Berdugo J. «Latest results of the Alpha Magnetic Spectrometer on the International Space Station» Вестник Московского университета. Серия 3: Физика. Астрономия, № 2, http://vmu.phys.msu.ru/toc/2022/2 (2022)

The Alpha Magnetic Spectrometer (AMS) is a general-purpose high-energy particle detector that was deployed to the International Space Station (ISS) on May 19, 2011 to perform a unique long duration mission of fundamental physics research from space. Among the scientific goals of AMS are the search for Dark Matter and Antimatter, the study of the propagation of cosmic rays and the exploration of new scientific phenomena that cannot be achieved on ground-based experiments. After ten years of operation in space, AMS has collected more than 180 billion cosmic ray events and provided accurate measurements of electrons, positrons, protons, antiprotons, and nuclei with energies of several TeV during nearly a complete solar cycle

Dolgov A.D. «Antistars in the Galaxy» Вестник Московского университета. Серия 3: Физика. Астрономия, № 2, http://vmu.phys.msu.ru/toc/2022/2 (2022)

Possible existence of antimatter in our Galaxy, in particular of antistars is discussed and the mechanism of their creation is described.

Palma F., Martucci M., Sotgiu A. «Status of the CSES-Limadou space mission after three years in flight» Вестник Московского университета. Серия 3: Физика. Астрономия, № 2, http://vmu.phys.msu.ru/toc/2022/2 (2022)

The China Seismo-Electromagnetic Satellite (CSES-01), in orbit since February 2, 2018, is the first element of an extended constellation of LEO (Low-Earth Orbit) satellites, dedicated to monitoring perturbations of electromagnetic fields, plasma and charged particle fluxes induced by natural sources and artificial emitters in the near-Earth space. The Limadou Collaboration, which is the Italian branch of the aforementioned mission, designed and built one of the nine payloads on board the satellite, i.e. the High-Energy Particle Detector (HEPD-01). HEPD-01 is optimized to detect electrons (3–100 MeV), protons (30–300 MeV), and light nuclei (up to a few hundreds of MeV) with a high energy resolution and a wide angular acceptance. The very good capabilities in particle identification together with the orbit of CSES01 make HEPD-01 well suited for measuring galactic particle fluxes and their solar modulation, and also for space weather purposes. In this work, we present some results obtained with HEPD-01 during the first three years in flight, including the observation of the August 2018 geomagnetic storm and the galactic cosmic-ray hydrogen spectra in the 40–250 MeV range.

Chakraborti M., Heinemeyer S., Saha I. «SUSY Dark Matter Direct Detection Prospects based on (g – 2)_μ» Вестник Московского университета. Серия 3: Физика. Астрономия, № 2, http://vmu.phys.msu.ru/toc/2022/2 (2022)

An electroweak (EW) sector of the Minimal Supersymmetric Standard Model (MSSM) with masses of a few hundred GeV can account for variety of experimental data, assuming the lightest neutralino to be the lightest supersymmetric (SUSY) particle: the non-observation at the LHC, searches owing to their small production cross sections, the results for the (upper limit of the) Dark Matter (DM) relic abundance and the DM Direct Detection (DD) limits. Such a light EW sector can in particular explain the reinforced 4.2 σ discrepancy between the experimental result for (g – 2)_μ, and its Standard Model (SM) prediction. Using the improved limits on (g – 2)_μ, we review the predictions for the future prospects of the DD experiments. This analysis is performed for several different realizations of DM in the MSSM: bino, bino/wino, wino and higgsino DM. We find that higgsino, wino and one type of bino scenario can be covered by future DD experiments. Mixed bino/wino and another type of bino DM can reach DD cross sections below the neutrino floor. In these cases future collider experiments must cover the remaining parameter space.

Alemanno F. «The DAMPE space mission: status and main results» Вестник Московского университета. Серия 3: Физика. Астрономия, № 2, http://vmu.phys.msu.ru/toc/2022/2 (2022)

The DArk Matter Particle Explorer (DAMPE) is a satellite orbiting at 500 km altitude in a Sun-synchronous orbit, taking data from its launch on December 17th, 2015. DAMPE is composed by several particle detectors, working together to identify incoming particles and nuclei. Main goals of the DAMPE space mission are: study of cosmic-rays and electron-positron energy spectra, gamma-ray astronomy, and indirect dark matter search. The main results achieved by DAMPE will be presented in this work.

