What's Happening

Young scientists of MEPhI about work in ATLAS

29.06.2017

MEPhI ATLAS group is among the youngest not only in university, but among the most of ATLAS collaborations. That provided for a big inflow of students from chair №40 «Physics of elementary particles» for past five years. Thanks to young scientists the group managed to expand their research and foothold at once in several directions of scientific activity on LHC. Now the staff works in areas, related with development of new and support of acting detectors in ATLAS, in physical research of proton-proton and ion-ion collisions, and also in IT areas. All this favorably impacted on the image not only of the chair of physics of elementary particles, but the whole university.

For the past several years staff from MEPhI ATLAS group annually represented university on several largest conferences on physics of high energies with reports from collaboration. At that same time the share of our authors in official collaboration of the ATLAS experiment grows. These achievements are the result of successful and fruitful work of our young specialists in collaboration.

The head of MEPhI ATLAS group Anatoliy Romaniuk told us about successes and plans of the group, and young scientists spoke about their scientific research, plans on future, studies in graduate school and experience of work in big collaborations.

From left to the right: Daniil Ponomarenko, Konstantin Vorobiev, Nikita Belyaev, Mikhail Borodin, Nadezhda Proklova, Anatoliy Romaniuk, Eugeniy Shulga, Petr Teterin, Dimitriy Krasnopevtsev, Eugeniy Soldatov.

 

Anatoliy Samsonovich, PhD in physics and maths, professor at chair №40

- Are there many young employees in MEPhI ATLAS group? What recent results of the group can you note?

 - In our group now practically all are young. There was such a period, when young people did not want to go in our specialty, i.e. in physics of high energies. Just the priorities were different for them. It's true that work in this area of science is hard and salaries are low. It partially is true now, but interest is bigger, partially because of LHC. We do very much for popularization in these directions. It was hard for young people at first. Preparation at MEPhI was not sufficient to join work effectively. It was necessary to actively grow, and now some already get very interesting results. We have a group, which does research of vector bosons’ production in proton-proton collisions. The group already published several articles, which for the first time were reviewing processes of interaction of vector bosons, sensitive to new physics. If such physics exists, in these processes you can observe deviations from predictions of Standard Model in certain range of energies of particles. They did good work, statistically significant deviations were  not found, and articles present restrictions on options, describing physics beyond SM. Here it is necessary to continue research at higher energies, because already in these works there was small excess compared with predictions of the theory. We talk now only about several events, but it is necessary to continue and understand what the matter is: this statistical fluctuation or new effect.

The second achievement, which seems important, is results on search of dark matter. We consider hypothesis about compositional dark matter, which represents a particle, for example with charge of two, associated with helium nucleus. Helium nucleus is positively charged, but hypothetical particle - negatively. The substance, formed after their association, practically does not interact with anything. In our research we already managed to install strict restrictions on mass of such particles. In case, if we do not find such particles in statistics of this and next years, we may talk about closing this hypothesis. For fundamental science this is an important result.

- Tell us, please, about contribution of Russian universities in work of LHC.

 - At the creation of LHC Russia did very much for this project to take place. For example, in Novosibirsk there were made more than thousand magnets for CERN. On each experiment of LHC there is a part, which was made in the RF. For example, calorimeter in experiment CMS is from special heavy glass, which was produced in Bogoroditsk. Hadron calorimeter in ATLAS was in large degree made in Dubna. Our group provides support for the detector, which was ideologically born in MEPhI. Boris Dolgoshein was the head of these developments. I remember, in 1989 he invited me and said: «There is a task. Will it be interesting for you?». The project seemed very promising. We then only were thinking of Transition radiation tracker (TRT). Boris Dolgoshein could make creative atmosphere. He wanted to work and check various ideas, even if they seemed complex in implementation. After many efforts we then have developed proposal on creation of TRT. The proposal was approved and building process began. Scientists from CERN have also made huge contribution in creation of detector from the engineering viewpoint. Assembly of the detector was conducted in Russia and in America. Our group conducted scientific research to ensure recommendations. We developed thin-walled plastic proportional tubes – this is an absolutely unique detector element. Such tubes in detector count for 300 thousand. These tubes are not only radiation resistant. Inside them there occur complex electrochemical processes, which destroy usual materials. As a result of processes, related with ionization of working gas inside tubes, our detectors produce five kilowatt of energy. With the use of this technology there was created also a detector of transitional radiation for another experiment, AMS, which now flies in space.

- What is planned at MEPhI ATLAS group within a year?

 - The most important task is to do so, that our appliance, track detector of transitional radiation, worked  stable and allowed to continue research, for which it is intended, in complex for its work conditions. Further conditions will be tougher and we must find a method, to ensure quality physical data. Another direction is the analysis of physical data. Now statistics is gathered, and I think our group has all chances to get very interesting results in those directions of analysis, where we work.

Nikita belyaev, graduate student at MEPhI chair №40

- At the moment you spend a lot of time in room of ATLAS experiment management. What is your work about?

