Measuring the depth of shower maximum of extensive air showers using Cherenkov light

Abstract

A method is proposed to reconstruct the depth at which showers reach the maximum number of charged particles (Xmaxcharged) using atmospheric Cherenkov telescopes. The dependence of the Cherenkov signal with telescope distance from shower core is explored and a region in which the measurement is possible is determined (150 to 200 m). A parametrization is presented to reconstruct Xmaxcharged. The resolution of the method is studied as a function of energy, for different primary particle types and for telescope fields of view ranging from 3.5∘ to 10∘. Good resolution ( ∼ 25 g/cm2) is achieved for most of the cases of primary particle type (gamma ray, proton and iron nuclei) and energy (10 TeV < E < 300 TeV). Very good resolution ( < 15 g/cm2) is achieved in the best cases and not so good resolution ( > 40 g/cm2) is seen for energies below 30 TeV. The results presented here contribute to the understanding of the development of gamma-ray showers and suggest another possibility of using atmospheric Cherenkov telescopes to study cosmic rays in the TeV-PeV energy range.