Intensity of muon bundles at large zenith angles and hadron interaction models at energy of 1018 eV

Characteristics of muon bundles detected with the DECOR detector are compared to predictions based on different hadron interaction models and various assumptions as to the spectrum and mass composition of primary cosmic rays. The intensity of primary cosmic rays derived from the muon bundle data is considerably higher than that measured by means of the fluorescence technique. Either changes in the hadron interaction characteristics at ultrahigh energies or a revision of the energy calibration in the fluorescence technique of measuring EAS energy is required to explain these results.     

Comparative measurements of thermal neutron fluxes at ground level at the baksan neutrino observatory and LGNS laboratory

Thermal neutron fluxes were measured using two types of scintillation detectors based on the inorganic scintillator ZnS(Ag): ⁶LiF+ZnS(Ag) and ¹⁰B₂O₃ + KCl+ZnS(Ag). The preliminary results from these measurements are given. The thermal neutron concentration as a function of altitude above sea level was determined. The measurements were performed at three locations: in Moscow, at the Baksan Neutrino Observatory of the Russian Academy of Sciences, and at the Gran Sasso National Laboratory. Variations of neutron count rates associated with lunar cycles were observed at the remote laboratories.     

A Comparison of Neutron Identification Methods in Inorganic ZnS-based Scintillators

Physics of Atomic Nuclei - The paper presents a comparison of three neutrons identifying methods in scintillators based on ZnS with 6Li and 10B: charge integration method, pulse gradient analysis,...     

Primary Cosmic Ray Energy Spectrum Above the ‘‘Knee’’ Measured with PRISMA-32 Array

Physics of Atomic Nuclei - PRISMA-32 (PRImary Spectrum Measurement Array) is working since 2012 in the Scientific & Educational Center NEVOD (NRNU ‘‘MEPhI’’,...     

Thermal neutron flux monitoring using new-type detectors

The applicability of new-type unshielded detectors based on zinc sulfide ZnS(Ag) and lithium fluoride enriched with ⁶Li isotope to 90% to thermal neutron measurements is demonstrated. The results of measurements of the thermal neutron counting rate and flux near the Earth’s surface are presented. The existence of the concentration gradient of thermal neutrons near the Earth’s surface at placing the counter at the various levels (from −4 to 10.5 m) in an experimental building is shown. The effect of meteoparameters on the counting rate of thermal neutrons for a long time is shown.     

Study of the temporal structure of the EAS neutron component

Experimental data on detecting the thermal neutrons that accompany extensive air showers (EAS) over a long period of time (May 2009–April 2010) are presented. The data were obtained by means of prototype for an innovative new array (PRISMA) for EAS study. The workability of this array and its ability to yield completely new information on the hadron and electron components of EAS was checked experimentally over long period of time (in the minimal version of the prototype).     

Thermal neutron flux produced by EAS at various altitudes

The results of Monte-Carlo simulations of extensive air showers are presented to show the difference of the hadronic component content at various altitudes with the aim to choose an optimal altitude for a PRISMA-like experiment. The CORSIKA program for EAS simulations with QGSJET and GHEISHA models was used to calculate the number of hadrons reaching the observational level inside a circle of 50 m radius around the EAS axis. Then the number of neutrons produced by the hadronic component was calculated using an empirical relationship between the two components. We have tested the results with the ProtoPRISMA array at sea level, and recorded the neutrons which are consistent with the simulation results.     

Investigation of the properties of the flux and interaction of ultrahigh-energy cosmic rays by the method of local-muon-density spectra

A new method for studying extensive air showers is considered. The method is based on the phenomenology of the localmuon density. It is shown that measurement ofmuon-density spectra at various zenith angles makes it possible to obtain information about the energy spectrum, mass composition, and interaction of cosmic rays over a broad range of energies (10¹⁵–10¹⁸ eV) by using a single array of comparatively small size. The results obtained from a comparison of experimental data on muon bundles from the DECOR coordinate detector with the results of simulation performed under various assumptions on the properties of the primary flux and for various hadron-interaction models are presented, and possible versions of the interpretation of these results are discussed.     

Investigation of cosmic rays above the knee by means of muon bundles detected in a wide range of zenith angles

The results of investigation of muon bundles at the Earth’s surface in a wide range of zenith angles on the basis of the new phenomenological characteristic of extensive air showers—spectra of local muon density—have been investigated. Features of the local-density spectra are considered within a simple analytical model. The expected distributions of muon density in a wide range of zenith angles and primary energies, calculated on the basis of the CORSIKA code, are compared with the experimental data.