Estimation of the height of the first interaction in gamma-ray showers observed by Cherenkov telescopes

TL;DR

This paper explores two methods to estimate the first interaction height in gamma-ray showers using Cherenkov telescopes, aiming to improve gamma/hadron separation and sensitivity in high-energy astrophysics observations.

Contribution

It introduces and tests two simple, independent methods for estimating the first interaction height in gamma-ray showers with Cherenkov telescopes.

Findings

Estimated first interaction height improves gamma/hadron separation by 10-20%.

Methods tested using Monte Carlo simulations for CTA's Large Size Telescopes.

Potential to enhance sensitivity in the 30-200 GeV energy range.

Abstract

Very high energy gamma rays entering the atmosphere initiate Extensive Air Showers (EAS). The Cherenkov light induced by an EAS can be observed by ground-based telescopes to study the primary gamma rays. An important parameter of an EAS, determining its evolution, is the height of the first interaction of the primary particle. However, this variable cannot be directly measured by Cherenkov telescopes. We study two simple, independent methods for the estimation of the first interaction height. We test the methods using the Monte Carlo simulations for the 4 Large Size Telescopes (LST) that are part of the currently constructed Cherenkov Telescope Array (CTA) Observatory. We find that using such an estimated parameter in the gamma/hadron separation can bring a mild improvement (~10-20%) in the sensitivity in the energy range ~30-200 GeV.