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

TL;DR

This paper presents a method to determine the mass composition of primary cosmic rays in the energy range 10^15-10^16 eV using muon multiplicity spectra and applies it to data from the Baksan telescope, identifying the fractions of protons, helium, and heavy nuclei.

Contribution

The paper introduces a two-stage method for extracting cosmic ray mass composition from muon data, improving accuracy over previous approaches.

Findings

Protons constitute approximately 23.5% of cosmic rays in the studied energy range.

Helium nuclei account for about 29%, and heavy nuclei for around 47%.

The method effectively constrains primary composition fractions using muon multiplicity spectra.

Abstract

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.