Exploring thermalization in cosmic ray-air interactions and a new method for muon multiplicity measurement with the GRAPES-3 experiment

Abstract

Cosmic rays (CRs) are high-energy charged particles that continuously arrive on Earth, almost isotropically, from outer space. These particles cover an extraordinary energy range from 108 eV to 1020 eV and are constituted mainly of protons and helium nuclei followed by other heavier nuclei. At low energies (≲ 100 TeVs), they are detected directly either by satellite-borne or balloonborne detectors. However, these experiments suffer from low statistics beyond this limit due to the steeply falling nature of the CR energy spectrum. Thus, beyond this range, CRs are detected by ground-based indirect experiments. Indirect experiments detect the particles produced as a result of interactions of CRs with atmospheric nuclei. These interactions create showers of particles spread over large areas, known as Extensive Air Showers (EAS). Proper modelling of such EAS is necessary to determine the properties of the initial primary cosmic ray (PCR) that initiated the shower. Multiple models for EAS development that are tuned to reproduce the data from various accelerator experiments are now available.