Nuclear interactions of 300-GeV protons in emulsion

Abstract

Results from a study of $p$-nucleus interactions in emulsion at an incident energy of 300 GeV are presented. The observed events were separated into those belonging to the light (C,N,O) and the heavy (Ag, Br) groups of target nuclei. Some characteristics of the fast-charged- (shower-) particle multiplicity and angular distributions for the light and heavy groups, as well as for emulsion, are reported and compared with the results from our previous experiments at 200 GeV. The average number of shower particles, $〈n_s〉$, has the values ${〈n_s〉}_{\mathrm{CNO}} = 12.1\pm 0.5$, ${〈n_s〉}_{\mathrm{AgBr}} = 16.7 \pm 0.5$, and ${〈n_s〉}_{\mathrm{em}} = 15.1 \pm 0.2$. The quantity $R_A$, defined as the ratio of created charged particles in $p$-nucleus and $p-p$ collisions, is consistent with the relation $R_A = A^{0.19}$. While the width of the shower-particle distribution as measured by the dispersion $D$ is greater at 300 GeV than at 200 GeV, the value of $\frac{〈n_s〉}{D}$ is about 1.68 at both energies. The average number of slow charged particles resulting from the evaporation of the target nucleus remains virtually unchanged at the two energies. The angular distributions of shower particles plotted in terms of $\eta = -\ln \mathrm{}\tan \left(\frac{\theta }{2}\right)$ show that, for a given nucleus, there are more particles at smaller angles at the higher energy, while there is no change in the distribution at large angles. In addition, for a given energy, the number of shower particles at larger angles increases with increasing size of the target nucleus.