhi Fizicheskikh Nauk, Russian Academy of Sciences.
Gas Pixel Detector (GPD) technology offers new possibilities, which make them very attractive for application in existing and future accelerator experiments and beyond. GPDs combine advantages of silicon and gaseous detectors. They can be produced radiation hard and with low power consumption using relatively cheap technology. Low capacitance of the individual pixel channel allows us to obtain a large signal to noise ratio. Using a time projection method for GPD readout one obtains 3D track image with precise coordinate (31 rim) and angular information (0.40 degrees). This feature would allow us to achieve performance of one GPD layer equal to a few layers of silicon detectors. Implementation of a fast readout and data processing at the front-end level allows one to reconstruct a track segment in less than 1 his, and to use this information for the first level trigger generation. The relevant algorithms of data acquisition and analysis are described and the results of simulations are presented in this paper.
The production cross sections of the Bsup+/sup, Bsup0/sup, and Bs sup0/sup mesons, and of their charge conjugates, are measured via exclusive hadronic decays in p+Pb collisions at the center-of-mass energy √SNN = 5.02 TeV with the CMS detector at the CERN LHC. The data set used for this analysis corresponds to an integrated luminosity of 34.6 nbsup-1/sup. The production cross sections are measured in the transverse momentum range between 10 and 60 GeV/c. No significant modification is observed compared to proton-proton perturbative QCD calculations scaled by the number of incoherent nucleon-nucleon collisions. These results provide a baseline for the study of in-medium b quark energy loss in Pb+Pb collisions. © 2016 CERN.
ALICE is one of four large experiments at the CERN Large Hadron Collider near Geneva, specially designed to study particle production in ultra-relativistic heavy-ion collisions. Located 52 meters underground with 28 meters of overburden rock, it has also been used to detect muons produced by cosmic ray interactions in the upper atmosphere. In this paper, we present the multiplicity distribution of these atmospheric muons and its comparison with Monte Carlo simulations. This analysis exploits the large size and excellent tracking capability of the ALICE Time Projection Chamber. A special emphasis is given to the study of high multiplicity events containing more than 100 reconstructed muons and corresponding to a muon areal density ρμ > 5.9 msup-2/sup. Similar events have been studied in previous underground experiments such as ALEPH and DELPHI at LEP. While these experiments were able to reproduce the measured muon multiplicity distribution with Monte Carlo simulations at low and intermediate multiplicities, their simulations failed to describe the frequency of the highest multiplicity events. In this work we show that the high multiplicity events observed in ALICE stem from primary cosmic rays with energies above 10sup16/sup eV and that the frequency of these events can be successfully described by assuming a heavy mass composition of primary cosmic rays in this energy range. The development of the resulting air showers was simulated using the latest version of QGSJET to model hadronic interactions. This observation places significant constraints on alternative, more exotic, production mechanisms for these events. © 2016 CERN for the benefit of the ALICE Collaboration.
Exposures of test samples of nuclear track emulsion were analyzed. The formation of high-multiplicity nuclear stars was observed upon irradiating nuclear track emulsions with ultrarelativistic muons. Kinematical features studied in this exposure of nuclear track emulsions for events of the muon-induced splitting of carbon nuclei to three cr-particles are indicative of the nuclear-diffraction interaction mechanism.
The structures of surface layers of the tool material, adapted to the conditions of the thermomechanical loading during the cutting process, can be formed with the use of different processing methods, the most effective of which is to deposit functional coatings on working surfaces of the cutting tool. During the studies, two nanostructured multilayer composite coatings (NMCCs) were considered: Ti-TiN-(TiCrAl)N and Zr-ZrN-(ZrNbCrAl)N. Metallographic studies were conducted, and the phase compositions of the coatings were determined by X-ray crystal analysis. The efficiency of tools made of carbide T14K8 with developed coatings was determined by comparative evaluation of tool life of a tool without coating, a tool with standard coating (TiN), and a tool with elaborated coatings (Ti-TiN-(TiCrAl)N and Zr-ZrN-(ZrNbCrAl)N) in turning structural steel 45. These tests allow noting the increase in tool life of a tool with elaborated NMCCs by up to 4 times as compared with tool life of an uncoated tool and by up to 2 times as compared with tool life of standard coating TiN. Meanwhile, NMCC of Ti-TiN-(TiCrAl) showed lifetime about 10% longer than NMCC of Zr-ZrN-(ZrNbCrAl)N). The longer lifetime of NMCC of Ti-TiN-(TiCrAl) conforms to its better adhesion characteristics and thinner nanosublayers of its wear-resistant layer. © 2016 Trans Tech Publications, Switzerland.
The decays (Formula presented.) and (Formula presented.) are studied with the ATLAS detector at the LHC using a dataset corresponding to integrated luminosities of 4.9 and 20.6 fb-1 of pp collisions collected at centre-of-mass energies (Formula presented.) TeV and 8 TeV, respectively. Signal candidates are identified through (Formula presented.) and (Formula presented.) decays. With a two-dimensional likelihood fit involving the (Formula presented.) reconstructed invariant mass and an angle between the (Formula presented.) candidate momenta in the muon pair rest frame, the yields of (Formula presented.) and (Formula presented.), and the transverse polarisation fraction in (Formula presented.) decay are measured. The transverse polarisation fraction is determined to be (Formula presented.) = 0.38 0.23 0.07(Formula presented.), and the derived ratio of the branching fractions of the two modes is (Formula presented.), where the first error is statistical and the second is systematic. Finally, a sample of (Formula presented.) decays is used to derive the ratios of branching fractions (Formula presented.) and (Formula presented.) = 10.4 3.1 1.5 0.6(Formula presented.), where the third error corresponds to the uncertainty of the branching fraction of (Formula presented.) decay. The available theoretical predictions are generally consistent with the measurement. © 2015, CERN for the benefit of the ATLAS collaboration.
The behavior of fine-grained (1–5 μm) boron and tungsten powders upon exposure to heat, electric field, and argon and hydrogen plasma ions is studied. A wide range of powder modifications caused by the above factors is sequentially considered. The driving forces and processes controlling the describedmodifications are presented. © 2016, Allerton Press, Inc.
The features of linear simulators with beam-plasma discharge are examined. A description of five discharge modes is provided. They can be implemented in such devices, depending on working-gas pressure, operating parameters of the electron gun and collecting electrode: vacuum beam transport, diffuse discharge, beam-plasma discharge, vacuum arc and self-oscillating modes. We describe how to use these modes in combination with diagnostics methods and sample holders, which allow studies of thermal and plasma loading, thermal cycling, sputtering, redeposition, gas capture, cleaning of deposited layers, development of instabilities, and ion etching. © 2016, Pleiades Publishing, Ltd.
The production of Z bosons in pPb collisions at sNN=5.02 TeV is studied by the CMS experiment via the electron and muon decay channels. The inclusive cross section is compared to pp collision predictions, and found to scale with the number of elementary nucleon-nucleon collisions. The differential cross sections as a function of the Z boson rapidity and transverse momentum are measured. Though they are found to be consistent within uncertainty with theoretical predictions both with and without nuclear effects, the forward-backward asymmetry suggests the presence of nuclear effects at large rapidities. These results provide new data for constraining nuclear parton distribution functions. © 2016 The Author.
Aspects of steel sheet perforation are studied experimentally. Calculations show that the mechanisms of thin sheet perforation change as the focal spot size is increased at a constant laser power. If the spot is small, the melt is removed and the film is disrupted by steel boiling in the spot center. With larger spots, the melt is removed by the force of gravity. The hole diameter grows along with the focal spot size and sheet thickness and is reduced upon an increase in laser power. © 2016, Allerton Press, Inc.
Nowadays, it is important to perform in-situ analysis of composition and thickness of ultra-thin (similar to 5-50 angstrom) surface layers in the course of the surface exposure to plasma or its components. For this aim, a new experimental facility based on the MEPhI Mass Monochromator is being developed, where low and medium energy ion spectroscopy of samples is used just after or during plasma exposure/ion treatment. A differentially pumped energy analyzer is used for recoil ion spectroscopy under grazing incidence conditions in the automated ion mass monochromator. A built-in Penning plasma source is used for plasma/ion treatment of samples. In this paper, the influence of the working gas (during the plasma source operation) on the energy spectra of reflected and recoil ions is studied. It is shown that the peak shape of the energy spectrum of scattered H+ ions increases during gas injection, and, at the same time, the signal intensity of the ionized recoils from the sample decreases. Nevertheless, analysis of the surface composition and thickness of the outer layer could be done at pressures ranging up to 10(-4) Torr.
Targets prepared from Reduced Activation Ferritic Martensitic (RAFM) steel F82H were exposed to low-energy (200eV) deuterium (D) plasma at various temperatures with highfluxes of about 10sup22/sup D/msup2/sups to various fluences in the range from 10sup25/sup to 2.5×10sup26/sup D/msup2/sup. Under the plasma exposure, micro-structured layers are formed on the target surfaces, and the surface morphology is dependent on the exposure temperature. The erosion yield of the F82H samples increases by a factor of about two as the exposure temperature rises in the range from 403 to 773K. © 2016 The Authors.
The effect of the nanostructure and chemical composition of thin Mo–Se–C films on the run-in of the diamond-like carbon coating (a-C) and the steel counterbody during ball-on-disk sliding test is studied. At the final stage of the deposition of the a-C coating on the steel substrate, a flow of atoms from the MoSe2 target was added to the flow of atoms being deposited. The influence of the air humidity on the selection of optimum structure and chemical composition of the film, which provide a fairly low (<0.07) coefficient of friction during the entire period of the run-in stage, is considered. In order to explain the effect of the modifying films, analysis of the specific features of the friction-induced changes in the composition of the films during wear debris formation has been carried out using Raman spectroscopy. © 2016, Allerton Press, Inc.
Metal Vapor Vacuum Arc (MEVVA) ion source (IS) is a unique tool for production of high intensity metal ion beam that can be used for material surface modification. From the other hand, the duoplasmatron ion source provides the high intensity gas ion beams. The MEVVA and duoplasmatron IS developed in Institute for Theoretical and Experimental Physics were used for the reactor steel surface modification experiments. Response of ferritic-martensitic steel specimens on titanium and nitrogen ions implantation and consequent vacuum annealing was investigated. Increase in microhardness of near surface region of irradiated specimens was observed. Local chemical analysis shows atom mixing and redistribution in the implanted layer followed with formation of ultrafine precipitates after annealing. © 2015 AIP Publishing LLC.
Ternary intermetallics, A2Co12As7 (A=Ca, Y, Ce-Yb), have been synthesized by annealing mixtures of elements in molten Bi at 1223K. The materials obtained crystallize in the P63/m variant of the Zr2Fe12P7 structure type. The unit cell volume shows a monotonic decrease with the increasing atomic number of the rare-earth metal, with the exception of Ce-, Eu-, and Yb-containing compounds. An examination of these outliers with X-ray absorption near edge structures (XANES) spectroscopy revealed mixed valence of Ce, Eu, and Yb, with the average oxidation states of +3.20(1), +2.47(5), and +2.91(1), respectively, at room temperature. Magnetic behavior of A2Co12As7 is generally characterized by ferromagnetic ordering of Co 3d moments at 100-140K, followed by low-temperature ordering of rare-earth 4f moments. The 3d-4f magnetic coupling changes from antiferromagnetic for A=Pr-Sm to ferromagnetic for A=Ce and Eu-Yb. Polarized neutron scattering experiments were performed to support the postulated ferro- and ferrimagnetic ground states for Ce2Co12As7 and Nd2Co12As7, respectively. © 2015 Elsevier Inc.
The use of an all-metal first wall in future magnetic fusion reactors equipped with a divertor may impose severe limitations on the capabilities of optical diagnostics in the main chamber because of the divertor stray light (DSL) produced by reflections of the intense light emitted in the divertor. Here, we introduce a synthetic H-alpha diagnostics to estimate the errors of solutions of the inverse problems aimed at recovering the neutral hydrogen parameters (density and isotope ratio) in the scrape-off layer (SOL) with allowance for (a) strong DSL on the observation chords in the main chamber, (b) substantial deviation of the neutral atom velocity distribution function from a Maxwellian in the SOL, and (c) the data from the direct observation of the divertor. The results of recovering the relative contributions of all three sources to the signal along an observation chord in the main chamber (namely, from the high-field-side and low-field-side SOL sections of the observation chord, and the DSL), together with the isotope ratios in the SOL, are presented for the flattop stage of Q10 inductive operation of ITER.
Temperature distribution along a single crystal fiber molten zone in the laser heated pedestal growth (LHPG) process of pure sapphire (Al2O3) and yttrium-aluminum garnet (Y3Al5O12) fiber was measured for the first time. The temperature was determined from thermal radiation spectra measurements in the visible spectral range. Our measurements indicate the existence of local temperature minimum in the region of source rod melting. © 2015 Elsevier B.V.
Recent results have strongly confirmed that multiple supernovae happened at distances of ∼100 pc, consisting of two main events: one at 1.7-3.2 million years ago, and the other at 6.5-8.7 million years ago. These events are said to be responsible for excavating the Local Bubble in the interstellar medium and depositing sup60/supFe on Earth and the Moon. Other events are indicated by effects in the local cosmic ray (CR) spectrum. Given this updated and refined picture, we ask whether such supernovae are expected to have had substantial effects on the terrestrial atmosphere and biota. In a first look at the most probable cases, combining photon and CR effects, we find that a supernova at 100 pc can have only a small effect on terrestrial organisms from visible light and that chemical changes such as ozone depletion are weak. However, tropospheric ionization right down to the ground, due to the penetration of ≥TeV CRs, will increase by nearly an order of magnitude for thousands of years, and irradiation by muons on the ground and in the upper ocean will increase twentyfold, which will approximately triple the overall radiation load on terrestrial organisms. Such irradiation has been linked to possible changes in climate and increased cancer and mutation rates. This may be related to a minor mass extinction around the Pliocene-Pleistocene boundary, and further research on the effects is needed. © 2016. The American Astronomical Society. All rights reserved.
The new limit on the electron lifetime is obtained from data of the Borexino experiment. The expected signal from the e - gamma nu decay mode is a 256 keV photon detected in liquid scintillator. Because of the extremely low radioactive background level in the Borexino detector it was possible to improve the previous measurement by two orders of magnitude.
The SOX (Short distance neutrino Oscillations with BoreXino) project aims at testing the light sterile neutrino hypothesis. To do so, two artificials sources of antineutrinos and neutrinos respectively will be consecutively deployed at the Laboratori Nazionali del Gran Sasso (LNGS) in close vicinity to Borexino, a large liquid scintillator detector. This document reports on the 0, source production and transportation. The source should exhibit a long lifetime and a high decay energy, a requirement fullfilled by the Ce-144-Pr-144 pair at secular equilibrium. It will be produced at FSUE "Mayak" PA using spent nuclear fuel. It will then be shielded and packed according to international regulation and shipped to LNGS across Europe. Knowledge of the Cerium antineutrino generator (CeANG) parameters is crucial for SOX as it can strongly impact the experiment sensitivity. Several apparatuses are being used or designed to characterize CeANG activity, radioactive emission and content. An overview of the measurements performed so far is presented here.
Gamma-ray bursts (GRBs) are the most luminous explosions in the Universe, yet the nature and physical properties of their energy sources are far from understood. Very important clues, however, can be inferred by studying the afterglows of these events. We present optical and X-ray observations of GRB 130831A obtained by Swift, Chandra, Skynet, Reionization And Transients Infra-Red camera, Maidanak, International Scientific Optical-Observation Network, Nordic Optical Telescope, Liverpool Telescope and Gran Telescopio Canarias. This burst shows a steep drop in the X-ray light curve at similar to 10(5) s after the trigger, with a power-law decay index of a similar to 6. Such a rare behaviour cannot be explained by the standard forward shock (FS) model and indicates that the emission, up to the fast decay at 105 s, must be of 'internal origin', produced by a dissipation process within an ultrarelativistic outflow. We propose that the source of such an outflow, which must produce the X-ray flux for similar to 1 d in the cosmological rest frame, is a newly born magnetar or black hole. After the drop, the faint X-ray afterglow continues with a much shallower decay. The optical emission, on the other hand, shows no break across the X-ray steep decrease, and the late-time decays of both the X-ray and optical are consistent. Using both the X-ray and optical data, we show that the emission after similar to 10(5) s can be explained well by the FS model. We model our data to derive the kinetic energy of the ejecta and thus measure the efficiency of the central engine of a GRB with emission of internal origin visible for a long time. Furthermore, we break down the energy budget of this GRB into the prompt emission, the late internal dissipation, the kinetic energy of the relativistic ejecta, and compare it with the energy of the associated supernova, SN 2013 fu.
In this paper, we have calculated the dependence of critical current density jc on the radius R and concentration of extended ferromagnetic defects in the system simulating a high-temperature superconductor (HTSC) layer. It was shown that at fixed volume concentration of ferromagnetic fraction the jc (R) dependence, as against nonmagnetic defects, has one maximum or two maxima at certain magnetization values of ferromagnetic fraction. We found that these maxima are due to the interplay of two parameters: concentration and effective depth of potential wells of defects. © 2016 Elsevier B.V.
DarkSide-50 at Gran Sasso underground laboratory (LNGS), Italy, is a direct dark matter search experiment based on a liquid argon TPC. DS-50 has completed its first dark matter run using atmospheric argon as target. The detector performances and the results of the first physics run are presented in this proceeding. © The Authors, published by EDP Sciences.
DarkSide is a graded experimental project based on radiopure argon, and is now, and will be, used in direct dark matter searches. The present DarkSide-50 detector, operating at the Gran Sasso National Laboratory, is a dual-phase, 50 kg, liquid argon time-projection-chamber surrounded by an active liquid scintillator veto. It is designed to be background free in 3 years of operation. DS-50 performances, when filled with atmospheric argon, are reported. However DS-50 filled with underground argon, shows impressive reduction of the sup39/supAr isotope. The application of this powerful technology in a future generation of the DarkSide program is discussed. © 2016 IOP Publishing Ltd and Sissa Medialab srl.
In this work, we study the influence of size effects on magnetic properties of quasi-one-dimensional spin-Peierls magnet CuGeO3. It was found that the reduction of the crystallite’s size to nanometer scale (~300 × 30 nm) leads to full suppression of spin-Peierls transition, which takes place in the bulk material at (Formula presented.) K. Combined analysis of electron spin resonance (ESR) and magnetic susceptibility measurements allowed separating of the dynamic magnetization of Cu chains (Formula presented.). Its temperature dependence is found to be typical for one-dimensional magnets with quantum critical (QC) behavior and is described by Curie–Weiss law (Formula presented.) at high temperatures, turning into power law asymptotic (Formula presented.)(Formula presented.) with temperature decrease. The data for two samples with different synthesis times (24 and 96 h) are analyzed in the framework of the QC behavior model. Although the values of magnetic parameters strongly depend on the synthesis time, the qualitative behavior is similar for both samples, which is shown by a comparative study of QC behavior of CuGeO3 doped with 1 % of Fe. We argue that the reason for the observed behavior is the competition between the onset of the staggered magnetic field and dimerization effects. © 2016 Springer-Verlag Wien
Crystallization and phase transition processes taking place in the Dy2O3–TiO2 system during the isothermal annealing of the precursors synthesized by co-precipitation were studied. The phase composition of the obtained powders is determined by not only the chemical composition of the precursor (Dy2O3: TiO2 ratio) and annealing temperature but also by the procedure of precursor synthesis determining the uniformity of Dy and Ti distribution in the precursor precipitate. Higher homogeneity of precursor particles provides the formation of almost single-phase nanocrystaline dysprosium titanate (Dy2TiO5, Dy2Ti2O7) powders at annealing temperatures of 800–1000°C. © 2016, Pleiades Publishing, Ltd.
In complex transition metal oxides (TMO) an arrested electronic phase separation (PS) appears by tuning the system near a Lifshitz transition in multiband Hubbard models. The PS in La2CuO4+y near insulator to metal transition (IMT) is made of short range Charge Density Wave (CDW) order inhomogeneity coexisting with quenched lattice disorder. While at high doping y = 0.1 percolation gives a single superconducting phase, near the IMT at y = 0.06 two coexisting superconducting phases appear: the first one with a critical temperature T-c1 = 16 K and the second one with T-c2 = 29 K. It is known that the two superconducting phases are characterized by two different space geometry because of two different spatial distributions of both CDW order and dopants self-organization. Here we show that these two phases show different flux dynamic regimes using alternating current (AC) multi-harmonic susceptibility experiments. This is a unique technique capable to investigate multi-phase superconductors and characterize their transport properties in a percolative scenario. Results point out that the low critical temperature phase is well described by a bulk-like flux pinning with a 2D geometry while the phase with higher critical temperature shows a 'barrier pinning' mechanism providing direct evidence of two different superconducting vortex dynamics in different complex geometrical spaces.
It has been found that the pulsed laser deposition of a thin tungsten selenide film, followed by thermal treatment at 550A degrees C in an Ar + O-2 mixture of gases, results in the formation of a hybrid structure that is made up of ultrathin WSe2 and WO3-y platelets. The structural and size characteristics of the nanoplatelets deposited on microcrystalline graphite provide the effective hydrogen evolution reaction in a 0.5 M H2SO4 solution, with the cathode current made about seven times higher at a potential of-100 mV and the slope of the Tafel characteristic reduced from 340 to 90 mV/dec.
In order to perform a resolutive measurement to clarify the neutrino anomalies and to observe possible short distance neutrino oscillations, the SOX (Short distance neutrino Oscillations with BoreXino) experiment is under construction. In the first phase, a 100 kCi Ce-144-Pr-144 antineutrino source will be placed under the Borexino detector at the Laboratori Nazionali del Gran Sasso (LNGS), in center of Italy, and the rate measurement of the antineutrino events, observed by the very low radioactive background Borexino detector, will be compared with the high precision ( 1%) activity measurement performed by two calorimeters. The source will be embedded in a 19 mm thick tungsten alloy shield and both the calorimeters have been conceived for measuring the thermal heat absorbed by a water flow. In this report the design of the calorimeters will be described in detail and very preliminary results will be also shown.
The magnetization of layered high-temperature superconductors (HTSCs) has been studied by using the Monte Carlo method. Typical parameters of promising HTSCs such as BSCCO, MgB2, and iron-based superconductors have been used for simulations, and the magnetization reversal loops were obtained. Anisotropy dependence of magnetic properties was analyzed. The ferromagnetic nanorods of arbitrary radius and constant magnetization were considered as pinning centers, and the pinning properties of extended ferromagnetic defects were analyzed. The analytic solution for the interaction of the vortex line and the ferromagnetic nanorod was obtained in the Lawrence-Doniach model. The simulations were done for both ferromagnetic and nonmagnetic extended defects.
The Spectr-W-3 database was developed in 2001-2013 and is available online (http://spectrw3. snz.ru). The database contains information on various spectroscopic constants of atoms and ions such as the wavelengths and probabilities of radiative transitions, energy levels of atoms and ions, ionization potentials, autoionization rates, and the parameters of analytical approximation of cross sections and rates of collisional transitions in atoms and ions. Spectr-W-3 presently contains around 450 thousand records and is the world's largest factual database on spectral properties of multicharged ions. A new stage of development of Spectr-W-3, which involves adding a new section titled "Emission Spectrograms" to the database, commenced in 2014. In contrast to the already existing sections that contain tabulated data, this new section provides graphical data (with necessary explanatory notes) on the spectrograms of emission of atoms and ions excited in various plasma sources. The structure of sections of the Spectr-W-3 database is characterized, and examples of queries and the corresponding search results are given.
Nuclear recoil events produced by neutron scatters form one of the most important classes of background in WIMP direct detection experiments, as they may produce nuclear recoils that look exactly like WIMP interactions. In DarkSide-50, we both actively suppress and measure the rate of neutron-induced background events using our neutron veto, composed of a boron-loaded liquid scintillator detector within a water Cherenkov detector. This paper is devoted to the description of the neutron veto system of DarkSide-50, including the detector structure, the fundamentals of event reconstruction and data analysis, and basic performance parameters. © 2016 IOP Publishing Ltd and Sissa Medialab srl.
The magnetic dynamic response of a PrB6 single crystal has been studied using inelastic neutron scattering in a temperature range of 10-120 K, which is above the temperatures of the phase transitions to the magnetic-ordered state. The study is aimed at revealing peculiarities of the state with a low magnetic moment in a temperature range of 7 K T a parts per thousand currency sign 20 K, which was identified in a number of magnetometric experiments. In addition to a quasielastic signal, a weak-dispersion excitation with an energy of similar to 1 meV has been detected, which exists at temperatures below 24 K. The results have been analyzed from the viewpoint of the formation of a spatially nonuniform state based on domains with short-range magnetic correlations at temperatures of 10-20 K. Judging by the dispersion of excitations, the character of the correlation is similar to that observed in a state with long-range magnetic order which arises at lower temperatures.
Results from three-dimensional modeling of plasma edge transport and plasma-wall interactions during application of resonant magnetic perturbation (RMP) fields for control of edge-localized modes in the ITER standard 15 MA Q = 10 H-mode are presented. The full 3D plasma fluid and kinetic neutral transport code EMC3-EIRENE is used for the modeling. Four characteristic perturbed magnetic topologies are considered and discussed with reference to the axisymmetric case without RMP fields. Two perturbation field amplitudes at full and half of the ITER ELM control coil current capability using the vacuum approximation are compared to a case including a strongly screening plasma response. In addition, a vacuum field case at high q(95) = 4.2 featuring increased magnetic shear has been modeled. Formation of a three-dimensional plasma boundary is seen for all four perturbed magnetic topologies. The resonant field amplitudes and the effective radial magnetic field at the separatrix define the shape and extension of the 3D plasma boundary. Opening of the magnetic field lines from inside the separatrix establishes scrape-off layer-like channels of direct parallel particle and heat flux towards the divertor yielding a reduction of the main plasma thermal and particle confinement. This impact on confinement is most accentuated at full RMP current and is strongly reduced when screened RMP fields are considered, as well as for the reduced coil current cases. The divertor fluxes are redirected into a three-dimensional pattern of helical magnetic footprints on the divertor target tiles. At maximum perturbation strength, these fingers stretch out as far as 60 cm across the divertor targets, yielding heat flux spreading and the reduction of peak heat fluxes by 30%. However, at the same time substantial and highly localized heat fluxes reach divertor areas well outside of the axisymmetric heat flux decay profile. Reduced RMP amplitudes due to screening or reduced RMP coil current yield a reduction of the width of the divertor flux spreading to about 20-25 cm and cause increased peak heat fluxes back to values similar to those in the axisymmetric case. The dependencies of these features on the divertor recycling regime and the perpendicular transport assumptions, as well as toroidal averaged effects mimicking rotation of the RMP field, are discussed in the paper.
The magnetic hyperfine (MHF) splitting of the ground and low-energy 3/2+(7.8±0.5 eV) levels in the Th229 nucleus in the muonic atom (μ1S1/2-Th229)∗ is calculated considering the distribution of the nuclear magnetization in the framework of the collective nuclear model with wave functions of the Nilsson model for the unpaired neutron. It is shown that (a) deviation of the MHF structure of the isomeric state exceeds 100% from its value for a pointlike nuclear magnetic dipole (the order of sublevels is reversed); (b) partial inversion of levels of the Th229 ground-state doublet and spontaneous decay of the ground state to the isomeric state occur; (c) the E0 transition, which is sensitive to differences in the mean-square charge radii of the doublet states, is possible between mixed sublevels with F=2; and (d) MHF splitting of the 3/2+ isomeric state may be in the optical range for certain values of the intrinsic gK factor and a reduced probability of a nuclear transition between the isomeric and the ground states. © 2016 American Physical Society.
Recent results of the Fayans energy density functional (EDF) for spherical nuclei are reviewed. A comparison is made with predictions of several Skyrme EDFs. The charge radii and characteristics of the first 2sup+/sup excitations in semi-magic nuclei are briefly discussed. The single-particle spectra of doubly magic nuclei are considered in more detail. The phonon-particle coupling effects are analyzed including the tadpole term. © 2016 Owned by the authors, published by EDP Sciences.
We show that there exists a non-trivial topological phase in circular two-dimensional quantum dots with an odd number of electrons. The possible non-zero value of this phase is explained by axial symmetry of two-dimensional quantum systems. The particular value of this phase ((Formula presented.)) is fixed by T-invariance and the Pauli exclusion principle and leads to half-integer values of the angular orbital momentum for ground states of such systems. This conclusion agrees with the experimental data for ground-state energies of few-electron circular quantum dots in perpendicular magnetic field (Schmidt et al. in Phys Rev B 51:5570, 1995). Hence, these data may be considered as the first experimental evidence for the existence of topological phase leading to half-integer quantization of the orbital angular momentum in circular quantum dots with an odd number of electrons. © 2016 Springer-Verlag Wien
A combination of a pixel chip and a gas chamber (GasPixel detectors) opens new opportunities for particle detectors. GasPixel detectors consist of an electron drift volume, an amplification gap and an anode plane based on a semiconductor chip. This technology promises large benefits in high-energy charged-particle tracking. It allows reconstruction of a 3D image of a particle track segment in a single detector layer with high accuracy. Several prototypes of GasPixel detectors based on micromegas technology with different gas mixtures and drift gaps were studied in a test beam. A spatial resolution of 8 μm and angular accuracy of about 0.2° in a chip plane were obtained. A dedicated Monte Carlo simulation of GasPixel detectors shows good agreement with experimental data. © 2015 Elsevier B.V. All rights reserved.
