R. A. Mukhamedshin

Intense bundles of particles in cores of nuclear-electromagnetic cascades in the atmosphere with energies around 100 PeV (gamma-families with halo)

An appreciable fraction of gamma-families are accompanied by a halo, a narrow bundle of high-energy particles (energy density > 20 TeV/mm2) recorded in X-ray emulsion chambers as a diffuse dark spot in the central region of a gamma-family. Gamma-families in the experiment “Pamir” are compared with simulations by three different codes of quark-gluon string model (MQ, MCO and QGSJet) based on extrapolating accelerator data up to energy Eo = 3 ∗ 1018 eV and under various assumptions on mass composition of primary cosmic rays (PCR). The spectrum of halo area, S, is analyzed, especially at S > 100 mm2. Simulations by different codes predict that at a PCR energy Eo ∼ 1018 eV the probability of initiating a halo with S ∼ 1000 mm2 is 60% for primary protons and 40% for Fe nuclei. The fraction of protons in PCR composition at E0 = 1016 ÷ 1017 eV is estimated.

Fraction of protons in primary cosmic rays according to data from the PAMIR experiment in consideration of the response of X-ray emulsion chambers

Adjusted data on the fraction of protons in the mass composition of primary cosmic rays (PCRs) in the energy range of 1015–1017 eV are presented. Adjustments are made according to detailed calculations of the response of the X-ray emulsion chamber in the PAMIR experiment. It is demonstrated that the fraction of protons in a PCR is 16–18% for E0 ≈ 1015–1016 eV and does not change within the error for E0 ≈ 1016–1017 eV.

Studying the nature of the long-flying component of cosmic rays using X-ray emulsion chambers exposed in the Pamirs and Tien Shan

The origin of an excess of hadrons observed in deep homogeneous lead X-ray emulsion chambers (XRECs) at depths of more than 70 radiation length units is analyzed. Preliminary experimental data on the absorption of cosmic-ray hadrons in a two-storied XREC with a large air gap, exposed in the Tien Shan mountains, are presented. The chamber was designed to test the hypothesis that the main source of the excess of dark spots detected on X-ray films deep inside the XREC was substantial growth of the charmed-particle production cross section at energy Elab ∼ 75 TeV. The experimental data obtained using a two-storied REC and in experiments with deep homogeneous XRECs are compared to the results from calculations using the FANSY 1.0 model. The comparison shows qualitative agreement between the experimental and the model data, assuming high values of the charmed-particle production cross section when Elab ∼ 75 TeV in the forward kinematic region with xF ≥ 0.1.

Revised data on γ-families observed in X-ray emulsion chambers of the Experiment PAMIR

Recently essential efforts were made to improve measurement routine with X-ray films exposed in the X-ray emulsion chambers at the Pamirs. Analysis of X-ray emulsion response upon recorded events show that gamma-family energy and intensity in early publications were over estimated. The main physical results of the new analysis are presented.Recently essential efforts were made to improve measurement routine with X-ray films exposed in the X-ray emulsion chambers at the Pamirs. Analysis of X-ray emulsion response upon recorded events show that gamma-family energy and intensity in early publications were over estimated. The main physical results of the new analysis are presented.

Characteristics of the fragmentation region in h-A interactions at superhigh energies according to XREC data

Experimental and calculation data on γ-ray-hadron families, obtained using X-ray emulsion chambers at superhigh energies (E0 ≳ 1015 eV) in stratospheric and high-mountain investigations of cosmic rays, are discussed. Relations between model characteristics and experimental data on the transverse size and alignment of the most energetic subcores in γ-h families are considered. Lateral characteristics of γ-ray families are shown to be independent of secondary particles 〈pt〉 in h-A interactions but are strongly determined by the pt(xLab) dependence at 0.05 ≲ xLab ≲ 0.20. Conclusions on properties of h-A interactions at superhigh energies are drawn.

Study of primary cosmic rays on the Moon’s surface and in orbit around the Moon

A mathematical model for experiments aimed at studying the primary cosmic rays on the Moon’s surface and in orbit around the Moon is considered. The feasibility of simultaneously registering in three components (secondary neutrons, gamma rays, and radio emission) particles of primary cosmic rays via reverse current in showers developing in the lunar regolith is demonstrated.

A new method of XREC data processing based on recognition and analysis of CCD images and simulation of direction of γ families in XREC by the ECSim2.1 program

The passage of γ families through X-ray emulsion chambers (XRECs) is simulated and XREC-induced variations in different characteristics are analyzed. Experimental measuring procedures are also simulated; a new approach to recognition of overlapping dark spots in the families based on the Relay criterion is applied; the comparative analysis of the data of PAMIR experiment and model calculations with regard to the XREC response and measuring procedures is presented.

Energy spectra of secondary particles in γ families and their sensitivity to the spectrum of primary cosmic rays

Spectra of secondary particles (γ-rays) in γ-families detected in the X-ray chambers in the Pamirs (H = 600 g cm−2) have been analyzed. These γ-ray spectra show a bend at the energy E*γ ≈ (ΣEγ)min, where (ΣEγ)min is the lowest total energy of γ-rays in the families above which γ-families were selected. The bend is not related to the knee in the spectrum of primary particles; it is due to the use of the ΣEγ selection criterion. The Eγ spectrum slope is sensitive to the spectrum of the primary cosmic rays in the region Eγ ≥ (ΣEγ)min.

The HERO project for the study of high-energy primary cosmic radiation

Proposals for the High-Energy Ray Observatory (HERO) comprising scientific equipment with increased power availability are presented. Under the long exposure (>7 years), it is proposed to investigate the spectrum and charge composition of cosmic-ray nuclei up to E0 ∼ 1016 eV and to determine the behavior of the energy spectrum in the energy regions >100 GeV for cosmic-ray electrons and >50 GeV for γ radiation. The geometrical factor of the apparatus is 6.0–9.0 m2 sr depending on the type of particles.

Spatial distribution of aligned muons in groups

The phenomenon of alignment along one line for the highest energy secondary particles in the γ-ray-hadron families was observed for the first time in the “Pamir” experiment using the x-ray emulsion chambers and was related to coplanar production of secondary particles at energy E0 > 1016 eV. The distributions of distances between the muon pairs in the muon groups are obtained using the Baksan underground scintillation telescope of the Institute for Nuclear Research (Russian Academy of Sciences) for the threshold energies of 0.85–3.2 TeV for the period of 7.7 years. A difference between spatial distributions of all groups and aligned groups was not detected.