Method to infer about the nuclear UHE cosmic-ray composition from the EAS lateral development

Results from a detailed Monte-Carlo simulation for electromagnetic and hadronic cascades in the atmosphere, generated by primary γ-rays, p, O and Fe are provided in the primary energy range 1012–1016 eV for vertical incident showers. In the simulation of the Extensive Air Showers (EAS) development, the CORSIKA (COsmic Ray SImulator for KAscade) code has been used to perform a full simulation of the electromagnetic and hadronic interactions. The lateral development of the electromagnetic component, for both, pure electromagnetic and hadronic cascades have been deeply investigated and the NKG-type functions have been fitted to the lateral developments, to determine the lateral age parameters. Results on the variation of the shower size with the lateral age parameter and primary energy are obtained, as well as fluctuations on shower size at maximum development depth of the EAS and at mountain altitude (X = 800 g cm−2). in aim of this work is to obtain an accurate procedure to discriminate the nuclear composition of the UHE cosmic rays from the gamma rays background. We also seek to provide relations to interpret the experimental data, for those who do not have detailed simulation calculations available and also to provide material for a full and deep comparison of air shower Monte-Carlo codes.