On the mass composition of primary cosmic rays in the energy region 10^15-10^16 eV

The method of a determination of the Primary Cosmic Ray mass composition is presented. Data processing is based on the theoretical model representing the integral muon multiplicity spectrum as the superposition of the spectra corresponding to different kinds of primary nuclei. The method consists of two stages. At the first stage, the permissible intervals of primary nuclei fractions f_i are determined on the base of the EAS spectrum vs the total number of muons (E_mu > 235 GeV). At the second stage, the permissible intervals of f_i are narrowed by fitting procedure. We use the experimental data on high multiplicity muon events (n_mu > 114) collected at the Baksan underground scintillation telescope. Within the framework of three components (protons, helium and heavy nuclei), the mass composition in the region 10^15-10^16 eV has been defined: f_p = 0.235 +- 0.02, f_He = 0.290 +- 0.02$, f_H = 0.475 +- 0.03.Comment: 14 pages, 6 figure

Multiplicity of photohadronization and photon--hadron scaling violation

The method of scaling transformations permitting to carry out the reconstruction of cross sections of $\gamma N$ and $\gamma\gamma$ interactions on the basis of cross sections of nucleon-(anti)nucleon interactions is suggested. The photon--hadron scaling violation is a consequence of dependence of scaling transformation parameter $\bar n(s)$ on the energy. The universal function $\bar n(s)$ is interpreted as the multiplicity of photohadronization. This function is established by processing the data on $\gamma p$ cross sections in the low energy region \sqrt{s}< 20 \GeV and is extrapolated to the high energy region up to \sqrt{s}\sim 200 \GeV. The results of the reconstruction of $\gamma N$ cross sections at high energies and of $\gamma\gamma$ ones at all energies are in a remarkable agreement with available experimental data.Comment: 5 pages, 3 figures; v2: reference correcte