Beam-driven Alfven eigenmodes (AEs) have been studied in the TJ-II low-magnetic-shear flexible heliac (B-0 = 0.95 T, R = 1.5 m, a = 0.22 m), in L-mode hydrogen plasmas with hydrogen NBI and ECR heating (P-NBI
We derive a quantum master equation for an atom coupled to a heat bath represented by a charged particle many-body environment. In the Born-Markov approximation, the influence of the plasma environment on the reduced system is described by the dynamical structure factor. Expressions for the profiles of spectral lines are obtained. Wave packets are introduced as robust states allowing for a quasiclassical description of Rydberg electrons. Transition rates for highly excited Rydberg levels are investigated. A circular-orbit wave-packet approach has been applied in order to describe the localization of electrons within Rydberg states. The calculated transition rates are in a good agreement with experimental data. © 2016 American Physical Society.
The production of prompt charmed mesons Dsup0/sup, Dsup+/sup and Dsup∗+/sup, and their antiparticles, was measured with the ALICE detector in Pb-Pb collisions at the centre-of-mass energy per nucleon pair, (Formula presented.) , of 2.76 TeV. The production yields for rapidity |y| < 0.5 are presented as a function of transverse momentum, pT, in the interval 1–36 GeV/c for the centrality class 0–10% and in the interval 1–16 GeV/c for the centrality class 30–50%. The nuclear modification factor RAA was computed using a proton-proton reference at (Formula presented.) TeV, based on measurements at (Formula presented.) TeV and on theoretical calculations. A maximum suppression by a factor of 5-6 with respect to binary-scaled pp yields is observed for the most central collisions at pT of about 10 GeV/c. A suppression by a factor of about 2-3 persists at the highest pT covered by the measurements. At low pT (1-3 GeV/c), the RAA has large uncertainties that span the range 0.35 (factor of about 3 suppression) to 1 (no suppression). In all pT intervals, the RAA is larger in the 30-50% centrality class compared to central collisions. The D-meson RAA is also compared with that of charged pions and, at large pT, charged hadrons, and with model calculations. © 2016, The Author(s).
We present a measurement of b jet transverse momentum (pT) spectra in proton-lead (pPb) collisions using a dataset corresponding to about 35 nbsup-1/sup collected with the CMS detector at the LHC. Jets from b quark fragmentation are found by exploiting the long lifetime of hadrons containing a b quark through tagging methods using distributions of the secondary vertex mass and displacement. Extracted cross sections for b jets are scaled by the effective number of nucleon-nucleon collisions and are compared to a reference obtained from pythia simulations of pp collisions. The pythia-based estimate of the nuclear modification factor is found to be 1.22±0.15(stat+syst pPb)±0.27(syst pythia) averaged over all jets with pT between 55 and 400 GeV/c and with |ηlab|<2. We also compare this result to predictions from models using perturbative calculations in quantum chromodynamics. © 2016 CERN for the benefit of the CMS Collaboration.
The results on trapping and desorption of hydrogen isotopes under irradiation of zirconium by deuterium atoms of thermal energies are presented. It is shown that the addition of oxygen to the operating gas during the irradiation causes the increase of the oxide layer thickness, the amount of hydroxyl groups in it and deuterium trapping in zirconium. Accelerated transport of deuterium atoms through the oxide layer saturated by hydroxyl groups is observed. Mechanisms of trapping and desorption of hydrogen isotopes and the role of oxygen in these processes are discussed. © 2016 Elsevier Ltd.
We demonstrate the possibility of fabricating high-efficiency semiconductor hydrogen detectors based on tangsten-oxide thin films deposited onto silicon-carbide crystals by reactive pulsed-laser deposition. The obtained WO3/SiC structures ensure a noticeable voltage shift ΔU on the reverse branch of the I−V characteristics without commonly used catalyst layers of platinum-group metals. The ΔU value reached 2.1 V at a detected hydrogen concentration of 0.2% in air at 350°C. The response times to hydrogen inlet and recovery of the WO3/SiC structure after hydrogen outlet are found to be much shorter than those for the Pt/WO3/SiC structure. The high performances of the fabricated WO3/SiC sensor are due to the layered structure of the orthorhombic phase of tungsten oxide, which consists of loosely packed microcrystalline plates containing nanocrystals smaller than 100 nm. © 2016, Pleiades Publishing, Ltd.
The proton microscope design for 9 GeV proton radiography facility is described. Basic principles of proton microscope development are discussed. Two variants of microscope optical scheme are proposed. Simulation of the proton beam dynamics is carried out, the results showing the possibility to obtain the microscope spatial resolution not worse than 10 mu m.
Generation of high-voltage high-current electron beams in a low-pressure (P = 0.1–1 Torr) gas discharge is studied experimentally as a function of the discharge voltage and the sort and pressure of the plasma-forming gas. The density of the plasma formed by a high-current electron beam is measured. Experiments on ultrahigh charging of targets exposed to a pulsed electron beam with an energy of up to 25 keV, an electron current density of higher than 1 A/cmsup2/sup, a pulse duration of up to 1 μs, and a repetition rate of up to 1 kHz are described. A numerical model of ultrahigh charging of dust grains exposed to a high-energy electron beam is developed. The formation of high-energy positive ions in the field of negatively charged plane and spherical targets is calculated. The calculations performed for a pulse-periodic mode demonstrate the possibility of achieving neutron yields of higher than 10sup6/sup ssup–1/sup cmsup–2/sup in the case of a plane target and about 10sup9/sup ssup–1/sup in the case of 10sup3/sup spherical targets, each with a radius of 250 μm. © 2016, Pleiades Publishing, Ltd.
Because of their immense scalability and manufacturability potential, the HfO2-based ferroelectric films attract significant attention as strong candidates for application in ferroelectric memories and related electronic devices. Here, we report the ferroelectric behavior of ultrathin Hf0.5Zr0.5O2 films, with the thickness of just 2.5 nm, which makes them suitable for use in ferroelectric tunnel junctions, thereby further expanding the area of their practical application. Transmission electron microscopy and electron diffraction analysis of the films grown on highly doped Si substrates confirms formation of the fully crystalline non-centrosymmetric orthorhombic phase responsible for ferroelectricity in Hf0.5Zr0.5O2. Piezoresponse force microscopy and pulsed switching testing performed on the deposited top TiN electrodes provide further evidence of the ferroelectric behavior of the Hf0.5Zr0.5O2 films. The electronic band lineup at the top TiN/Hf0.5Zr0.5O2 interface and band bending at the adjacent nsup+/sup-Si bottom layer attributed to the polarization charges in Hf0.5Zr0.5O2 have been determined using in situ X-ray photoelectron spectroscopy analysis. The obtained results represent a significant step toward the experimental implementation of Si-based ferroelectric tunnel junctions. © 2016 American Chemical Society.
Borexino is an unsegmented neutrino detector operating at LNGS in central Italy. The experiment has shown its performances through its unprecedented accomplishments in the solar and geoneutrino detection. These performances make it an ideal tool to accomplish a state-of-the-art experiment able to test the existence of sterile neutrinos (SOX experiment). For both the solar and the SOX analysis, a good understanding of the detector response is fundamental. Consequently, calibration campaigns with radioactive sources have been performed over the years. The calibration data are of extreme importance to develop an accurate Monte Carlo code. This code is used in all the neutrino analyses. The Borexino-SOX calibration techniques and program and the advances on the detector simulation code in view of the start of the SOX data taking are presented.
We propose a unified model of primordial black holes and soliton dark matter formation. Dynamic of spherically symmetric clumps of scalar field is considered in Newtonian approximation. The formation of hidden mass of the Universe is discussed. Numerical solution of the system of interacting scalar and gravitational fields is used to obtain the mass of a clumps.
Contradictory data on the observation of Gamow-Teller resonances in the Sb-118 compound nucleus are discussed along with the available interpretation of these data and planned experimental and theoretical investigations into Gamow-Teller resonances in a number of antimony isotopes.
The algorithm of reconstruction of particle energy spectrum from electrostatic spectrometer data under condition of angular dependence of the energy distribution of the charged particles flow at the spectrometer entrance. It is shown that, assuming a linear relationship between the potentials, a standard method of recovering the spectrum by means of dividing the recorded signal by the scanning voltage gives the correct result in the first approximation.
A Summary paper on advanced probe edge diagnostics techniques for fusion devices is presented.
The erosion of divertor targets caused by high heat fluxes during transients is a serious threat to ITER operation, as it is going to be the main factor determining the divertor lifetime. Under the influence of extreme heat fluxes, the surface temperature of plasma facing components can reach some certain threshold, leading to an onset of intense material evaporation. The latter results in formation of cold dense vapor and secondary plasma cloud. This layer effectively absorbs the energy of the incident plasma flow, turning it into its own kinetic and internal energy and radiating it. This so called vapor shielding is a phenomenon that may help mitigating the erosion during transient events. In particular, the vapor shielding results in saturation of energy (per unit surface area) accumulated by the target during single pulse of heat load at some level E-max. Matching this value is one of the possible tests to verify complicated numerical codes, developed to calculate the erosion rate during abnormal events in tokamaks. The paper presents three very different models of vapor shielding, demonstrating that E-max depends strongly on the heat pulse duration, thermodynamic properties, and evaporation energy of the irradiated target material. While its dependence on the other shielding details such as radiation capabilities of material and dynamics of the vapor cloud is logarithmically weak. The reason for this is a strong (exponential) dependence of the target material evaporation rate, and therefore the "strength" of vapor shield on the target surface temperature. As a result, the influence of the vapor shielding phenomena details, such as radiation transport in the vapor cloud and evaporated material dynamics, on the E-max is virtually completely masked by the strong dependence of the evaporation rate on the target surface temperature. However, the very same details define the amount of evaporated particles, needed to provide an effective shielding to the target, and, therefore, strongly influence resulting erosion rate. Thus, E-max cannot be used for validation of shielding models and codes, aimed at the target material erosion calculations. (C) 2016 AIP Publishing LLC.
In this work the effect of vibrations on critical current density (Jc) of superconductors has been studied. The vibrations are shown to affect Jc of all types of superconductors during their measurements, employing a vibrating sample magnetometer (VSM). Increasing vibration frequency (f) and/or amplitude (A) leads to progressive reduction of Jc as a function of magnetic field (Ba). The effect of vibrations is substantially stronger in thin films. It leads to development of unexpected kinks on curves. Analysis of magnetization loops and relaxation of magnetization in YBCO films revealed that the vibration effect can be treated as the effective reduction of pinning potential. The asymmetry of the vibration effect in ascending and descending Ba is observed, indicating differences in free energy of the corresponding vortex structures. Thermal effects induced by vibrations with large f and A are shown to have rather insignificant influence, while the vibrational vortex dynamics exhibit a strong impact. The irreversibility field () is shown to be instrumentally defined, and its value depends on VSM settings. In addition, the practical importance of for Jc modeling is demonstrated. © 2016 IOP Publishing Ltd.
An in situ transmission electron microscopy study of the B2 ↔ B19′ martensitic transformation in Ti40.7Hf9.5Ni44.8Cu5 shape memory alloy was carried out. It was observed that the sequence of the martensite crystals shrinking on heating differed from the sequence of the martensite crystal appearance on previous cooling. This was shown that strain nanodomain formation on cooling prior to the forward martensitic transformation resulted in accumulation of the elastic energy. This led to the dependences of the elastic energy stored on cooling or released on heating on the volume fraction of the martensite phase became different. In this case, at the same volume fraction of the martensite phase, the configuration of the martensite crystals on cooling and heating was different and it was a reason for a violation of the sequence of the martensite crystal formation on cooling and its shrinking on heating. © 2016 Informa UK Limited, trading as Taylor & Francis Group
The ATLAS experiment at the Large Hadron Collider has an ambitious program of the detector upgrade to meet an expected rise of accelerator luminosity. The first large system which supposed to be installed in 2019 is the New Small Wheel (NSW) for ATLAS muon spectrometer. In order to ensure high quality and reliability of NSW chambers an X-ray scanning technique is being developed. One of the main components of the X-ray scanner is a special software visualization tool which would allow a fast and clear representation of scanning results and an identification of possible chamber defects.
Wavelet analysis results are presented for evolution of the spectral fluctuation characteristics of the edge plasma density and potential in the L-2M stellarator for fast and slow transport transitions. The fast transition comes out as a sharp increase of the energy and electron density within similar to 0.1ms and the slow one as a weak parameter change during a 0.5 to 1 ms time interval. It is shown that the use of the "Mexican hat" and Morlet wavelets allows one to detect the moment of the fast transition, whereas applying the Haar wavelet adds to this also an estimate of its duration, conforming to the analytical calculations, and reveals the temporal structure of the slow transition.
Results of the study of spectra and yields of p, d, t formed in stopped pion absorption by nuclei are presented. Data on charged particle formation have been obtained for 17 isotopes in wide atomic mass range (6 A 209). Empirical model was proposed to describe A-dependences of primary p, d, t yields.
In this paper we derive the set of general transport equations for multicomponent partially ionized reactive plasma in the presence of electric and magnetic fields taking into account the internal degrees of freedom and electronic excitation of plasma particles. Our starting point is a generalized Boltzmann equation with the collision integral in the Wang-Chang and Uhlenbeck form and a reactive collision integral. We obtain a set of conservation equations for such plasma and employ a linearized variant of Grad's moment method to derive the system of moment (or transport) equations for the plasma species nonequilibrium parameters. Full and reduced transport equations, resulting from the linearized system of moment equations, are presented, which can be used to obtain transport relations and expressions for transport coefficients of electrons and heavy plasma particles (molecules, atoms and ions) in partially ionized reactive plasma. © 2015 Elsevier B.V.
The previously obtained in (Zhdanov and Stepanenko, 2016) general transport equations for partially ionized reactive plasma are employed for analysis of electron transport properties in molecular and atomic plasmas. We account for both elastic and inelastic interaction channels of electrons with atoms and molecules of plasma and also the processes of electron impact ionization of neutral particles and three-body ion-electron recombination. The system of scalar transport equations for electrons is discussed and the expressions for non-equilibrium corrections to electron ionization and recombination rates and the diagonal part of the electron pressure tensor are derived. Special attention is paid to analysis of electron energy relaxation during collisions with plasma particles having internal degrees of freedom and the expression for the electron coefficient of inelastic energy losses is deduced. We also derive the expressions for electron vector and tensorial transport fluxes and the corresponding transport coefficients for partially ionized reactive plasma, which represent a generalization of the well-known results obtained by Devoto (1967). The results of numerical evaluation of contribution from electron inelastic collisions with neutral particles to electron transport properties are presented for a series of molecular and atomic gases. © 2016 Elsevier B.V.
The Russian Scientific R&D Cable Institute is involved in many projects on R&D high-temperature superconducting (HTS) power cables including those made of modern second generation (2G) HTS wires. Evaluation of ac losses and methods for the reduction of the ac losses are important in the design of the cables. A fine experimental technique has been developed and implemented to measure ac losses in representative cable models with a length of ∼5 m. However, only calculation can provide ac loss prediction in cases when it could be difficult to make measurements. Thus, we need a comprehensive simulation model to calculate ac losses. In HTS cables made of 2G wires, the main ac loss is a hysteresis loss, which only numerical simulation can predict for full-size 2G cables. We develop a finite-element method model to solve the electromagnetic problem for the calculation of ac losses. The model takes into account the strong nonlinear resistivity of the HTS materials, the hysteresis behavior of the magnetic substrate, the nonuniformity of critical current density across the tapes of the cable, and the possible ferromagnetism of a substrate. The model also takes into account any geometrical aspect of the 2G HTS cables. The details of the model and comparisons of calculations with our measurements of the ac losses are presented. © 2002-2011 IEEE.
A microscopic calculation of α-cluster preformation probability and α-decay width in the typical α emitter Po212 is presented. Results are obtained by improving a recent approach to describe α preformation in Po212 [Phys. Rev. C 90, 034304 (2014)PRVCAN0556-281310.1103/PhysRevC.90.034304] implementing four-nucleon correlations (quartetting). Using the actually measured density distribution of the Pb208 core, the calculated α-decay width of Po212 agrees fairly well with the measured one. © 2016 American Physical Society.
We present new experimental data on the acceleration of deuterons in a small-size magnetically insulated diode. Plasma containing deuterons was created at the anode during irradiation of a TiD target by a focused laser beam with a wavelength of 1.06 μm. The accelerating voltage pulse was formed by an Arkadiev-Marx generator. A circular cathode was arranged symmetrically relative to the anode and represented a permanent ring magnet with an inner radius not exceeding 0.02 m and a magnetic induction of up to 0.4 T at the center, which ensured magnetic insulation of the accelerating gap. The experiments showed that the current of accelerated deuterons with energies of up to 300 eV can reach a level of 0.5 kA at pulse durations of ≤0.5 μs. © 2015, Pleiades Publishing, Ltd.
We present estimations of systematic corrections and results of their experimental studies for our neutron lifetime experiment carried out in 2008-2010 at ILL. Taking into account these systematic corrections, we reduce the data of three independent sets of measurements (obtained during period 2008-2010) performed with different energy spectra of ultracold neutrons (UCNs) at different trap temperatures to the mean neutron lifetime value equal to 880.2(1.2) s. © 2015 The Authors.
A method is suggested for estimation of structural properties of amorphous spsup2/sup carbon and applied to amorphous fullerene and its derivatives produced by vacuum annealing. The method is based on the fitting of the neutron or x-ray powder diffraction patterns for scattering wave vector's modulus in the range from few units to several tens of inverse nanometers. The respective inverse problem assumes that the nanostructure of a sample is representable by a limited number, Ninfstr/inf, of candidate structures (e.g. fullerenes, carbon flakes with graphene-like atom arrangement) of a limited number of atoms, Ninfatom/inf. These structures are packed heterogeneously, in the domains with various average densities of atoms and various total potential energy, using the rigid body molecular dynamics with variable parameter of pair interaction of atoms in the neighboring nanostructures. The method is applied to interpreting the data of neutron diffraction by an amorphous Cinf60/inf fullerene annealed at 600, 800, 850, 900 and 1000°C. The results for Ninfstr/inf = 36 and Ninfatom/inf = 14 ÷ 285 enabled us to quantify structural properties of the samples in terms of the average size and curvature of the spsup2/sup carbon structures, and analyze sensitivity of results to the layout of these structures in the domains. © 2015 Elsevier B.V. All rights reserved.
A model is developed for multi-pass absorption of external electron cyclotron radiation (ECR) in tokamaks, which is used at initial stage of discharge to overcome the impurity radiation barrier (burn-through). Model is based on a semi-analytical solution of the ECR transport problem in the case of multiple reflection of radiation from the wall of the vacuum chamber. We estimate the efficiency of absorption of injected radiation for typical values of the electron temperature and density at the initial stage of discharge in ITER. © Owned by the authors, published by EDP Sciences, 2015.
An experimental platform to study the interaction of two colliding high-velocity (0.01-0.2 c; 0.05-20 MeV) proton plasmas in a high strength (20 T) magnetic field is introduced. This platform aims to study the collision of magnetized plasmas accelerated via the Target-Normal-Sheath-Acceleration mechanism and initially separated by distances of a few hundred microns. The plasmas are accelerated from solid targets positioned inside a few cubic millimeter cavity located within a Helmholtz coil that provides up to 20 T magnetic fields. Various parameters of the plasmas at their interaction location are estimated. These show an interaction that is highly non-collisional, and that becomes more and more dominated by the magnetic fields as time progresses (from 5 to 60 ps). Particle-in-cell simulations are used to reproduce the initial acceleration of the plasma both via simulations including the laser interaction and via simulations that start with preheated electrons (to save dramatically on computational expense). The benchmarking of such simulations with the experiment and with each other will be used to understand the physical interaction when a magnetic field is applied. Finally, the experimental density profile of the interacting plasmas is shown in the case without an applied magnetic magnetic field, so to show that without an applied field that the development of high-velocity shocks, as a result of particle-to-particle collisions, is not achievable in the configuration considered. © 2014 Elsevier B.V.
The microwave breakdown in air is simulated numerically within a simple 1D model taking into account a perturbation of electromagnetic field by plasma. The simulations were performed using two qualitatively different codes. One of these codes is based on computation of Maxwell equations, whereas the other one utilizes an approximation of quasi-monochromatic electromagnetic field. There is a good agreement between simulation results obtained by using both codes. Calculations have been carried out in a wide range of air pressures and field frequencies; also varied were initial spatial distributions of plasma density. The results reveal strong dependence of the breakdown evolution on the relation between the field frequency and the gas pressure as well as on the presence of extended rarefied background plasma. At relatively low gas pressures (or high field frequencies), the breakdown process is accompanied by the stationary ionization wave propagating towards the incident electromagnetic wave. In the case of a high gas pressure (or a relatively low field frequency), the peculiarities of the breakdown are associated with a formation of plasma filament array. The extended background plasma can suppress formation of the plasma filament array completely even at high pressures (or low frequencies). © 2015 AIP Publishing LLC.
A search for high-mass resonances decaying into tau(+)tau(-) final states using proton-proton collisions at root s = 8 TeV produced by the Large Hadron Collider is presented. The data were recorded with the ATLAS detector and correspond to an integrated luminosity of 19.5-20.3 fb(-1). No statistically significant excess above the Standard Model expectation is observed; 95% credibility upper limits are set on the cross section times branching fraction of Z' resonances decaying into tau(+)tau(-) pairs as a function of the resonance mass. As a result, Z' bosons of the Sequential Standard Model with masses less than 2.02 TeV are excluded at 95% credibility. The impact of the fermionic couplings on the Z' acceptance is investigated and limits are also placed on a Z' model that exhibits enhanced couplings to third-generation fermions.
A search for new particles that decay into top quark pairs is reported. The search is performed with the ATLAS experiment at the LHC using an integrated luminosity of 20.3 fb(-1) of proton-proton collision data collected at a centre-of-mass energy of root s = 8TeV. The lepton-plus-jets final state is used, where the top pair decays to W (+) bW(-)(b) over bar, with one W boson decaying leptonically and the other hadronically. The invariant mass spectrum of top quark pairs is examined for local excesses or deficits that are inconsistent with the Standard Model predictions. No evidence for a top quark pair resonance is found, and 95% confidence-level limits on the production rate are determined for massive states in benchmark models. The upper limits on the cross-section times branching ratio of a narrow Z' boson decaying to top pairs range from 4.2 pb to 0.03 pb for resonance masses from 0.4 TeV to 3.0 TeV. A narrow leptophobic topcolour Z' boson with mass below 1.8 TeV is excluded. Upper limits are set on the cross-section times branching ratio for a broad colour-octet resonance with Gamma/m = 15% decaying to tt. These range from 4.8 pb to 0.03 pb for masses from 0.4 TeV to 3.0 TeV. A Kaluza-Klein excitation of the gluon in a Randall-Sundrum model is excluded for masses below 2.2 TeV.
The electron component is the main channel for anomalous power loss and the main indicator of transient processes in the tokamak plasma. The electron temperature and density profiles mainly determine the operational mode of the machine. This imposes demanding requirements on the precision and on the spatial and temporal resolution of the Thomson scattering (TS) measurements. Measurements of such high electron temperature with good accuracy in a large fusion device such as ITER using TS encounter a number of physical problems. The 40 keV TS spectrum has a significant blue shift. Due to the transmission functions of the fibres and to their darkening that can occur under a strong neutron irradiation, the operational wavelength range is bounded on the blue side. For example, high temperature measurements become impossible with the 1064 nm probing wavelength since the TS signal within the boundaries of the operational window weakly depends on T-e. The second problem is connected with the TS calibration. The TS system for a large fusion machine like ITER will have a set of optical components inaccessible for maintenance, and their spectral characteristics may change with time. Since the present concept of the TS system for ITER relies on the classical approach to measuring the shape of the scattered spectra using wide spectral channels, the diagnostic will be very sensitive to the changes in the optical transmission. The third complication is connected with the deviation of the electron velocity distribution function from a Maxwellian that can happen under a strong ECRH/ECCD, and it may additionally hamper the measurements. This paper analyses the advantages of a 'multi-laser approach' implementation for the current design of the core TS system. Such an approach assumes simultaneous plasma probing with different wavelengths that allows the measurement accuracy to be improved significantly and to perform the spectral calibration of the TS system. Comparative analysis of the conservative and advanced approaches is given.
Emission spectra of LT-GaAs photoconductive antennas based on epitaxial films of "low-temperature" gallium arsenide (LT-GaAs) are measured in the terahertz frequency region by the Fourier transform spectroscopy. © 2015 The Authors.
A two-phase emission detector containing 5 kg of liquid Xe is installed at the horizontal experimental channel of the research nuclear reactor IRT MEPhI to measure the liquid Xe response to nuclei recoils with kinetic energies below 1 keV. Preliminary tests have demonstrated that ≥ 15 μs electron lifetime in liquid Xe and ~ 10 photoelectrons single ionization electron signal are achieved. These parameters are sufficient to detect and identify events at the single electron level.
A miniature γ probe for nuclear medicine based on a LaBr3:Ce scintillation crystal and a silicon photomultiplier is described. The γ ray detection efficiency is 29% for 137Cs (662 keV) and 70% for 57Co (122 keV). The spatial resolution and selectivity measured with a tungsten collimator for 57Co are 8 mm and 26°, respectively.
The results of calculations of stable configurations of atomic hydrogen in the tungsten bulk, in the presence of vacancies, as well as on the surface (100) and in the near-surface layers are given. Activation barriers for interstitial diffusion, on-surface diffusion, trapping in a vacancy, detrapping from the vacancy, and transitions between on-surface and under-surface sites are calculated. Hydrogen-vacancy interaction is considered for the case of several H atoms trapped in a vacancy. © 2015 The Authors.
Almost fully stripped Fe ions accelerated up to 0.9 GeV are demonstrated with a 200 TW femtosecond high-intensity laser irradiating a micron-thick Al foil with Fe impurity on the surface. An energetic low-emittance high-density beam of heavy ions with a large charge-to-mass ratio can be obtained, which is useful for many applications, such as a compact radio isotope source in combination with conventional technology.
We review wide-ranging research that combines inelastic neutron scattering spectroscopy with phenomenological and ab initio calculations to study the lattice dynamics and specifics of the electron phonon interaction in three-dimensional boron cluster network systems MB6 and MB12 (M = La, Sm, and Yb, Lu, Zr). A close similarity is found between the atomic vibration spectra of these systems, which is fundamentally due to a strong hierarchy of interatomic interaction in these systems and which manifests itself both in the shape of the low-energy phonon dispersion and in the position of the high-energy edge of the spectrum. Manifestations of strong electron phonon interactions in the lattice vibration spectra of borides are studied in detail and their relation to the nature and features of the valence-unstable state of rare-earth ions is examined. Resonance nonadiabaticity and magnetovibration interaction effects in spin- and valence-fluctuating systems are given special attention.
The amplitude and timing properties of a Geiger discharge in a stand-alone SiPM cell have been investigated in detail. Use of a single stand-alone SiPM cell allows us to perform measurements with better accuracy than the multicell structure of conventional SiPMs. We have studied the dependence of the output charge and amplitude from an SiPM cell illuminated by focused light vs the number of primary photoelectrons. We propose a SPICE model which explains the amplitude over saturation (when the SiPM's amplitude is greater than the sum over all cells) characteristics of SiPM signals for more than one initial photoelectrons. The time resolutions of a SiPM cell have been measured for the case of single (SPTR) and multiphoton light pulses. The Full Width Half Max (FWHM) for SPTR has been found to be at the level of 30. ps for focused and 40. ps for unfocused light (100. ?m cell size).
Processes of relaxation of space charges formed by impurities carriers in isotropic films of vinylidene fluoride and tetrafluoroethylene copolymers of the composition 71/29 and 94/6 were studied. Al and Au symmetric electrodes deposited by evaporation in vacuum have been used. In the case of Al electrodes at temperatures above 100°C, giant low frequency dielectric dispersion was observed, while it is absent in films with Au electrodes. Causes of this phenomenon were studied by the X-ray photoelectron spectroscopy. It was shown that at Al deposition, new functional groups, such as Al-C, Al-F, and Al2O3, which are not characteristic of the copolymer film surface, formed. They were supposed to be traps for impurity carriers and because of this the electrode became partially blocked. This led to appearance of the giant electrode polarization on the metal-polymer boundary, which did not take place in the case of Au electrodes. Parameters of the Au4f line for the copolymer with different contents of fluorine atoms in the chain were analyzed. An increase in the number of these atoms was shown to result in the line shift to higher energies. This phenomenon was associated with an increase in the shift of the electron density from Au atoms to the F ones which has a high affinity to electrons. © 2015 AIP
An analysis is presented of events containing jets including at least one b-tagged jet, sizeable missing transverse momentum, and at least two leptons including a pair of the same electric charge, with the scalar sum of the jet and lepton transverse momenta being large. A data sample with an integrated luminosity of 20.3 fbsup−1/sup of pp collisions at √s = 8 TeV recorded by the ATLAS detector at the Large Hadron Collider is used. Standard Model processes rarely produce these final states, but there are several models of physics beyond the Standard Model that predict an enhanced rate of production of such events; the ones considered here are production of vector-like quarks, enhanced four-top-quark production, pair production of chiral b′-quarks, and production of two positively charged top quarks. Eleven signal regions are defined; subsets of these regions are combined when searching for each class of models. In the three signal regions primarily sensitive to positively charged top quark pair production, the data yield is consistent with the background expectation. There are more data events than expected from background in the set of eight signal regions defined for searching for vector-like quarks and chiral b′-quarks, but the significance of the discrepancy is less than two standard deviations. The discrepancy reaches 2.5 standard deviations in the set of five signal regions defined for searching for four-top-quark production. The results are used to set 95% CL limits on various models. © 2015, The Author(s).
Electrodynamic characteristics (EDC) of higher order modes (HOM) were calculated for a superconducting 9-cell accelerating cavity of eLinac accelerator with operating frequency of 1300 MHz. Several HOM damping techniques including damping with grooved, fluted and ridged beam pipes were analyzed and compared. The influence of the parameters of the drift tube on the HOM damping and on the parameters of the fundamental wave was analyzed. © 2015 The Authors.
