D. D. Dzhappuev

Modernization of the Carpet-2 array of the Baksan Neutrino Observatory

The state of the art and the project of modernization of the extensive-air-shower array Carpet-2 of the Baksan Neutrino Observatory of the Institute for Nuclear Research, Russian Academy of Sciences are described. The modernized array will allow the performance of detailed study of variations in the cosmic ray intensity, the energy spectra and composition of primary cosmic rays in the energy range 1013–1016 eV, and the anisotropy of primary cosmic rays with energies above 1013 eV.

Experimental search for gamma-ray bursts from evaporating primordial black holes

The energy spectra and temporal characteristics of high-energy gamma-ray bursts from evaporating primordial black holes have been calculated using various evaporation models. The currently existing theoretical uncertainties in the shape of the evaporated photon spectrum are discussed. The data from the Andyrchy and Carpet-2 arrays of the Baksan Neutrino Observatory (Institute for Nuclear Research, Russian Academy of Sciences) obtained in the mode of detection of a single cosmic-ray component are used to search for cosmic gamma-ray bursts with a primary photon energy of about 8 GeV. New upper limits have been obtained for the number density of evaporating black holes in a local region of space with a characteristic size of ∼10−3 pc for various evaporation models.

Analysis of variations in the thermal neutron flux at an altitude of 1700 m above sea level

The results of detection of thermal neutron flux by a large open scintillation detector of thermal neutrons are reported. Detailed analysis of the experimental data is performed. Meteorological, astronomical, and geophysical aspects of the variations observed are considered.

Studying the muon and hadron components of extensive air showers with the Carpet-2 array

The method of separating muons and hadrons recorded by the Muon Detector of the Carpet-2 air shower array of Baksan Neutrino Observatory (Institute for Nuclear Research, Russian Academy of Sciences) is described. The results of studying characteristics of the muon and hadron components of extensive air showers (EAS) with Ne ≥ 105 are presented. For the range of distances 40–55 m from shower axes the numbers of hadrons with energies higher than 30 GeV and muons with energies above 1 GeV are obtained as functions of the shower size Ne.

Reconstruction of the direction of the true anisotropy of galactic cosmic rays

A method of reconstructing the declination of galactic cosmic ray anisotropy is described, and its results are presented. The method is based on analysis of delay distributions in symmetrically arranged detectors of an air shower array, and it represents a modification of the crossed telescopes method. It is shown that the declination of the true anisotropy vector is close to 60° (i.e., this vector lies approximately within the galactic plane). Because of this, the true degree of anisotropy of galactic cosmic rays is severalfold higher than the first harmonic of intensity in the sidereal time (the quantity measured directly), and it equals about 0.2%.

How does the EAS look like in thermal neutrons

The first experimental data on detection of thermal neutrons accompanying extensive air showers (EASs) which were obtained at two prototypes of the future novel PRISMA EAS array are reported. The operation of this array (even in the minimum prototype version) and its ability to yield completely new information on the hadron and electron components of the EAS were experimentally checked.

The Carpet-3 experiment to search for diffuse gamma rays with energies of more than 100 TeV

An experiment for measuring the flux of cosmic diffuse gamma rays with energies above 100 TeV (the Carpet-3 air shower array) is now being prepared at the Baksan Neutrino Observatory, Institute for Nuclear Research, Russian Academy of Sciences. The preparations entail a substantial increase of the areas of both the muon detector and the surface air shower array. The experiment’s sensitivity to showers generated by primary gamma rays is estimated for different configurations of the array. In addition, preliminary estimates of the upper limit on the flux of diffuse gamma rays with energies higher than 1.3 PeV, derived using experimental data from the old Carpet-2 array, are presented for a net exposure time of 9.2 years.

Lateral distribution function of charged particles in EAS near the axis

High-precision measurements of the lateral distribution function (LDF) of charged particles near the axis of extensive air showers (EASes) were performed with the CARPET air shower array of the Baksan Neutrino Observatory for several ranges of Ne, including the knee region. For the sake of comparison with the experiment, calculations for primary protons and iron nuclei were made using the CORSIKA code (the QGSJET01C model of interaction). The measured experimental LDF is compared with our calculations.

Hadrons with energies higher than 50 MeV in EASes with Ne = 105–107

Characteristics of the hadronic component of EASes with hadron energies Eh > 50 MeV were measured on the CARPET-2 complex shower array at the Baksan Neutrino Observatory of the Institute for Nuclear Research, Russian Academy of Sciences. Hadrons were registered using a 6-NM-64 neutron monitor; the data collection system of this array enables us to register the time intervals between pulses of neutron monitor counters with an error of up to 1 μs. For EASes with Ne = 105–107 whose axes are located in CARPET, we obtain the dependence of the mean neutron multiplicity in the neutron monitor on the total number of charged particles in the EAS.

Neutron multiplicity: Local hadronic showers and extensive air showers

A detailed analysis of events with neutron multiplicity M = 3−30 on neutron monitors (NMs) in Barentsburg (Spitsbergen), Baksan (North Caucasus), and Apatity (Murmansk region) is performed on the data obtained using a unique new data collection system. It is now possible for the first time to register local showers in cosmic rays on NMs and to investigate their structure with a high precision. Multiplicity on NMs is simulated using the GEANT4 Monte Carlo toolkit. Local hadronic cascades in the atmosphere with transverse sizes of 1 to 6 m were observed for the first time using the NM data. NM multiplicity generated by EAS hadronic cascades is studied on the data set on coupling NMs with the CARPET EAS facility.