Comparison of AGASA data with CORSIKA simulation

Abstract

An interpretation of Akeno giant air shower array (AGASA) data by comparing the experimental results with the simulated ones by cosmic ray simulation for KASCADE (CORSIKA) has been made. General features of the electromagnetic component and low energy muons observed by AGASA can be well reproduced by CORSIKA. The form of the lateral distribution of charged particles agrees well with the experimental one between a few hundred metres and 2000 m from the core, irrespective of the hadronic interaction model studied and the primary composition (proton or iron). It does not depend on the primary energy between 10 17.5 and 10 20 eV as the experiment shows. If we evaluate the particle density measured by scintillators of 5 cm thickness at 600 m from the core S 0(600), suffix 0 denotes the vertically incident shower) by taking into account the similar conditions as in the experiment, the conversion relation from S 0(600) to the primary energy is expressed as E ( eV)=2.15×10 17S 0(600) 1.015 within 10% uncertainty among the models and composition used, which suggests the present AGASA conversion factor is the lower limit. Although the form of the muon lateral distribution fits well to the experiment within 1000 m from the core, the absolute values change with hadronic interaction model and primary composition. The slope of the ρ μ(600) (muon density above 1 GeV at 600 m from the core) vs. S 0(600) relation in experiment is flatter than that in simulation of any hadronic model and primary composition. As the experimental slope is constant from 10 15 to 10 19 eV, we need to study this relation in a wide primary energy range to infer the rate of change of chemical composition with energy.