Systematic Investigation of Ultrahigh-Energy Interactions. I

Abstract

Nuclear interactions in the energy range of 1000 GeV are studied by means of a large nuclear-emulsion stack. Particular emphasis is placed on collecting the samples of jets in an unbiased way, as well as on estimating the primary energy with better accuracy. For this purpose families of interactions initiated by heavy primary cosmic-ray particles are analyzed. A slightly modified Castagnoli method was applied to each family of jets to estimate the incident energy per nucleon. The method also enables one to select the quasimonoenergetic nucleons. The distribution of $K_{\mathrm{ch}}$, the fraction of the primary energy imparted to the charged secondaries, is obtained from the interactions caused by the quasimonoenergetic nucleons. The arithmetic mean of $K_{\mathrm{ch}}$ is 0.28. The mean transverse momentum of the nucleons which have interacted in the parent collision is estimated to be ${0.5}_2$±0.2 GeV/c.