Analysis of seasonal variations of the cosmic ray muon flux and neutrons produced by muons in the LVD detector

The Russian-Italian Large Volume Detector (LVD) is located at the Gran Sasso underground laboratory at a depth of 3300 m w.e. To study the seasonal variations of the penetrating component of cosmic rays, the data on cosmic ray muons detected in 2001–2008 was analyzed, along with those associated with neutrons produced by muons since April 2003. One-year periodic variations of muons and neutrons produced by them were found. The maximum intensity is observed in July, in accord with theoretical concepts.     

Neutrons produced by muons in the LVD matter

The calculation results on the production, transport, and capture of neutrons produced by muons passing through the LVD are presented. The calculations are performed using the Monte Carlo transport codes GEANT4 and SHIELD. The efficiency of detecting the neutrons produced in both the scintillator and the detector’s structure is determined.     

A direct measurement of the energy spectrum of cosmic ray muons in the Mont Blanc underground laboratory

Using a transition radiation detector we have neasured the energy of cosmicray muons in the Mont Blanc laboratory, where the NUSEX experiment is located. With this technique we have been able to cover linearly the energy range from 0.1 TeV to about 0.5 TeV, where the detector response begins to saturate. The measurements are consistent with a muon energy spectrum deduced from a E^−3.71 distribution folded with 5000 hg/cm² standard rock absorption.     

Energy spectrum of cosmic ray muons above 10 TeV according to BUST data

The energy spectrum of cosmic ray muons in the range of several TeV to PeV obtained through the analysis of multiple interactions of muons (the pair meter technique) in the Baksan Underground Scintillation Telescope (BUST) is presented. Results are compared with prior BUST data on the muon energy spectrum measurements and data of other experiments, along with calculations for different muon spectrum models.     

Single and multiple muons and the generation of neutrons in the LVD experiment

The large geometric factor and good spatial resolution of the Large Volume Detector (LVD) ensures statistically significant and highly accurate measurements of muon trajectories and determination of the multiplicity of muon groups. The developed algorithm allows us to reconstruct 2 × 10⁶ muon events (single muons and muon groups). Characteristics of muon groups are obtained and the specific yield of neutrons produced by single muons, muon groups, and showers is determined.     

Strong variations of cosmic ray muons during thunderstorms

Experimental data about a strong decrease of the intensity of cosmic ray muons are presented. The event occurred during a thunderstorm on September 24, 2007 in Baksan Valley (North Caucasus). The threshold energy of muons is 100 MeV. In comparison with other events of this type detected previously, this event is remarkable by a longer duration (more than an hour and a half) and by the fact that well-pronounced correlations with lightning strokes are observed for the first time.     

Statistical properties of variations in cosmic ray muons during thunderstorms

An analysis is made of experimental data on variations in muons with a threshold of 100 MeV, detected by the CARPET air shower array in the Baksan Valley during thunderstorms of 2008. It is shown that with using a special criterion for selecting statistically significant variations (0.2%), muon intensity variations are observed in the majority of cases. Their characteristic duration is ∼8 min. Their amplitudes can have different polarities and do not exceed 1%.     

Lateral distribution of EAS muons measured for the primary cosmic ray energy around 100 TeV

The muonic component of the extensive air showers (EAS) is of great importance for the astroparticle physics. It carries the information about the properties of primary cosmic ray (CR) particles, such as their mass, and electromagnetic and hadronic nature. It provides a sensitive test for the hadronic interaction models, which are inevitable for describing the cascade shower development of cosmic rays in EAS experiments. The YangBaJing Hybrid Array (YBJ-HA) experiment has been in operation since the end of 2016. Surface detectors are used for the measurements of primary energy, angular direction and core position of a shower event, while underground muon detectors are used for measuring the density of muons at various locations. Using the data obtained by the YBJ-HA experiment,this work reports the first measurement of the lateral muon distribution for the primary cosmic ray energy in the 100TeV region. The punch-through effect is evaluated via MC simulation.     

Significance of the second dip in the ultra-high energy cosmic ray spectrum

A new feature in the spectrum of ultra high energy cosmic rays (UHECR) has been announced in the paper by Berezinsky, Gazizov and Kachelrieβ. The ratio of the solution of the exact transport equation to its solution in the continuous energy loss limit shows intriguing features which, according to the Authors, are related to the very nature of the energy loss processes of UHECR: the very sharp second dip predicted at 6.3 × 10¹⁹ eV can be used as an energy calibration point and also as the UHECR mass indicator for big future cosmic ray experiments. In the present paper we would like to advocate that this statement is an overinterpretation. The second dip is a result of an inappropriate approximation used, and thus it cannot help to understand the nature of UHECR in any way.      

Induction mechanism of cosmic ray production and kinks in the cosmic ray spectrum

Two kinks are observed in the energy spectrum of galactic cosmic rays. It is shown that the entire spectrum can be described, to a good approximation, by a single formula obtained on the basis of the hypothesis that the particles are produced and accelerated in plasma pinches by an induction mechanism under the assumption that three hierarchical groups of currents are present—interstellar, galactic, and metagalactic. Pis’ma Zh. éksp. Teor. Fiz. 64, No. 4, 225–230 (25 August 1996)     

Study of the charge asymmetry in electromagnetic interactions of cosmic ray muons

The Durgapur cosmic ray spectrograph has been utilised to study the electromagnetic interaction of cosmic ray muons in iron in the momentum range 5–100 GeV/c. The dependence of the interaction cross section on the charge of the muons for the production of a single electron secondary due to the knock-on process and for two and more two electrons due to both knock-on and pair production has been investigated.The ratio of the interaction cross section for positive muons to that for negative muons in the magnetic-iron has been found to be 0.952 ± 0.045 for the production of one secondary particle. For production of two and more than two secondaries the ratios are 1.05 ± 0.09 and 0.91 ± 0.08 respectively. The present results do not indicate any charge asymmetry of cosmic ray muons in respect of electromagnetic interactions in iron.     

