Primary cosmic ray chemical composition in the energy region around 10**16 eV investigated by means of gamma-hadron families

TL;DR

This study investigates the chemical composition of primary cosmic rays around 10^16 eV using gamma-hadron family data, finding results consistent with a normal composition and challenging heavy-dominant models.

Contribution

It introduces new methods for identifying Fe-like families and demonstrates that observed data aligns with normal chemical composition models, contradicting heavy-dominant hypotheses.

Findings

Observed gamma-hadron family characteristics match normal composition simulations.

Heavy-dominant models are inconsistent with experimental data.

New recognition methods for Fe-like families are validated.

Abstract

Primary Cosmic Ray Chemical Composition is investigated in energy region close to 10**16 eV. Studies are based on comparisons of gamma-hadron families observed by Pamir and Pamir-Chacaltaya Collaboration, with families generated by means of quasi-scaling model MC0. It is shown, that all characteristics of observed families, including their intensity, are in a very good agreement with simulated event properties at the normal chemical composition and are in disagreement at heavy dominant compositions. Code CORSICA with VENUS and DPM models also contradicts with experimental data of families. One- and multi-dimensional methods of recognition of Fe-like families is worked up and approved. They are based on family characteristics sensitive to atomic number of induced nuclei and are not correlated between each others. It is shown that the fraction of Fe-like families is consistent with the normal chemical composition and strongly contradicts to heavy dominant ones. The success of MC0 model, in description of families properties, is due to large inelasticity coefficient of soft interactions at superhigh energies.