Test of high - energy interaction models using the hadronic core of

Using the large hadron calorimeter of the KASCADE experiment, hadronic cores of extensive air showers have been studied. The hadron lateral and energy distributions have been investigated in order to study the reliability of the shower simulation program CORSIKAwith respect to particle transport, decays, treatment of low-energy particles, etc. A good description of the data has been found at large distances from the shower core for several interaction models. The inner part of the hadron distribution, on the other hand, reveals pronounced differences among interaction models. Several hadronic observables are compared with CORSIKA simulations using the QGSJET, VENUS and SIBYLL models. QGSJET reproduces the hadronic distributions best. At the highest energy, in the 10 PeV region, however, none of these models can describe the experimental data satisfactorily. The expected number of hadrons in a shower is too large compared with the observed number, when the data are classified according to the muonic shower size.