The work presents an analysis of the rigidity spectrum of Forbush decreases observed over 24–25 Solar Cycles. The URAGAN muon hodoscope and Moscow neutron monitor data were used as information on cosmic ray variations. To determine the rigidity spectrum of Forbush decreases, the median rigidity method was utilized. The dependence of the spectrum index on the phase of solar activity and the polarity of the general magnetic field of the Sun is discussed.

The Spin Physics Detector collaboration proposes to install a universal detector in the second interaction point of the NICA collider under construction (JINR, Dubna) to study the spin structure of the proton and deuteron and other spin-related phenomena using a unique possibility to operate with polarized proton and deuteron beams at a collision energy up to 27 GeV and a luminosity up to 10^32 cm^-2 s^-1. As the main goal, the experiment aims to provide access to the gluon TMD PDFs in the proton and deuteron, as well as the gluon transversity distribution and tensor PDFs in the deuteron, via the measurement of specific single and double spin asymmetries using different complementary probes such as charmonia, open charm, and prompt photon production processes. Other polarized and unpolarized physics is possible, especially at the first stage of NICA operation with reduced luminosity and collision energy of the proton and ion beams. This document is dedicated exclusively to technical issues of the SPD setup construction.

BM@N (Baryonic Matter at Nuclotron) is the first experiment operating and taking data at the Nuclotron/NICA ion-accelerating complex.The aim of the BM@N experiment is to study interactions of relativistic heavy-ion beams with fixed targets. We present a technical description of the BM@N spectrometer including all its subsystems.

The data of cosmic ray NEVOD-DECOR experiment on the investigation of inclined muon bundles for a long time period (May 2012 - March 2021) are presented. The analysis showed that the observed intensity of muon bundles at primary cosmic ray energies of about 1 EeV and higher can be compatible with the expectation in frame of widely used hadron interaction models only under the assumption of an extremely heavy mass composition. This conclusion is consistent with data of several experiments on investigations of muon content in air showers, but contradicts the available fluorescence data on X_{max} Xmax which favor a light mass composition at these energies. In order to clarify the nature of the "muon puzzle", investigations of the muon bundle energy deposit in the detector material were carried out. For the first time, experimental estimates of the average energy of muons in the bundles of inclined air showers initiated by primary particles with energies from 10 to 1000 PeV have been obtained.

First physics results of the BM@N experiment at the Nuclotron/NICA complex are presented on π+ and K+ meson production in interactions of an argon beam with fixed targets of C, Al, Cu, Sn and Pb at 3.2 A GeV. Transverse momentum distributions, rapidity spectra and multiplicities of π+ and K+ mesons are measured. The results are compared with predictions of theoretical models and with other measurements at lower energies.

NEVOD-DECOR is the unique experiment where systematic studies of cosmic ray muon bundles in a wide range of zenith angles and, accordingly, the energies of primary cosmic rays are carried out. Impressive experimental material (more than 100 thousand events) has been accumulated over a long time period from May 2012 to December 2022. The earlier developed method of local muon density spectra allows us to compare experimental data on muon bundles with the results of the EAS muon component simulations. The analysis showed that the observed intensity of muon bundles at primary cosmic ray energies of about 1 EeV and higher can be compatible with the expectation (in frame of widely used hadronic interaction models) only under the assumption of an extremely heavy mass composition. It is consistent with data of several other experiments on investigations of air shower muon content, but contradicts the available measurements of the depth of the shower maximum in the atmosphere by means of fluorescent technique, which favor a light mass composition at these energies. This probably leads to the need to revise the existing hadronic interaction models.

Results are presented from measuring the energy characteristics of muon bundles in inclined extensive air showers in the NEVOD-DECOR experiment. Estimates of the average energy of muons in the bundles are obtained in the 10 to 1000 PeV range of primary particle energies and compared to values calculated under different assumptions about the composition of cosmic radiation and models of hadronic interactions. An excess of experimental values of the average muon energy relative to calculations is found for high local densities corresponding to primary particle energies above 100 PeV.

The Nuclotron-based Ion Collider fAcility (NICA) is under construction at the Joint Institute for Nuclear Research (JINR), with commissioning of the facility expected in late 2022. The Multi-Purpose Detector (MPD) has been designed to operate at NICA and its components are currently in production. The detector is expected to be ready for data taking with the first beams from NICA. This document provides an overview of the landscape of the investigation of the QCD phase diagram in the region of maximum baryonic density, where NICA and MPD will be able to provide significant and unique input. It also provides a detailed description of the MPD set-up, including its various subsystems as well as its support and computing infrastructures. Selected performance studies for particular physics measurements at MPD are presented and discussed in the context of existing data and theoretical expectations.

