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.     

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.     

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.     

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.     

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%.     

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)     

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.     

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.     

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.     

Variations of the flux and the energy spectrum of neutrons born in the galactic cosmic ray proton interactions with the matter of Earth''s satellites and orbital stations

This paper presents the energy spectra of secondary neutrons obtained from Monte Carlo simulations of the interactions of protons of galactic cosmic rays with the material of a spacecraft, and also the variation of the fluxes of these particles as a function of latitude. The variations of the secondary neutron flux with changing geometry and orientation of the craft, and detector position were evaluated as well. The simulations were conducted over a wide range of masses of spacecraft, from 300 kg (Earth Probe Total Ozone Mapping Spectrometer) to 420,000 kg (International Space Station in its full configuration), with calculations for the ISS also being carried out for its first development stage (mass of approx. 20,400 kg) and its configuration with a mass of approx. 81,000 kg. The calculations were carried out for circular orbits at altitudes of 500 km and for the energy intervals 0.001–10 MeV and 10–10,000 MeV, for both maximum and minimum solar activity. The results obtained agree reasonably well with results from previous calculations and do not contradict experimental data.     

Determination of erosion rates with cosmic ray produced36Cl

We present results of the determination of³⁶C1 (T _1/2=3.0·10⁵a) in rock samples produced in situ by cosmic rays and natural radioactivities. These experiments were designed to determine the feasibility of using³⁶Cl for studying erosion processes in calcium rich minerals like limestone or dolomite. The³⁶Cl/Cl ratios in the samples have been determined with accelerator mass spectrometry (AMS) at the Munich accelerator laboratory. A first application is the investigation of the erosion in the last million years in Allchar (Yugoslavia) for the feasibility study of the geochemical²⁰⁵Tl solar neutrino experiment.Dedicated to Prof. Dr. P. Kienle on the occasion of his 60th birthday. Supported by DFG     

On the energy spectrum of cosmogenic neutrons

The processes of the generation of cosmogenic neutrons (cg-neutrons) underground are considered. The neutrons produced by cosmic-ray muons in their interactions with matter are called cosmogenic. Deep-inelastic πA-collisions of pions in muon-induced hadronic showers are mainly their source at energies above 30 MeV. The characteristics of the energy spectrum for the generation of cg-neutrons have been determined by invoking the additive quark model of deep-inelastic soft processes and the mechanism for the interactions of high-energy nucleons in a nucleus. The three-component shape of the spectrum is explained, and the energy of the “knee” in the spectrum has been found to depend on the mass number A. The peculiarities of deep-inelastic πA-scattering lead to the conclusion that the spectrum of cg-neutrons steepens sharply at energies above 1 GeV. The calculated quantitative characteristics of the spectrum are compared with those obtained in measurements.