LXII. On the nature of particles produced in extremely energetic nuclear collisions

Abstract

A detailed investigation into nuclear collisions of energy between 10¹²-10¹³ ev is reported. The ratio of π^o-mesons to charged shower particles has been determined with high statistical accuracy yielding a value R = 0.383+0.044. The central cores of the ‘jets’ have been carefully scanned to detect secondary interactions produced by the shower particles and the ratio, Q, of the number of interactions produced by neutral to the number produced by charged shower particles has been obtained. Q = 0.25+0.09. If we assume that in nuclear collisions of very high energy, neutral and charged particles (other than π-mesons) are created in approximately equal numbers and that the interaction mean free path for such praticles does not differ appreciably from that of π-mesons, the values R and Q enable an estimate to be made of the fraction of shower particles which are not π-mesons. The results indicate that ∼25% of the shower particles must be heavy mesons, hyperons, nucleon-antinucleon pairs, and ejected nucleons. In order to estimate the contribution to the above fraction from heavy mesons, a detailed analysis of the products of secondary disintegrations has been carried out. The results, although preliminary, are compared with those of Dahanayake et al. (1955) and are consistent with the assumption that most of these unidentified shower particles in the core are heavy unstable particles. The lifetime of the π^o-meson has been determined by a method which does not involve the determination of the energy of the meson. The mean life obtained is 1.8^+3.2 _−1.1 × 10⁻¹⁵sec.