Alexandrov A. «Directional Dark Matter Search with NEWSdm» Вестник Московского университета. Серия 3: Физика. Астрономия, № 2, http://vmu.phys.msu.ru/toc/2022/2 (2022)

Despite significant searches for dark matter, experiments have so far produced no results. The latest generation of nuclear emulsions, Nano Imaging Trackers (NIT), has nanometric precision and was created specifically for a directional DM search. The NIT emulsion is used as both the Weakly Interactive Massive Particle (WIMP) target and the nanometric-accuracy tracking device in the Nuclear Emulsion WIMP Search with Directional Measurement (NEWSdm) experiment, which is housed in the Gran Sasso underground laboratory in Italy. Detector design, the super-resolution readout technology, expected backgrounds, physics potential, and near-future plans are all discussed here.

Arbuzova E. «New Options for SUSY-kind Dark Matter» Вестник Московского университета. Серия 3: Физика. Астрономия, № 2, http://vmu.phys.msu.ru/toc/2022/2 (2022)

In the conventional cosmology masses of the stable supersymmetric relics, candidates for the dark matter (DM) particles, should be typically below 1 TeV. This is in conflict with the LHC bounds on the low energy SUSY. However, in R2-gravity the masses of the stable particles with the interaction strength typical for SUSY could be much higher depending upon the dominant decay mode of the scalaron. We discuss the bounds on the masses of DM particles for the following dominant decay modes: to minimally coupled massless scalars, to massive fermions, and to gauge bosons.

Bernabei R., Belli P., Bussolot «Recent results from DAMA/LIBRA and comparisons» Вестник Московского университета. Серия 3: Физика. Астрономия, № 2, http://vmu.phys.msu.ru/toc/2022/2 (2022)

The long-standing model-independent annual modulation effect measured by DAMA deep underground at the Gran Sasso National Laboratory (LNGS) of the I.N.F.N. using different experi- mental configurations is summarized also including the results of two new annual cycles collected by DAMA/LIBRA-phase2; the total exposure of DAMA/LIBRA–phase2 over 8 annual cycles is 1.53 ton·yr. The evidence of a signal that meets all the requirements of the model independent Dark Matter (DM) annual modulation signature is further confirmed at 11.8 σ C.L. in the energy region (1–6) keV. In the energy region between 2 and 6 keV, where data are also available from DAMA/NaI and DAMA/LIBRA–phase1, the achieved C.L. for the full exposure (2.86 ton·yr) is 13.7 σ.

Busoni G. «Capture of Dark Matter in Neutron Stars» Вестник Московского университета. Серия 3: Физика. Астрономия, № 2, http://vmu.phys.msu.ru/toc/2022/2 (2022)

The extreme conditions in Neutron Stars make them ideal test facilities for fundamental inter- actions. A Neutron Star can capture Dark Matter via scattering. As a result of the scattering, Dark Matter kinetic energy is transferred to the star. An observational consequence of this can be the warming of old neutron stars to near-infrared temperatures. Different approximations or simplifications have been applied to previous analyses of the capture process. In this article, we summarise a significantly improved treatment of Dark Matter capture, which properly accounts for all relevant physical effects over a wide range of Dark Matter masses. Among them are gravitational focusing, a fully relativistic scattering treatment, Pauli blocking, neutron star opacity and multiple scattering effects. This paper cites general expressions that allow the capture rate to be computed numerically, and simplified expressions for particular types of interactions or mass regimes, which greatly increase the efficiency of computation. As a result of our method, we are able to model the scattering of Dark Matter from any neutron star constituent as well as the capture of Dark Matter in other compact objects. Our results are applied to scattering of Dark Matter from neutrons, protons, leptons and exotic baryons. For leptonic targets, we found that a relativistic description is essential. In our analysis of the capture of Dark Matter in Neutron Stars, we include two important effects that are generally ignored by most studies. Because the scattering of Dark Matter with nucleons in the star exhibits large momentum transfers, the nucleon structure must be considered via momentum-dependent hadronic form factors. Moreover, because of the extreme densities of matter inside Neutron Stars, we should consider nucleon interactions instead of assuming all nucleons are a perfect Fermi gas. Taking into account these effects results in a decrease of up to three orders of magnitude in the dark matter capture rate. The potential Neutron Star sensitivity to DM-lepton scattering cross sections is much greater than electron-recoil experiments, particularly in the sub-GeV regime, with a sensitivity to sub- MeV DM well beyond the reach of future terrestrial experiments. We also present results for DM- Baryon scatterings in Neutron Stars, where the sensitivity is expected to exceed that of current DD experiments for spin-dependent cases across the entire mass range, and for spin-independent cases across the high and low mass range.

