A study of EAS cores detected by the hybrid experiment at Mt.Chacaltaya

Correlations among three components in the air-showers, i.e., air-shower size, burst-size and accompanied family energy, observed by Chacaltaya hybrid experiment, are studied by comparing those of simulated data. Burst-density in each block of hadron calorimeters, located at the center of air-shower array, are newly calculated using the GEANT4 simulation code in oder to compare directly to the experimental data. Air-shower size is also recalculated using EGS4 in the CORSIKA package and also taking into accounts contributions of scintillator response of gamma-ray component in the air-shower. It is shown no model can describe well observed correlations between burst-size and family energy. The burst-density of the events accompanied by atmospheric family is systematically larger than expectation and also the observed family energy accompanied by the air-showers with larger burst-size is systematically smaller than that expected in the simulated events. Effects of a fluctuation in the cross-section of hadronic interactions are studied to settle the disagreement between experimental data and simulations. Inclusion of the fluctuation of the cross-section makes less attenuation of energy flow of the hadronic component in the air-shower and explains some characteristics of the experimental data.