- This kind of work takes quite a lot of time. It's an important task, after all it is directed on support of working capacity in all experiment. I watch as internal detector of ATLAS experiment works and how data is gathered. In domestic detector we register tracks of charged particles. It is from two semiconductor detectors and tracking detector of transitional radiation. Our group from MEPhI is responsible for TRT support. The intensity of work strongly depends on time of the year. Usually in the beginning of the year accelerator does not work, there are no proton collisions, and therefore we watch only for technical state of the detectors. This is, usually, very serene time. At the moment, when protic beams return in the ring of accelerator, and data gathering begins. There appears need to watch for configuration a beam, how detectors react to the reset, check if there is interruption with supply. When situation stabilizes and usual record of information goes on, there may be a break.

 -What attracts you in work at room management?

- Foremost, this is interesting. You can relate directly to experiment. My theoretical research is impossible to compare with experimental. This is a very exciting feeling, when you see, how mass peak of Z bosons is gained.  In this minute an experiment is conducted, results of which depend on you as well. Our responsibility also includes update of calibration in dependence from conditions of collection of data, during appearance of stable beams to derive detectors in working mode etc. I also think, very important is communication with other experts, who work close. During such discussions you gather experience, this is always useful in work and studies.

Eugeniy Soldatov, PhD in physics and maths, assistant at MEPhI chair №40

- Tell us, please, about your work in ATLAS collaborations.

- We quite recently released an interesting article together with colleagues from the US. This study is devoted to associated production of Z bosons with one or with two photons. We investigated processes, where Z boson breaks down to a pair of charged leptons (electrons, muons) or to a pair of neutrino. The processes with one photons have been studied earlier, with participation of our group, but production with two gamma quanta on LHC was studied for the first time. We reached high accuracy in measurement of sections for processes with one photon and have shown, that deviations from predictions of Standard Model were not observed. We managed to put most strict restrictions on new physics – expansion of existing theory, in which  there are abnormal interactions of three neutral calibration bosons.  As for channel with two photons, here statistics was small, but even this turned out enough, to notice small deviations from predictions of SM at large energies with invariant mass of two photons. These deviations have low significance, therefore we can't talk about discovery. But we hope to continue research on new data, and by 2019, I think, we may expect at least one interesting article. Besides, our group separately does research of rare type of associate production of Z boson and photon, namely together with two hadron jets. This is a very rare process, which became available for study only on LHC experiments. Associate production of Z boson and photon can take place with the help of several mechanisms: strong or electroweak interaction. First process has greatest probability, however with the help of selection events with hadron jets we can highlight second component. Our group from MEPhI therein study also worked with foreign colleagues. The received results were already sent for printing. The research, completed by employees of MEPhI in framework of this collaborations and related with study of associate production of Z boson and photon with subsequent collapse of Z boson in neutrino, is first in world. But there are competitors, foremost from experiment CMS. Now we start a new and more detailed study of this process on data from proton-proton collisions with energy of 13 TeV.

 - You have recently defended candidate thesis, what was most complex for you?

- I have done quite a big work in research and document preparation. The positive side is you perfect your language, and this helps then with applications for grants, because they ask about that same: novelty, practical significance, urgency of research.

- What expects young candidate of sciences after defense?

 - Foreign experience says that after defense you are looking for postdoctoral position. You can charge management of group of students and graduate students. A possible option is, when you work as a link from professor to his graduate students, this in some sense pyramidal model. In Russian system we now get closer to the same. I would try to guide a group, this is interesting. At present moment I plan to continue to apply for grants and participate in development of our MEPhI ATLAS group, its subgroup, which does study of joint production of vector bosons. In Russia this is not easy. Here more want fast results from project, from research.

Nadezhda Proklova, graduate student at MEPhI chair №40

- Tell us, please, about your experience of studying at once in two PhDs.

- When i finished MEPhI magistracy, I had a choice: go in postgraduate there or try to find another option. My priority, certainly, was postgraduate studies in MEPhI, but competition was big, and I was afraid not to pass. Therefore, I also sent applications in foreign colleges for position of PhD. I got a reply from university of Nijmegen in Netherlands and in which has a branch Nikhef (largest national research institute on subatomic physics), with an option to join graduate school. Then there was a compulsory agreement between two universities. According to this agreement I study mostly at MEPhI, but necessarily three months in year should stay in Netherlands. Defense is expected to take place at university of Nijmegen with direct participation of delegates from MEPhI. I have two scientific supervisors now: one from MEPhI, another from institute of Nijmegen. It is difficult, and interesting simultaneously.

- With what is connected your work connected?

 - My work is connected with search of Higgs boson. I will explore channel of  disintegration of Higgs boson, in which appears Z boson with associate photon. This is a very rare process and will be fixed only on data and of 2017-2018. If all goes as planned, we will be able to confirm prediction of SM with more high precision.

- In framework its work in collaborations you helped to prepare detector for launch. How did this go?

- Yes, this year i took part in preparation of ATLAS to a new session of collisions. We went down and crawled inside detector with such small vacuum cleaners and cleaned everything inside, worked two days in several groups, each group four hours. ATLAS detector is huge, and it is necessary check each millimeter. This is importantly, because a small thing left can knock out work of the whole detector. For me it was very interesting to look on detector from inside. This is a very large installation - size of many-storey house. Inside everything looks as in space ship. It is nice to have such possibility to get close to the very experiment.

 

 

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