Four-momentum dependence of inelastic scattering of cosmic ray muons on nucleons

Data taken by a combination of a horizontal solid iron muon spectrograph and an interaction calorimeter have been analysed with respect to the process of inelasticμN-scattering. The muon momentum range covered by the spectrograph extended from 7 GeV/c≦p _μ ≦1000 GeV/c. Energy transfers to hadrons between 0.3 GeV≦v≦10 GeV were recorded. The results at low four-momentum transfers are consistent with precocious scaling.     

Bremsstrahlung photons from cosmic ray muons of high and ultrahigh energies

The results from calculations for fluxes of bremsstrahlung photons generated at different depths in the atmosphere by cosmic ray muons with energies of up to 10¹⁰ GeV are presented. It is shown that the generation of charmed particles in the atmosphere, along with the generation of J/ψ mesons, must be taken into account in interpretations of experimental data on studying EASes at high and ultrahigh energies.     

雷暴电场对宇宙射线次级粒子μ 子的影响研究

西藏羊八井宇宙射线观测站的中子监测器主要探测宇宙射线次级粒子中能量在500 MeV—20 GeV的核子成分和少量的负μ子成分. 本文分析了2008—2010年观测站附近发生的62次雷暴期间中子监测器和大气平均电场仪的同步观测资料, 发现27次雷暴期间中子监测器计数率发生明显变化, 显著性S>5σ, 其中13次变化显著, 显著性S>10σ . 显著性S>10σ的13次个例信号变化百分比与地面电场场强幅值之间存在大体一致的变化趋势, 而显著性在5σ <S<10σ之间的14次个例信号变化百分比与地面电场场强幅值之间不存在相似的变化趋势. 较强雷暴当顶时中子监测器计数率变化一般不明显, 而中子监测器计数率变化明显的个例则多发生于雷暴云不当顶, 但探测器仍处于雷暴云下部正电荷层的控制范围之内时, 或者当顶雷暴处于形成或消散阶段. Dorman等把雷暴期间中子监测器计数率的变化归因于雷暴云内电场对宇宙射线次级粒子μ子的作用, 并建立了雷暴期间中子监测器计数率变化与雷暴地面电场相关联的理论. 本文分析发现雷暴期间羊八井中子监测器计数率变化与地面电场场强之间相关性较小或者没有相关性, 不支持Dorman的理论.     

Expected energy spectrum of cosmic ray protons and helium below4 PeV measured by LHAASO

The Large High Altitude Air Shower Observatory(LHAASO) is a composite cosmic ray observatory consisting of three detector arrays: kilometer square array(KM2 A), which includes the electromagnetic detector array and muon detector array, water Cherenkov detector array(WCDA) and wide field-of-view Cherenkov telescope array(WFCTA). One of the main scientific objectives of LHAASO is to precisely measure the cosmic rays energy spectrum of individual components from 10~(14) eV to 10~(18) eV. The hybrid observation will be employed by the LHAASO experiment, in which the lateral and longitudinal distributions of extensive air shower can be observed simultaneously. Thus, many kinds of parameters can be used for primary nuclei identification. In this paper, high purity cosmic ray simulation samples of the light nuclei component are obtained using multi-variable analysis. The apertures of 1/4 LHAASO array for pure proton and mixed proton and helium(HHe) samples are 900 m~2 Sr and1800 m~2 Sr, respectively. Prospect of obtaining proton and HHe spectra from 100 TeV to 4 PeV is discussed.     

The first results of observations of acoustic signals generated by cosmic ray muons in a seismically stressed medium

The first results of observations of acoustic signals generated by high-energy muons of extensive air showers, which propagate in a seismically stressed medium are presented. The cosmophysical method for monitoring the volume stressed state is tested using the experimental setup developed in the earthquake-prone region of Almaty at the Tien Shan High-Altitude Scientific Station of the Lebedev Physical Institute. High-amplitude acoustic signals correlated with the passage and interaction of muon groups in the Earth’s crust are detected for the first time.     

Variations of neutrons and muons generated by cosmic rays in the atmosphere and in thunderstorm electric fields

We investigate the interrelation between cosmic rays (CRs) and the electric field of the Earth during thunderstorms established by various investigators. The data from simultaneous measurements by spectrograph of CRs and the electric field in Yakutsk are used. It is noted that in seven recorded events of prolonged (up to 9 hours) variations in the electric field by ±5 kV m⁻¹ and in one event of a one-hour increase in the field value up to +20 kV m⁻¹ the CR index rose substantially. During the thunderstorm of the latter event, the intensity of neutrons fell by a considerable 1%. At the same time, a drop of ∼0.3% was observed in the CR muon component. Such effects was not observed for higher energy muons.     

Cosmic ray spectrum produced by galactic supernova remnants

Cosmic ray acceleration by supernova shocks is considered. A new numerical code is used to describe the cosmic ray acceleration and shock wave evolution. The magnetohydrodynamic turbulence generation in the shock precursor by streaming instability of accelerated particles is taken into account. The cosmic ray spectrum produced by supernova explosion in uniform interstellar medium is simulated.