Multiple Meson Production by Heavy Primary Nuclei of Cosmic Origin and their Fragmentation Products at Energies above1012eV

Abstract

Studies were made of the interactions initiated by fragments, including nucleons, from the gradual breakup of ultra high-energy heavy nuclei in a large block of nuclear emulsion. The results obtained by this approach are free from the detection biases that arise in scanning for, e.g., high-energy electromagnetic cascades. For one family of genetically related interactions the primary per-nucleon energy could be reliably established as \ensuremath{\sim}1.3 TeV. The sample of nucleon-induced interactions with average multiplicity ${n}_{s}<25$, with primary energies in the region of 1 TeV, show strong bimodality in the angular distribution of the created particles. An upper limit of 1.5 $\frac{\mathrm{BeV}}{c}$ is found for the average transverse momentum of the possible fireballs that could have given rise to this bimodality. The average inelasticity for the same sample of collisions is \ensuremath{\sim}0.6. The average multiplicity ${n}_{s}$ for the nucleon-induced interactions with ${N}_{h}\ensuremath{\le}5$ is \ensuremath{\sim}11.5. For the interactions initiated by heavy nuclei the lower limit to the average per-nucleon multiplicity, $\frac{{n}_{s}}{\ensuremath{\Delta}A}$, in the energy interval 1-20 TeV is consistent with the average multiplicity for the nucleon-induced interactions at about 1 TeV. A linear superposition, in nucleus-nucleus collisions, of elementary nucleon-nucleon acts of meson production is suggested.