Neoclassical theory provides usable expressions for studying transport in toroidal plasmas and computing the associated radial electric field. An algebraic and three semi-analytical models are used here to study the radial electric field in TJ-II plasmas and compare it with experimental data from a heavy ion beam probe (HIBP) and with DKES calculations. Good qualitative agreement as well as reasonable quantitative agreement is found which allows us to validate the models for describing TJ-II radial electric fields. Furthermore, a simple algebraic formulation (2005 Plasma Phys. Rep. 31 14) provides physical insight for the interpretation of experimental data from the TJ-II heliac in spite of its complicated geometry, like the place of the transition from the electron to the ion root of the radial electric field, which occurs at the maximum value of collisionality, for example. © 2015 IOP Publishing Ltd.
In this article, the prospects for studying the tensor structure of the HZZ vertex with the LHC experiments are presented. The structure of tensor couplings in Higgs di-boson decays is investigated by measuring the asymmetries and by studying the shapes of the final state angular distributions. The expected background contributions, detector resolution, and trigger and selection efficiencies are taken into account. The potential of the LHC experiments to discover sizeable non-Standard Model contributions to the HZZ vertex with 300 and 3000 fb(-1) is demonstrated.
Measurements of the five most significant angular coefficients, Ainf0/inf through Ainf4/inf, for Z bosons produced in pp collisions at s=8 TeV and decaying to μsup+/supμsup-/sup are presented as a function of the transverse momentum and rapidity of the Z boson. The integrated luminosity of the dataset collected with the CMS detector at the LHC corresponds to 19.7fbsup-1/sup. These measurements provide comprehensive information about the Z boson production mechanisms, and are compared to the QCD predictions at leading order, next-to-leading order, and next-to-next-to-leading order in perturbation theory. © 2015 CERN for the benefit of the CMS Collaboration.
For many applications of ReBa2Cu3O7-x (ReBCO) tapes it is needed to know the anisotropic properties of the used conductor in a broad range of magnetic field. In this paper we present the results of transport measurements on the SuNAM tape (GdBaCuO) with the rotation of the sample in magnetic fields up to 5 T in liquid nitrogen. The critical current over the magnetic field orientation (Ic(θ)) curves demonstrate the appearance of distinct second peak around c-axis in low fields. This peak almost vanishes in the fields over 3 T. The evolution of the ab-peak form is also presented: the peak consistently reduces its height with the magnetic field going up and in the high fields the shoulders rise, changing the type of the distribution. To describe experimental curves the vortex path model was applied to the angular distributions of the critical current in magnetic field. Good agreements of the experimental data with the analytical expressions were obtained that confirm the vortex path model approach. © 2015, Korea Institute of Applied Superconductivity and Cryogenics. All rights reserved.
We show that the isotropic conductivity in the normal state of rare-earth tritelluride RTe3 compounds is broken by the occurrence of the unidirectional charge density wave (CDW) in the (a,c) plane below the Peierls transition temperature. In contrast with quasi-one-dimensional systems, the resistivity anomaly associated with the CDW transition is strong in the direction perpendicular to the CDW wave vector Q (a-axis) and very weak in the CDW wave vector Q direction (c-axis). We qualitatively explain this result by calculating the electrical conductivity for the electron dispersion with momentum-dependent CDW gap as determined by angle-resolved photoemission spectroscopy (ARPES). Nonlinear transport properties in TbTe3 and GdTe3 have been studied along different crystallographic orientations. The pronounced effect of collective CDW motion is observed along c-axis and is absent completely in the perpendicular direction demonstrating the unidirectional character of the CDW. The threshold electric field for CDW sliding is linearly temperature dependent in a wide range of temperature. (C) 2014 Elsevier B.V. All rights reserved.
We present resistivity measurements of the upper critical field as a function of temperature for Nd2-xCexCuO4+δ/SrTiO3 single crystal films near antiferromagnetic-superconducting phase boundary (x = 0.14) in magnetic fields up to 90kOe at temperatures down to 0.7K. The data are well described by a two-band/two-gap model for a superconductor in the dirty limit. © (2015) Trans Tech Publications, Switzerland.
It is shown that one of the effective methods for assessing “similarity” of electrophysiological signals is a parametric analysis of their synchronicity, the technical implementation of which is advisable to be performed using analog interfaces of AFE type, focused on the collection and preprocessing of analog signals. © 2015 Springer Science+Business Media New York
Nanodispersed gold is widely used as a marker in different analytical systems. For such purposes, it is usually obtained by the reduction of salts. This work studied the potential analytical applications of nanodispersed gold obtained by laser ablation because gold produced with this method has no chemical coating. The nanoparticles produced were characterized by transmission electron microscopy and spectrophotometry. The average size of the particles was 24.5 nm. Concentration dependences of antibody immobilization on ablative gold were obtained. With the use of antibody-conjugated nanoparticles, an immunochromatographic system was constructed for the detection of zearalenone mycotoxin. This immunoassay was characterized by a detection limit of 0.1 ng/ml antigen with an assay duration of only 15 min, which is on par with current test systems comprising nanodispersed gold obtained by chemical reduction. The simplicity of ablative dispersing makes this a prospective method for the labeling of various antibodies for analytical use. © 2015 Elsevier Inc. All rights reserved.
The operational space (I-p - n) for long-pulse scenarios (Delta t(burn) similar to 1000 s, Q = 5) of ITER has been assessed by 1.5D core transport modelling with pedestal parameters predicted by the EPED1 code by a set of transport codes under a joint activity carried out by the Integrated Operational Scenario ITPA group. The analyses include the majority of transport models (CDBM, GLF23, Bohm/gyroBohm (BgB), MMM7.1, MMM95, Weiland, scaling-based) presently used for interpretation of experiments and ITER predictions. The EPED1 code was modified to take into account boundary conditions predicted by SOLPS4 for ITER. In contrast to standard EPED1 assumptions, EPED1 with the SOLPS boundary conditions predicts no degradation of the pedestal pressure as density is reduced. Lowering the plasma density to n(e) similar to (5-6) x10(19) m(-3) leads to an increased plasma temperature (similar pedestal pressure), which reduces the loop voltage and increases the duration of the burn phase to Delta t(burn) similar to 1000 s with Q = 5 for I-p = 13MA at moderate normalized pressure (beta(N) similar to 2). These ITER plasmas require the same level of additional heating power as the reference Q = 10 inductive scenario at 15MA (33MWNBI and 17-20MWEC heating and current drive power). However, unlike the hybrid' scenarios considered previously, these H-mode plasmas do not require specially shaped q profiles nor improved confinement in the core for the transport models considered in this study. Thus, these medium density H-mode plasma scenarios with I-p = 13MA present an attractive alternative to hybrid scenarios to achieve ITER's long-pulse Q = 5 scenario and deserve further analysis and experimental demonstration in present tokamaks.
An investigation of the probability of hydrogen atom ionization by ultra-short electromagnetic pulses is carried out in the frame of perturbation theory We consider the case when the electric field strength amplitude Einf0/inf in a pulse by two orders lower than characteristic atomic field strength Einfa/inf (Einfa/inf ≅ 5.1 · 10sup9/sup V/cm). A detailed investigation of the dependence of the probabilities on the pulse duration was performed for Gaussian pulse shapes. In the case where the carrier frequency of the Gaussian pulse is larger than the atomic ionization potential, the probability goes to the standard limit of perturbation per unit time. At the same pulse durations, the probabilities for carrier frequencies less than the ionization potential go to zero. The frequency dependence of the ionization probability becomes equal to the standard threshold dependence with increasing pulse duration time. A comparison between the ionization effects caused by wavelet pulses without carrier frequency and Gaussian pulses with carrier frequency shows that the same ionization probability values are achieved when the pulse carrier frequency is detuned by about 20% from the ionization threshold. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
An algorithm for recovering the effective temperature of atoms of hydrogen (and its isotopes) in the tokamak scrape-off layer from the asymmetry of the Balmer-alpha line shape is proposed. The algorithm is based on the parametrization of the asymmetry of the line shape caused by the nonlocal character of neutral hydrogen flux from the wall into the tokamak plasma. The accuracy of the algorithm is tested against the results of simulations of the velocity distribution function of deuterium neutrals in the scrape-off layer by the EIRENE code with the use of the source data on the main plasma component in the quasi-stationary stage of the inductive mode of ITER operation calculated by the SOLPS4.3 (B2-EIRENE) code.
This paper reviews and extends searches for the direct pair production of the scalar supersymmetric partners of the top and bottom quarks in proton–proton collisions collected by the ATLAS collaboration during the LHC Run 1. Most of the analyses use 20 fbsup-1/sup of collisions at a centre-of-mass energy of √s = 8 TeV, although in some case an additional 4.7 fb-1 of collision data at √s = 7 TeV are used. New analyses are introduced to improve the sensitivity to specific regions of the model parameter space. Since no evidence of third-generation squarks is found, exclusion limits are derived by combining several analyses and are presented in both a simplified model framework, assuming simple decay chains, as well as within the context of more elaborate phenomenological supersymmetric models. © 2015, CERN for the benefit of the ATLAS collaboration.
An automation system of the MEPhI large mass-monochromator setup with a duoplasmatron as an ion source and a remote quarter-spherical energy analyzer of ions, reflected and knocked out from a target, is described. The creation of a computer control system allowed us to perform ion-beam experiments in the automatic programmable mode, including the simultaneous determination of the elemental composition and thickness of surface films in the process of plasma/ion action.
The modern version (2015) of Simulation Environment of Virtual Electrophysics Labs, including the set of virtual laboratories for basic subsystems of charged particles accelerators research are presented in the article. There is way to provide safe realization of works with options, that require using of hard measures of accident (large electric power, supertension, different types of radiation and so on) and to prevent high expenses. The Simulation Environment can be used, both in educational and in pre-project researches, and also for analysis and optimization of operating abilities. © 2015 IEEE.
The effect of the QSPA-T pulsed plasma irradiation on the crystalline boron carbide B4C coating was examined. The duration of the rectangular plasma pulses was 0.5 ms with 5-10 min interval between pulses. The maximal power density in the central part of plasma stream was 1 GW/m2. The coating thickness varies from 20 to 40 μm on the different surface areas. Modification of the surface layers and coating transformation at the elevated temperature under plasma pulse irradiation during four successive series of impulses are de-scribed. It is shown that boron carbide coating withstood all test cycle by plasma irradiation total amount of 100 pulses with peak power density 1 GW/m2. Constitutive surface deterioration was not detected and boron carbide coating kept crystal structure B4C throughout irradiation zone at the surface depth no less 2 μm.
The equations of charged particle motion in the earth’s magnetic field are analyzed. Analytical data allow us to estimate important parameters of the charge dynamics, such as the charge capture conditions, oscillation amplitude and frequency, and longitudinal drift, and also relate these parameters to the parameters of the charged particles and the height of their trajectory. The results may be used in designing space vehicles intended for investigation of the near-earth space, specifically, earth’s magnetosphere, with charged particle beams. © 2015, Pleiades Publishing, Ltd.
In this work, which is devoted to the longitudinal dynamics of charged particles in the field of traveling wave, on which the theory of the resonance method of acceleration is based, a transition is made from the dynamics of individual charges to the dynamics of charge bunches as a whole in order to increase the effectiveness of mathematical modeling. A similar problem has already been solved for nonrelativistic bunches. Using the same method, the solution is extended to relativistic bunches. The method is based on the Lagrange equation for the longitudinal motion of a charged-particle bunch in the field of traveling wave; the solutions are the longitudinal size of a bunch and the width of the energy spectrum. The self-field of the bunch is taken into account in the equation and the limitations of linear approximations are eliminated. © 2015 Springer Science+Business Media New York
A procedure and basic experimental results of studying the spatial structure of plasma objects in the X-ray emission range are presented. The measurement results of spectral characteristics of X-ray sources of plasma objects are given. The studies are performed using the designed position-sensitive pulse X-ray spectrometer. © 2015, Pleiades Publishing, Inc.
In this work, the X-ray diagnostics of autooscillation secondary emission discharge was conducted for the first time. Spectrometer based on termoluminescent detectors was the main part of the X-ray diagnostics. The investigations show us high energy group of electrons in the reverse flow, their increment exceeds energy, that they get from oscillating collector's voltage by one turn.
The possibility of using thermoluminescent detectors for diagnosing plasmas is analyzed. The key characteristics of the thermoluminescent detectors, based on which a small-sized pulse X-ray spectrometer was developed and constructed, are studied. The basic experimental results obtained in the investigation of the X-ray spectra of plasma objects are presented.
A complex of diagnostic equipment for studying impulse X-ray radiation from high-current discharge plasma is presented. The complex provides measurements within an X-ray energy range of 1–300 keV and has a dynamic range of 10sup12/sup. The results of investigating the spectral characteristics of X rays from plasma that is generated in the “low-inductive vacuum spark” device are presented as functions of the discharge current for various electrode materials. © 2015, Pleiades Publishing, Inc.
The results are presented on the study of the electronic structure of thorium atoms adsorbed by the liquid atomic layer deposition from aqueous solution of thorium nitrate on the surface of CaFinf2/inf. The chemical state of the atoms and the change of the band structure in the surface layers of Th/CaFinf2/inf system on CaFinf2/inf substrate were investigated by XPS and REELS techniques. It was found that REELS spectra for Th/CaFinf2/inf system include peaks in the region of low energy losses (3-7 eV) which are missing in the similar spectra for pure CaFinf2/inf. It is concluded that the presence of the observed features in the REELS spectra is associated with the chemical state of thorium atoms and is caused by the presence of uncompensated chemical bonds at the Th/CaFinf2/inf interface, and, therefore, by the presence of unbound 6d- and 7s-electrons of thorium atoms. Assuming the equivalence of the electronic configuration of thorium-229 and thorium-232 atoms, an estimate was made on the time decay of the excited state of thorium-229 nuclei through the channel of the electron conversion. It was found that the relaxation time is about 40 μs for 6d-electrons, and about 1 μs for 7s-electrons. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
The excitation spectrum of two-dimensional FeAs-clusters modeling iron-based superconductors has been obtained by using a quantum Monte Carlo algorithm within the limits of the full two-orbital model. The first data are presented for clusters of size up to 10×10 FeAs-cells. The influence of interaction strength on dispersion is analyzed. © 2015 The Authors.
Program CAMFT is developed to simulate the intense charged particle bunch dynamics in external magnetic fields with arbitrary geometry. The program solves the motion equation for each particle of the intense bunch by means of using a scheme of parallel computing so the bunch with intensity up to 10E10 can be treated. The program is written on C++ language and uses standard OpenMP (version 2.0), so the dynamics of the intense bunch can be simulated without artificial numerical effects which usually restrict the applicability of the programs based on a PIC method. The program has the means of post-treatment such as Visual C++, Qt 4.8.3 of qtcreator and in-built means based on wavelet transformations for result visualization. The actual CAMFT version is checked while the accelerating structure with racetrack geometry simulated. Modified CAMFT version now is verified by means of simulation of the beamline of ITEP Experimental facility for material science based on a Bernas ion source. © 2015 IEEE.
Heavy ion beam may be used for the matter extreme state creation, a forming beamline must satisfy to certain requirements on beam characteristics and focus position at the target. The original method of hollow ion beam formation, namely wobbler system, was proposed to deposit the beam energy at cylindrical target [1]. The disagreement of wobbler deflector frequencies leads to undesirable violation of experiment requirements. In the paper presented the results of simulation are described that show the symmetry violation of the target irradiation caused by the frequency shift while the fixed beamline geometry. © 2015 IEEE.
The history of the discovery of Cherenkov radiation is reviewed. Its early observations in particle accelerators and cosmic rays are described, and how it forms is qualitatively discussed. Types and high-energy physics applications of Cherenkov detectors are briefly outlined.
A system for visualizing X rays from pulsed discharges in the real-time mode using X-ray intensifying screens is described. Using the system, it is possible to record images of X-ray sources in the energy range of 1–100 keV with a spatial resolution of ∼100 μm. The proposed visualization system has been tested while optimizing the radiative characteristics of the high-current vacuum pulsed discharge. It may be employed when studying of a wide class of x-ray pulsed sources. © 2015, Pleiades Publishing, Inc.
Nonthermal electron beams formed in plasma of a high-current vacuum spark have been studied by polarization spectroscopy techniques. Experiments showed that the polarization of bremsstrahlung radiation depends on the ratio of its photon energy and the energy of beam electrons. It is established that the electrode configuration influences the efficiency of spark discharge pinching and the energy of nonthermal electron beams formed in the vacuum spark discharge.
Influence of heat, electric field and particle irradiation of powders of boron and tungsten are presented and discussed in the paper. It is shown that the particles of both powders are emitted from their surface when electric field applied normally to the powder surface exceeds some minimal magnitude. Simultaneous influence of electric field and irradiation by hydrogen- and argon plasma ions or by hydrogen atoms activates particle emission at the temperatures <1300. K. Hydrogen- and argon plasma ion irradiation in the temperature range 1300-1800. K stimulates a succession of powder modifications with the increase of powder temperature and power of ion irradiation.Driving forces and processes of powder modifications were found to be electric field forces, irradiation enhanced diffusion, interatomic forces, surface tension, sputtering by ion irradiation and ion induced stresses in the newly formed uniform layers.
This work is devoted to consideration of recombination effects of long-range interacting dark matter. It includes some calculation details and discussion of questions which remained outside the scope of arXiv:1506.03094. © 2015 The Authors.
Clusters of primordial black holes may cause the formation of quasars in the early Universe. In turn, radiation from these quasars may lead to the reionization of the Universe. However, the evaporation of primordial black holes via Hawking's mechanism may also contribute to the ionization of matter. The possibility of matter ionization via the evaporation of primordial black holes with allowance for existing constraints on their density is discussed. The contribution to ionization from the evaporation of primordial black holes characterized by their preset mass spectrum can roughly be estimated at about 10(-3).
Here, we briefly discuss the possibility to solve simultaneously with primordial black holes (PBHs) the problems of dark matter (DM), reionization of the universe, origin of positron line from Galactic center and supermassive black hole (BH) in it. Discussed scenario can naturally lead to a multiple-peak broad-mass-range distribution of PBHs in mass, which is necessary for simultaneous solution of the problems.
Primordial black holes (PBHs) with mass 10(16) - 10(17) g almost escape constraints from observations so could essentially contribute to dark matter density. Hawking evaporation of such PBHs produces with a steady rate gamma- and e(+/-)-radiations in MeV energy range, which can be absorbed by ordinary Simplified estimates show that a small fraction of evaporated energy had to be absorbed by baryonic matter what can turn out to be enough to heat the matter so it is fully ionized at the redshift z similar to 5...10. The result is found to be close to a borderline case where the effect appears, what makes it sensitive to the approximation used. In our approximation, degree of gas ionization reaches 50-100% by z similar to 5 for PBH mass (3...7) x 10(16) g with their abundance corresponding to the upper limit.
Study of the gg → Η → τsup+/supτsup–/sup process was performed at Monte Carlo level within the framework of searching for CP-violating effects. The sensitivity of chosen observables to CP-parity of the Higgs boson was demonstrated for hadronic 1-prong τ decays (τsup±/sup → πsup±/sup, ρsup±/sup). Monte Carlo samples for the gg → Η → τsup+/supτsup-/sup process were generated including the parton hadronisation to final state particles. This generation was performed for the Standard Model Higgs boson, the pseudoscalar Higgs boson, the Z → τsup+/supτsup–/sup background, and mixed CP-states of the Higgs boson. © 2015, Pleiades Publishing, Ltd.
The pseudoelasticity effect was studied in amorphous-crystalline Ti40.7Hf9.5Ni44.8Cu5 shape-memory alloy with different volume fractions of the crystalline phase. Pseudoelastic behaviour was found in the samples with a volume fraction of the crystalline phase of 60% and above. An increase in the volume fraction of the crystalline phase led to a rise in the strain accumulated due to stress-induced martensite, an increase in the mechanical hysteresis and a decrease in the stress needed for the appearance of the stress-induced martensite. It was found that the dependences of the pseudoelasticity effect parameters on the volume fraction of the crystalline phase were due to the influence of the surface energy on the formation of martensite crystals with preferable orientation. An increase in the volume fraction of the crystalline phase led to an increase in the grain sizes and, as a result, a decrease in the surface energy. It provided an increase in the number of preferably oriented martensite variants appearing in the grain under load. © 2015 IOP Publishing Ltd.
The physics goals of the next Large Hadron Collider run include high precision tests of the Standard Model and searches for new physics. These goals require detailed comparison of data with computational models simulating the expected data behavior. To highlight the role which modeling and simulation plays in future scientific discovery, we report on use cases and experience with a unified system built to process both real and simulated data of growing volume and variety.
The influence of plasma on different effects of gravitational lensing is reviewed. Using the Hamiltonian approach for geometrical optics in a medium in the presence of gravity, an exact formula for the photon deflection angle by a black hole (or another body with a Schwarzschild metric) embedded in plasma with a spherically symmetric density distribution is derived. The deflection angle in this case is determined by the mutual combination of different factors: gravity, dispersion, and refraction. While the effects of deflection by the gravity in vacuum and the refractive deflection in a nonhomogeneous medium are well known, the new effect is that, in the case of a homogeneous plasma, in the absence of refractive deflection, the gravitational deflection differs from the vacuum deflection and depends on the photon frequency. In the presence of a plasma nonhomogeneity, the chromatic refractive deflection also occurs, so the presence of plasma always makes gravitational lensing chromatic. In particular, the presence of plasma leads to different angular positions of the same image if it is observed at different wavelengths. It is discussed in detail how to apply the presented formulas for the calculation of the deflection angle in different situations. Gravitational lensing in plasma beyond the weak deflection approximation is also considered. © 2015, Pleiades Publishing, Ltd.
In this paper we review a recently developed approximate method for investigation of dynamics of compressible ellipsoidal figures. Collapse and subsequent behaviour are described by a system of ordinary differential equations for time evolution of semi-axes of a uniformly rotating, three-axis, uniform-density ellipsoid. First, we apply this approach to investigate dynamic stability of non-spherical bodies. We solve the equations that describe, in a simplified way, the Newtonian dynamics of a self-gravitating non-rotating spheroidal body. We find that, after loss of stability, a contraction to a singularity occurs only in a pure spherical collapse, and deviations from spherical symmetry prevent the contraction to the singularity through a stabilizing action of nonlinear non-spherical oscillations. The development of instability leads to the formation of a regularly or chaotically oscillating body, in which dynamical motion prevents the formation of the singularity. We find regions of chaotic and regular pulsations by constructing a Poincare diagram. A real collapse occurs after damping of the oscillations because of energy losses, shock wave formation or viscosity. We use our approach to investigate approximately the first stages of collapse during the large scale structure formation. The theory of this process started from ideas of Ya. B. Zeldovich, concerning the formation of strongly non-spherical structures during nonlinear stages of the development of gravitational instability, known as 'Zeldovich's pancakes'. In this paper the collapse of non-collisional dark matter and the formation of pancake structures are investigated approximately. Violent relaxation, mass and angular momentum losses are taken into account phenomenologically. We estimate an emission of very long gravitational waves during the collapse, and discuss the possibility of gravitational lensing and polarization of the cosmic microwave background by these waves. © 2015 Cambridge University Press.
An exact analytic solution of self-similar equations is obtained for propagation of a strong shock in a flat expanding Friedman universe. The time and radial dependences of the density and velocity of the polytropic gas behind the shock wave are obtained. The shock velocity in the expanding medium decreases as ~tsup−1/5/sup, slower than the shock velocity in the static uniform medium (~tsup−3/5/sup), and its radius increases ~tsup4/5/sup, more rapidly than in a uniform non-gravitating medium (~tsup2/5/sup). So, the shock propagates in the direction of a decreasing density at a larger speed than in a static medium due to accelerating action of the decreasing density, even in the presence of self-gravity. © 2015, Pleiades Publishing, Ltd.
Dark energy limits a radius of big clusters of galaxies, and may accelerate hot gas outflowing from the cluster as a wind. Collision of accelerated winds, in presence of a magnetic field, produce a situation favorable for acceleration of EHECR.
We show that the Wightman function of a free quantum field generates any complete set of solutions of the relativistic wave equations. Using this approach, we construct the complete set of solutions of the two-dimensional Dirac equation consisting of eigenfunctions of the generator of Lorentz rotations (boost operator). We show that at the surface of the light cone, the boost modes for a fermion field contain the Gelfand delta function of a complex argument. Because of the presence of such a singularity, excluding even a single mode with an arbitrary value of the boost quantum number makes the set of boost modes incomplete. This results in the nonapplicability of the Unruh quantization scheme to a massive fermion field in the two-dimensional Minkowski space-time. Hence, in full accordance with the boson case, the Unruh procedure for a fermion field cannot be used to prove the existence of the Unruh effect. © 2015, Pleiades Publishing, Ltd.
Boron carbide was proposed as a material of in-situ protecting coating for tungsten tiles of ITER divertor. To prove this concept the project including investigation of regimes of plasma deposition of B4C coating on tungsten and tests of boron carbide layer in ITER-like is started recently. The paper contends the first results of the project. The results of B4C coating irradiation by the plasma pulses of QSPU-T plasma accelerator are presented. The new device capable of B4C film deposition on tungsten and testing of the films and materials with ITER-like heat loads and ion- and electron irradiation is described. The results of B4C coating deposition and testing of both tungsten substrate and coating are shown and discussed.
A device intended for boron carbide coating deposition and material testing under high heat loads is presented. A boron carbide coating 5 μm thick was deposited on the tungsten substrate. These samples were subjected to thermocycling loads in the temperature range of 400–1500°C. Tungsten layers deposited on tungsten substrates were tested in similar conditions. Results of the surface analysis are presented. © 2015, Pleiades Publishing, Ltd.
The possibility of detecting a gas-liquid Coulomb phase transition in nondegenerate nonideal two-component low-temperature plasma is discussed using the results of calculating parameters of the critical point and binodal of the gas-liquid phase transition by the Monte Carlo method in the basic pseudopotential low-temperature plasma “shelf coulomb” model. Based on these results, a range of values of thermodynamic functions is found in which the Coulomb phase transition can be observed. It is shown that this range of parameters is beyond the domain of existence of strongly ionized nondegenerate low-temperature two-component plasma. © 2015, Pleiades Publishing, Ltd.
Conical diffraction in one dimensional lattice formed by waveguide array results in the two quasi beams. Scattering of the electromagnetic wave of either of two beams on defect is investigated. The defect is represented by the waveguide fabricated from negative refractive index material. It is embedded into waveguide array that consists of waveguides with positive refractive index. The numerical simulation demonstrates the strong reflection of the electromagnetic wave from defect of this kind. © 2015 The Authors.
A mathematical model of surface cracking under pulsed heat load was developed. The model correctly describes a smooth brittle-ductile transition. The elastic deformation is described in a thin-heated-layer approximation. The plastic deformation is described with the Hollomon equation. The time dependence of the deformation and stresses is described for one heating-cooling cycle for a material without initial plastic deformation. The model can be applied to tungsten manufactured according to ITER specifications. The model shows that the stability of stress-relieved tungsten deteriorates when the base temperature increases. This proved to be a result of the close ultimate tensile and yield strengths. For a heat load of arbitrary magnitude a stability criterion was obtained in the form of condition on the relation of the ultimate tensile and yield strengths. © 2015 Elsevier B.V.
We study the transmission and reflection of a plane electromagnetic wave through a two-dimensional array of rf-SQUIDs. The basic equations describing the amplitudes of the magnetic field and current in the split-ring resonators are developed. These yield in the linear approximation the reflection and transmission coefficients. The polarization of the reflected wave is independent of the frequency of the incident wave and of its polarization; it is defined only by the orientation of the split ring. The reflection and transmission coefficients have a strong resonance that is determined by the parameters of the rf-SQUID; its strength depends essentially on the incident angle. © 2015 American Physical Society.
Measurements of the centrality and rapidity dependence of inclusive jet production in sNN=5.02 TeV proton-lead (p+Pb) collisions and the jet cross-section in s=2.76 TeV proton-proton collisions are presented. These quantities are measured in datasets corresponding to an integrated luminosity of 27.8 nbsup-1/sup and 4.0 pbsup-1/sup, respectively, recorded with the ATLAS detector at the Large Hadron Collider in 2013. The p+Pb collision centrality was characterised using the total transverse energy measured in the pseudorapidity interval -4.9<η<-3.2 in the direction of the lead beam. Results are presented for the double-differential per-collision yields as a function of jet rapidity and transverse momentum (pinfT/inf) for minimum-bias and centrality-selected p+Pb collisions, and are compared to the jet rate from the geometric expectation. The total jet yield in minimum-bias events is slightly enhanced above the expectation in a pinfT/inf-dependent manner but is consistent with the expectation within uncertainties. The ratios of jet spectra from different centrality selections show a strong modification of jet production at all pinfT/inf at forward rapidities and for large pinfT/inf at mid-rapidity, which manifests as a suppression of the jet yield in central events and an enhancement in peripheral events. These effects imply that the factorisation between hard and soft processes is violated at an unexpected level in proton-nucleus collisions. Furthermore, the modifications at forward rapidities are found to be a function of the total jet energy only, implying that the violations may have a simple dependence on the hard parton-parton kinematics. © 2015 CERN for the benefit of the ATLAS Collaboration.
The nuclear modification factor, R-AA, of the prompt charmed mesons D-0, D+ and D*+, and their antiparticles, was measured with the ALICE detector in Pb-Pb collisions at a centre-of-mass energy root s(NN) = 2 : 76 TeV in two transverse momentum intervals, 5 p(T) 8 GeV/c and 8 p(T) 16 GeV/c, and in six collision centrality classes. The R-AA shows a maximum suppression of a factor of 56 in the 10% most central collisions. The suppression and its centrality dependence are compatible within uncertainties with those of charged pions. A comparison with the R-AA of non-prompt J/psi from B meson decays, measured by the CMS Collaboration, hints at a larger suppression of D mesons in the most central collisions.
