Cosmic ray composition measurements and cosmic ray background free gamma-ray observations with Cherenkov telescopes

TL;DR

This paper proposes using Cherenkov telescopes to measure muon content in extensive air showers, enabling cosmic ray composition analysis and background suppression in gamma-ray observations across a broad energy spectrum.

Contribution

It introduces a novel method to measure muon content in EAS with Cherenkov telescopes, enhancing cosmic ray composition studies and gamma-ray background rejection.

Findings

Muon detection can be achieved in a broad energy range using Cherenkov telescopes.

The technique can improve gamma-ray flux sensitivity by up to two orders of magnitude above 10 PeV.

It enables composition measurements across the knee, ankle, and Galactic-to-extragalactic transition energies.

Abstract

Muon component of extensive air showers (EAS) initiated by cosmic ray particles carries information on the primary particle identity. We show that the muon content of EAS could be measured in a broad energy range from 10-100 TeV up to ultra-high-energy cosmic ray range using wide field-of-view imaging atmospheric Cherenkov telescopes observing strongly inclined or nearly horizontal EAS from the ground of from high altitude. Cherenkov emission from muons in such EAS forms a distinct component (halo or tail) of the EAS image in the telescope camera. We show that detection of the muon signal could be used to measure composition of the cosmic ray spectrum in the energy ranges of the knee, the ankle and of the Galactic-to-extragalactic transition. It could also be used to veto the cosmic ray background in gamma-ray observations. This technique provides a possibility for up to two orders of magnitude improvement of sensitivity for gamma-ray flux in the energy band above 10 PeV, compared to KASCADE-Grande, and an order-of-magnitude improvement of sensitivity in the multi-EeV energy band, compared to Pierre Auger Observatory.