AN INVESTIGATION OF MASS COMPOSITION OF ULTRA-HIGH ENERGY COSMIC RAYS WITH ENERGIES ABOVE 1019 eV VIA THE STUDY OF EXTENSIVE AIR SHOWERS

SUMMARY: The electron and muon components of extensive air shower (EAS) with energies above 1019 eV are analyzed via various giant EAS arrays. A varying property of showers is observed for two energy ranges; higher and lower than (3− 4) × 1019 eV. The age parameter, zenith angle, shower size dependence on muon size and shower size dependence on primary energy show an increment of mass composition (MC) above (3−4)×1019eV. Comparison of the observed EAS results with the simulations of Capdevielle et al. (2000) and Shinozaki et al. (2005) gives at most 20 % photon fraction for primary energies above 1019 eV. The arrival directions of showers above 4×1019 eV indicate an increasing concentration towards the super galactic plane. Key words. cosmic rays 1