Hadronic- and electromagnetic cores of air-showers observed by hybrid experiments at high mountains

Abstract

Characteristics of the high energy families (bundle of high energy e, gamma) and hadrons in the air-showers detected in the hybrid experiment together with emulsion chamber and AS-array at Mt.Chacaltaya are studied in detail by comparing with those of CORSIKA simulations using interaction models of QGSJET and EPOS. Because the atmospheric families and hadron component have more direct information of the nuclear interaction, correlations between atmospheric families and burst (hadron component of air-showers) accompanied to air-showers are more sensitive to the mechanism of the the cosmic-ray interactions. The burst size dependence of the family energy is compared with those of simulations. It is found that the family energy accompanied by the air-showers with the larger burst-size is systematically smaller than that expected in the simulated events. The experimental results can not be described simply by changing the chemical composition of primary cosmic-rays and this indicates that the x-distribution of secondary particles in cosmic-ray interactions becomes much steeper than that assumed in the simulation models.