We present a measurement of inclusive J/psi production in p-Pb collisions at root S-NN = 5.02 TeV as a function of the centrality of the collision, as estimated from the energy deposited in the Zero Degree Calorimeters. The measurement is performed with the ALICE detector down to zero transverse momentum, p(T), in the backward (-4.46 y(cms) -2.96) and forward (2.03 y(cms) 3.53) rapidity intervals in the dimuon decay channel and in the mid-rapidity region (-1.37 y(cms) 0.43) in the dielectron decay channel. The backward and forward rapidity intervals correspond to the Pb-going and p-going direction, respectively. The p(T)-differential J/psi production cross section at backward and forward rapidity is measured for several centrality classes, together with the corresponding average p(T) and p(T)(2) values. The nuclear modification factor is presented as a function of centrality for the three rapidity intervals, and as a function of p(T) for several centrality classes at backward and forward rapidity. At mid-and forward rapidity, the J/psi yield is suppressed up to 40% compared to that in pp interactions scaled by the number of binary collisions. The degree of suppression increases towards central p-Pb collisions at forward rapidity, and with decreasing p(T) of the J/psi. At backward rapidity, the nuclear modification factor is compatible with unity within the total uncertainties, with an increasing trend from peripheral to central p-Pb collisions.
We report measurements of the primary charged-particle pseudorapidity density and transverse momentum distributions in p-Pb collisions at root s(NN) = 5.02 TeV and investigate their correlation with experimental observables sensitive to the centrality of the collision. Centrality classes are defined by using different event-activity estimators, i.e., charged-particle multiplicities measured in three different pseudorapidity regions as well as the energy measured at beam rapidity (zero degree). The procedures to determine the centrality, quantified by the number of participants (N-part) or the number of nucleon-nucleon binary collisions (N-coll) are described. We show that, in contrast to Pb-Pb collisions, in p-Pb collisions large multiplicity fluctuations together with the small range of participants available generate a dynamical bias in centrality classes based on particle multiplicity. We propose to use the zero-degree energy, which we expect not to introduce a dynamical bias, as an alternative event-centrality estimator. Based on zero-degree energy-centrality classes, the N-part dependence of particle production is studied. Under the assumption that the multiplicity measured in the Pb-going rapidity region scales with the number of Pb participants, an approximate independence of the multiplicity per participating nucleon measured at mid-rapidity of the number of participating nucleons is observed. Furthermore, at high-pT the p-Pb spectra are found to be consistent with the pp spectra scaled by N-coll for all centrality classes. Our results represent valuable input for the study of the event-activity dependence of hard probes in p-Pb collisions and, hence, help to establish baselines for the interpretation of the Pb-Pb data.
A procedure for manufacturing detectors (with a diameter of ∼1 mm and thickness of 0.1 mm) based on high-purity epitaxial layers of 4H-SiC polytype is described, and results of investigation of their parameters are presented. It is shown that the designed detectors have good spectrometric characteristics in α particle detection in a wide energy range. The measured 241Am γ ray spectra are also given.
Abstract A method of shadow-masked pulsed laser deposition was applied to obtain W-Se and W-Se-C films using pure argon (Ar) gas and a mixture of Ar and methane, respectively. The gas pressure was varied in a range of 2-10 Pa. The deposition in Ar caused the formation of Se-enriched W-Se films (Se/W ∼ 5) with pronounced surface roughness because of an effective nanoparticle growth. Heating or DC/RF biasing the substrate modified the film composition (Se/W ∼ 1.7-4) and surface smoothing. The use of methane resulted in a doping of W-Se-C films with carbon, and the C concentration was increased to ∼67 at.% under RF biasing of the substrate. The films with smooth surface had high coefficients (∼30%) of light reflection. The formation of nanoparticles and density-graded surface texture decreased the reflectance to 3.8%. Antireflective properties and high area of the rough surface may play an essential role in enhancing the photovoltaic and catalytic properties of W-Se films. Dense structure, smooth surface, optimal Se/W ratio, and preferential spsup2/sup-bonding of C atoms promote the high tribological performance of nanocomposite W-Se-C coatings. © 2015 Elsevier Ltd.
We present modification of difference frequency generator of coherent THz radiation in a nonlinear GaSe crystal using dual-wavelength diode-pumped solid-state Nd:YLF laser. Generation at the two wavelengths (1.047 and 1.053 μm) was carried out by equalization of the gains at these wavelengths near the frequency degeneracy of the transverse modes in resonator cavity, Q-switched by acousto-optical modulator. The main parameters of the device were measured: angular synchronism (width 0.6 degrees), polarization ratio (1:100), conversion efficiency (10-7), pulse power (0.8 mW), frequency and width (53,8 μm-1, 0,6 μm-1), pulse width and repetition rate (10 ns, 7 kHz). The method is promising for practical purposes. © 2015 Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license.
We report the first measurement at the LHC of coherent photoproduction of ρsup0/sup mesons in ultra-peripheral Pb-Pb collisions. The invariant mass and transverse momentum distributions for ρsup0/sup production are studied in the πsup+/supπsup−/sup decay channel at mid-rapidity. The production cross section in the rapidity range |y| < 0.5 is found to be dσ/dy = 425 ± 10(stat.)inf− 50/inf sup+ 42/sup (sys.) mb. Coherent ρsup0/sup production is studied with and without requirement of nuclear breakup, and the fractional yields for various breakup scenarios are presented. The results are compared with those from lower energies and with model predictions. © 2015, The Author(s).
We have performed the first measurement of the coherent ψ(2S) photo-production cross section in ultra-peripheral Pb. Pb collisions at the LHC. This charmonium excited state is reconstructed via the ψ(2S)→l+l- and ψ(2S)→J/ψπ+π- decays, where the J/ψ decays into two leptons. The analysis is based on an event sample corresponding to an integrated luminosity of about 22 μb-1. The cross section for coherent ψ(2S) production in the rapidity interval -0.9<y<0.9 is dσψ(2S)coh/dy=0.83±0.19(stat+syst) mb. The ψ(2S) to J/ψ coherent cross section ratio is 0.34-0.07+0.08(stat+syst). The obtained results are compared to predictions from theoretical models. © 2015 CERN for the benefit of the ALICE Collaboration.
A measurement of the Higgs boson mass is presented based on the combined data samples of the ATLAS and CMS experiments at the CERN LHC in the H -- gamma gamma and H -- ZZ -- 4l decay channels. The results are obtained from a simultaneous fit to the reconstructed invariant mass peaks in the two channels and for the two experiments. The measured masses from the individual channels and the two experiments are found to be consistent among themselves. The combined measured mass of the Higgs boson is m(H) = 125.09 +/- 0.21 (stat) +/- 0.11 (syst) GeV.
The results obtained by the comparative investigation of low-field emission currents from the surfaces of various plasma-facing materials used in thermonuclear facilities are presented. It is demonstrated that emission currents can only be compared under the same experimental conditions and after degassing of the surfaces under study. The determined macroscopic current densities enable us to rank the examined materials in terms of the probability of the ignition of unipolar arcs. Such materials can be arranged in descending order of probabilities as follows: MPG-8 graphite with a rough surface, tungsten “nanofuzz,” tungsten oxide “grass,” carbon–carbon composite, MPG-8 graphite with a smooth surface, and polished tungsten. © 2015, Pleiades Publishing, Ltd.
The objective of this work is to compare the deuterium retention in tungsten pre-damaged with electron (e) beam, ions and neutrons. Self-ion irradiation was performed at IPP (Garching) and e-beam irradiation at MEPhI (Moscow). Neutron irradiation was done at Oak Ridge National Laboratory in high-flux isotope reactor (HFIR) by Hatano et al. (2013). After pre-damaging, specimens were exposed to deuterium plasma in well-defined laboratory conditions. © 2015 The Authors.
A comparison of the differential cross sections for the processes Z/gamma* + jets and photon (gamma)+ jets is presented. The measurements are based on data collected with the CMS detector at root s = 8TeV corresponding to an integrated luminosity of 19.7 fb(-1). The differential cross sections and their ratios are presented as functions of p(T). The measurements are also shown as functions of the jet multiplicity. Differential cross sections are obtained as functions of the ratio of the Z/gamma* p(T) to the sum of all jet transverse momenta and of the ratio of the Z/gamma* p(T) to the leading jet transverse momentum. The data are corrected for detector effects and are compared to simulations based on several QCD calculations.
A comparison of the differential cross sections for the processes Z/gamma* + jets and photon (gamma)+ jets is presented. The measurements are based on data collected with the CMS detector at root s = 8TeV corresponding to an integrated luminosity of 19.7 fb(-1). The differential cross sections and their ratios are presented as functions of p(T). The measurements are also shown as functions of the jet multiplicity. Differential cross sections are obtained as functions of the ratio of the Z/gamma* p(T) to the sum of all jet transverse momenta and of the ratio of the Z/gamma* p(T) to the leading jet transverse momentum. The data are corrected for detector effects and are compared to simulations based on several QCD calculations.
Atomic-layer deposition (ALD) technique in combination with in vacuo X-ray photoelectron spectroscopy (XPS) analysis has been successfully employed to obtain fully ALD-grown planar TiN/HfO2/TiN metal-insulator-metal structures for resistive random access memory (ReRAM) memory elements. In vacuo XPS analysis of ALD-grown TiN/HfO2/TiN stacks reveals the presence of the ultrathin oxidized layers consisting of TiON (∼0.5nm) and TiO2 (∼0.6nm) at the bottom TiN/HfO2 interface (i); the nonoxidized TiN at the top HfO2/TiN interface (ii); the oxygen deficiency in the HfO2 layer does not exceed the XPS detection limit (iii). Electroformed ALD TiN/HfO2/TiN stacks reveal both conventional bipolar and complementary types of resistive switching. In the complementary resistive switching regime, each programming sequence is terminated by a reset operation, leaving the TiN/HfO2/TiN stack in a high-resistance state. The observed feature can avoid detrimental leaky paths during successive reading operation, which is useful in the passive ReRAM arrays without a selector element. The bipolar regime of resistive switching is found to reveal the gradual character of the SET and RESET switching processes. Long-term potentiation and depression tests performed on ALD-grown TiN/HfO2/TiN stacks indicate that they can be used as electronic synapse devices for the implementation of emerging neuromorphic computation systems.
Key issues of design of the divertor and the first wall of DEMO-FNS are presented. A double null closed magnetic configuration was chosen with long external legs and V-shaped corners. The divertor employs a cassette design similar to that of ITER. Water-cooled first wall of the tokamak is made of Be tiles and CuCrZr-stainless steel shells. Lithium injection and circulation technologies are foreseen for protection of plasma facing components. Simulations of thermal loads onto the first wall and divertor plates suggest a possibility to distribute heat loads making them less than 10 MW msup-2/sup. Evaluations of sputtering and evaporation of plasma-facing materials suggest that lithium may protect the first wall. To prevent Be erosion at the outer divertor plates either the full detached divertor operation or arrangement of the renewal lithium flow on targets should be implemented. Test bed experiments on the Tsefey-M facility with the first wall mockup coated by tiles and cooled by water are presented. The temperature of the surface of tiles reached 280-300 ° at 5 MW msup-2/sup and 600-650 ° at 10.5 MW msup-2/sup. The mockup successfully withstood 1000 cycles with the lower thermal loading and 100 cycles with higher thermal loading. © 2015 IAEA, Vienna.
The results of a comprehensive analysis of the possibility of developing in our country a powerful proton accelerator-driver as an element of subcritical electro-nuclear facility are presented. The investigations are performed taking account of the latest advances of accelerator technology and the real capabilities of industry. The design layout developed for the accelerator is discussed. It is shown that in principle a prototype of a similar to 1 GeV accelerator-driver with current 1-5 mA, which can subsequently be increased to 10-15 mA, can be built in Russia.
One of the perspective methods of water microleakages detection in thermonuclear devices is presented. Method is based on the secondary electron emission instability of Debye near-electrode layers in the contact of nonequilibrium plasma with electrode surface covered by thin dielectric film. Method is based on detection of beam-plasma discharge transition into auto-oscillation regime. It is observed when balance between oxidation and sputtering of a contact surface covered by thin dielectric film is shifted. The method has better sensitivity (< 10sup16/sup mol/s) and response time (< 60 s) as compared with spectroscopic methods (> 10sup16/sup mol/s and > 2000 s, respectively). In addition, it allows detecting negligible oxygen-containing admixture. In perspective, this method will allow to localize a water microleakage in vacuum chambers of thermonuclear devices and determine a water vapor flow by features of IV-curve. © 2015 The Authors.
The third International Symposium on Lithium Application for Fusion Device (ISLA-2013) was held on 9-11 October 2013 at ENEA Frascati Centre with growing participation and interest from the community working on more general aspect of liquid metal research for fusion energy development. ISLA-2013 has been confirmed to be the largest and the most important meeting dedicated to liquid metal application for the magnetic fusion research. Overall, 45 presentation plus 5 posters were given, representing 28 institutions from 11 countries. The latest experimental results from nine magnetic fusion devices were presented in 16 presentations from NSTX (PPPL, USA), FTU (ENEA, Italy), T-11M (Trinity, RF), T-10 (Kurchatov Institute, RF), TJ-II (CIEMAT, Spain), EAST(ASIPP, China), HT-7 (ASIPP, China), RFX (Padova, Italy), KTM (NNC RK, Kazakhstan). Sessions were devoted to the following: (I) lithium in magnetic confinement experiments (facility overviews), (II) lithium in magnetic confinement experiments (topical issues), (III) special session on liquid lithium technology, (IV) lithium laboratory test stands, (V) Lithium theory/modelling/comments, (VI) innovative lithium applications and (VII) special Session on lithium-safety and lithium handling. There was a wide participation from the fusion technology communities, including IFMIF and TBM communities providing productive exchange with the physics oriented magnetic confinement liquid metal research groups. This international workshop will continue on a biennial basis (alternating with the Plasma- Surface Interactions (PSI) Conference) and the next workshop will be held at CIEMAT, Madrid, Spain, in 2015.
The ATLAS experiment at the LHC has measured the Higgs boson couplings and mass, and searched for invisible Higgs boson decays, using multiple production and decay channels with up to 4.7 fb(-1) of pp collision data at root S = 7 TeV and 20.3 fb(-1) at root s = 8 TeV. In the current study, the measured production and decay rates of the observed Higgs boson in the gamma gamma, ZZ, WW, Z gamma, bb, tau tau, and mu mu decay channels, along with results from the associated production of a Higgs boson with a top-quark pair, are used to probe the scaling of the couplings with mass. Limits are set on parameters in extensions of the Standard Model including a composite Higgs boson, an additional electroweak singlet, and two-Higgs-doublet models. Together with the measured mass of the scalar Higgs boson in the gamma gamma and ZZ decay modes, a lower limit is set on the pseudoscalar Higgs boson mass of m(A) 370 GeV in the "hMSSM" simplified Minimal Supersymmetric Standard Model. Results from direct searches for heavy Higgs bosons are also interpreted in the hMSSM. Direct searches for invisible Higgs boson decays in the vector-boson fusion and associated production of a Higgs boson with W/Z (Z - ll, W/Z - jj) modes are statistically combined to set an upper limit on the Higgs boson invisible branching ratio of 0.25. The use of the measured visible decay rates in a more general coupling fit improves the upper limit to 0.23, constraining a Higgs portal model of dark matter.
Measurements of the ZZ and WW final states in the mass range above the 2minfZ/infand 2minfW/infthresholds provide a unique opportunity to measure the off-shell coupling strength of the Higgs boson. This paper presents constraints on the off-shell Higgs boson event yields normalised to the Standard Model prediction (signal strength) in the ZZ 4l ZZ → 2ℓ2ν and WW → eνμν final states. The result is based on pp collision data collected by the ATLAS experiment at the LHC, corresponding to an integrated luminosity of 20.3 fbsup-1/supat a collision energy of s=8 TeV. Using the $$CL_s$$CLs method, the observed 95% confidence level (CL) upper limit on the off-shell signal strength is in the range 5.1–8.6, with an expected range of 6.7–11.0. In each case the range is determined by varying the unknown gg → ZZ and gg → WW background K-factor from higher-order quantum chromodynamics corrections between half and twice the value of the known signal K-factor. Assuming the relevant Higgs boson couplings are independent of the energy scale of the Higgs boson production, a combination with the on-shell measurements yields an observed (expected) 95% CL upper limit on (formula presented) in the range 4.5–7.5 (6.5–11.2) using the same variations of the background K-factor. Assuming that the unknown gg → VV background K-factor is equal to the signal K-factor, this translates into an observed (expected) 95 $$$$% CL upper limit on the Higgs boson total width of 22.7 (33.0) MeV. © 2015, CERN for the benefit of the ATLAS collaboration.
Stringent limits are set on the long-lived lepton-like sector of the phenomenological minimal supersymmetric standard model (pMSSM) and the anomaly-mediated super-symmetry breaking (AMSB) model. The limits are derived from the results presented in a recent search for long-lived charged particles in proton-proton collisions, based on data collected by the CMS detector at a centre-of-mass energy of 8 TeV at the Large Hadron Collider. In the pMSSM parameter sub-space considered, 95.9% of the points predicting charginos with a lifetime of at least 10 ns are excluded. These constraints on the pMSSM are the first obtained at the LHC. Charginos with a lifetime greater than 100 ns and masses up to about 800 GeV in the AMSB model are also excluded. The method described can also be used to set constraints on other models.
The paper presents objectives and activities of IAEA Coordinated Research Projects 'Conceptual development of steady-state compact fusion neutron sources' and 'Utilisation of a network of small magnetic confinement fusion devices for mainstream fusion research'. The background and main projects of the CRP on FNS are described in detail, as this is a new activity at IAEA. Recent activities of the second CRP, which continues activities of previous CRPs, are overviewed.
A new set of Heavy Ion Beam Probe diagnostic (HIBP-2) was recently installed in the TJ-II stellarator. HIBP-2 is being operated simultaneously with the previously existing HIBP-1 to provide the coherence data analysis aiming for the 3D studies of the Long-Range Correlations and Alfvenic Eigenmodes. A new Control and Data Acquisition System (CDAS) of high performance and high reliability has been made to operate HIBP-2. The CDAS of HIBP-1 is being upgraded to a similar configuration. The distributed architecture implementing a client-server model provides flexibility and system scalability. The developed CDAS has shown reliable operation of dual HIBP. This paper describes the CDAS of this dual diagnostics.
The requirements are formulated for a new type of nanomaterials based on transition metal dichalcogenides (TMD), which are promising to create relatively cheap and effective catalysts for electrochemical hydrogen evolution reaction. The possibility of implementation of some important requirements for the structure of these materials is investigated by the example of thin-film coatings containing tungsten diselenide and carbon. WSex/C coatings are prepared via pulsed laser deposition in an inert and reactive (CH4) gas in a standard configuration and using an antidroplet screen. In some cases, low DC voltage or pulsed high-voltage bias are applied to the substrate, initiating ion bombardment of the coatings. Factors exerting an important influence on the chemical composition, morphology, and surface topography of the coatings are established. Modes of formation of a rough coating surface with a high density of WSe2 edges are determined, which is essential for high catalytic activity and performance of TMD-containing nanocatalysts. The carbon phase with a high concentration of sp2 bonds is needed for effective current transport in the formed layers. © 2015, Pleiades Publishing, Ltd.
The statistics of the ionisation response amplitude measured at selected points and their surroundings within sensitive regions of integrated circuits (ICs) under focused femtosecond laser irradiation is obtained for samples chosen from large batches of two types of ICs. A correlation between these data and the results of full-chip scanning is found for each type. The criteria for express validation of IC single-event effect (SEE) hardness based on ionisation response measurements at selected points are discussed.
Geodesic acoustic mode (GAM) of electrostatic potential and density fluctuations are simultaneously measured by Heavy Ion Beam Probe (HIBP) and Correlation Reflectometry (CR). The regimes with Ohmic and electron cyclotron resonance heating (ECRH) were studied (B = 2.2 T, I-p = 210 - 240 kA, n(e) = (2.3 - 3.7). 10(19) m(-3), P-EC 0.6 MW). GAMs are more pronounced during ECRH, when the typical frequencies were seen in the narrow band from 22 to 27 kHz for the main peak and 25-30 kHz for the higher frequency satellite peak. The local values of electric potential and density fluctuations show the significant coherency and constant phase shift at GAM frequency range. The existence of the long-distance (one quarter of the torus) correlations of core electric potential and density for GAM implying that GAM is a global mode, was shown for the first time in tokamaks.
A closed-form equation is derived for the critical nucleus charge Z = Zcr at which a discrete level with the Dirac quantum number touches the lower continuum of the Dirac equation solutions. For the Coulomb potential cut off rectangularly at the short distance r0 = Rh/mc, R 蠐 1, the critical nucleus charge values are obtained for several values of k and R. It is shown that the partial scattering matrix of elastic positron-nucleus scattering, Sk = exp (2iδk(εp)), is also unitary for Z > Zcr. For this range, the scattering phase δj(εp). is calculated as a function of the positron energy Ep = εpmcsup2/sup, as are the positions and widths of quasidiscrete levels corresponding to the scattering matrix poles. The implication is that the single-particle approximation for the Dirac equation is valid not only for Z < Zcr but also for Z > Zcr and that there is no spontaneous creation of esup+/supesup-/sup pairs from the vacuum. © 2015 Uspekhi Fizicheskikh Nauk, Russian Academy of Sciences.
A closed-form equation is derived for the critical nucleus charge Z = Zc(r) at which a discrete level with the Dirac quantum number touches the lower continuum of the Dirac equation solutions. For the Coulomb potential cut off rectangularly at the short distance r(o) = Rh/mc, R 1, the critical nucleus charge values are obtained for several values of K and R. It is shown that the partial scattering matrix of elastic positron nucleus scattering, S-kappa Z(cr) For this range, the scattering phase delta(kappa)(epsilon(p)) is calculated as a function of the positron energy E-p = epsilon(p)mc(2), as are the positions and widths of quasidiscrete levels corresponding to the scattering matrix poles. The implication is that the single-particle approximation for the Dirac equation is valid not only for Z Z(cr) but also for Z Z(cr) and that there is no spontaneous creation of e(+)e(-) pairs from the vacuum.
The characteristics of charge carriers in graphene with dopants having charge Z and deposited onto a SiC substrate are analyzed. The closed set of explicit equations determining the spectrum of charge carriers are obtained for the case of the Coulomb potential modified at small distances. The critical values Z (cr) of the dopant charge at which the energy level with the given quantum numbers crosses the valence band boundary are determined. At Z Z (cr), for the lowest values of the orbital angular momentum, the position of the energy level corresponding to the bound state is obtained as a function of charge Z. For Z Z (cr), the position and width of the quasistationary state are calculated. The problem concerning the screening of the impurity charge is also considered.
The critical current angular distributions in the magnetic field range from 0 up to 8 T have been measured for Zr doped MOCVD (metalorganic chemical vapor deposition) tape produced by Super Power Inc. The vortex path model was used to fit these distributions to specify a tilted peak near c-Axis that corresponds to the presence of BaZrO3 columnar defects in the tape. The orientation of such defects was found to be 10.3o with respect to the c-Axis direction. Peak in the ab direction was observed in the whole field range and it could be interpreted as pinning on spacer layers between CuO planes. The appearance of gauss distribution was found in high fields that confirms chosen model. © 2015 The Authors.
Nowadays MgB2 wires are attractive for designing real devices like motors and magnets. The latest production technologies allow to increase critical current value of wires. However, there is a problem of wire performance degradation under bending strain. Thus, there is a problem of manufacturing solenoids with small diameters, especially from ex situ MgB2 wires produced by powder-in-tube (PIT) technology. In this work, influence of bending on critical current Ic multifilament PIT ex situ MgB2 tape and wire has been studied. Critical current dependencies on external magnetic field Ic(H) were measured at liquid helium temperature in the range of fields from 2.5 T up to 8 T. Measurements were carried out in parallel (H||), and perpendicular (H) orientation of external magnetic field to the sample surface. Voltage current characteristics (V-I) on tape samples were measured with bending on diameters D=30; 40; 60; 70; 80; 90;100 mm. It was shown that critical current density (Jc) decreases by 24% and by 28% for tape and wire respectively with decreasing bending diameter from 100 mm to 60 mm. It was found that the tape still had superconductive properties even with bending diameter D=30 mm, but its Jc decreased by 44% in comparison with Jc(D=100 mm). One more feature that was found is the appearance of resistive component in the voltage current characteristics for all bend diameters in magnetic fields H3.5 T. © 2015 The Authors.
In this paper we present the development of a new hybrid energy transfer line with 30 m length. The line is essentially a flexible 30 m hydrogen cryostat that has three sections with different types of thermal insulation in each section: simple vacuum superinsulation, vacuum superinsulation with liquid nitrogen precooling and active evaporating cryostatting (AEC) system. We performed thermo-hydraulic tests of the cryostat to compare three thermo-insulating methods. The tests were made at temperatures from 20 to 26 K, hydrogen flow from 70 to 450 g/s and pressure from 0.25 to 0.5 MPa. It was found that AEC thermal insulation was the most effective in reducing heat transfer from room temperature to liquid hydrogen in ?10 m section of the cryostat, indicating that it can be used for long superconducting power cables. High voltage current leads were developed as well. The current leads and superconducting MgB2 cable passed high voltage DC test up to 50 kV DC. Critical current of the cable at ?21 K was 3500 A. It means that the 30 m hybrid energy system developed is able to deliver ?50-60 MW of chemical power and ?50-75 MW of electrical power, i.e. up to ?135 MW in total.
Among dark atom scenarios, the simplest and most predictive one is that of O-helium (OHe) dark atoms, in which a leptonlike doubly charged particle (Formula presented.) is bound to a primordial helium nucleus, and is the main constituent of dark matter. The OHe cosmology has several successes: it leads to a warmer-than-cold-dark matter scenario for large-scale-structure formation, it can provide an explanation for the excess in positron annihilation line in the galactic bulge and it may explain the results of direct dark matter searches. This model liberates the physics of dark atoms from many unknown features of new physics, but it is still not free from astrophysical uncertainties. It also demands a deeper understanding of the details of known nuclear and atomic physics, which are still somewhat unclear in the case of nuclear interacting “atomic” shells. These potential problems of the OHe scenario are also discussed. © 2015 World Scientific Publishing Company
This paper describes the method of study of the critical current density distribution across a tape in a background magnetic field. We measured the current distribution by the scanning Hall probe method. Then we measured field across a tape by a set of 10 Hall probes placed on a single substrate. By comparison of data from these two experiments we determined positions of Hall probes at a tape. Then we measured the current distribution of current density across a tape inside a magnet in parallel and perpendicular magnetic field of 30 mT. The details of measuring method and results are presented. © 2015 The Authors.
We review the status of the theory of ionization of atoms and ions by intense laser radiation (Keldysh's theory). We discuss the applicability of the theory, its relation to the Landau-Dykhne method, and its application to the ionization of atoms by ultrashort nonmonochromatic laser pulses of an arbitrary shape. The semiclassical imaginary time method is applied to describe electron sub-barrier motion using classical equations of motion with an imaginary time t ! it for an electron in the field of an electromagnetic wave. We also discuss tunneling interference of transition amplitudes, a phenomenon occurring due to the existence of several saddle points in the complex time plane and leading to fast oscillations in the momentum distribution of photoelectrons. Nonperturbatively taking the Coulomb interaction between an outgoing electron and the atomic residual into account causes significant changes in the photoelectron momentum distribution and in the level ionization rates, the latter usually increasing by orders of magnitude for both tunneling and multiquantum ionization. The effect of a static magnetic field on the ionization rate and the magnetic cumulation process is examined. The theory of relativistic tunneling is discussed, relativistic and spin corrections to the ionization rate are calculated, and the applicability limits of the nonrelativistic Keldysh theory are determined. Finally, the application of the Fock method to the covariant description of nonlinear ionization in the relativistic regime is discussed. © 2015 Uspekhi Fizicheskikh Nauk, Russian Academy of Sciences.
A model of the current flowing in the contact of a plasma with an electrode with a thin dielectric film on the surface has been developed to describe the observed features of the current-voltage characteristics of such a contact: a segment with small current near the floating potential corresponding to the film recharging and a segment with large current, where the mechanism of field electron emission through the film into the plasma occurs, leading to an N-shaped current-voltage characteristic. Such current-voltage characteristics are observed for W, Al, and Ta electrodes with a self-oxide film and for a stainless steel electrode with a silicon oxide film in a beam-plasma discharge in hydrogen. The model is based on the calculation of the equilibrium potential of the film surface faced to the plasma for the region of the negative bias of the electrode with respect to the plasma potential. Balance involves currents of ions and electrons from the plasma, secondary emission currents, and field electron emission current from the electrode into the plasma through the insulator. The film recharging voltage calculated within the model is in exact agreement with experimental data. This allows the determination of the thickness of the dielectric layer on the electrode surface from its current-voltage characteristic.
A simple setup for the generation of ultra-intense quasistatic magnetic fields, based on the generation of electron currents with a predefined geometry in a curved snail (or 'escargot') target, is proposed and analyzed. Particle-in-cell simulations and qualitative estimates show that gigagauss scale magnetic fields may be obtained with existent laser facilities. The described mechanism of the strong magnetic field generation may be useful in a wide range of applications, from laboratory astrophysics to magnetized inertial confinement fusion schemes.
