Fluctuations in Čerenkov photon density in extensive air showers

Abstract

In the absence of a standard source of γ-rays or hadrons of known energy one has to study the details of production of Cerenkov light at the observation level only through detailed simulation studies. Recently such studies have become all the more important in view of the various techniques resulting from such studies, to distinguish between γ-ray initiated events from those generated by much more abundant hadronic component of cosmic rays. We have carried our detailed simulation studies using the CORSIKA package in order to study the Cerenkov photon density fluctuations for 5 different energies in the range 50 GeV to 1000 GeV, at various core distances, both for γ - ray and proton primaries incident vertically at the top of the atmosphere. The density fluctuations are found to be significantly non-statistical. Also proton showers are found to show more fluctuations in shower size as well as density compared to γ - ray showers, at all energies. We have studied the contributions to fluctuations from various known processes, including Coulomb scattering of electrons, fluctuations in the height of first point of interaction and fluctuations in electron energy spectra. In principle, the differences in density fluctuations could be used to identify the nature of primary.