Parametrization of the angular distribution of Cherenkov light in air showers

Luan B Arbeletche,Vitor De Souza

doi:10.1140/epjc/s10052-021-08971-7

Luan B Arbeletche, Vitor De Souza

Open Access

https://doi.org/10.1140/epjc/s10052-021-08971-7

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Abstract

The Cherenkov light produced in air showers largely contributes to the signal observed in ground-based gamma-ray and cosmic-ray observatories. Yet, no description of this phenomenon is available covering both regions of small and large angles to the shower axis. To fill this gap, a parametrization of the angular distribution of Cherenkov photons is performed in terms of a physically-motivated parametric function. Model parameters are constrained using simulated gamma-ray and proton showers with energies in the TeV to EeV region. As a result, a new parametrization is obtained that improves the precision of previous works. Results presented here can be used in the reconstruction of showers with imaging Cherenkov telescopes as well as in the reconstruction of shower profiles with fluorescence detectors.

Highlights

A large amount of Cherenkov light is produced in extensive air showers [1] and several experimental techniques have been proposed to explore this signal to study astroparticle physics
Imaging Atmospheric Cherenkov Telescopes (IACT) are of fundamental importance for the Very High Energy (VHE) gamma-ray astronomy (E0 > 100 GeV)
Beside the needed update of the parametrizations concerning the new shower models made available after the previous works, this paper aims at the improvement of the precision requested by the new generation of experiments [7,19] and at the refinement demanded by the new uses of Cherenkov light as the main signal source in Fluorescence Detectors (FD) analyses [15,16]

Summary

Introduction

A large amount of Cherenkov light is produced in extensive air showers [1] and several experimental techniques have been proposed to explore this signal to study astroparticle physics. The emission of Cherenkov light by relativistic electrons including geometry, intensity, and wavelength is explained by classical electrodynamics [2], which has been used as an inspiration for the development of robust detection techniques. The identification and the reconstruction of the primary gammaray are done by interpreting the Cherenkov light detected by telescopes at ground. The Cherenkov Telescope Array (CTA) [7] is the nextgeneration IACT system presently under development. The angular distribution of Cherenkov photons in an air shower determines the image shape detected by IACTs and is a key aspect in many reconstruction techniques [8,9,10]

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