Direct dark matter searches put severe constraints on the weakly interacting massive particles (WIMPs). These constraints cause serious troubles for the model of stable neutrino of fourth generation with mass around 50(Formula presented.)GeV. Though the calculations of primordial abundance of these particles make them in the charge symmetric case a sparse subdominant component of the modern dark matter, their presence in the universe would exceed the current upper limits by several orders of the magnitude. However, if quarks and leptons of fourth generation possess their own Coulomb-like (Formula presented.)-interaction, recombination of pairs of heavy neutrinos and antineutrinos and their annihilation in the “neutrinium” atoms can play important role in their cosmological evolution, reducing their modern abundance far below the experimental upper limits. The model of stable fourth generation assumes that the dominant part of dark matter is explained by excessive (Formula presented.) antiquarks, forming (Formula presented.) charged clusters, bound with primordial helium in nuclear-interacting O-helium (OHe) dark atoms. The (Formula presented.) charge conservation implies generation of the same excess of fourth generation neutrinos, potentially dangerous WIMP component of this scenario. We show that due to (Formula presented.)-interaction recombination of fourth neutrinos with OHe hides these WIMPs from direct WIMP searches, leaving the negligible fraction of free neutrinos, what makes their existence compatible with the experimental constraints. © 2015 World Scientific Publishing Company
Features of structural phase transitions under the high-pressure torsion of layered amorphouscrystalline Tiinf50/infNiinf25/infCuinf25/inf composite with 3 : 1 ratios of the layer thicknesses of the amorphous and crystalline phases, respectively, are analyzed by means of X-ray diffraction and transmission electron microscopy. The applied pressure is varied from 2 to 8 GPa. It is found that the structure of the layered Tiinf50/infNiinf25/infCuinf25/inf composite evolves in different ways in different parts of the material. © 2015, Allerton Press, Inc.
The electron and phonon spectra, as well as the densities of electron and phonon states of the SH3 phase and the stable orthorhombic structure of hydrogen sulfide SH2, are calculated for the pressure interval 100–225 GPa. It is found that the I4/mmm phase can be responsible for the superconducting properties of metallic hydrogen sulfide along with the SH3 phase. Sequential stages for obtaining and conservation of the SH2 phase are proposed. The properties of two (SH2 and SH3) superconducting phases of hydrogen sulfide are compared. © 2015, Pleiades Publishing, Inc.
Precise measurements of a magnetic moment relaxation of YBainf2/infCuinf3/infOinf7/inf-film were carried out at temperature T = 32 K at the magnetic fields H 1600 Oe. The moment M, relaxation rates R =-dM / dln t and S = R / M as well as glassy exponent were analyzed in partly and fully penetrated critical state in dependence on increasing and decreasing field. We demonstrated that a demagnetization affects the magnetic moment and the rate R but it does not influence on the normalized rate S and . Obtained value 1 and observed suppression of the critical current by the magnetic field evince creep of small bundles of vortices. © 2015 The Authors.
This article provides newinsight into previous and newexperimental data regarding behaviour of small-scale density fluctuations in T-10 ohmic and electron cyclotron resonance heated (ECRH) discharges. The experiments demonstrate the existence of certain peaked-'marginal' normalized plasma pressure profiles in both ohmic and discharges with on-axis ECRH. Strong particle confinement degradation occurred when the normalized plasma pressure gradient exceeded this marginal profile gradient (fast density decay in ohmic, 'density pump out' in ECRH). The marginal profile could be achieved either with a flat density and peaked temperature profile or vice versa. Minimal turbulence level did not depend on heating power and was observed with the ` optimal' pressure profile, which was slightly broader than the marginal profile. The density fluctuations did not significantly contribute to the heat transport but determined particle fluxes to maintain the pressure profile. The experimental density behaviour could be reasonably described with the modified model of canonical profiles, which includes particle confinement deterioration under marginal pressure profile conditions.
Copper coatings were deposited on monocrystalline Si substrates using a magnetron discharge with a liquid cathode in the metal vapour plasma. During the deposition, the bias voltage in the range from 0 V to–400 V was applied to the substrate. The prepared films were investigated by a scanning electron microscope, and their adhesive properties were studied using a scratch tester. It was demonstrated that the adhesion of the deposited films strongly depends on the bias voltage and varies in a wide range. © 2015, Pleiades Publishing, Ltd.
High-current low-inductance vacuum spark (HLVS) discharges are powerful sources of charged particles. Thus, wide prospects of their application are opened. In this case, it is important to bear in mind that plasma flows influence on parts of installation framework and the diagnostic equipment. In this paper the results of the integrated study of plasma flows emitted by HLVS are presented. The flow velocity was determined using a probe technique. The flow density was determined using values of gaskinetic pressure obtained earlier by a non-contacting laser technique. © 2015 The Authors.
Studies of the spin and parity quantum numbers of the Higgs boson in the WW* - ev mu v final state are presented, based on proton-proton collision data collected by the ATLAS detector at the Large Hadron Collider, corresponding to an integrated luminosity of 20.3 fb(-1) at a centre-of-mass energy of root s = 8 TeV. The Standard Model spin-parity J(CP) = 0(++) hypothesis is compared with alternative hypotheses for both spin andCP. The case where the observed resonance is a mixture of the Standard-Model-like Higgs boson and CP-even (J(CP) = 0(++)) or CP-odd (J(CP) = 0(+-)) Higgs boson in scenarios beyond the Standard Model is also studied. The data are found to be consistent with the Standard Model prediction and limits are placed on alternative spin and CP hypotheses, including CP mixing in different scenarios.
The method for experimental determination of the sensitivity and detection threshold of the interferometer phase is proposed. Based on the method the indicated parameters for an adaptive fiber-optic interferometer are estimated using the dynamic hologram formed in the photorefractive CdTe crystal.
With an integrated luminosity of 2.47 fb-1 recorded by the ATLAS experiment at the LHC, the exclusive decays Bs0→J/ψφ and Bd0→J/ψK∗0 of B mesons produced in pp collisions at s=7 TeV are used to determine the ratio of fragmentation fractions fs/fd. From the observed Bs0→J/ψφ and Bd0→J/ψK∗0 yields, the quantity (fs/fd)[B(Bs0→J/ψφ)/B(Bd0→J/ψK∗0)] is measured to be 0.199±0.004(stat)±0.008(syst). Using a recent theory prediction for [B(Bs0→J/ψφ)/B(Bd0→J/ψK∗0)] yields (fs/fd)=0.240±0.004(stat)±0.010(syst)±0.017(th). This result is based on a new approach that provides a significant improvement of the world average. © 2015 CERN., for the Atlas Collaboration. Published by the American Physical Society under the terms of the »http://creativecommons.org/licenses/by/3.0/» Creative Commons Attribution 3.0 License. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.
Abstract: The normalized differential cross section for top-quark pair production in association with at least one jet is studied as a function of the inverse of the invariant mass of the tt¯(Formula presented.) + 1-jet system. This distribution can be used for a precise determination of the top-quark mass since gluon radiation depends on the mass of the quarks. The experimental analysis is based on proton-proton collision data collected by the ATLAS detector at the LHC with a centre-of-mass energy of 7 TeV corresponding to an integrated luminosity of 4.6 fbsup−1/sup. The selected events were identified using the lepton+jets top-quark-pair decay channel, where lepton refers to either an electron or a muon. The observed distribution is compared to a theoretical prediction at next-to-leading-order accuracy in quantum chromodynamics using the pole-mass scheme. With this method, the measured value of the top-quark pole mass, mt suppole/sup, is:mtpole=173.7±1.5stat.±1.4syst.−0.5+1.0theoryGeV.(Formula presented.). This result represents the most precise measurement of the top-quark pole mass to date.[Figure not available: see fulltext.] © 2015, The Author(s).
Reduction of the tritium accumulation is important requirement for fusion reactor materials. Tungsten is promising material for protect a first wall of the vacuum chamber of fusion devices. The tungsten plates will be exposed to intense fluxes of accelerated of deuterium (D), tritium (T), helium (He) particles from fusion plasma. Results of recent studies (2008-2014) on deuterium retention in tungsten exposed to high flux helium-seeded deuterium plasma carried out in Japan Atomic Energy Agency (Japan), Max-Planck Institute for Plasma Physics (Germany) and NRC Kurchatov Institute (Russia) are summarized in the present review. It has been shown that addition of helium ions into the D plasma at elevated temperatures significantly reduces the D retention in tungsten, both without and with ion-induced defects, compared to that for the pure plasma exposure. It has been also found that significant part of deuterium initially retained in tungsten after deuterium plasma exposure is released during sequential exposure to protium plasma. However, exposure of the D-plasma-exposed W samples to helium-protium plasma reduces the amount of released deuterium as compared to pure protium plasma irradiation.
Regularities of deuterium trapping into zirconium with the oxidized surface layer under irradiation by deuterium atoms with thermal energies were studied. Desorption of deuterium atoms trapped into the sample irradiated by D-Atoms in Dinf2/inf gaseous ambience increased by more than 2 times in comparison with the one exposed to Dinf2/inf molecules. Addition of gaseous oxygen to the operating gas during atomic irradiation intensified significantly the deuterium accumulation in zirconium due to the increase of energetic yield of the surface processes that lead to trapping. During the cooling of zirconium sample after atomic irradiation in deuterium-oxygen gas mixture the surface states Zr-D(H) were being created. Up to 75% of these states were formed with participation of deuterium atoms from gaseous ambience, the rest of them involved hydrogen isotopes from the subsurface area. © 2015 The Authors.
The problems of deuteron extraction from the plasma of a vacuum arc were examined. The experimental dependence of the deuterons yield on the voltage of the pulse was obtained. The effects of Langmuir waves in plasma on the deuteron current were shown. An expression for the deuteron current from pulsed plasma source was obtained. © 2015 The Authors.
A method of creating modern linear displacement guide rails is presented and the construction of instruments for measurement of the geometry of a surface with measuring base 200 mm, range of height measurements 100 mm, and deviations from linearity by height 15 nm is presented. Approaches for eliminating vibrations that arise at the guide rail - carriage interface as well as a modernized system of recording the profile of a surface in combination with a more sensitive variable inductance transducer are proposed.
ITER will have about 50 diagnostic systems for machine protection, plasma control and optimization, and understanding the physics of burning plasma. The implementation in the ITER machine is challenging, particularly for the in-vessel diagnostics, region defined between the vacuum vessel and first wall (FW) contours, where space is constrained by the high number of systems. This paper describes the current status of design integration efforts to implement diagnostics in the ITER first wall. These approaches are the basis for detailed optimization and improvement of conceptual interfaces designs between systems. © 2015 Elsevier B.V. All rights reserved.
The most important part of the particle accelerators [1] - is the power generator together with the whole feeding system [2]. All types of generators, such as klystrons, magnetrons, solid state generators cover their own field of power and pulse length values. For the last couple of year the Inductive Output Tubes (IOT) becomes very popular because of their comparative construction simplicity: it represents the klystron output cavity with the grid modulated electron beam injected in it. Now such IOTs are used with the superconductive particle accelerators at 700 MHz operating frequency with around 1MW output power. Higher frequencies problem - is the inability to apply high frequency modulated voltage to the grid. Thus we need to figure out some kind of RF gun. But this article is about the first steps of the geometry and beam dynamics simulation in the six beam S-band IOT, which will be used with the compact biperiodic accelerating structure. © 2015 The Authors.
Various differential cross-sections are measured in top-quark pair (t (t) over bar) events produced in proton-proton collisions at a centre-of-mass energy of root s = 7 TeV at the LHC with the ATLAS detector. These differential cross-sections are presented in a data set corresponding to an integrated luminosity of 4.6 fb(-1). The differential cross-sections are presented in terms of kinematic variables, such as momentum, rapidity and invariant mass, of a top-quark proxy referred to as the pseudo-top-quark as well as the pseudo-top-quark pair system. The dependence of the measurement on theoretical models is minimal. The measurements are performed on tt events in the lepton+jets channel, requiring exactly one charged lepton and at least four jets with at least two of them tagged as originating from a b-quark. The hadronic and leptonic pseudo-top-quarks are defined via the leptonic or hadronic decay mode of the W boson produced by the top-quark decay in events with a single charged lepton. Differential cross-section measurements of the pseudo-top-quark variables are compared with several Monte Carlo models that implement next-to-leading order or leading-order multi-leg matrix-element calculations.
The DarkSide experiment is designed for the direct detection of Dark Matter with a double phase liquid Argon TPC operating underground at Laboratori Nazionali del Gran Sasso. The TPC is placed inside a 30 tons liquid organic scintillator sphere, acting as a neutron veto, which is in turn installed inside a 1 kt water Cherenkov detector. The current detector is running since November 2013 with a 50 kg atmospheric Argon fill and we report here the first null results of a Dark Matter search for a (1422 +/- 67) kg.d exposure. This result correspond to a 90% CL upper limit on the WIMP-nucleon cross section of 6.1 x10(-44) cm(2) (for a WIMP mass of 100 GeV/c(2)) and it's currently the most sensitive limit obtained with an Argon target.
The thermal and electromagnetic loads related to disruptions in ITER are substantial and require careful design of tokamak components to ensure they reach the projected lifetime and to ensure that safety relevant components fulfil their function for the worst foreseen scenarios. The disruption load specifications are the basis for the design process of components like the full-W diverton the blanket modules and the vacuum vessel and will set the boundary conditions for ITER operations. This paper will give a brief overview on the disruption loads and mitigation strategies for ITER and will discuss the physics basis which is continuously refined through the current disruption R&D programs. (C) 2014 ITER Organization. Published by Elsevier B.V. All rights reserved.
We present a method for disseminating reference radio frequencies over a fiber-optic line. We describe a circuit for electronic compensation of phase perturbations in a transmitted 100 MHz reference signal over an optical fiber. We give experimental measurement results for the Allan deviation of a 100 MHz reference signal transmitted to the remote end of a 100-km fiber link.
This paper presents distributions of topological observables in inclusive three- and four-jet events produced in pp collisions at a centre-of-mass energy of 7 TeV with a data sample collected by the CMS experiment corresponding to a luminosity of 5.1 fb(-1). The distributions are corrected for detector effects, and compared with several event generators based on two- and multi-parton matrix elements at leading order. Among the considered calculations, MadGraph interfaced with PYTHIA6 displays the overall best agreement with data.
A new method for exact determination of the masses and spins of black holes from the observations of quasi-periodic oscillations is discussed. The detected signal from the hot clumps in the accretion plasma must contain modulations with two characteristic frequencies: the frequency of rotation of the black hole event horizon and the frequency of the latitudinal precession of the clump’s orbit. Application of the method of two characteristic frequencies for interpretation of the observed quasi-periodic oscillations from the supermassive black hole in the Galactic center in the X-rays and in the near IR region yields the most exact, for the present, values of the mass and the spin (Kerr parameter) of the Sgr A* black hole: M = (4.2 ± 0.2) × 10sup6/supM⊙ and a = 0.65 ± 0.05. The observed quasi-periodic oscillations with a period of about 11.5 min are identified as the black hole event horizon rotation period and those with a period of about 19 min are identified as the latitudinal oscillation period of the hot spot orbits in the accretion disk. © 2015, Pleiades Publishing, Ltd.
The processes of magnetization reversal by the transport current self-field of a high-temperature superconductor sample with ferromagnetic particles as defects in the presence of an external magnetic field and current-voltage characteristics of the system have been calculated using the Monte Carlo method. It has been found that an S-shaped feature is observed in the current-voltage characteristics due to a change in the effective interaction of the magnetic moments of impurity particles with a vortex system of the superconductor, which is induced by the magnetization reversal of ferromagnetic impurities under the influence of the local magnetic field of the vortex lattice. It has been demonstrated that, in the vicinity of the instability, there is the motion of a wave of magnetization reversal of magnetic defects (magnetic domain) and waves of annihilation of Abrikosov vortices (vortex density domains). © 2015, Pleiades Publishing, Ltd.
We present the investigation results of the in-plane ?(T) resistivity tensor at the temperature range 0.4-40 K in magnetic fields up to 90 kOe (H || c, J || ab) for electron-doped Nd2-xCexCuO4+d with different degree of disorder near antiferromagnetic-superconducting phase boundary. We have experimentally found that for optimally doped compound both the upper critical field slope and the critical temperature decrease with increasing of the disorder parameter (d-wave pairing) while in the case of the underdoped system the critical temperature remains constant and dHc2/dT increases with increasing of the disorder (s-wave pairing). These features suggest a possible implementation of the complex mixture state as the s+id pairing.
We present the investigation results of the in-plane ρ(T) resistivity tensor at the temperature range 0.4-40 K in magnetic fields up to 90 kOe (H || c, J || ab) for electron-doped Nd2-xCexCuO4+δ with different degree of disorder near antiferromagnetic-superconducting phase boundary. We have experimentally found that for optimally doped compound both the upper critical field slope and the critical temperature decrease with increasing of the disorder parameter (d-wave pairing) while in the case of the underdoped system the critical temperature remains constant and dHc2/dT increases with increasing of the disorder (s-wave pairing). These features suggest a possible implementation of the complex mixture state as the s + id pairing. © 2015 AIP Publishing LLC.
A new experimental run of searching for EC/EC decay of Cd-106 was performed at the Modane underground laboratory (4800 m w.e.) using the TGV-2 spectrometer and similar to 23.2 g Cd-106 with enrichment of 99.57%. The limit on 2 nu EC/EC decay of Cd-106 -T-1/2(2 nu EC/EC) 3.1x10(20) y, at 90% C. L was obtained from the preliminary calculation of experimental data accumulated for 7018 h of measurement. The limits on the resonance neutrino-less double electron capture decay of Cd-106 were obtained from the measurement of similar to 23.2 g of Cd-106 with the low-background HPGe spectrometer OBELIX lasted 395 h -T-1/2(KL, 2741 keV) 0.9x10(20) y and T-1/2(KK, 2718 keV) 1.4x10(20) y at 90% C.L.
We report on the existence and properties of discrete gap solitons in zigzag arrays of alternating waveguides with positive and negative refractive indices. The zigzag quasi-one-dimensional configuration of the waveguide array introduces strong next-to-nearest neighbor interaction in addition to nearest neighbor coupling. Effective diffraction can be controlled both in size and in sign by the value of the next-to-nearest neighbor coupling coefficient and can even be canceled completely. In the regime where instabilities occur, we found different families of discrete solitons bifurcating from the gap edges of the linear spectrum. We show that both staggered and unstaggered discrete solitons can become highly localized states near the zero diffraction points even for low powers. Stability analysis has shown that the soliton solutions are stable over a wide range of parameters and can exist in focusing, defocusing, and even in an alternating focusing-defocusing array. © 2015 American Physical Society.
The modulation instability is analytically investigated in a zigzag array of tunnel-coupled optical waveguides with alternating refractive indices and Kerr nonlinearity. Particular solutions to a system of coupled nonlinear equations are found. They describe the propagation of electromagnetic waves that are uniform along the waveguide and their instability is studied. It is shown that the coupling coefficient between the waveguides, which are non-nearest neighbours, has a significant effect on the instability of the waves in question. When the coupling coefficient exceeds a certain threshold, the modulation instability disappears regardless of the radiation power. The influence of the ratio of the wave amplitudes in adjacent waveguides to the instability of the particular solutions is studied. Different variants of the nonlinear response in waveguides are considered. The studies performed present a new unusual type of the modulation instability in nonlinear periodic systems.
New proton-proton collision data from theLHC have considerably extended the energy range over which the structure of the proton-proton interaction region can be studied. In this paper, we combine the unitarity relation with experimental data on elastic scattering in the diffraction cone to show how the shape and the darkness of the inelastic interaction region of colliding protons change with increasing the proton energy. In particular, at LHC energies, small-impact-parameter collisions become fully absorptive, with some implications for inelastic processes as well. The possibility of changing from the blackcore scenario at LHC energies to the fully transparent scenario at higher energies is discussed-a phenomenon that implies changing from the black disk to black toroid terminology. As the asymptotic behavior is approached, a different regime may arise. The parameter determining the opacity of central collisions also crucially affects the differential cross section of elastic scattering outside the diffraction cone, where all phenomenological models fail for the LHC energies. It is in this region where the ratio of the real to imaginary part of the elastic scattering amplitude in nonforward scattering becomes a decisive factor, as indeed it should according to the unitarity condition. Our results make it possible for the first time to estimate this ratio outside the diffraction cone by comparing with data for LHC energies, and it turns out to be drastically different from the values measured at forward scattering. Moreover, both real and imaginary parts are found to behave differently in different phenomenological models and in the approach based on the unitarity condition. This problem is still to be resolved. All the conclusions are made solely in the framework of the indubitable unitarity condition using experimental data on elastic proton scattering in the diffraction cone, without resorting to other theoretical methods, such as quantum chromodynamics or phenomenological models. © 2015 Uspekhi Fizicheskikh Nauk, Russian Academy of Sciences.
It is shown that the impact parameter profile of inelastic hadron collisions is robust to admissible variations of the shape of the diffraction cone of elastic scattering. This conclusion is obtained using the unitarity condition and experimental data only with no phenomenological model inputs.
It is shown that the interaction region of colliding protons appears almost totally absorbing (black) at impact parameters to 0.4–0.5 fm and LHC energy of 7 TeV. The blackness of the proton interaction region for central interactions is completely defined by the ratio of the diffraction cone slope B in elastic scattering to the total cross section. The corresponding parameter is close to unity at LHC energies. The behavior of this ratio at higher energies will determine whether the interaction region structure will remind a torus or a black disk. Recent phenomenological fittings of experimental data at 7 TeV give no way of distinguishing these cases due to inaccuracies of experiments and uncertainties of the extrapolation to unmeasured regions of transferred momenta.
Using the unitarity relation in combination with experimental data about the elastic scattering in the diffraction cone, it is shown how the shape and the darkness of the inelastic interaction region of colliding protons change with increase of their energies. In particular, the collisions become fully absorptive at small impact parameters at LHC energies that results in some special features of inelastic processes. Possible evolution of this shape with the dark core at the LHC to the fully transparent one at higher energies is discussed that implies that the terminology of the black disk would be replaced by the black toroid. The approach to asymptotics is disputed. The ratio of the real to imaginary parts of the nonforward elastic scattering amplitude is briefly discussed. All the conclusions are only obtained in the framework of the indubitable unitarity condition using experimental data about the elastic scattering of protons in the diffraction cone without any reference to quantum chromodynamics (QCD) or phenomenological approaches.
This paper presents the development and description of research aimed at investigation of nanosecond surface microdischarge plasma effect on biomaterials. The technique is based on application of a simple discharge device. The device is assembled on a standard microscope slide from inexpensive materials. An optical microscope equipped with a digital camera is used for visualization of the studied samples and microdischarges. Many images of the microdischarges on the biological objects are presented in this paper. Spatial resolution of the images allows studying the discharges along the cellular structure of the tissue.
The paper presents the results of investigation of the gas exchange processes induced on a stainless steel surface under low energy neutral and ion irradiation. Experiments were performed in the Multifunctional Investigation Complex for Mass-Analysis allowing sample irradiation with neutral atom beam and plasma ions and thermal desorption analysis. The stainless steel surface was irradiated by thermal deuterium atoms generated in (D2+O2) atmosphere and by (D2+O2) plasma ions. Irradiation activated trapping of deuterium in stainless steel, desorption of hydrogen dissolved in stainless steel in the form of HD, H2, HDO, H2O are measured and analyzed. The role of the chromium oxide surface layer in these processes and the processes providing particle diffusion through the surface layer are discussed. © 2015 The Authors. Published by Elsevier B.V.
We address the question of regular primordial black holes with de Sitter interior, their remnants and gravitational vacuum solitons G-lumps as heavy dark matter candidates providing signatures for inhomogeneity of early universe, which is severely constrained by the condition that the contribution of these objects in the modern density does not exceed the total density of dark matter. Primordial black holes and their remnants seem to be most elusive among dark matter candidates. However, we reveal a nontrivial property of compact objects with de Sitter interior to induce proton decay or decay of neutrons in neutron stars. The point is that they can form graviatoms, binding electrically charged particles. Their observational signatures as dark matter candidates provide also signatures for inhomogeneity of the early universe. In graviatoms, the cross-section of the induced proton decay is strongly enhanced, what provides the possibility of their experimental searches. We predict proton decay paths induced by graviatoms in the matter as an observational signature for heavy dark matter searches at the IceCUBE experiment.
A natural atom placed into a cavity with time-dependent parameters can be parametrically excited due to interaction with the quantized photon mode. One of the channels for this process is the dynamical Lamb effect, induced by a nonadiabatic modulation of the atomic-level Lamb shift. However, in experiments with natural atoms it is quite difficult to isolate this effect from other mechanisms of atom excitation. We point out that a transmission line cavity coupled with a superconducting qubit (an artificial macroscopic atom) provides a unique platform for observation of the dynamical Lamb effect. A key idea is to exploit a dynamically tunable qubit-resonator coupling, which was implemented quite recently. By varying the coupling nonadiabatically, it is possible to parametrically excite a qubit through a nonadiabatic modulation of the Lamb shift, even if the cavity was initially empty. The dynamics of such a coupled system is studied within the Rabi model with a time-dependent coupling constant and beyond the rotating-wave approximation. An efficient method to increase the effect through the periodic and nonadiabatic switching of the qubit-resonator coupling energy is proposed.
The dynamics of a high-current relativistic electron beam is studied experimentally and by numerical simulation. The beam is formed in a magnetically insulated diode with a transverse-blade explosive-emission cathode. It is found experimentally that the radius of a 500-keV beam with a current of 2 kA and duration of 500 ns decreases with time during the beam current pulse. The same effect was observed in numerical simulations. This effect is explained by a change in the shape of the cathode plasma during the current pulse, which, according to calculations, leads to a change in the beam parameters, such as the electron pitch angle and the spread over the longitudinal electron momentum. These parameters are hard to measure experimentally; however, the time evolution of the radial profile of the beam current density, which can be measured reliably, coincides with the simulation results. This allows one to expect that the behavior of the other beam parameters also agrees with numerical simulations.
Axial plasma jets at the final stage of plasma focus discharge filled by neon or argon were studied by the method of shearing interferometry. It was found that neon plasma is more stable than argon one and jets in neon are stronger than in argon. The velocity of current sheath, taken from experiment, is V-sh = (2-3) x 10(6) cm/s, while the velocity of cumulative jet is V-j = (3-4) x 10(7) cm/s. These features are supported by theoretical interpretation given in the frame of 2D MHD model.
In this paper, we investigate coupled quintessence with scaling potential assuming specific forms of the coupling as A namely, (Formula presented.) and (Formula presented.), and present phase space analysis for three different interacting models. We focus on the attractor solutions that can give rise to late time acceleration with (Formula presented.) of order unity in order to alleviate the coincidence problem. © 2015, The Author(s).
The dynamics of the high-current ion beam (HCIB) in a section of the linear induction accelerator (LIA), con-sisting of magneto-isolated accelerating gap and the two drift spaces, is studied. In the most suitable variant of the HCIB compensation by accompanying and colliding beams of electrons, the current of the ion beam at the exit of the first drift gap is close to the original.The optimization of the system parameters (the value of magnetic field pro-duced by the coils with opposing currents, the size of the system, the parameters of the beams) at which a uniform on the length of the gap acceleration of the HCIB is achieved, has been carried out. Wherein the quality of the ion beam at the exit of the LIA section is kept acceptable for heavy-ion inertial fusion. © 2015, National Science Center, Kharkov Institute of Physics and Technology. All rights reserved.
The topological structure of lattice gluodynamics is studied at intermediate resolution scale in the deconfining phase with the help of a cluster analysis. UV-filtered topological charge densities are determined from a fixed number of low-lying eigenmodes of the overlap Dirac operator with three types of temporal boundary conditions applied to the valence quark fields. This method usually allows us to find all three distinguished (anti)dyon constituents in the gauge field of Kraan-van Baal-Lee-Lu (anti)caloron solutions. The clustering of the three topological charge densities in Monte Carlo generated configurations is then used to mark the positions of anticipated (anti)dyons of the corresponding type. In order to support this interpretation, inside these clusters, we search also for timelike Abelian monopole currents (defined in the maximally Abelian gauge) as well as for local holonomies with at least two approximately degenerated eigenvalues. Our results support the view that light dyon-antidyon pairs-in contrast to the heavy (anti)caloron dyon constituents-contribute dominantly to thermal Yang-Mills fields in the deconfinement phase.
In this work, we compare the effect of different types of thermal annealing on the morphological, structural and optical properties of Cu2ZnSnS4 (CZTS) thin films grown by reactive Pulsed Laser Deposition in H2S flow. Rutherford backscattering spectrometry, atomic force microscopy, X-ray diffraction, Raman spectroscopy and optical spectrophotometry data reveal dramatic increase of the band gap and the crystallite size without the formation of secondary phases upon annealing in N-2 at the optimized conditions. (C) 2015 Elsevier B.V. All rights reserved.
The tantalum oxide-platinum interface electronic properties determined by X-ray photoelectron spectroscopy are found to depend on the dielectric stoichiometry and platinum chemical state. We demonstrate the slow charging of the tantalum oxide in cases of Tainf2/infOinf5/inf/Pt and Tainf2/infOinf5-y/inf/Pt interfaces under the X-ray irradiation. This behavior is proposed to be related to the charge accumulation at oxygen vacancies induced traps. Based on the proposed methodology, we define the intrinsic conductive band offset (CBO) ∼1.3 V (both for Tainf2/infOinf5/inf/Pt and Tainf2/infOinf5-y/inf/Pt) and CBO after the full saturation of the traps charging ∼0.5 V, while the last one defines the energy position of charged traps below the bottom of conduction band. We demonstrate also the pining at the both Tainf2/infOinf5/inf/Pt and Tainf2/infOinf5-y/inf/Pt interfaces even in the "intrinsic" state, apparently induced by the presence of additional interfacial states. No shifts of Ta4f line and band alignment in over stoichiometric Tainf2/infOinf5+x/inf/Pt structure during X-ray irradiation, as well as the absence of pinning, resulting in increase of CBO up to 2.3 V are found. This behavior is related to the PtOinf2/inf interfacing layer formation at Tainf2/infOinf5+x/inf/Pt, blocking the charging of the surface states and associated dipole formation. © 2015 AIP Publishing LLC.
Low-frequency modulation of the gyrotron power at the L-2M stellarator was studied at different modes of plasma confinement. The plasma was heated at the second harmonic of the electron gyrofrequency. The effect of reflection of gyrotron radiation from the region of electron-cyclotron resonance plasma heating, as well as of backscattering of gyrotron radiation from fluctuations of the plasma density, on the modulation of the gyrotron power was investigated. © 2015, Pleiades Publishing, Ltd.
