Cross Calibration of Telescope Optical Throughput Efficiencies using Reconstructed Shower Energies for the Cherenkov Telescope Array

TL;DR

This paper presents a new method for calibrating telescope optical efficiencies in the Cherenkov Telescope Array by using reconstructed shower energies for cross calibration, achieving accuracy at a few percent level.

Contribution

It introduces a novel calibration approach based on reconstructed energies, enabling cross calibration across different telescope types within IACT arrays.

Findings

Calibration recovers relative telescope responses at a few percent accuracy.

Monte Carlo simulations validate the method for CTA layouts.

Applicable to diverse telescope types within the array.

Abstract

For reliable event reconstruction of Imaging Atmospheric Cherenkov Telescopes (IACTs), calibration of the optical throughput efficiency is required. Within current facilities, this is achieved through the use of ring shaped images generated by muons. Here, a complementary approach is explored, achieving cross calibration of elements of IACT arrays through pairwise comparisons between telescopes, focussing on its applicability to the upcoming Cherenkov Telescope Array (CTA). Intercalibration of telescopes of a particular type using eventwise comparisons of shower image amplitudes has previously been demonstrated to recover the relative telescope optical responses. A method utilising the reconstructed energy as an alternative to image amplitude is presented, enabling cross calibration between telescopes of varying types within an IACT array. Monte Carlo studies for two plausible CTA layouts have shown that this calibration procedure recovers the relative telescope response efficiencies at the few percent level.