The Experimental complex NEVOD includes several different setups for studying various components of extensive air showers (EAS) in the energy range from 10 10 to 10 18 eV. The NEVOD-EAS array for detection of the EAS electron-photon component began its data taking in 2018. It is a distributed system of scintillation detectors installed over an area of about 10 4 m 2 . A distinctive feature of this array is its cluster organization with different-altitude layout of the detecting elements. The main goal of the NEVOD-EAS array is to obtain an estimation of the primary particle energy for events measured by various detectors of the Experimental complex NEVOD. This paper describes the design, operation principles and data processing of the NEVOD-EAS array. The criteria for the event selection and the accuracy of the EAS parameters reconstruction obtained on the simulated events are discussed. The results of the preliminary analysis of experimental data obtained during a half-year operation are presented.

Data of the NEVOD-DECOR experiment on investigations of inclined cosmic ray muon bundles for a long time period (May 2012 – March 2021) are presented. Their comparison with the results of calculations based on simulations of EAS muon component allows one to study the behavior of the energy spectrum and mass composition of primary cosmic rays and/or to check the validity of hadron interaction models in a wide energy range from about 10^16 to more than 10^18 eV. The analysis showed that the observed intensity of muon bundles at primary particle energies of about 10^18 eV and higher can be compatible with the expectation only under the assumption of an extremely heavy mass composition of cosmic rays. This conclusion is consistent with data of a number of other experiments investigating the muon component of air showers at ultra-high energies. On the contrary, measurements of the depth of the shower maximum in the atmosphere (Xmax) in the experiments using air fluorescence technique favor a light mass composition of primary cosmic rays at these energies. This contradiction (so-called “muon puzzle”) cannot be resolved without serious changes of the existing hadron interaction models.

MegaScience projects are unique scientific experiments and facilities of a large scale that were initiated to allow to go beyond modern knowledge in the field of fundamental sciences and open up new opportunities in the technological development. The implementation of such complex projects requires the combined efforts of many scientists and institutions at national and multinational level. The paper presents an analysis of new trends in the training of researchers in the field of elementary particle physics, high energy physics and cosmophysics for research projects and experiments at MegaScience facilities. The authors consider the vast experience of extensive training of MEPhI students for fundamental science and analyzed new approaches to organizing the individual training of researchers at the university. The result of this work was presented and discussed within the proceedings of the Third Conference “Personnel training and legal support for the implementation of scientific projects of the Mega-science class” organized by National Research Nuclear University MEPhI and Kutafin Moscow State Law University on 17 June 2021.

Results from an analysis of URAGAN muon hodoscope data are used to identify effects observed in connection with thunderstorms recorded above and at considerable distances from the setup. These include quasiperiodic disturbances of the muon flux characteristics, reductions in the count rate, and changes in the muon flux anisotropy. An algorithm is created for selecting thunderstorm events that have a response in the muon data. It is found that abrupt drops in the muon count rate are not directly related to precipitation.

Muonography is an analog of other similar concepts such as X-ray radiography, electronography, neutronography, etc. based on the detection of penetrating radiation whose interaction with objects under study causes changes in the initial flux of the used particles. Unlike all other ‘‘graphies’’ which use artificially formed particle fluxes, muons are of natural origin, since they are formed as a result of interactions of primary cosmic rays with the nuclei of atoms in the atmosphere. Since muons keep well the direction of motion of primary particles, muon flux allows studying of disturbances in the heliosphere and magnetosphere of the Earth which lead to variations of the flux of primary cosmic rays. Also, disturbances in the atmosphere directly affect the muon flux, thus it can be used to study atmospheric processes. The paper considers the main ideas of the method of muonography, as well as the examples of its application for studying various processes and phenomena in the heliosphere, magnetosphere and atmosphere of the Earth. In frames of the further development of muonography, we discuss the expediency of creating a network of muon hodoscopes in the Russian Federation for early detection of hazardous processes and phenomena over its territory.

Using muon flux characteristics obtained by the URAGAN muon hodoscope, 235 thunderstorm event candidates were identified in 2014–2020, 211 of them were accompanied by thunderstorm cell detection. Comparative visualization of weather maps and muonographs (‘‘muon snapshots’’) for these events is presented. Possible explanations for the observed effect are discussed. Temporal distributions of the thunderstorm event candidates and muon flux wavelet analysis results are presented with discussion of the further prospects for the research.

An analysis is performed of the diurnal variation in cosmic-ray muons measured with the URAGAN muon hodoscope from 2007 to 2019. Characteristics are given of the yearly average diurnal variation in the count rate in several zenith-angle intervals. The results are compared to the diurnal variations in the count rate of neutrons from ten neutron monitors.

The high-speed solar wind is one of the main reasons for disturbances in the interplanetary magnetic field during years of low solar activity. These disturbances lead to modulations of cosmic ray fluxes that penetrate the Earth’s magnetosphere. This work presents results from analyzing disturbances in the angular distribution of cosmic rays in the GSE system registered by the URAGAN muon hodoscope for years of geomagnetic disturbances during the periods of solar activity minima in 2009–2010 and 2018–2019.