PREPRINT

# Background rejection using image residuals from large telescopes in imaging atmospheric Cherenkov telescope arrays

Laura Olivera-Nieto, Helena X. Ren, Alison M. W. Mitchell, Vincent Marandon, Jim Hinton

Submitted on 23 November 2022

## Abstract

Identification of Cherenkov light generated by muons has been suggested as a promising way to dramatically improve the background rejection power of Imaging Atmospheric Cherenkov Telescope (IACT) arrays at high energies. However, muon identification remains a challenging task, for which efficient algorithms are still being developed. We present an approach in which, rather than identifying Cherenkov light from muons, we simply consider the presence of Cherenkov light other than the main shower image in IACTs with large mirror area. We show that in the case of the H.E.S.S. array of five telescopes this approach results in background rejection improvements at all energies above 1 TeV. In particular, the rejection power can be improved by a factor $\sim 3-4$ at energies above 20 TeV while keeping $\sim 90\mathrm{%}$ of the original gamma-ray efficiency.

## Preprint

Comment: Accepted for publication in EPJC

Subjects: Astrophysics - High Energy Astrophysical Phenomena; Astrophysics - Instrumentation and Methods for Astrophysics