Belli P., Bernabei R., Caracciolo V. «Crystal scintillators for the Dark Matter directionality approach» Вестник Московского университета. Серия 3: Физика. Астрономия, № 2, http://vmu.phys.msu.ru/toc/2022/2 (2022)

Low background anisotropic detectors can offer a unique way to study those Dark Matter (DM) candidate particles able to induce nuclear recoils through the directionality technique. This approach is based on studying the correlation between the nuclear recoils' direction and the Earth motion in the galactic rest frame. Thanks to the anisotropic features of such detectors, a signal, induced by the DM candidates, is expected to change with a particular behaviour as a function of the sidereal time. The ZnWO4 has unique features and it is an excellent candidate for the purposes. Both the light output and the scintillation pulse shape depend on the impinging direction of heavy particles (p, nuclear recoils, etc.) with respect to the crystal axes and can supply two independent modes to study the directionality and to discriminate the radiation (that does not give rise to any anisotropic effects). In this work, the measurements to study the anisotropic response of a ZnWO4 scintillation detector to particles and to nuclear recoils, induced by neutron scattering, are brie γ summarised.

Klasen M. «What a direct neutrino mass measurement might teach us about the dark sector» Вестник Московского университета. Серия 3: Физика. Астрономия, № 2, http://vmu.phys.msu.ru/toc/2022/2 (2022)

Searches for Dark Matter suggest that it couples to ordinary matter only very weakly and possibly only through the Higgs or other scalar bosons. On the other hand, neutrinos might not couple to the Higgs boson directly, but only through a loop of Dark Matter particles, which would naturally explain the small neutrino masses. We demonstrate that current experimental constraints on such a \scotogenic" scenario allow to make the linear dependence of the lightest neutrino mass on the dark sector-Higgs coupling explicit, so that a measurement by the KATRIN experiment would directly determine its value.

Kopylov A., Orekhov I., Petukhov V «PHELEX: Present Status» Вестник Московского университета. Серия 3: Физика. Астрономия, № 2, http://vmu.phys.msu.ru/toc/2022/2 (2022)

The paper reports the latest results obtained in PHELEX. The focus of work is on diurnal variations of the count rate of single electrons emitted from a cathode as a way to prove that the observed effect is really from dark photons. The authors outline their plans for the future.

Dokuchaev V.I. «Visualization of black hole images» Вестник Московского университета. Серия 3: Физика. Астрономия, № 2, http://vmu.phys.msu.ru/toc/2022/2 (2022)

A fast progress in the observational technologies in astrophysics provides the unique possibility for detailed observations of black holes in the nearest future. It would be possible to verify general relativity and its numerous modifications in the strong field limit by using observational data from the advanced cosmic interferometric observatories. We review the modeled images of the rotating black hole in different appropriate cases: the luminous distant background, the thin accreting disk and the luminous moving hot spots in relativistic jets along the black hole rotation axis.

Kim J.E. «Black Hole Information» Вестник Московского университета. Серия 3: Физика. Астрономия, № 2, http://vmu.phys.msu.ru/toc/2022/2 (2022)

Information of a blackhole inside has a long history. After mentioning the original information idea, we show that local gauge invariance can connect the inside information to the outside surface area due to the Sperner's lemma.

Panasenko L. «Gravitational waves over arbitrary background» Вестник Московского университета. Серия 3: Физика. Астрономия, № 2, http://vmu.phys.msu.ru/toc/2022/2 (2022)

Equation for gravitational wave (GW) propagation over arbitrary curved spacetime is derived in the presented work. Two new terms are found which absent in the conventional homogeneous and isotropic Friedmann cosmology. In conclusion we emphasize that these new terms can significantly change the character of solutions and assume that one of the terms may be the cause of relic GW amplitude suppression.

