Gigantic gamma-ray family events with ΣE _γ≥1000 TeV and hadronic interactions

The characteristic features of big family events with ΣE _γ≥10³ TeV, which were observed with emulsion chambers at Mt. Fuji (3776 m above sea-level), are presented in comparison with the results of the Monte Carlo simulation. Moreover, the behaviour of the halo accompanying big family events is described in connection with that of high-energy gamma-rays incident upon the chamber. On the basis of the experimental data, some inferences about the hadronic interactions at energies around 10⁴ TeV are discussed. The general tendency of our data does not seriously contradict the scaling prediction if the primaries are adequately mixed with heavy nuclei. In this case, the cross-sections should increase rapidly with energy up to 10⁴ TeV at least. There exist no clear signs showing a rapid increase of the average transverse momentum.