The formation conditions of the Pt/WOinfx/inf/SiC thin-film system on a silicon carbide (6H-SiC) single crystal are optimized. The prepared system possesses stable characteristics and makes it possible to effectively record hydrogen at low concentrations in air at a temperature of ∼350°C, as well as to hold hydrogen in the WOinfx/inf lattice at room temperature for a long time. The voltage shift of reverse portions of the current–voltage characteristics at a hydrogen concentration of ∼0.2% reach 6.5 V at a current of 0.4 µA because of large series resistance, which is defined by space-charge regions in WOinfx/inf and SiC. Structural-phase investigations of the oxide layer are performed under various effect modes of the hydrogen-containing medium on the Pt/WOinfx/inf/SiC system. A correlation in the variations of its electrical properties (ability to accumulate charge and vary the resistivity) and structural state of the oxide layer is revealed. An explanation for the variation in the current transport through the Pt/WOinfx/inf/SiC and its contact regions (barrier layers) under the effect of hydrogen is proposed. © 2015, Pleiades Publishing, Ltd.
The work deals with the research of the effect of pulsed laser radiation (λ=248 nm) on the structure and the manifestation of the shape memory effects (SMEs) in the Ti50Ni25Cu25 alloy, produced by melt spinning technique. It has been revealed that the proposed method of laser treatment leads to the formation of structural amorphous-crystalline composite demonstrating the pronounced two-way SME. A dependence of the two-way SME on the number of laser radiation pulses was determined. © 2015 The Authors.
The effect of optimization of the ionic composition of the hydrogen beam-plasma discharge (BPD) in the proton component when filling water vapor into the setup vacuum chamber is described. Experiments for studying the effect of controllable filling of water vapor on properties of highly nonequilibrium plasma show that under certain conditions the discharge ionic composition is redistributed toward increasing the atomic ion fraction. It is assumed that this effect is caused by the interaction of water vapor with the wall of the vacuum chamber of the plasma setup, which results in surface oxidation and a decrease in the recombination coefficient. Furthermore, the presence of active OH radical shifts chemical equilibrium toward increasing the atomic ion fraction. © 2015, Allerton Press, Inc.
Electromagnetic field scattering on a 2D array of rf-SQUIDs is considered. We show that the scattering changes for large amplitudes of the incident electromagnetic wave; above a critical amplitude, two different refraction states occur (bistability). In particular, for these two states, the transmitted wave polarization and angle of refraction are different. One could then switch the direction of propagation of the electromagnetic wave and its polarization with a "thin film", whose thickness is much smaller than the wavelength. © 2015 Owned by the authors, published by EDP Sciences.
Electromagnetic field scattering on a 2D array of rf-SQUIDs is considered. We show that the scattering changes for large amplitudes of the incident electromagnetic wave; above a critical amplitude, two different refraction states occur (bistability). In particular, for these two states, the transmitted wave polarization and angle of refraction are different. One could then switch the direction of propagation of the electromagnetic wave and its polarization with a "thin film", whose thickness is much smaller than the wavelength. © 2015 Owned by the authors, published by EDP Sciences.
The statistical model for calculations of the electron impact ionization cross sections of multielectron ions is developed for the first time. The model is based on the idea of collective excitations of atomic electrons with the local plasma frequency, while the Thomas-Fermi model is used for atomic electrons density distribution. The electron impact ionization cross sections and related ionization rates of tungsten ions from W+ up to W63+ are calculated and then compared with the vast collection of modern experimental and modeling results. The reasonable correspondence between experimental and theoretical data demonstrates the universal nature of statistical approach to the description of atomic processes in multielectron systems. © 2015, Pleiades Publishing, Inc.
The rare earth porphyrins represent a promising class of materials, due to their physical-chemical properties. A detailed study of the local structure of the RE series of porphyrins RETPP (RE = Yb, Er) was carried out by X-ray absorption spectroscopy (XAFS) using the synchrotron radiation. XAFS experiments prove the trivalent state of rare earth metals (Er, Yb) in metalloporphyrins. The relationship between the extended fine structure and the atomic structure of the porphyrin macrocycle with a central rare earth element (Yb, Er) is presented and discussed. © 2015 The Authors.
Kinetics of intrasubband energy relaxation of electrons in the system of Landau levels lying below the optical phonon energy is studied. Extraordinary behavior of the relaxation of electronic subsystem excitation energy is detected. Despite the fact that its main channel is optical phonon emission, the total relaxation time exceeds the characteristic times of scattering on optical phonons by several orders of magnitude. © 2015, Allerton Press, Inc.
We review the physical processes that occur at the center of the Galaxy and that are related to the supermassive black hole SgrA∗ residing there. The discovery of high-velocity S0 stars orbiting SgrA∗ for the first time allowed measuring the mass of this supermassive black hole, the closest one to us, with a 10% accuracy, with the result Mh = (4.1 ± 0.4) × 10sup6/supM⊙. Further monitoring can potentially discover the Newtonian precession of the S0 star orbits in the gravitational field of the black hole due to invisible distributed matter. This will yield the 'weight' of the elusive dark matter concentrated there and provide new information for the identification of dark matter particles. The weak accretion activity of the 'dormant quasar' at the galactic center occasionally shows up as quasiperiodic X-ray and near-IR oscillations with mean periods of 11 and 19 min. These oscillations can possibly be interpreted as related to the rotation frequency of the SgrA∗ event horizon and to the latitude oscillations of hot plasma spots in the accretion disk. Both these frequencies depend only on the black hole gravitational field and not on the accretion model. Using this interpretation yields quite accurate values for both the mass Mh and the spin a (Kerr rotation parameter) of SgrA∗: Mh = (4.2 ± 0.2) × 10sup6/supM⊙ and a = 0.65 ± 0.05. © 2015 Uspekhi Fizicheskikh Nauk, Russian Academy of Sciences.
We elaborate the model of the influence of the diffuse dark matter, invisible stars or stellar mass black holes on the motion of the observed fast moving S0 stars [1-4] around the supermassive black hole SgrA∗in the Galactic center with a mass MBH = 4·106. We will call all this invisible mass as a dark matter. The additional mass perturbs the elliptical orbits of the S0 mass resulting in the so called Newtonian precession of the elliptical orbits. The major aim of our research is the fitting of the published dates on the observed orbital positions of the S0 stars by the theoretically modeling orbit with a power-law profile of the additional (dark matter) mass. Nowadays the observational data provide only the upper limit on the additional mass. In the nearest years the observations of the S0 stars may provide the real weighing of the dark matter inside the orbits of these S0 stars in the Galactic center. This method is a very perspective for the elucidation of the formation and evolution of the dark matter in the Galactic nucleus. © 2015 The Authors.
Stationary solutions of the Dirac equation in the metric of the charged Reissner–Nordstrom black hole are found. In the case of an extremal black hole, the normalization integral of the wave functions is finite, and the regular stationary solution is physically self-consistent. The presence of quantum electron levels under the Cauchy horizon can have an impact on the final stage of the Hawking evaporation of the black hole, as well as on the particle scattering in the field of the black hole. © 2015, Pleiades Publishing, Ltd.
A promising method for measuring the total mass of the dark matter near a supermassive black hole at the center of the Galaxy based on observations of nonrelativistic precession of the orbits of fast S0 stars together with constraints on the annihilation signal from the dark matter particles has been discussed. An analytical expression for the precession angle has been obtained under the assumption of a power-law profile of the dark matter density. In the near future, modern telescopes will be able to measure the precession of the orbits of S0 stars or to obtain a strong bound on it. The mass of the dark matter necessary for the explanation of the observed excess of gamma radiation owing to the annihilation of the dark matter particles has been calculated with allowance for the Sommerfeld effect. © 2015, Pleiades Publishing, Inc.
The erosion of Be and W marker layers was investigated using long-term samples during the first ITER-like wall discharge campaign 2011-2012. The markers were mounted in Be coated Inconel tiles between the inner wall guard limiters (IWGL). They were analyzed using Rutherford backscattering (RBS) before and after exposure. All samples showed strong erosion. The results were compared to the data for Be and W erosion rates for the 2005-2009 and the 2001-2004 campaigns, respectively, when JET was operated with a carbon wall. In 2005-2009 Be and C samples were used, and W samples were used in 2001-2004. The mean W erosion rates and the toroidal and poloidal distributions of the W erosion were the same for the 2001-2004 and the 2011-2012 campaigns. The mean erosion rate of Be during the 2011-2012 campaign was smaller by a factor of about two compared to the 2005-2009 campaign and showed a different poloidal distribution. The mean erosion rate of the inner JET ITER-like wall was about 4-5 times smaller than the mean erosion rate of the carbon wall.
Erosion of the plasma-facing materials in particular evaporation of the materials in a fusion reactor under intense transient events is one of the problems of the ITER. The current experimental data are insufficient to predict the properties of the erosion products, a significant part of which will be formed during transient events (edge-localized modes (ELMs) and disruptions). The paper concerns the experimental investigation of the graphite and tungsten erosion products deposited under pulsed plasma load at the QSPA-T: heat load on the target was 2.6 MJ/m2 with 0.5 ms pulse duration. The designed diagnostics for measuring the deposition rate made it possible to determine that the deposition of eroded material occurs during discharge, and the deposition rate is in the range (0.1–100) × 1019 at/(cm2 s), which is much higher than that for stationary processes. It is found that the relative atomic concentrations D/C and D/(W + C) in the erosion products deposited during the pulse process are on the same level as for the stationary processes. An exposure of erosion products to photonic energy densities typical of those expected at mitigated disruptions in the ITER (pulse duration of 0.5–1 ms, integral energy density of radiation of 0.1–0.5 MJ/m2) significantly decreases the concentration of trapped deuterium. © 2015, Pleiades Publishing, Ltd.
The results of computation-experimental modeling of single-event latchup effects under the laser radiation focused on the IC crystal backside—the substrate side—are presented. Possibilities of applying the technique of local laser irradiation to evaluate equivalent linear energy transfer of heavy ions in the case of the laser irradiation from the substrate side of IC crystal are analyzed. The experimental results obtained using the pulsed laser installation and accelerators of charged particles for a series of modern LSI ICs are compared.
Abstract: Results of a search for H → ττ decays are presented, based on the full set of proton-proton collision data recorded by the ATLAS experiment at the LHC during 2011 and 2012. The data correspond to integrated luminosities of 4.5 fbsup−1/sup and 20.3 fbsup−1/sup at centre-of-mass energies of √s = 7 TeV and √s = 8 TeV respectively. All combinations of leptonic (τ→ℓνν¯ with ℓ = e, μ) and hadronic (τ → hadrons ν) tau decays are considered. An excess of events over the expected background from other Standard Model processes is found with an observed (expected) significance of 4.5 (3.4) standard deviations. This excess provides evidence for the direct coupling of the recently discovered Higgs boson to fermions. The measured signal strength, normalised to the Standard Model expectation, of μ = 1. 43inf− 0.37/inf; sup+ 0.43/sup is consistent with the predicted Yukawa coupling strength in the Standard Model.[Figure not available: see fulltext.] © 2015, The Author(s).
We consider a unique case of a propagating internal gravity wave that has generated in situ a compact and thin layer of noctilucent clouds (NLC) at 82.7-85.2 km with a characteristic horizontal scale of 65-70 km, as observed in the Moscow region on the night of 18-19 July 2013. This particular transient isolated gravity wave together with the whole NLC layer suddenly appeared in the clear twilight sky and lasted about 1h traveling eastward, which differs significantly from previously observed cases of gravity waves propagating through preexisting NLC layers. Our model studies demonstrate that the wave had a tropospheric source connected to the passage of an occluded front. The wave was likely generated due to strong horizontal wind shears at about 5 km altitude. © 2015. American Geophysical Union. All Rights Reserved.
This Letter reports evidence of triple gauge boson production pp - W(l nu)gamma gamma + X, which is accessible for the first time with the 8 TeV LHC data set. The fiducial cross section for this process is measured in a data sample corresponding to an integrated luminosity of 20.3 fb(-1), collected by the ATLAS detector in 2012. Events are selected using the W boson decay to e nu or mu nu as well as requiring two isolated photons. The measured cross section is used to set limits on anomalous quartic gauge couplings in the high diphoton mass region.
The ATLAS detector at the LHC consists of several sub-detector systems. Both data taking and Monte Carlo (MC) simulation rely on an accurate description of the detector conditions from every subsystem, such as calibration constants, different scenarios of pile-up and noise conditions, size and position of the beam spot, etc. In order to guarantee database availability for critical online applications during data-taking, two database systems, one for online access and another one for all other database access, have been implemented. The long shutdown period has provided the opportunity to review and improve the Run-1 system: revise work flows, include new and innovative monitoring and maintenance tools and implement a new database instance for Run-2 conditions data. The detector conditions are organized by tag identification strings and managed independently by the different sub-detector experts. The individual tags are then collected and associated into a global conditions tag, assuring synchronization of various sub-detector improvements. Furthermore, a new concept was introduced to maintain conditions over all different data run periods into a single tag, by using Interval of Validity (IOV) dependent detector conditions for the MC database as well. This allows on the fly preservation of past conditions for data and MC and assures their sustainability with software evolution. This paper presents an overview of the commissioning of the new database instance, improved tools and work flows, and summarizes the actions taken during the Run-2 commissioning phase in the beginning of 2015.
The bilayer film Pt/WOinfx/inf was deposited by pulsed laser ablation on a silicon carbide monocrystal plate (6H-SiC) to form an Hinf2/inf sensor for high temperature application. The study demonstrates high sensitivity of the Pt/WOinfx/inf/SiC structure to a low Hinf2/inf concentration. For 0.2 H2% in air at 350 C, the shift of voltage on the reverse branch of the current-voltage characteristic reached 6.5 V at a current of 0.4 μA. After the high temperature interaction with Hinf2/inf, the sample can confine hydrogen atoms in the WOinfx/inf layer at room temperature for a long time. The study explores the influence of operation conditions as well as the H2 action on the structure and electrical characteristics of the layers in the system. Phase transformation of the crystalline structure of the WOinfx/inf film due to hydrogen penetration was detected and this process initiated pronounced electrical properties changes. © 2015 The Authors.
It has been shown that, at elevated temperatures (∼350°C), the most distinct response to Hinf2/inf from the thin film structure Pt/WOinfx/inf/SiC is achieved at registration of change in voltage for the reverse branch of a current-voltage characteristic. Comparative studies of electric current conduction through the structure and over its surface (with deposited Pt film) have led to the conclusion that a change in properties of the Pt/WOinfx/inf and WOinfx/inf/SiC interfaces under action of Hinf2/inf mostly determines efficiency of response of the structure in the case of “transverse” measuring geometry. In the case of a 2% concentration of Hinf2/inf in air the voltage shift for the reverse branch at a current of ∼10 μA reached 5 V against 2 V on the forward branch and “planar” geometry of measurements. © 2015, Pleiades Publishing, Ltd.
A new functional model of the prototype of closed Li circuit for protection of the chamber wall was tested in T-11M tokamak by simultaneous use of the vertical Li limiter as an emitter of Li and a new longitudinal Li limiter as its collector. Such technological scheme can be suggested for the steady-state fusion neutron source on the tokamak basis. During plasma shots the cryogenic target of T-11M collected Li flow emitted by the vertical capillary Li limiter almost completely (up to 80%). These Li and hydrogen isotopes were captured and extracted outside the tokamak vacuum chamber without venting of the vessel which is a key requirement for the use of Li in the steady-state tokamak reactor. © 2015 IAEA, Vienna.
The data are presented on the evolution of the shape and position of the Linf23/infVV Auger line for the surface of single-crystal silicon Si(111) during its thermal oxidation. The fine structure of the high-energy region of the Auger spectrum is found to be related to the loss of energy by Auger electrons for plasmon excitation and electronic interband transitions, while the low-energy region may be associated with the effect of extension fine Auger structure (EXFAS). By the example of Si atoms in a thin surface layer of SiOinf2/inf, it is shown that, similarly to studying the ordinary oscillations of the EXAFS absorption spectra, the EXFAS technique can be used to solve the problems of the restoration of the local environment of atoms. The interatomic distances calculated using the Fourier transform of the right-hand sides of the Auger spectra (EXFAS spectra) for the pure and oxidized silicon surfaces appear to be 2.2 and 1.7 Å, respectively, thereby coinciding with the published values within determination error. © 2015, Pleiades Publishing, Ltd.
The plasma structures in a high-current impulse magnetron discharge (HCIMD) were studied by means of a fast gated camera facing the cathode target, made from Cu, Ti, and Mo. The current-voltage characteristics of HCIMD were obtained for the range of transverse magnetic field on the cathode surface B s =40-65mT and working gas (Ar) pressures p Ar =0.5-2Pa. Fast camera images were recorded throughout the pulses for all experimental regimes, and the regions of plasma non-uniformity were found. The I-V curves studied in detail revealed from three to five distinct discharge regimes with quite different plasma appearance and behaviour, depending on the target material. Our observations of the initial stage of HCIMD indicate that in a certain discharge current range there is a characteristic time (~tens μs) needed for the azimuthally symmetric structure of spokes to build up, even while the discharge current remains constant. During a quasi-stationary stage of HCIMD a well-defined spoke structure may rotate or remain stable depending on the discharge power. © 2015.
There-deposition of constructional materials inside the chamber of a fusion device is undesirable mainly for increased capture of hydrogen isotopes in the deposited layers. Currently, a variety of methods for wall cleaning from the deposited layers are developed, including a special "cleaning" discharge inside the chamber with an oxygen puff. Special attention is paid to film removal in gaps and regions shaded from the plasma. The study of CH-films deposition and their removal in gaps and regions shaded from the plasma were conducted in the linear simulator with a beam-plasma discharge PR-2 in a mode with automatic generation of high-frequency current oscillations, which ensured the presence of RF fields. High efficiency of cleaning the films in gaps is demonstrated in the discharge in oxygen with the presence of RF fields. The film cleaning rate was up to 1.7 μm for 2 hours. © 2015 The Authors.
First calculations for deformed nuclei using the Fayans functional are carried out for the uranium and lead isotopic chains. The ground state deformations and deformation energies are compared to Skyrme-Hartree-Fock-Bogolyubov HFB-17 and HFB-27 functional results. For the uranium isotopic chain, the Fayans functional property predictions are rather similar to HFB-17 and HFB-27 predictions. However, there is a disagreement for the lead isotopic chain. Both of the Skyrme HFB functionals lead to predictions of rather strong deformations for the light Pb isotopes, which does not agree with the experimental data on charge radii and magnetic moments of the odd Pb isotopes. On the other hand, the Fayans functional leads to the prediction of a spherical ground state for all of the lead isotopes, in accordance with the data and the results known from the literature obtained with the Gogny D1S force and the SLy6 functional as well. The deformation energy curves are calculated and compared against those derived from four Skyrme functionals-SLy4, Sly6, SkM* and UNEDF1-for the U-238 nucleus and several lead-deficient Pb isotopes. In the first case, the resulting Fayans functional is rather close to SkM* and UNEDF1, which-in particular the latter-describe the first and second barriers in U-238 rather well. For the light lead isotopes, the Fayans deformation energy curves are qualitatively close to those derived from the SLy6 functional.
Energies of 8410.1 ± 0.4, 20743.9 ± 0.3, and 63121.6 ± 1.2 eV were determined for the 8.4 keV M1 + E2, 20.7 keV M1 + E2, and 63.1 keV E1 nuclear transitions in sup169/supTm (generated in the EC decay of sup169/supYb, respectively, by means of the internal conversion electron spectroscopy. The sup169/supYb sources used were prepared by vacuum evaporation deposition on polycrystalline carbon and platinum foils as well as by ion implantation at 30keV into a polycrystalline aluminum foil. The relevant conversion electron spectra were measured by a high-resolution combined electrostatic electron spectrometer at 7 eV instrumental resoluition. Values of 0.0326(14) and 0.0259(17) were derived from our experimental data for the E2 admixture parameter |δ (E2/M1)| for the 8.4 and 20.7 keV transitions, respectively. A possible effect of nuclear structure on multipolarity of the 20.7 keV transition was also investigated. © 2015, SIF, Springer-Verlag Berlin Heidelberg.
We report the first results of DarkSide-50, a direct search for dark matter operating in the underground Laboratori Nazionali del Gran Sasso (LNGS) and searching for the rare nuclear recoils possibly induced by weakly interacting massive particles (WIMPs). The dark matter detector is a Liquid Argon Time Projection Chamber with a (46.4±0.7)kg active mass, operated inside a 30 t organic liquid scintillator neutron veto, which is in turn installed at the center of a 1 kt water Cherenkov veto for the residual flux of cosmic rays. We report here the null results of a dark matter search for a (1422±67)kgd exposure with an atmospheric argon fill. This is the most sensitive dark matter search performed with an argon target, corresponding to a 90% CL upper limit on the WIMP-nucleon spin-independent cross section of 6.1×10-44cm2 for a WIMP mass of 100Gev/c2. © 2015 The Authors.
The process of Tbinf2/infHfinf2/infOinf7/inf nanocrystals formation upon calcinations up to 1600°C has been investigated by means of X-ray absorption fine structure (XAFS) spectroscopy combined with X-ray diffraction (XRD) and analysis of pair distribution function (PDF). The structure ordering and the growth of nanocrystals upon calcination were estimated independently from XRD patterns and PDF. The probable content of Tb4+ cations in Tbinf2/infHfinf2/infOinf7/inf was estimated from XANES. All studies indicate a high disorder and a large number of local structure defects in Tbinf2/infHfinf2/infOinf7/inf pyrochlore structure. © 2015 The Authors.
Results are presented from analyzing the yields of protons (p), deuterons (d), and tritons (t) in pre-equilibrium stopped pion absorption reactions. Phenomenological formulas are proposed for describing the mass-number (A) dependences of these yields accurate to within 10–20% in the mass-number range of 6 < A < 209 (59 < A < 209 for t). The final results do not contradict the hypothesis that the predominant role in the formation of deuterons and tritons is played by pick-up on the surface of nuclei. © 2015, Allerton Press, Inc.
The technique of thin film forming of NaThxFy compounds on the Si (111) surface by electron-beam evaporation was developed. It is shown that the band gap of pure thorium fluoride is 6.7 eV; of sodium fluoride-9.5 eV, while in compounds of thorium-sodium fluoride NaThl.3F6.2 it takes the value 7.1 eV. It was found that prolonged electron beam exposure leads to the recovery of thorium fluoride followed by oxidation of thorium atoms. © 2015 Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license.
Thin ribbons of Tiinf50/infNiinf25/infCuinf25/inf (at %) alloy are produced by melt spinning in the amorphous, amorphous–crystalline, and crystalline states, depending on the melt cooling rate. It is shown that laminated amorphous–crystalline composite displays two-way shape memory behavior in bending with no additional thermomechanical treatment. It is established that a slower cooling rate results in a thicker crystalline layer and greater reversible bending deformation in this structural composite. © 2015, Allerton Press, Inc.
Abstract: The strength of forward-backward (FB) multiplicity correlations is measured by the ALICE detector in proton-proton (pp) collisions at s$$ s $$ = 0.9, 2.76 and 7 TeV. The measurement is performed in the central pseudorapidity region (|η| < 0.8) for the transverse momentum pinfT/inf> 0.3 GeV/c. Two separate pseudorapidity windows of width (δη) ranging from 0.2 to 0.8 are chosen symmetrically around η = 0. The multiplicity correlation strength (binfcorr/inf) is studied as a function of the pseudorapidity gap (ηinfgap/inf) between the two windows as well as the width of these windows. The correlation strength is found to decrease with increasing ηinfgap/inf and shows a non-linear increase with δη. A sizable increase of the correlation strength with the collision energy, which cannot be explained exclusively by the increase of the mean multiplicity inside the windows, is observed. The correlation coefficient is also measured for multiplicities in different configurations of two azimuthal sectors selected within the symmetric FB η-windows. Two different contributions, the short-range (SR) and the long-range (LR), are observed. The energy dependence of binfcorr/inf is found to be weak for the SR component while it is strong for the LR component. Moreover, the correlation coefficient is studied for particles belonging to various transverse momentum intervals chosen to have the same mean multiplicity. Both SR and LR contributions to binfcorr/inf are found to increase with pinfT/inf in this case. Results are compared to PYTHIA and PHOJET event generators and to a string-based phenomenological model. The observed dependencies of binfcorr/inf add new constraints on phenomenological models.[Figure not available: see fulltext.] © 2015, The Author(s).
In the context of mathematical hydrodynamics, we consider the group theory structure which underlies the so named ABC flows introduced by Beltrami, Arnold and Childress. Main reference points are Arnold's theorem stating that, for flows taking place on compact three manifolds a"(3)(3), the only velocity fields able to produce chaotic streamlines are those satisfying Beltrami equation and the modern topological conception of contact structures, each of which admits a representative contact one-form also satisfying Beltrami equation. We advocate that Beltrami equation is nothing else but the eigenstate equation for the first order Laplace-Beltrami operator a similar to... (g) d, which can be solved by using time-honored harmonic analysis. Taking for a"(3)(3), a torus T (3) constructed as a"e(3)/I , where I is a crystallographic lattice, we present a general algorithm to construct solutions of the Beltrami equation which utilizes as main ingredient the orbits under the action of the point group B (A) of three-vectors in the momentum lattice *I . Inspired by the crystallographic construction of space groups, we introduce the new notion of a Universal Classifying Group which contains all space groups as proper subgroups. We show that the a similar to... (g) d eigenfunctions are naturally arranged into irreducible representations of and by means of a systematic use of the branching rules with respect to various possible subgroups we search and find Beltrami fields with non trivial hidden symmetries. In the case of the cubic lattice the point group is the proper octahedral group O-24 and the Universal Classifying Group is a finite group G(1536) of order |G(1536)| = 1536 which we study in full detail deriving all of its 37 irreducible representations and the associated character table. We show that the O-24 orbits in the cubic lattice are arranged into 48 equivalence classes, the parameters of the corresponding Beltrami vector fields filling all the 37 irreducible representations of G(1536). In this way we obtain an exhaustive classification of all generalized ABC-flows and of their hidden symmetries. We make several conceptual comments about the need of a field-theory yielding Beltrami equation as a field equation and/or an instanton equation and on the possible relation of Arnold-Beltrami flows with (supersymmetric) Chern-Simons gauge theories. We also suggest linear generalizations of Beltrami equation to higher odd-dimensions that are different from the non-linear one proposed by Arnold and possibly make contact with M-theory and the geometry of flux-compactifications.
A new technique is proposed and applied to study the frequency drift of an external-cavity semiconductor laser, locked to the transmission resonances of a thermally stabilised Fabry - Perot interferometer. The interferometer frequency drift is measured to be less than 2 MHz h(-1). The laser frequency is measured using an Angstrom wavemeter, calibrated using an additional stabilised laser. It is shown that this system of laser frequency control can be used to identify Rydberg transitions in ultracold Li-7 atoms.
We describe this paper as a Sentimental Journey from Hydrodynamics to Supergravity. Beltrami equation in three dimensions that plays a key role in the hydrodynamics of incompressible fluids has an unsuspected relation with minimal supergravity in seven dimensions. We show that just D=7 supergravity and no other theory with the same field content but different coefficients in the lagrangian, admits exact two-brane solutions where Arnold-Beltrami fluxes in the transverse directions have been switched on. The rich variety of discrete groups that classify the solutions of Beltrami equation, namely the eigenfunctions of the star, opend operator on a three-torus, are by this newly discovered token injected into the brane world. A new quite extensive playing ground opens up for supergravity and for its dual gauge theories in three dimensions, where all classical fields and all quantum composite operators will be assigned to irreducible representations of discrete crystallographic groups Γ. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Ta2O5-based metal-insulator-metal stacks for resistive random access memory were grown by atomic layer deposition technique only with the emphasis on different top metal-oxide interface engineering. The impact of top TiN electrode growth and NH3 treatment on dielectric chemical and electrical properties was discussed. In addition the TiN/Ta2O5/Al2O3/TiN stack with bilayer dielectric was grown and studied too. According to in vacuo XPS analysis at top interface both TiN/Ta2O5/TiN and TiN/Ta2O5 (NH3-treated)/TiN stacks comprise the TaOxNy, interlayer which is twice thicker in the case of stack with NH3 treatment (similar to 1.3 nm) in comparison with untreated one (similar to 0.7 nm). In vacuo XPS analysis also showed that 2 nm Al2O3 insert between Ta2O5 and top TiN electrode allowed to completely block formation of TaOxNy interlayer at TiN/Ta2O5/Al2O3/TiN stack. As a result it was found that TiN/Ta2O5/TiN demonstrated gradual and rather slow (similar to 10(-3) s) character of resistive switching while the switching at stack with bilayer Ta2O5/Al2O3 dielectric is much more abrupt, faster and it reveals more than one order of magnitude higher endurance. (C) 2015 Elsevier B.V. All rights reserved.
The parametric interaction of electromagnetic waves in a medium with a negative index of refraction is considered. Two cases of Kerr and quadratic nonlinearities are investigated. The properties of nonlinear coupler, channels of which made of material with opposing signs of refraction index, are studied. Dynamics of extremely short pulses in the homogeneous doubly-resonant medium is analyzed in the framework of Maxwell-Duffing-Lorentz model. The new type of quasi-solitons is presented.
We consider the coupled electromagnetic waves propagating in a nonlinear medium, which is featured by a positive and negative refraction indexes. The backward waves can be propagating in this case. The example of the true soliton is discussed. In general case the coupled forward and backward solitary wave can be found. They are analogues to the optical solitons. © Published under licence by IOP Publishing Ltd.
This paper discusses the refraction of an ultrashort pulse of an electromagnetic field at a nonlinear interface of dielectric media. The nonlinearity is caused by the presence of a thin film of resonance-absorbing atoms. When local-field effects are negligible, the system of model equations is completely integrable, and this makes it possible to find an exact solution. It is shown that the refracted pulse breaks up into several solitons, whose number depends on the angle of incidence. (C) 2015 Optical Society of America.