Spirin P. «Gravitational interaction of the cosmic string with pointlike particles» Вестник Московского университета. Серия 3: Физика. Астрономия, № 2, http://vmu.phys.msu.ru/toc/2022/2 (2022)

The gravitational interaction of spinless relativistic particle and infinitely thin cosmic string is considered within the classical linearized-theory framework. We compute the reciprocal action of the particle on the cosmic string. We derive the retarded string's excitation, which includes the longitudinal (with respect to the unperturbed-particle motion) z and totally-transverse (y) string perturbations.

Zakharov A.F. «Orbits of bright stars near the Galactic Center as a tool to test gravity theories» Вестник Московского университета. Серия 3: Физика. Астрономия, № 2, http://vmu.phys.msu.ru/toc/2022/2 (2022)

Precise observations of trajectories of bright stars near the Galactic Center give an opportunity to evaluate the gravitational potential since bounded stars move along the trajectories which are very close to elliptical ones. Since the Sgr A* position is very close to foci of the bound trajectories astronomers conclude that the Newtonian potential is a very good approximation for available observational data. In 2018 (2019) GRAVITY and Keck collaborations found that gravitational redshifts for S2 star near its pericenter passage are fitting by the first post-Newtonian correction of General Relativity (GR). In 2020 the GRAVITY collaboration found that the Schwarzschild precession for S2 star is in accordance with GR predictions. Therefore, GR successfully passed important test for the Galactic Center and astronomers got new confirmations of the universality of gravity law predictions. In last years we considered several versions of alternative theories of gravity and showed that observations of bright stars give an opportunity to constrain parameters of such theories. Choosing suitable models for galactic centers is an extremely important astrophysical task. The Galactic Center is the closest object for astronomers for which a large amount of observational data has been obtained. Observations of the trajectories of bright stars in the vicinity of the Galactic Center have shown that there is a compact distribution of matter, which is interpreted as a supermassive black hole with a mass of the order of M=4:3·10⁶M_⊙. In 2015, Rufini, Arguelles, Rueda (RAR) proposed a model for the distribution of dark matter with a dense core and a diluted halo, and later the authors declared that there is not a supermassive black hole, but a core of dark matter with constant density in the Galactic Center. In 2020–2021, claims were made that the RAR model could better fit the trajectories of bright stars than the traditional model involving a supermassive black hole. The RAR-approach was actively promoted as a reliable model for the Galactic Center. In our work, we showed that the trajectories of stars considered in the framework of the RAR model are elliptical, but the properties of these trajectories are di

Agafonova N., Ashikhmin V., Dobrynina E., Enikeev R., Ryazhskaya O., Shakyrianova I., Yakushev V. «Search for neutrino radiation from the collapse of stellar cores using LVD detector» Вестник Московского университета. Серия 3: Физика. Астрономия, № 2, http://vmu.phys.msu.ru/toc/2022/2 (2022)

The article presents the latest results with the experiment of the Large Volume Detector located in the Gran Sasso Laboratory at the depth of 3650 m.w.e. LVD has been in operation since 1992 on the program a search for neutrino bursts from stellar core colapses, variations of the cosmic ray muon flux, and investigations of background sources at detecting rare events. According to the data of the LVD neutrino telescope for 29 years of operation (1992–2021), an experimental limitation on the frequency of neutrino bursts from gravitational collapses of stars in the Galaxy was obtained: less than 1 event in 12.6 years (f=0.08 year^–1) at a 90% confidence level.

Dvornikov M. «Neutrino oscillations in gravitational fields and astrophysical applications» Вестник Московского университета. Серия 3: Физика. Астрономия, № 2, http://vmu.phys.msu.ru/toc/2022/2 (2022)

The neutrino propagation and oscillations in various gravitational fields are studied. First, we consider the neutrino scattering of a black hole accounting for the neutrino spin precession. Then, we study the evolution of avor neutrinos in stochastic gravitational waves. The astrophysical applications of the obtained results are considered.

Fil'chenkov M., Laptev Yu. «Field Interpretation of General Relativity Revisited» Вестник Московского университета. Серия 3: Физика. Астрономия, № 2, http://vmu.phys.msu.ru/toc/2022/2 (2022)

A field interpretation of General Relativity has been presented for a static field of black holes and de Sitter's vacuum describing dark energy. The gravitational potential satisfies Poisson's equation. Einstein–Hilbert's equations in these cases prove to be superiuous.