Simulation of extensive air showers at ultra-high energy using the CORSIKAMonte Carlo code

Extensive simulations have been carried out with CORSIKA version 5.62 to in vestigate the general properties of giant cosmic air shower in the energy r ange 1-100 EeV. The comparison between protons, heavy nuclei and gamma init iated showers exhibits unexpected and interesting features. The apparent mu on electron ratio at great distances (greater than or equal to 1.5 km from axis) tends to be comparable at ultra-high energy in both photon-induced ca scades and hadronic cascades (compensation between the enhancement versus e nergy of photo-production cross-section and of the decrease of both pair pr oduction cross-section and the bremsstrahlung cross-section, with Landau-Po meranchuk-Migdal effect); for proton and nuclei primaries, a correlation wi th lateral electron profile suggests a new energy estimator, in complement to electrons size or density at 600 m, suitable for the determination of th e total primary energy spectrum. Another tendency is the local contrast in the abundance of positive and negative muons (with a possible ellipticity i n the lateral muon distribution) induced by the geomagnetic field, especial ly visible for some azimuthal and zenith angles. These distortions are more intense for heavy primaries; they can be exploited on the most favorable h orizontal axis or areas, for the discrimination between nuclei and protons. (C) 2000 Elsevier Science B.V. All rights reserved.