We demonstrate the efficient amplification of small signals in a spectral range of 2020-2120 nm by an all-fiber Ho-doped amplifier pumped at 1125 nm. A maximum gain of 35.8 dB was achieved at a wavelength of 2050 nm. A gain greater than 30 dB was obtained over the whole range. © 2015 Astro Ltd.
We study the possible existence of static traversable wormholes without invoking exotic matter in the framework of the Einstein–Cartan theory. A family of exact static, spherically symmetric wormhole solutions with an arbitrary throat radius, with flat or AdS asymptotic behavior, has been obtained with sources in the form of two noninteracting scalar fields with nonzero potentials. Both scalar fields are canonical (that is, satisfy the weak energy condition), one is minimally and the other nonminimally coupled to gravity, and the latter is a source of torsion. © 2015, Pleiades Publishing, Ltd.
We study the possible existence of static traversable wormholes without invoking exotic matter in the framework of the Einstein–Cartan theory. A family of exact static, spherically symmetric wormhole solutions with an arbitrary throat radius, with flat or AdS asymptotic behavior, has been obtained with sources in the form of two noninteracting scalar fields with nonzero potentials. Both scalar fields are canonical (that is, satisfy the weak energy condition), one is minimally and the other nonminimally coupled to gravity, and the latter is a source of torsion. © 2015, Pleiades Publishing, Ltd.
We study a class of two-dimensional compact extra spaces isomorphic to the sphere S 2 in the framework of multidimensional gravitation. We show that there exists a family of stationary metrics that depend on the initial (boundary) conditions. All these geometries have a singular point. We also discuss the possibility for these deformed extra spaces to be considered as dark matter candidates. © 2015 The Authors.
We elaborate the possibility for a deformed extra space to be considered as the dark matter candidate. To perform calculations, a class of two-dimensional extra metrics was considered in the framework of the multidimensional gravity. It was shown that there exists a family of stationary metrics of the extra space possessing point-like defect. Estimation of cross-section of scattering of a particle of the ordinary matter on a spatial domain with deformed extra space is in agreement with the observational constraints.
A direct comparison of the deuterium (D) decoration of radiation-induced damage in polycrystalline tungsten irradiated with self-ions [present work] and neutrons in the high-flux isotope reactor (HFIR) (Hatano et al., 2013) shows a reasonably good agreement at least up to 0.3 displacement per atom indicating that MeV heavy ions can be a good proxy to simulate neutron-produced damage at room temperature and low dpa. The coefficient of similarity between two kinds of irradiation was obtained experimentally to be Kexp ∼ 0.65 ± 0.1 in the case of the deuterium decoration of both kinds of radiation-induced defects with low and high de-trapping energies for deuterium. We introduced the theoretical estimation for coefficient of similarity between neutron- and self-ion-irradiations, which is a fraction of common area under the curves of two overlapping damage energy spectra of primary knock-on atom (PKA) produced in tungsten by these two types of irradiation. In other words, Ksim is a part of displaced atoms produced in the similar conditions under two different types of irradiation. The theoretical values of Ksim = 0.34 and Ksim = 0.29 were obtained for tungsten target irradiated with 20 MeV self-ions in comparison to irradiation with neutrons in HFIR reactor (>0.1 MeV) and 14 MeV neutrons, respectively. The theoretical value of Ksim = 0.34 is about two times less than the experimental value of Kexp = 0.65. It means that high energy PKAs can play more important role in the production of similar damage structure by irradiation with self-ions and neutrons which is responsible for deuterium retention. The model assuming that all cascades with an energy higher than Tc = 150 keV split into identical sub-cascades gives the value of Ksim = 0.64 ± 0.01 for the coefficient of similarity between HFIR-neutron and 20 MeV self-ion irradiations that is in an agreement with experimental value of Kexp = 0.65 ± 0.1. Consequently, splitting of high-energy part of cascades might take place in W that results in a reduction of the effective PKA spectrum and a change of types and density of post-radiation defects.
The patterns of gas exchange between deuterium plasma and the walls of a vacuum chamber made from 12Cr18Ni10Ti (0.12% C, 18% Cr, 10% Ni, less than 1% Ti) stainless steel and irradiated with deuterium atoms in an atmosphere of deuterium with the addition of oxygen or with ions and atoms of a discharge in deuterium with the addition of oxygen are studied. It is demonstrated that irradiation of the surface of stainless steel under the indicated conditions promotes the diffusion of hydrogen from stainless steel; the implantation of deuterium into stainless steel; and the production on the surface and the desorption of H2O, HDO, D2O, HD, and H2 molecules. Almost all oxygen from the gas mixture in the oxygen concentration range from 0.5 to 30 at % is involved in the production of protonated and deuterated water molecules on the surface. When the oxygen concentration in the mixture of deuterium with oxygen is increased, the release of hydrogen from steel is enhanced. The amount of deuterium captured by stainless steel is lower than the amount of hydrogen removed from it. It is demonstrated that the diffusion of hydrogen towards the surface, its reactions with deuterium and oxygen from the working gas, and the trapping of deuterium in steel may be driven by consecutive surface exothermic reactions initiated by the interaction of deuterium atoms and ions with chromium oxide on the surface of stainless steel.
It is demonstrated that in the framework of the perturbation theory on laser field strength and the Fermi equivalent photon method expressions for photon transition, probabilities can be obtained that permit the derivation of scaling laws in terms of atomic state quantum numbers and pulse duration. A unified approach is developed that identifies universal scaling parameters for energy and pulse duration that allow analytical investigation of the interrelation of scaling laws for the two important regimes of above and below-threshold ionization. Numerical studies are presented that illuminate the conditions for linear and nonlinear regimes of photoionization, as dependent on the cycle number and carrier frequencies. We also discuss analytical asymptotic forms of the different regimes of photoionization. Finally, we develop a generalized unified approach that permits studies in terms of principal and orbital quantum numbers as well as in pulse duration for any regime of carrier frequencies. © 2016 IOP Publishing Ltd.
Core-shell Al@Ti nanoparticles are generated by ablation of a composite Ti-Al target in liquid isopropanol saturated with molecular hydrogen using a Nd:YAG laser with pulse duration of 10ps and repetition rate of 200kHz. The target is made of two plates of corresponding metals stacked together and placed into a flowing cell reactor. Transmission Electron Microscopy analysis of generated NPs reveals their core-shell structure with Ti core and Al shell. Average size of NPs determined by means of measuring disk centrifuge is around 40nm. Saturation of NPs by hydrogen is due to sharp dependence of its solubility in these metals on temperature. XRD studies of generated NPs show the peaks of both metallic Ti and Al with some amount of TiO2. No peaks of Ti-Al alloys are observed.
The scheme generating UV pulses with a duration 15 ps and output energy up to 11.5 mJ is implemented in the system consisting of a picosecond Nd3+ : YAG laser with multistage nonlinearoptical conversion of fundamental frequency radiation into radiation with a wavelength 193 nm followed by an excimer ArF amplifier. The temporal characteristics and the contrast of the amplified pulses are measured.
The H→. ZZ decay mode is usually considered as one of the most promising ways to discover new heavy neutral scalar H. We show that in the Georgi-Machacek model it is possible to get large enhancement of double SM-like Higgs boson production due to H decays while ZZ and WW decay channels could be highly suppressed. © 2015 The Authors.
The dynamic mechanism of the Thomas-Ehrman shift in three-cluster systems is studied by using the example of Ne-16 and C-16 isobaric mirror partners. We predict configuration mixings for 0(+) and 2(+) states in Ne-16 and C-16. Large isospin symmetry breaking on the level of wave function component weights is demonstrated for these states and discussed as a three-body mechanism of the Thomas-Ehrman shift. It is shown that the description of the Coulomb displacement energies requires consistency among three parameters: the Ne-16 decay energy ET, the F-15 ground-state energy E-r, and the configuration mixing parameters for the Ne-16 and (16)C0(+) and 2(+) states. Based on this analysis we infer the (15)F1/2(+) ground-state energy to be E-r = 1.39-1.42 MeV.
We studied the rare muon decay process μ+ → e+ e - e + ve v-μ. This Standard Model process is the background with respect to the signal process μ+ → e+ e - e + which is predicted by many extensions of the SM. We show that the process μ+ → e+ e - e + ve v-μ could be suppressed by cuts on the total energy of charged leptons in the kinematic region where the signal of new physics such as is expected to appear. Also, we demonstrated that angular distributions of decay products in the process μ+ → e+ e - e + ve v-μ are sensitive to the muon polarization and could be used to distinguish the signal of new physics μ+ → e+ e - e + from the background process μ+ → e+ e - e + ve v-μ. © 2015 The Authors.
Within the “nuclear medium cooling” scenario of neutron stars all reliably known temperature—age data, including those of the central compact objects in the supernova remnants of Cassiopeia A and XMMU-J1732, can be comfortably explained by a set of cooling curves obtained by variation of the star mass within the range of typical observed masses. The recent measurements of the masses of the pulsars PSR J1616-2230, PSR J0348-0432 and J00737-3039B and the companion of J1756-2251 provide independent proof for the existence of neutron stars with masses in a broad range from 1.2 to 2Minf⊙/inf The values M > 2Minf⊙/inf call for sufficiently stiff equations of state for neutron star matter. We investigate the response of the set of neutron star cooling curves to a stiffening of the nuclear equation of state so that maximum masses of about 2.4Minf⊙/inf would be accessible and to a deconfinement phase transition from such stiff nuclear matter in the outer core to color superconducting quark matter in the inner core. Without a readjustment of cooling inputs the mass range required to cover all cooling data for the stiff DD2 equation of state should include masses of 2.426Minf⊙/inf for describing the fast cooling of CasA while the existence of a quark matter core accelerates the cooling so that CasA cooling data are described with a hybrid star of mass 1.674Minf⊙/inf. © 2015, Pleiades Publishing, Ltd.
A kinetic theory of low-frequency currents induced in plasma by an ultrashort high-frequency radiation pulse is developed. General expressions for the currents flowing along the propagation direction of the pulse and along the gradient of the field energy density are analyzed both analytically and numerically for pulse durations longer or shorter than or comparable with the electron collision time in plasma. It is demonstrated that the nonlinear current flowing along the gradient of the field energy density can be described correctly only when the modification of the isotropic part of the electron distribution function is taken into account. © 2015, Pleiades Publishing, Ltd.
Amodified mechanism of the formation of large-scale antimatter regions is proposed. Antimatter appears owing to fluctuations of a complex scalar field that carries a baryon charge in the inflation era. © 2015, Pleiades Publishing, Ltd.
In this paper, we discuss a generation of large antimatter regions with sizes exceeding the critical surviving size. In the modern epoch, domains with high antimatter density evolve to single galaxies with a peculiar content of antihelium and antideuterium.
The effect of strong thermal radiation on the structure of quasi-stationary laser ablation fronts is investigated under the assumption that all the laser flux is absorbed at the critical surface. Special attention is paid to adequate formulation of the boundary-value problem for a steady-state planar ablation flow. The dependence of the laser-to-x-ray conversion efficiency φ r on the laser intensity IinfL/inf and wavelength λinfL/inf is analyzed within the non-equilibrium diffusion approximation for radiation transfer. The scaling of the main ablation parameters with IinfL/inf and λinfL/inf in the strongly radiative regime 1 - φ r 蠐 1 is derived. It is demonstrated that strongly radiating ablation fronts develop a characteristic extended cushion of "radiation-soaked" plasma between the condensed ablated material and the critical surface, which can efficiently suppress perturbations from the instabilities at the critical surface. © 2015 AIP Publishing LLC.
Knowledge of HTS materials behavior at overload currents is important to design fault current limiters or fault protection systems of electro-technical devices. There are sharp voltage peaks and voltage oscillations during rectangular current pulses (DC current) on HTS tapes cooled by liquid nitrogen. It is common knowledge that a homogeneous liquid can withstand certain amount of overheating before switching to the boiling phase. In the liquid nitrogen during the increase of the heat flux there is superheating (temperature overshoot) and boiling hysteresis takes place. We explain voltage peaks and voltage oscillations by the hysteresis phenomenon in boiling nitrogen during the increase and decrease of the heat flux in the nitrogen which is a result of current redistribution in the HTS tapes. Based on the measurements of voltage and temperature of the HTS tapes during current overload and numerical analysis of the process we estimated the heat-transfer characteristics from the HTS tapes to liquid nitrogen. We also obtained the information about limiting superheating of the liquid nitrogen. The influence of covers of the HTS tapes on superheating of the nitrogen is also discussed. © 2015 The Authors.
Heavy Ion Beam Probing (HIBP) is a unique diagnostics for core plasma potential. Advanced HIBP is operating now in the T-10 tokamak (a=0.3 m, R=1.5 m, Bt=1.5-2.4 T, IP=140-330 kA, PECRH<1.2 MW) and TJ-II flexible heliac (<a>=0.22 m, <R>=1.5 m, Bt =1 T, PECRH 0.6 MW, PNBI 1 MW). The fine focused (<1cm) and intense (100A) beams provide the measurements in the wide density interval ne=(0.3-5)10sup19/sup msup-3/sup, while the advanced control system for primary and secondary beams provides the measurements in the wide range of the plasma current in T-10 and magnetic configurations in TJ-II, including Ohmic, ECR and NBI heated plasmas. The time evolution of the radial profiles and/or local values of plasma parameters from High Field Side (HFS) to Low Field Side (LFS),-1<<1, is observed in TJ-II by 125 keV Cs+ ions in a single shot, while LFS (+0.2<<1) profiles are observed in T-10 by 300 keV Tl+ ions. Multi-slit energy analyzers provide simultaneously the data on plasma potential (by beam extra energy), plasma density ne (by beam current) and Bpol (by beam toroidal shift) in poloidally shifted sample volumes. Thus Epol =(1/= (-2 //= (-)/x, x∼1 cm, and the electrostatic turbulent particle flux pol ( ) 1/ ( ) ( ) E B t e t B n t E t is derived. The density oscillations cross-phase produces the phase velocity of poloidal propagation of perturbation or plasma rotation and the poloidal mode number m. Dual HIBP, consisting of two identical HIBPs located 1/4 torus apart, recently installed in TJ-II, provides the long-range correlations in core plasma parameters. Low noise high gain (10sup7/sup V/A) preamplifiers with 300 kHz bandwidth and 2 MHz sampling allows us to study broadband turbulence and quasi-coherent modes like Geodesic Acoustic Modes, Alfven Eigenmodes, Suprathermal electron induced modes, etc. Finally, HIBP becomes multipurpose diagnostics to study plasma electric potential and turbulence properties in the middle size toroidal devices. © Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike Licence.
Recent experiments have been performed on the Tokamak a configuration variable (TCV) to investigate the confinement properties of high density plasmas and the mechanism behind the density limit. In a limiter configuration with plasma elongation kappa = 1.3-1.4 and triangularity delta = 0.2-0.3 the operational density range has been extended up to 0.65 of the Greenwald density at I-p = 200 kA (q(95) = 3.7) and even to the Greenwald value at low plasma current I-p = 110 kA (q(95) = 7). A transition from the linear to the saturated ohmic confinement regime is observed at high density similar to 0.4n(GW). A further density increase leads to sawtooth stabilization and is accompanied by a decrease of the energy and particle confinement times. The development of the disruption at the density limit was preceded by sawtooth stabilization. It is shown that electron cyclotron heating leads to the prevention of sawtooth stabilization and then to the increase of the density limit value.
High power pulsed magnetron sputtering is a promising physical vapor deposition technique with two minor challenges that obstruct its broader implementation in industry and its use by researchers. The first challenge is the availability of low cost HPPMS power supplies with output power under 2. kW. Such power supplies are suited for circular planar magnetrons with target diameters between 50. mm to 150. mm. The second challenge is the overall lower deposition rates of HPPMS when compared with direct current magnetron discharges. The "ε" magnet pack designed for a 100. mm sputter magnetron which was developed by the Center for Plasma Material Interactions at the University of Illinois at Urbana Champaign in collaboration with Kurt J. Lesker Company was capable of producing twice higher deposition rates in HPPMS compared to a conventional magnet pack. The cylindrically symmetric "TriPack" magnet pack presented here was developed based on magnetic field design solutions from the "ε" magnet pack in order to keep the high deposition rates, but improve deposition uniformity, without the need for substrate rotation. The new cylindrically symmetric magnet pack for 100. mm diameter targets, along with a specially designed cooling well provides stable operation at 2. kW average power, even with low-temperature melting-point target materials. The deposition rates from the TriPack magnet pack is compared with a commercial conventional magnet pack for DC and HPPMS power supplies. © 2015 Elsevier B.V.
High frequency (60 GHz) electron spin resonance (ESR) has been studied for the quantum critical system Mninf1-x/infFeinfx/infSi (0 x 0.24) at temperatures up to 50 K by using the original experimental technique. The analysis of ESR line shape allowed detecting the full set of spectroscopic parameters (oscillating magnetization, line width and g factor). The violation of classical Korringa-type relaxation and scaling behavior of the ESR line width was found to a result from iron doping. Non-Fermi-liquid effects in the temperature dependence of the ESR line width observed at quantum critical points
High power pulsed magnetron sputtering (HPPMS) is a state-of-the-art physical vapor deposition technique with several industrial applications. One of the main disadvantages of this process is its low deposition rate. In this work, the authors report a new magnetic field configuration, which produces deposition rates twice that of conventional magnetron's dipole magnetic field configuration. Three different magnet pack configurations are discussed in this paper, and an optimized magnet pack configuration for HPPMS that leads to a higher deposition rate and nearly full-face target erosion is presented. The discussed magnetic field produced by a specially designed magnet assembly is of the same size as the conventional magnet assembly and requires no external fields. Comparison of deposition rates with different power supplies and the electron trapping efficiency in complex magnetic field arrangements are discussed. © 2015 American Vacuum Society.
Abstract The new phase of YbAginf2/inf was obtained using high-pressure and high-temperature reaction. YbAginf2/inf crystallizes in the MgZninf2/inf structure (the space group P6inf3/inf/mmc space group, No 194) with a = 5.68153(3) Å and c = 9.31995(7) Å and the unit cell volume V = 260.54(3) Åsup3/sup. The XANES analysis showed that the valence state of Yb is +2.8. The low-temperature dependences of the electrical resistivity and magnetic susceptibility can be adequately described by a Tsup2/sup term that supports the Fermi-liquid picture. The Kadowaki-Woods relation gives a low value of the degeneracy (N = 2). © 2015 Elsevier B.V.
Impulse magnetron with a liquid cathode operated in copper vapour without the working gas has been experimentally investigated. Stable discharge regimes were obtained through applying the high-current pulses over a 1.5kW direct current magnetron discharge operated on a liquid copper target. The current-voltage characteristic of the discharge as well as the temporal evolution of the impulse current-voltage relations have been acquired for a constant magnetic field value on the target's surface. The pulsed Langmuir probe diagnostics has been utilized to measure the plasma parameters along the symmetry axis. The pulsed probe diagnostics revealed strong dependences of electron temperature and plasma density on the distance to the target's surface. Electron temperature measured 5cm away from the target did not exceed 2eV, and reduced down to 1eV at longer distances. The maximum value of plasma density along the target's centerline was 2×1013 cm-3, as measured at a distance of 5cm. © 2015.
We study a two-component dark matter candidate inspired by the minimal walking technicolor (WTC) model. Dark matter consists of a dominant strongly interactive massive particle (SIMP)-like dark atom component made of bound states between primordial helium nuclei and a doubly charged technilepton and a small WIMP-like component made of another dark atom bound state between a doubly charged technibaryon and a technilepton. This scenario is consistent with direct search experimental findings because the dominant SIMP component interacts too strongly to reach the depths of current detectors with sufficient energy to recoil and the WIMP-like component is too small to cause significant amount of events. In this context, a metastable technibaryon that decays to e(+) e(+), mu(+) mu(+) and tau(+) tau(+) can, in principle, explain the observed positron excess by AMS-02 and PAMELA, while being consistent with the photon flux observed by FERMI/LAT. We scan the parameters of the model and we find the best possible fit to the latest experimental data. We find that there is a small range of parameter space that this scenario can be realized under certain conditions regarding the cosmic ray propagation and the final state radiation (FSR). This range of parameters fall inside the region where the current run of large hadron collider (LHC) can probe, and therefore it will soon be possible to either verify or exclude conclusively this model of dark matter.
Highly excited states of sup6/supHe are sought in the reactions involved in the absorption of stopped pions by sup10,11/supB nuclei. Several levels in sup6/supHe are observed for the first time. A state with Einfx/inf ≈ 9.3(2) MeV and Γ ≈ 1.0(4) MeV is seen to form in two reactions: sup10/supB(πsup−/sup, pt)X and sup11/supB(πsup−/sup, dt)X. Two states are seen to form in the sup10/supB(πsup−/sup, pt)X reaction channel at energies above the threshold of sup6/supHe decay into two tritons (Einfx/inf ≥ 12.3 MeV): one state with Einfx/inf = 22(1) MeV, Γ = 2.7(1.4) MeV and the other with Einfx/inf = 27.0(8) MeV, Γ = 2.5(1.1) MeV. © 2015, Allerton Press, Inc.
Discussions are currently going on as to whether it is suitable to employ thorium in the nuclear fuel cycle. This work demonstrates that the 231Pa–232U–233U–Th composition to be produced in the thorium blanket of a hybrid thermonuclear reactor (HTR) as a fuel for light-water reactors opens up the possibility of achieving high, up to 30% of heavy metals (HM), or even ultrahigh fuel burnup. This is because the above fuel composition is able to stabilize its neutron-multiplying properties in the process of high fuel burnup. In addition, it allows the nuclear fuel cycle (NFC) to be better protected against unauthorized proliferation of fissile materials owing to an unprecedentedly large fraction of 232U (several percent!) in the uranium bred from the Th blanket, which will substantially hamper the use of fissile materials in a closed NFC for purposes other than power production. © 2015, Pleiades Publishing, Ltd.
Hydrocarbon film deposition was studied with cavity samples in remote areas of the inner and outer JET divertor and below the divertor septum during the 1999-2001 and 2005-2009 campaigns. Thick hydrocarbon films were formed inside the cavities. These deposited hydrocarbon layers have high D/C ratios close to 1. The formation of these films is mainly due to sticking of hydrocarbon particles with high surface loss probabilities 0.6. The observed surface loss probabilities depend on the position in the divertor and vary during different campaigns. The particles responsible for hydrocarbon layer formation originate from the divertor strike points. Except for the septum cavity the deposition of beryllium was very low and showed a very different distribution from that of deuterium and carbon. (C) 2014 Elsevier B.V. All rights reserved.
Processes of deuterium and hydrogen accumulation and redistribution are studied via the elastic recoil detection method with the help of a Plasma Focus (PF-4) setup. These processes proceed when high-temperature pulsed deuterium plasma acts on two external tungsten foils used as the main elements of hermetic chambers filled with distilled or heavy water and one internal tungsten foil inserted into an aqueous medium. It is established that, under the action of pulsed deuterium plasma on the heavy water-filled chamber, implanted deuterium atoms and those existing in the heavy water, as well as hydrogen contained in the tungsten foils, are redistributed over the entire thicknesses of the three foils. When the distilled water-filled chamber is irradiated with pulsed deuterium plasma, implanted hydrogen is observed across the whole thickness of the external tungsten foils with a depth distribution maximum. Hydrogen and deuterium reach their maxima on the foil surface immersed in liquid. The revealed phenomenon can be explained by the fact that chemical bonds in the heavy and distilled water are broken and, afterward, free hydrogen and deuterium atoms are transferred to tungsten foils under the action of intense shock waves excited in the chamber. © 2015, Pleiades Publishing, Ltd.
The regularities and mechanisms of the processes characterizing the behavior of hydrogen in the zirconium alloy E-110 with a chromium coating were studied at different stages of the experiment: during irradiation of the substrate by ions from argon plasma and in the process of coating deposition. After ion bombardment of the zirconium, the hydrogen was retained in the interior and in the defects of the surface layer of the zirconium, and hydrogen trapping decreased with increasing residual gas pressure during irradiation in the range 1.3–30 mPa. The hydrogen atoms trapped during deposition of the chromium coating were retained primarily in the zirconium. As the pressure of the deuterium added to the residual gas during coating deposition increased, the trapping of deuterium atoms increased in the zirconium and remained unchanged in the chromium coating. Hydrogen atoms were observed to transition from the interior of the zirconium to the trapping centers in the oxide layer, which was accompanied by a reduction of the hydrogen desorption temperature and observed during ion irradiation of the substrate and coating deposition in a low vacuum.
Hydrogen retention in vanadium and its binary alloys with titanium are investigated by means of hydrogen thermal desorption spectrometry. The samples are saturated with hydrogen for 2000 h at a temperature of 620 K in an autoclave, where hydrogen is fed at a pressure of 16.8 MPa. It is shown that in V-Ti alloys there are two main types of traps for hydrogen and from which the hydrogen release occurs in the temperature range of 780–790 (peak I) and 870–880 K (peak II) The position of peak I on the temperature scale does not depend on the alloy composition, and the intensity and position of peak II on the temperature scale are determined by the alloy composition. Titanium non-monotonically affects the amount of hydrogen retained: an addition of 0.5% Ti decreases, 1 and 5% Ti increases, and 10% Ti again decreases the amount of hydrogen in the alloy. A physical explanation of the appearance of two peaks of hydrogen thermal desorption and nonmonotonic influence of titanium on the amount of hydrogen in vanadium is proposed. © 2015, Pleiades Publishing, Ltd.
This paper describes the trigger and offline reconstruction, identification and energy calibration algorithms for hadronic decays of tau leptons employed for the data collected from pp collisions in 2012 with the ATLAS detector at the LHC center-of-mass energy root s = 8 TeV. The performance of these algorithms is measured in most cases with Z decays to tau leptons using the full 2012 dataset, corresponding to an integrated luminosity of 20.3 fb(-1). An uncertainty on the offline reconstructed tau energy scale of 2-4%, depending on transverse energy and pseudorapidity, is achieved using two independent methods. The offline tau identification efficiency is measured with a precision of 2.5% for hadronically decaying tau leptons with one associated track, and of 4% for the case of three associated tracks, inclusive in pseudorapidity and for a visible transverse energy greater than 20 GeV. For hadronic tau lepton decays selected by offline algorithms, the tau trigger identification efficiency is measured with a precision of 2-8%, depending on the transverse energy. The performance of the tau algorithms, both offline and at the trigger level, is found to be stable with respect to the number of concurrent proton-proton interactions and has supported a variety of physics results using hadronically decaying tau leptons at ATLAS.
The question of why the observed periods of anomalous X-ray pulsars (AXPs) and soft gamma-ray repeaters (SGRs) cluster in the range 2-12 s is discussed. The possibility that AXPs and SGRs are the descendants of high-mass X-ray binaries that have disintegrated in core-collapse supernova explosions is investigated. The spin periods of neutron stars in high-mass X-ray binaries evolve towards the equilibrium period, which is a few seconds, on average. After the explosion of its massive companion, the neutron star becomes embedded in a dense gaseous envelope, and accretion from this envelope leads to the formation of a residual magnetically levitating disk. It is shown that the expected mass of the disk in this case is 10(-7)-10(-8) M-aS (TM), which is sufficient to support accretion at the rate 10(14)-10(15) g/s over a few thousand years. During this period, the star manifests itself as an isolated X-ray pulsar with a number of parameters similar to those of AXPs and SGRs. The periods of such pulsars can cluster if the lifetime of the residual disk does not exceed the spin-down timescale of the neutron star.
This paper deals with the results of studying the impact of discharge current rate on electrode surface area of high-current lowinductance vacuum spark. Iron electrodes were utilized for research. It was discovered that the size of periodic structure cells on a cathode surface decreased from 600 nm (63 kA) to 150 nm (180 kA) as the discharge current rate grew along with switching to the micropinching mode. The discharge current rate exerted no significant impact on the size of structure elements on anode surface (the structure size at all currents was ∼ 400 nm). © 2015 The Authors.
The impact of holmium fibre laser radiation on the samples of biologic tissues (dura mater of spinal cord and adipose tissue with interlayers of muscle) is studied. The experimental results are evaluated by the size of carbonisation and coagulation necrosis zones. The experiment shows that in the case of irradiation of the spinal cord dura mater samples the size of carbonisation and coagulation necrosis zones is insignificant. In the adipose tissue the carbonisation zone is also insignificant, but the region of cellular structure disturbance is large. In the muscle tissue the situation is opposite. The cw laser operation provides clinically acceptable degree of destruction in tissue samples with a minimal carbonisation zone. © 2015 Kvantovaya Elektronika and Turpion Ltd.
The transverse momentum (p(T)) dependence of the nuclear modification factor R-AA and the centrality dependence of the average transverse momentum p(T) for inclusive J/psi have been measured with ALICE for Pb-Pb collisions at root S-NN = 2.76TeV in the e(+)e(-) decay channel at mid-rapidity (vertical bar y vertical bar 0.8). The p(T) is significantly smaller than the one observed for pp collisions at the same centre-of-mass energy. Consistently, an increase of RAA is observed towards low p(T). These observations might be indicative of a sizable contribution of charm quark coalescence to the J/psi production. Additionally, the fraction of non-prompt J/psi from beauty hadron decays, f(B), has been determined in the region 1.5 p(T) 10 GeV/c in three centrality intervals. No significant centrality dependence of fB is observed. Finally, the RAA of non-prompt J/psi is discussed and compared with model predictions. The nuclear modification in the region 4.5 p(T) 10 GeV/c is found to be stronger than predicted by most models.
