Proton Fraction in PCR Mass Composition at Energies of 10^15-10^17 eV (Experiment {\guillemotleft}Pamir{\guillemotright})

TL;DR

This study analyzes gamma-hadron family data to estimate the proton fraction in primary cosmic rays within 10^15-10^17 eV, indicating a gradual increase in heavier nuclei contribution with energy.

Contribution

It provides new insights into the energy-dependent composition of primary cosmic rays using gamma-hadron family analysis and Monte Carlo simulations.

Findings

Proton fraction decreases with energy, replaced by heavier nuclei.

Effective atomic number lnA increases from 2 to 2.5 between 10^15 and 10^17 eV.

Results suggest a gradual shift towards heavier cosmic ray components.

Abstract

The fraction of halo events among gamma-hadron families with SUM(Egamma) > 500 TeV is analyzed. The comparison of experimental data and Monte-Carlo simulations by MC0 code of quark-gluon string model under various assumptions on the PCR mass composition suggests a slowly increasing contribution of nuclei heavier than protons and alpha-particles to PCR mass composition. Effective atomic number of PCR particles changes in the energy interval 10^15-10^17 eV so that lnA grows from 2 to 2.5.