The RBC publication requested the opinion of MEPhI scientists regarding the LUX-ZEPLIN (LZ) experiment, which is being conducted at a depth of almost one and a half kilometers in a former gold mine in the US state of South Dakota. Reports have emerged that American scientists have detected a possible signal of dark matter. Below, we publish a detailed comment from Maxim Khlopov, a professor at the Department of Elementary Particle Physics at MEPhI, and a chief researcher at the Space Research Laboratory of Southern Federal University.

The world’s largest dark matter detector. Photo:news.fnal.gov

- Could you please tell us how you would evaluate the results of this experiment?

- The negative results of the search for massive weakly interacting particles of dark matter (WIMP — Weakly Interacting Massive Particles) appear to indicate that its nature is not WIMP‑based, so the results of this experiment may be the first sign of a shift to a different approach in interpreting the results of searches for dark matter in underground experiments. The LZ experiment recorded a single event, so it is hardly possible to speak of the statistical significance of the result. However, even a single such event is difficult to explain in terms of the WIMP effect, while our interpretation in terms of dark atoms (alpha‑particle nuclei whose electric charge is compensated by a hypothetical very heavy multi‑charged lepton) in the DAMA experiment at the Gran Sasso Underground Laboratory (where, over the past 30 years, the effect of hidden mass has been recorded with a very high level of statistical significance) can naturally explain this result.

- Could you explain in simple terms what dark matter theoretically could be? What are the chances of getting closer to detecting it?

- I prefer to use the term “hidden mass,” which has a historical precedent in Russian scientific literature. The body of data from precision cosmology indicates that the hidden mass of galaxies and their clusters must be five times greater than the mass of ordinary matter. Its physical nature must be linked to the existence of new forms of stable matter — from mirror images of ordinary particles (possessing only gravitational interaction with ordinary matter) to macroscopic objects such as primordial black holes. All these candidates have a fundamental basis in extensions of the set of fundamental particles and their interactions proposed to solve the problems of the standard model of elementary particles. The heavy, multi‑charged stable lepton, assumed in the dark atom model, is related to the possible composite nature of the Higgs boson — it may be a bound state of its charged constituents. Research into dark matter depends on its predicted properties, and it is possible that dark matter in the form of dark atoms was already detected and experimentally confirmed 30 years ago in the DAMA/NaI and DAMA/LIBRA experiments, and now it will be detected in other experiments as well.

- What could the potential discovery of dark matter offer to science and the world?

- Cosmological data indicate that we know and use the physical properties of less than 5% of the material composition of the Universe. The physics of hidden mass is associated with new forms of matter and new forces of Nature, so its discovery will make it possible to gain control over them. If hidden mass is explained by dark atoms, new types of nuclear transformations of this electrically neutral form of nuclear matter will be revealed. 

Earlier, in an interview with Maxim Khlopov, his concept of “dark atoms” was described in detail.