The two-way shape memory effect (TWSME) has been studied in an amorphous-crystalline thin ribbon of Ti40.7Hf9.5Ni44.8Cu5 shape memory alloy with different volume fractions of the crystalline phase. It is found that an increase in the volume fraction of the crystalline phase results in a non-monotonic variation in the value of the TWSME. A maximum strain of 1.1% is observed in the thin ribbon with a 50% crystalline phase. It is found that the TWSME in amorphous-crystalline Ti40.7Hf9.5Ni44.8Cu5 alloy is due to two mechanisms: the formation of high internal stresses on the amorphous/crystalline interfaces due to incompatible strain in amorphous and crystalline phases and the stress caused by defects induced in the crystalline phase during deformation. If the volume fraction of the crystalline phase is 50% or less, then the main contribution to the total TWSME is given by the formation of the internal stresses on the amorphous/crystalline interfaces. In this case, the TWSME value depends on the density of the amorphous/crystalline interfaces, plastic strain and volume fraction of the alloy undergoing a phase transition. If the volume fraction of the crystalline phase is higher than 50%, then the TWSME is due to the formation of the internal stresses on the defects in the crystalline phase and the TWSME value depends on the plastic strain in the crystalline phase and the volume fraction of the crystalline phase.
The influence of molecular clustering on the formerly suggested interpretation of diffraction patterns of hydrocarbon films formed in the vacuum vessel of the tokamak T-10 is analyzed numerically. The simulation of clustering of simple hydrocarbon molecules C(D, H)4, C2(D, H)4, and C6(D, H)6 and molecules composed of curved graphene (fullerenes and toroidal nanotubes) is carried out with the rigid body molecular dynamics method. It is shown that formerly neglected atomic correlations C–C and C–D(H) in the amorphous hydrocarbon component decrease the calculated values of the scattered intensity in the range of scattering vector modulus 5 q 20 nm–1 because of homogenization of scatters on the spatial scale of ~1 nm. The allowance for these correlations does not change the diffraction patterns in the range q 20 nm–1. The results suggest the necessity to introduce to the procedure of determining the structural content of the films, similar to those from the tokamak T-10, the clusters formed by the van der Waals adhesion of hydrocarbon molecules to “graphene” nanoparticles. This simplifies the mathematical optimization to the former level of complexity—but for an extended ensemble of objects—and makes it possible to calculate the diffraction patterns of these objects using the distributed computing resources. A modified algorithm of structural content identification on the basis of joint X-ray and neutron diffractometry is suggested. © 2015, Pleiades Publishing, Ltd.
Investigation of hydrogen isotopes behavior in fusion reactor materials is an important task for fusion. In this work deuterium retention in reduced activation ferritic-martensitic steel EK-181 (rusfer) after exposure to low-energy D-plasma with ion energy of 300 eV in the temperature range of RT-635 K was investigated. Deuterium concentration was measured using thermal desorption spectroscopy and nuclear reaction analysis using D(3He, p)4 He reaction with 3He+ energies between 0.69 and 4.5 MeV. The deuterium retention in rusfer was very small (around 10-3-10-2% at). The maximum deuterium accumulation was observed at exposure temperatures of 300-350 K. Further increase of the exposure temperature led to steep falling down of D accumulation at 400 K. Comparison of the retention measured by thermal desorption spectroscopy and nuclear reaction analysis shows that the deuterium trapped mainly in the bulk of the samples although the maximum concentration of deuterium is always near the surface.
An approach to the integrated modelling of plasma regimes in the projected neutron source DEMO-FNS based on different codes is developed. The consistency check of the steady-state regime is carried out, namely, the possibility of the plasma current ramp-up, acceptance of growth rates of MHD modes in the steady-state regime, heat loads to the wall and divertor plates and neutron yield value. The following codes are employed for the integrated modelling. ASTRA transport code for calculation of plasma parameters in the steady-state regime, NUBEAM Monte Carlo code for NBI incorporated into the ASTRA code, DINA free boundary equilibrium and evolution code, SPIDER free boundary equilibrium and equilibrium reconstruction code, KINX ideal MHD stability code, TOKSTAB rigid shift vertical stability code, edge and divertor plasma B2SOLPS5.2 code and Semi-analytic Hybrid Model (SHM) code for self-consistent description of the core, edge and divertor plasmas based on the experimental scaling laws. The consistent steady-state regime for the DEMO-FNS plasma and the plasma current ramp-up scenario are developed using the integrated modelling approach. Passive copper coils are suggested to reduce the plasma vertical instability growth rate to below similar to 30 s(-1). The outer divertor operation in the 'high-recycling' regime is numerically demonstrated with a maximal heat flux density of 7-9 MW m(-2) that is technically acceptable.
Using inelastic neutron scattering, we map a 14 meV coherent resonant mode in the topological Kondo insulator SmB6 and describe its relation to the low energy insulating band structure. The resonant intensity is confined to the X and R high symmetry points, repeating outside the first Brillouin zone and dispersing less than 2 meV, with a 5d-like magnetic form factor. We present a slave-boson treatment of the Anderson Hamiltonian with a third neighbor dominated hybridized band structure. This approach produces a spin exciton below the charge gap with features that are consistent with the observed neutron scattering. We find that maxima in the wave vector dependence of the inelastic neutron scattering indicate band inversion.
In this work we investigated co-deposition of lithium-deuterium (Li-D) films in magnetron discharge and interaction of deposited films with water vapor. It was demonstrated that even at room temperature interaction with water vapor led to release of a large portion of deuterium from the deposited layers. After 30 minutes exposure at the pressure about 10-1 Pa the main part of deuterium released from the sample and a characteristic peak for deuterium desorption from lithium films completely disappeared. © 2015 The Authors. Published by Elsevier B.V.
A fundamental to understanding physical processes in laser plasma is to study plasma density profile. We applied an optical interferometer of Mach-Zehnder and UV nitrogen laser that was used as a source of probe light (wavelength 337 nm, energy of ∼ 150 μJ, pulse duration ∼ 5 ns). Digital camera frame grabber captures individual interferometric pictures, so phase shift of fringes is easy photographed and analyzed in terms of plasma density. Powerful Nd-laser (wavelength 1.054 μm, pulse energy up to 20 J, pulse duration 15 ns) was used to generate laser plasma. The pulse of probing laser passed through the laser-induced plasma with delay td =5+50 ns. The results of interferometric measurements of electron density in laser-induced plasma from copper target are presented. © 2015 The Authors.
Electron density dynamics in air, nitrogen and argon femtosecond filament plasma channel is studied under different pressure up to hundreds of picoseconds after ionization by transverse interferometry method. It is revealed that initial electron density in nitrogen plasma rises significantly under the pressure over 4 atmospheres. Optical refractive index anisotropy, which precedes and accompanies ionization, related with intense pulse propagation is revealed. © 2015 The Authors.
The first excited, Jπ=2+ state of Ne16 at E∗=1.69(2) MeV is well populated in neutron knockout reactions with a Ne17 beam and the correlations between the momenta of the three final fragments following 2p decay were measured. The correlation pattern showed aspects of both sequential and diprotonlike decay, which were reproduced in three-body O14 + p+p calculations. These calculations suggest that interference between these processes is responsible for the observed features which can be described in terms of a "tethered decay mechanism." The intrinsic width of this state was constrained to be from 100 to 250 keV. Higher excited states populating the N13 + p+p+p exit channel were found at E∗=8.37(10) and 10.76(20) MeV. © 2015 American Physical Society.
A resonant tunneling periodic quantum well structure with asymmetric double quantum well period is proposed to achieve a population inversion and a frequency-tunable terahertz emission on intersubband transitions between Landau levels in a tilted magnetic field. The spatial redistribution of the subband wavefunctions caused by an asymmetric period design made it possible to achieve both a considerable increase in the population inversion and a high value of the dipole matrix element of the inter-Landau level radiative transition.
Highly excited states in sup9/supLi are sought in missing mass spectra measured in the stopped pion absorption reaction sup11/supB(πsup−/sup, dt)X. Observed for the first time in the two-particle reaction πsup−/sup + sup11/supB → d + sup9/supLi* was a highly excited sup9/supLi state with Einfx/inf = 12.0 ± 0.5 MeV that decayed with the emission of a triton. © 2015, Allerton Press, Inc.
The possibility of using plasma of the laser-induced vacuum discharge as a source of multiplecharged ions is considered. To this end, a sequence of measurements of the ion emission from discharge plasma was made. The laser radiation was focused on the anode surface in the focal spot with diameter D≤250 μm and with intensity on the target q≈5 ×10sup9/sup W/cmsup2/sup. The laser energy El = 50 ÷ 60 mJ. The choice of given geometry in this experiment has allowed us to successfully detect the ions emitted at a small angle (α≈21sup0/supwith respect to the discharge axis. We have already established earlier that the ion yield, in the case of focusing laser radiation on the cathode of discharge system, is significantly less. The use of the storage capacitor of C=0.22 μF enabled us to vary the amount of discharge energy in the range of Edr =5÷24 J. Depending on the discharge energy the intensity of ion emission and the spectrum of charge states changed. Our measurement results allowed us to make an assumption that the work in the range of discharge energies Edr = 10÷14 J is the most effective from the point of view of the quantity of emitted multiple-charged ions. The average ion flux density was Wp = (1.5÷ 3)1014 Ions/sr. © Copyright 2015 ITER Organization.
The characteristics of a Fe : ZnSe laser pumped by a single-pulse free-running Er : YAG laser and a repetitively pulsed HF laser are presented. An output energy of 4.9 J is achieved in the case of liquid-nitrogen cooling of the Fe2+ : ZnSe active laser element longitudinally pumped by an Er:YAG laser with a pulse duration of 1 ms and an energy up to 15 J. The laser efficiency with respect to the absorbed energy is 47%. The output pulse energy at room temperature is 53 mJ. The decrease in the output energy is explained by a strong temperature dependence of the upper laser level lifetime and by pulsed heating of the active element. The temperature dependence of the upper laser level lifetime is used to determine the pump parameters needed to achieve high pulse energies at room temperature. Stable repetitively-pulsed operation of the Fe2+ : ZnSe laser at room temperature with an average power of 2.4 W and a maximum pulse energy of 14 mJ is achieved upon pumping by a 1-s train of 100-ns HF laser pulses with a repetition rate of 200 Hz.
The magnetic field structure measurements are necessary for understanding of wave propagation in plasma of the auto-oscillating discharge in the open adiabatic trap PR-2. Measurements were made by the developed system for automatic positioning of magnetic probes placed inside the PR-2 vacuum chamber. All magnetic probes were pre-calibrated using Helmholtz coil. Four different circuit configurations were used to excite oscillations in wide frequency range. Observed frequencies of plasma oscillations using magnetic probes correspond to the circuit resonant frequencies. © 2015 The Authors.
The new Plasma Beam Facility (PBF) has been put into operation for assistance in testing of plasma faced components at Material Science Kazakhstan Tokamak (KTM). PBF includes a powerful electron gun (up to 30kV, 1A) and a high vacuum chamber with longitudinal magnetic field coils (up to 0.2T). The regime of high vacuum electron beam transportation is used for thermal tests with power density at the target surface up to 10GW/m2. The beam plasma discharge (BPD) regime with a gas-puff is used for generation of intensive ion fluxes up to 3dot operator1022 m- 2 s- 1. Initial tests of the KTM PBF's capabilities were carried out: various discharge regimes, carbon deposits cleaning, simultaneous thermal and ion impacts on radiation cooled refractory targets. With a water-cooled target the KTM PBF could be used for high heat flux tests of materials (validated by the experiment with W mock-up at the PR-2 PBF).
Interaction of deuterium with radiation defects in tungsten was studied by means of thermal desorption spectroscopy. The displacement damage in a recrystallized tungsten foil was produced by irradiation with 10 keV/D ions to the fluences in the range of 3-81019 D/m2 at room temperature. The resulted thermal desorption spectra consisted of three wide overlapping peaks. It was shown that annealing of the damaged sample at 550 K and subsequent implantation with 0.67 keV/D ions allows to isolate the peak corresponding to deuterium release from vacancies. © 2015 The Authors. Published by Elsevier B.V.
We consider the motion of classical spinning test particles in Schwarzschild and Kerr metrics and investigate innermost stable circular orbits (ISCO). The main goal of this work is to find analytically the small-spin corrections for the parameters of ISCO (radius, total angular momentum, energy, orbital angular frequency) of spinning test particles in the case of vectors of black hole spin, particle spin and orbital angular momentum being collinear to each other. We analytically derive the small-spin linear corrections for arbitrary Kerr parameter a. The cases of Schwarzschild, slowly rotating and extreme Kerr black hole are considered in detail. For a slowly rotating black hole, the ISCO parameters are obtained up to quadratic in a and particle's spin s terms. From the formulas obtained it is seen that the spin-orbital coupling has attractive character when spin and angular momentum are parallel and repulsive when they are antiparallel. For the case of the extreme Kerr black hole with co-rotating particle we succeed to find the exact analytical solution for the limiting ISCO parameters for arbitrary spin. It has been shown that the limiting values of ISCO radius and frequency do not depend on the particle's spin while values of energy and total angular momentum depend on it. We have also considered circular orbits of arbitrary radius and have found small-spin linear corrections for the total angular momentum, energy and frequency at given radius. System of equations for numerical calculation of ISCO parameters for arbitrary a and s is also explicitly written.
The jet energy scale (JES) and its systematic uncertainty are determined for jets measured with the ATLAS detector using proton–proton collision data with a centre-of-mass energy of (Formula presented.)(Formula presented.)TeV corresponding to an integrated luminosity of (Formula presented.)(Formula presented.)(Formula presented.)(Formula presented.). Jets are reconstructed from energy deposits forming topological clusters of alorimeter cells using the anti-(Formula presented.)(Formula presented.) algorithm with distance parameters (Formula presented.)(Formula presented.) or (Formula presented.)(Formula presented.), and are calibrated using MC simulations. A residual JES correction is applied to account for differences between data and MC simulations. This correction and its systematic uncertainty are estimated using a combination of in situ techniques exploiting the transverse momentum balance between a jet and a reference object such as a photon or a (Formula presented.)(Formula presented.) boson, for (Formula presented.)(Formula presented.) and pseudorapidities (Formula presented.)(Formula presented.). The effect of multiple proton–proton interactions is corrected for, and an uncertainty is evaluated using in situ techniques. The smallest JES uncertainty of less than 1 % is found in the central calorimeter region ((Formula presented.)(Formula presented.)) for jets with (Formula presented.)(Formula presented.). For central jets at lower (Formula presented.)(Formula presented.), the uncertainty is about 3 %. A consistent JES estimate is found using measurements of the calorimeter response of single hadrons in proton–proton collisions and test-beam data, which also provide the estimate for (Formula presented.)(Formula presented.) TeV. The calibration of forward jets is derived from dijet (Formula presented.)(Formula presented.) balance measurements. The resulting uncertainty reaches its largest value of 6 % for low-(Formula presented.)(Formula presented.) jets at (Formula presented.)(Formula presented.). Additional JES uncertainties due to specific event topologies, such as close-by jets or selections of event samples with an enhanced content of jets originating from light quarks or gluons, are also discussed. The magnitude of these uncertainties depends on the event sample used in a given physics analysis, but typically amounts to 0.5–3 %.
We have analysed the possibility of appearance of anti-Stokes lines in the spectrum of Raman scattering of a photon by a 'quasi-bound' charged particle in the regime of planar (axial) channelling. It is shown that radiation may emerge at the frequency, which is a combination of the incident photon frequency ?0 and transition frequency ?i in the transverse quantised motion of a channelled particle: ? = ?0 ± 2?;2?i, where ?; is the relativistic (Lorentz) factor of a channelled particle.
The nonlinear dynamics of resistive flow with a chemical reaction is studied. Proceeding from the Lagrangian description, the influence of a chemical reaction on the development of fluid singularities is considered. © 2015 The Royal Swedish Academy of Sciences.
The problem of the ejection of an s electron bound in a short-range potential well by a time-independent external electromagnetic field is considered. A simple formula for the probability of the decay of such a state in a tunneling-like process is derived. This formula is applied to the case of simultaneous action of uniform electric and magnetic fields. It is demonstrated that, in the case of a strong magnetic field, the previously reported results need to be refined. © 2015, Pleiades Publishing, Inc.
The magnetization of layered high-temperature superconductors (HTSC) with ferromagnetic nanorods as bulk pinning centers is studied in the 2D model of layered HTSC by using a Monte Carlo method. Magnetic part of the interaction energy between a ferromagnetic cylinder of arbitrary radius and constant magnetization and an Abrikosov vortex was calculated in London approximation. The periodic and non-periodic lattices of magnetic defects were considered. The magnetization was investigated at different radii of magnetic defects. The results of calculations were compared with the results for extended nonmagnetic defects. © 2015 The Authors.
The excitation spectrum is calculated for two-dimensional FeAs clusters modeling iron-based superconductors with the use of the quantum Monte Carlo algorithm in the framework of the full two-orbital model. The data for clusters of the size up to 10×10 FeAs cells are presented for the first time. The dependence of dispersion curves on temperature and interaction parameters is analyzed. © 2015 The Authors.
The generalized quantum Monte Carlo algorithm was used to obtain one-particle excitation spectrum and electron density of states for two-dimensional FeAs-clusters modeling iron-based superconductors within the limits of the full two-orbital model. The calculations were performed for clusters with sizes up to 10x10 FeAs-cells. The excitation spectra were reconstructed from Matsubara Green's function. The spectral density of states and the total density of states near the Fermi level were obtained. The data are in accordance with known experimental results. The influence of the cluster size, temperature, and the interaction strength on the density of states was analysed.
Two tunnel-coupled waveguides, one exhibiting positive refraction, the other exhibiting negative refraction, are analyzed. It is proposed that the positively refracting waveguide contains resonant admixture atoms, while the negatively refracting one has linear losses. The nonlinear properties of the positively refracting waveguide are related to saturation of resonance absorption. It is demonstrated that attenuation of a backward wave propagating in the studied antidirectional coupler can be compensated under certain conditions. © 2015, Pleiades Publishing, Ltd.
In a model which describes asymmetric oppositely directed nonlinear coupler it was observed in numerical simulations a phenomenon of solitary wave generation from the input constant continuous wave set at the entrance of a waveguide with negative refraction. The period of solitary wave formation decreases with increase of the continuum wave amplitude. © 2015 Owned by the authors, published by EDP Sciences.
The results of numerical simulation of solitary waves in an array of quantum dots are reported. It is shown that solitary waves are stable against collisions between themselves (both in case of interacting equally polarized waves and waves of different polarizations). Weak dipole-dipole interaction between neighbouring quantum dots does not change the solitary character of propagation of interacting solitary waves. © 2015 The Authors.
We consider a nonlinear coupler formed by two tunnel-coupled waveguides, one waveguide being made of a conventional dielectric and the other - of a negative-index material. The possibility of the formation of solitary waves from continuous radiation having a constant intensity is shown provided that the radiation is coupled into the input of a negative-index coupler channel (on the back side of the waveguide system). With increasing intensity of the input light, the speed and amplitude of the generated solitary waves increase and the period of their formation is reduced.
The multi-parameter character of supersymmetric dark-matter models implies the combination of their experimental studies with astrophysical and cosmological probes. The physics of the early Universe provides nontrivial effects of non-equilibrium particles and primordial cosmological structures. Primordial black holes (PBHs) are a profound signature of such structures that may arise as a cosmological consequence of supersymmetric (SUSY) models. SUSY-based mechanisms of baryosynthesis can lead to the possibility of antimatter domains in a baryon asymmetric Universe. In the context of cosmoparticle physics, which studies the fundamental relationship of the micro- and macro-worlds, the development of SUSY illustrates the main principles of this approach, as the physical basis of the modern cosmology provides cross-disciplinary tests in physical and astronomical studies. © 2015 by the authors.
The development of Zeldovich's ideas on the cosmological impact of particle theory is discussed in the context of cosmoparticle physics, studying fundamental relationship of macro- and micro-worlds.
The optical characteristics of sustained weak luminescence of liquid nitrogen were studied after exposure to a pulse of UV radiation. The luminescence consisted of a bulk emission of the liquid and localized luminous regions. The luminescence spectrum of liquid nitrogen in UV-VIS range was studied. The UV radiation parameters that influence the excitation of the luminescence of liquid nitrogen were investigated. A possible scheme of bulk luminescence of liquid nitrogen and a hypothesis of the formation of localized luminous regions were discussed. © 2015 AIP Publishing LLC.
The formation of near-electrode plasma regions during the discharge in an electrolyte with the help of the external magnetic field is considered. High-frequency oscillations in the discharge current circuit in the frequency range v = 30 kHz–60 MHz are analyzed. Spectral measurements of the plasma temperature and concentration are performed. Spectral emission lines indicate the presence of oscillatory processes. Stabilization of the working discharge regimes under the action of a magnetic field in the region of B = 100–300 G is detected. It is proposed that the observed effects can be due to plasma waves that can exist in a magnetic field. © 2015, Pleiades Publishing, Ltd.
The study of discharge plasma in electrolyte involves the use of external magnetic field. High-frequency oscillations of discharge are studied in the frequency range of 10 kHz-150 MHz. A regular structure of plasma flows is recorded at creation of magnetic field in the range of 50-600 Gs. The spectral measurements of temperature and concentration of plasma are performed. The origination of possible waves in discharge plasma in the magnetic field is discussed. © 2015 The Authors.
Properties of the plasma shell of a low-inductive vacuum spark are investigated. High-frequency oscillations in the range 1–120 MHz are registered in the current circuit. Spectral measurements of the plasma elemental composition and temperature are performed. The presence of oscillatory processes is also observed in spectral emission lines. Ring formations (with periods of 0.15–0.3 mm) and cellular structures (with sizes of 0.1–0.5 μm) are fixed on the electrode surface. Plasma waves are suggested to explain the registered oscillatory processes.
Capillary discharge with a metal atom content in the plasma is investigated. Spectroscopy was used to study the discharge under interaction with metal foils. The temperature distribution at the discharge axis was obtained. The autonomous domains are fixed in the area of the jet interaction with the aluminum foil. The conditions of the occurrence of such plasma domains are discussed.
We study relativistic mean-field (RMF) models including nucleons interacting with scalar, vector, and isovector mean fields and mean-field self- and cross-interaction terms. Usually, in such models the magnitude of the scalar field increases monotonically with the nucleon density, and the nucleon effective mass decreases. We demonstrate that the latter quantity stops decreasing and the equation of state stiffens, provided the mean-field self-interaction potential rises sharply in a narrow vicinity of the values of mean fields corresponding to nucleon densities nn∗>n0, where n0 is the nuclear saturation density. As a result the limiting neutron star mass increases. This procedure offers a simple way to stiffen the equation of state at densities above n∗ without altering it at densities nn0. The developed scheme allows a neutron star application of the RMF models, which are well fitted to finite nuclei but do not fulfill the experimental constraint on the limiting neutron star mass. The exemplary application of the method to the well-known FSUGold model allows us to increase the limiting neutron star mass from 1.72M to M≥2.01M. ©2015 American Physical Society.
The equation of state of cold baryonic matter is studied within a relativistic mean-field model with hadron masses and coupling constants depending on the scalar field. All hadron masses undergo a universal scaling, whereas the couplings are scaled differently. The appearance of hyperons in dense neutron star interiors is accounted for, however the equation of state remains sufficiently stiff if the reduction of the ϕ meson mass is included. Our equation of state matches well the constraints known from analyses of the astrophysical data and particle production in heavy-ion collisions. © 2015 The Authors.
We study viscosity of the neutron star matter and r-mode instability in rotating neutron stars. Contributions to the shear and bulk viscosities from various processes are calculated accounting for in-medium modifications of the nucleon-nucleon interaction. A softening of the pion mode at densities larger than the nuclear saturation density n0 and a possibility of the pion condensation at densities above 3n0 are included. The neutron-neutron and proton-proton pairings are incorporated where necessary. In the shear viscosity we include the lepton contribution calculated taking into account the Landau damping in the photon exchange, the nucleon contribution described by the medium-modified one-pion exchange, and some other terms, such as the novel phonon contribution in the 1S0 superfluid neutron phase and the neutrino term in the neutrino opacity region. The nucleon shear viscosity depends on the density rather moderately and proves to be much less than the lepton term. On the contrary, among the terms contributing to the bulk viscosity, induced by the delay of the relaxation of lepton concentrations in the star matter perturbed by the r-modes, the term from the two-nucleon medium-modified Urca reactions possesses strongest density dependence (rising by several orders of magnitude for massive stars) because of the pion softening. Also, contributions to the bulk viscosity arising from other reactions induced by charged weak currents, e.g., in the Urca processes on a pion condensate and in direct Urca processes, are included. The radiative bulk viscosity induced by charged and neutral weak currents in the region of the neutrino transparency of the star is also calculated accounting for in-medium effects. We exploit the equation of state, which is similar to the Akmal-Pandharipande-Ravenhall equation of state up to 4n0, but is stiffer at higher densities, producing the maximum neutron star mass compatible with observations. The direct Urca processes do not appear up to 5n0 (corresponding to the star mass M≃1.9M?). Computed with account of in-medium effects, the frequency boundary of the r-mode stability for the stars with the mass ?1.8M? proves to be above the frequencies of all rotating young pulsars. However, none of the conventional contributions to the viscosity are able to explain the stability of rapid rotation of old recycled pulsars in x-ray binaries. To solve this problem we propose a novel efficient mechanism associated with the appearance of condensates of low-lying modes of bosonic excitations with finite momentum and/or with an enhancement of the inhomogeneous pion/kaon condensates in some parts of the star, if the angular velocity exceeds a critical value.
Simple analytical formulas are derived for calculation of the electric field potential distribution in the magnetic pre-layer and the Debye layer near the plasma facing surfaces. It is shown that the calculated potential profiles are in good agreement with the dependences of the potential distribution on the magnetic field inclination obtained by solving the magnetic hydrodynamic (MHD) equations and modeling using the PIC code SPICE2. Dependences of the angular distribution of ions incident on the surface of plasma facing elements on the magnetic field inclination are obtained. Results of calculations demonstrate that the surface areas, on which the magnetic field is incident at sliding angles, are critical from the viewpoint of the increase of sputtering. © 2015 Springer Science+Business Media New York
Cosmological implications of Higgs field fluctuations during inflation are considered. This study is based on the Standard Model and the standard quadratic model of chaotic inflation where the Higgs field is minimally coupled to gravity and has no direct coupling to the inflaton. In the Standard model the renormalisation group improved effective potential develops an instability (an additional minimum and maximum) at large field values. It is shown that such a new maximum should take place at an energy scale above 1014GeV, otherwise a universe like ours is extremely unlikely. The extension to the case of the Higgs field interacting with the inflaton field is discussed. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA.
We construct explicit examples of globally regular static, spherically symmetric solutions in general relativity with scalar and electromagnetic fields describing traversable wormholes with flat and AdS asymptotics and regular black holes, in particular, black universes. (A black universe is a regular black hole with an expanding, asymptotically isotropic space-time beyond the horizon.) The existence of such objects requires invoking scalars with negative kinetic energy (“phantoms, ” or “ghosts”), which are not observed under usual physical conditions. To account for that, the so-called “trapped ghosts” were previously introduced, i.e., scalars whose kinetic energy is only negative in a restricted strong-field region of space-time and positive outside it. This approach leads to certain problems, including instability (as is illustrated here by derivation of an effective potential for spherical pertubations of such systems). In this paper, we use for model construction what we call “invisible ghosts, ” i.e., phantom scalar fields sufficiently rapidly decaying in the weak-field region. The resulting configurations contain different numbers of Killing horizons, from zero to four. © 2015, Pleiades Publishing, Ltd.
The short review of art of state of research in Russian Federation in the field of plasma surface interactions (PSI) related to the problems of plasma-faced materials in controlled fusion devices is presented. The most activity in this field in RF is concentrated on the theoretical, computer and experimental simulations of processes taking place at plasma and its components interactions with condensed matter. The main recent results in PSI obtained in RF are shortly listed including studies of elementary processes accompanied steady state plasma interactions with materials and components as well as results obtained during high power pulsed plasma simulations of transients and disruptions in tokamaks. Detailed list of recent publications is also presented. © 2015 The Authors.
The short review of art of state of research in Russian Federation in the field of plasma surface interactions (PSI) related to the problems of plasma-faced materials in controlled fusion devices is presented. The most activity in this field in RF is concentrated on the theoretical, computer and experimental simulations of processes taking place at plasma and its components interactions with condensed matter. The main recent results in PSI obtained in RF are shortly listed including studies of elementary processes accompanied steady state plasma interactions with materials and components as well as results obtained during high power pulsed plasma simulations of transients and disruptions in tokamaks. Detailed list of recent publications is also presented. © 2015 The Authors.
X-ray diffraction with synchrotron radiation has been used for comparative analysis of crystal structure evolution in Ln(2)Hf(2)O(7) (Ln = Sm-Dy) complex oxides with a fluorite-pyrochlore structure, synthesized by isothermal annealing of mixed hydroxides. It has been shown that heat treatment of the precursor in the temperature range 600-700A degrees C initiates the formation of nanocrystallites with a fluorite structure. Long-range cationic ordering of the pyrochlore type appears in Ln(2)Hf(2)O(7) (Ln = Sm-Tb) samples once a definite crystal size has been achieved at temperatures a parts per thousand yen1200A degrees C. In Dy2Hf2O7 samples, a defect fluorite structure persists in the entire range of heat-treatment temperatures.
Ablation of a bulk Ti target by 10ps laser pulses in water is experimentally studied in external DC electric field. It is demonstrated that both lateral size of nanostructures (NS) on Ti surface and their density depend on the electric field applied to the target. Scanning Electron Microscopy of NS reveals the shift of their size distribution function toward larger sizes with applied field (cathodic bias, 25V DC). Density of mushroom-like NS with applied electric field amounts to 1010 cm-2. X-ray diffraction of generated nanoparticles (NPs) shows difference in the crystallographic structure of NPs of non-stoichiometric Ti oxides generated with and without electric field. This conclusion is corroborated with the optical absorption spectroscopy of obtained colloids. Transmission Electron Microscopy of NPs also shows difference in morphology of particles produced with and without cathodic bias. The results are interpreted on the basis of instability
