Abstract
In this work, we use muon bundles, which are formed in extensive air showers and detected at the ground level, as a tool for searching for anisotropy in high-energy cosmic rays. Such choice ...is explained by the penetrating ability of muons that allows them to retain the direction of primary particles with good accuracy. In 2012–2022, we performed long-term muon-bundle detection with the coordinate-tracking detector DECOR, which is a part of the Experimental Complex NEVOD (MEPhI, Moscow). To search for cosmic-ray anisotropy, muon bundles arriving at zenith angles in the range from 15° to 75° in the local coordinate system are used. During the entire period of data taking, about 14 million of such events have been accumulated. In this paper, we describe some methods developed in the Experimental Complex NEVOD and implemented in our research, including: the method for compensating for the influence of meteorological conditions on the intensity of muon bundles at the Earth’s surface, the method for accounting for the design features of the detector and the inhomogeneity of the detection efficiency for different directions, as well as the method for estimating the primary energies of cosmic rays. Here we present the results of the search for the dipole anisotropy of cosmic rays with energies in the PeV region and also compare them with the results obtained at other scientific facilities.
Underground cosmic-ray experiments, including very large volume neutrino telescopes, depend on a precise description of the interaction cross sections of muons, which can travel large distances ...before reaching the detector. High-energy muons lose their energy almost exclusively via four processes: ionization, electron-positron pair production, bremsstrahlung and inelastic interaction with nuclei. At low energies, ionization is the dominant process, while above energies of about a TeV, the three other processes dominate the energy loss. We discuss the uncertainties of the cross sections of the energy loss processes used in the simulation chain of current very large volume neutrino telescopes and review recent theoretical improvements.
Four most widely used models of hadronic interactions at high energies implemented in CORSIKA program were compared basing on the simulation of the first nucleus–nucleus interactions of cosmic rays ...with the atmosphere. For this comparison the distributions of the number of produced particles of different types were obtained, as long as the mean values of these numbers. The dependences of the fraction of the collision energy carried by different secondary particles on the mass of the primary particle were calculated for each model. The check of the electric charge conservation law implementation was performed. Comparison shows vast differences between the models in some cases that may result in different interpretation of experimental data.
Investigation of lepton propagation through matter is of importance for cosmic-ray physics and neutrino astronomy. The diffractive scattering of virtual photons is considered as a process that leads ...to the energy loss of leptons emitting these photons. The interference between this process and bremsstrahlung makes a contribution that depends on the sign of the lepton charge.
The muon puzzle is an excess of muon bundles generated by primary cosmic rays (PCR) at energies above 10
eV compared to estimations that assume even a heavy composition of PCR. The appearance of such ...excess of muons can be caused both by cosmophysical (the change in the spectrum and composition of cosmic rays) and nuclear-physical (the changing features of the hadron interaction) reasons. To separate these two possibilities it is necessary to measure energy characteristics of muon bundles and their dependence on energy of primary particles. Today the complex NEVOD-DECOR is the only one for such type experiment conduction. To improve the conditions of this experiment a further development of the experimental complex is planned: construction of new coordinate-tracking detector TREK for increasing of the area and improving of spatial resolution of muon track detection, modernization of the Cherenkov water detector for optimization of its structure and improvement of accuracy of energy deposit of muon bundle measurement, inclusion of the installation NEVOD-EAS in the experiment for independent evaluation of primary particle energy.
The current status of the Geant4 toolkit and the recent developments for the geometry, electromagnetic and hadronic physics for medium and high energy are presented. The focus of many recent ...improvements of the toolkit are key applications including the simulation of large Hadron collider (LHC) experiments at CERN. These developments and physics model extensions provide new capabilities and improvements for other applications of the toolkit for radiation studies in high energy physics (HEP), space and medical research.
Influence of atmospheric temperature on muon flux at sea level is considered. Results of calculations of muon spectrum for normal atmospheric conditions, differential temperature coefficients (DTC) ...for muons at different zenith angles and threshold energies are presented. In calculations, a six-layer stationary spherical model of atmosphere is used, contributions of both pions and kaons as well as dependence of muon energy loss on muon energy are taken into account. Comparison of muon spectrum calculations and experimental data in a wide range of zenith angles and momentums shows a good agreement. Comparison of results of DTC calculations with results of earlier works exhibits only qualitative agreement; possible sources of differences are analyzed. Some practical questions of the use of DTC for muon hodoscope data analysis are discussed.
In comparison with calculations, the excess of multimuon events found in many experiments at ultrahigh energies of extensive air showers (EASs) cannot be explained using modern models of hadron ...interactions. The existence of muon excess is called the muon puzzle. One of the ways to solve this problem is to study the energy characteristics of the EAS muon component. For this purpose, the energy deposit of cosmic ray muon bundles is measured in the NEVOD–DECOR experiment. Registration of muon bundles in a wide range of zenith angles allows one to explore a wide range of energies of the primary particles of cosmic rays (from 10 to 1000 PeV) within a single experiment. The results of measurements of the energy deposit of muon bundles over a long observation period are presented.
The neutrino telescope IceCube is capable to reconstruct the energy spectrum of muons in very high energy region by means of measurements of muon-induced cascades. To compare with experimental data, ...the expected spectra of cascades were theoretically estimated. Calculations were performed for two variants of muon spectrum on the ice surface: a simple power-law energy spectrum with a differential slope index −3.7, and a composite spectrum combined of two power spectra with differential indexes −3.7 and −2.7. The differential spectra of cascades for different zenith angles and integral cascade spectra calculated for two variants of muon spectra are discussed.
In a typical approach to extensive air shower (EAS) investigations, horizontal arrays are used and near-vertical EAS are detected. In contrast, in this work vertically arranged muon detectors are ...used to study inclined EAS. At large zenith angles, EAS consisting solely of muon component are employed. The transverse dimensions of EAS rapidly increase when the zenith angle increases. Hence, EAS in a wide energy interval can be explored by means of a relatively small detector. Here we present results of the analysis of the data on inclined muon bundles accumulated from 2002 to 2016 in the DECOR experiment. For the first time, these results demonstrate with more than 3σ significance the existence of the second knee in the EAS muon component spectrum near 1017 eV primary energy. An excess of muon bundles at energies about 1 EeV found earlier in DECOR data has been confirmed and analyzed in detail. It is highly likely that the obtained outcomes indicate the appearance of new processes of muon generation.
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