Nuclear Interactions of Protons, Neutrons, and Shower Particles of Very High Energy in Nuclear Emulsion

Abstract

Eighty-four interactions of protons and neutrons were located in a 22 liter stack of nuclear emulsion by tracing back showers of minimum-ionizing particles to their origins. The distribution of the number of shower particles, and the number of heavily ionizing prongs are presented for 57 events with dip angles 17\ifmmode^\circ\else\textdegree\fi{}. The average energy of these events is 3.5\ifmmode\times\else\texttimes\fi{}${10}^{12}$ ev. The average number of shower particles emitted in nucleon-nucleon collisions at this energy is 15\ifmmode\pm\else\textpm\fi{}5, as estimated from 8 interactions without heavy prongs. The angular distributions of the shower particles are presented for the 57 events. They can be transformed into a system in which the angular distribution is roughly symmetric. This is true even for the collisions with heavy target nuclei (${N}_{h}5$). The degree of anisotropy of the angular distributions is in disagreement with a hydrodynamical model of nucleon-nucleus collisions. A lower limit for the collision mean free path of the primary particles of 20 cm in emulsion was obtained. By scanning the forward cone of the primary interactions, 76 secondary interactions of charged and neutral shower particles were found. The distribution of the prong numbers, of the energy, and the characteristics of their angular distribution are presented. The best estimate of the ratio of secondary collisions produced by neutral particles, and the number produced by charged particles is: $\frac{{N}_{n}}{{N}_{\mathrm{ch}}}=0.40\ifmmode\pm\else\textpm\fi{}0.11$. Adding this result to other published data, it is concluded that 30\ifmmode\pm\else\textpm\fi{}6% of the particles produced in collisions having a primary energy of several Tev are not $\ensuremath{\pi}$ mesons. A collision mean free path of 41\ifmmode\pm\else\textpm\fi{}8 cm was found for the forwardcone shower particles.