A Monte Carlo simulation study for cosmic-ray chemical composition measurement with Cherenkov Telescope Array

TL;DR

This study uses Monte Carlo simulations to evaluate the Cherenkov Telescope Array's capability to measure cosmic-ray chemical composition across a wide energy range, focusing on charge resolution and event detection rates.

Contribution

It provides a detailed simulation framework and preliminary results demonstrating CTA's potential for cosmic-ray composition analysis using Cherenkov photon detection.

Findings

Charge number resolution achieved for different nuclei

Estimated event count rates for various cosmic-ray species

Validation of CTA's extended energy coverage for composition measurement

Abstract

Our Galaxy is filled with cosmic-ray particles and more than 98% of them are atomic nuclei. In order to clarify their origin and acceleration mechanism, chemical composition measurements of these cosmic rays with wide energy coverage play an important role. Imaging Atmospheric Cherenkov Telescope (IACT) arrays are designed to detect cosmic gamma-rays in the very-high-energy regime ($\sim$TeV). Recently these systems proved to be capable of measuring cosmic-ray chemical composition in the sub-PeV region by capturing direct Cherenkov photons emitted by charged primary particles. Extensive air shower profiles measured by IACTs also contain information about the primary particle type since the cross section of inelastic scattering in the air depends on the primary mass number. The Cherenkov Telescope Array (CTA) is the next generation IACT system, which will consist of multiple types of telescopes and have a km$^2$-scale footprint and extended energy coverage (20 GeV to 300 TeV). In order to estimate CTA potential for cosmic ray composition measurement, a full Monte Carlo simulation including a description of extensive air shower and detector response is needed. We generated a number of cosmic-ray nuclei events (8 types selected from H to Fe) for a specific CTA layout candidate in the southern-hemisphere site. We applied Direct Cherenkov event selection and shower profile analysis to these data and preliminary results on charge number resolution and expected event count rate for these cosmic-ray nuclei are presented.