Arrival time distributions of muons from extensive air showers as signature of the mass composition of cosmic rays

Abstract

The central detector of the KASCADE experiment which is intended to study the main components of EAS will be equipped with a trigger and fast timing facility which will enable measurements of the arrival time distributions of the muons. In particular, at larger distances from the shower axis the arrival time distributions are expected to map the longitudinal development of the showers in the atmosphere and may provide additional information about the nature of the primary particle through differences between the mean free paths and the interaction cross sections with air nuclei. We have investigated this aspect with respect to the KASCADE set-up on the basis of EAS simulations using the Monte Carlo code CORSIKA. The mean arrival time distributions of muons, observed at various distances from the shower core and for different primary energies and shower sizes, respectively, have been analysed with advanced statistical techniques, based on Bayes decision rules and nonparametric multivariate analysing methods, in order to specify the merits of the mean arrival time information of the muon component as a signature for the mass composition of cosmic rays. It turns out that muon arrival time distributions, observed with the KASCADE facility, exhibit promising features and mass discrimination effects for larger shower sizes, i.e. higher primary energies, around 1016 eV.