2019 July 22
The height of the first interaction of an Extensive Air Shower (EAS) is one of the parameters determining the shower development in the atmosphere. We derived a geometrical method of estimation of such a parameter. We study the influence of the first interaction height on the gamma/hadron separation efficiency. Using Monte Carlo simulations of a subarray of 4 Large Size Telescopes (LST) of the Cherenkov Telescope Array we find that one of the methods of the estimation of the height of the first interaction brings a mild improvement (∼10-20%) in the sensitivity at the lowest energies (30-200 GeV). We test also the method on the MC simulations and data of currently operating MAGIC telescopes.