Hadronic interactions and primary-cosmic-ray composition at energies around 10(15)-10(16) eV derived from the analysis of high-energy gamma families.

Abstract

Gross features of gamma families observed at Mt. Kanbala (5500 m above sea level) and Mt. Fuji (3750 m) are summarized in comparison with a Monte Carlo simulation based on a plausible assumption about hadronic interactions and primary composition. Our analysis shows that the assumption of approximate Feynman scaling in the fragmentation region and a heavy-enriched primary composition in the energy range over 10/sup 15/ eV is wholly compatible with the experimental data. That is, there is no evidence of strong violation of Feynman scaling in the fragmentation region at least up to 10/sup 16/ eV. As to the primary cosmic rays, our data infer a steepening of proton spectrum at energies around 10/sup 14/ eV. The proton component in the primary cosmic rays is estimated to occupy 15--20 % of the total flux at 10/sup 15/ eV. Some other interesting implications on hadronic interactions are discussed with reference to the structures of gamma families.