Comparison of nonequilibrium processes in p+Ni and p+Au collisions at GeV energies

TL;DR

This study measures the energy and angular dependence of particle production in proton collisions with Ni at GeV energies, revealing the importance of nonequilibrium processes for accurate modeling.

Contribution

It introduces a phenomenological model of nonequilibrium emission processes that significantly improves data reproduction over traditional models.

Findings

Nonequilibrium processes account for about half of the total cross sections.

Model accurately reproduces energy and angular distributions of ejectiles.

Reaction mechanisms are similar for p+Ni and p+Au collisions.

Abstract

The energy and angular dependence of double differential cross sections d2sigma/dOmega dE were measured for p, d, t, 3,4,6He, 6,7,8Li, 7,9,10Be, 10,11B, and C produced in collisions of 1.2, 1.9, and 2.5 GeV protons with a Ni target. The shape of the spectra and angular distributions does almost not change whereas the absolute value of the cross sections increases by a factor about 1.7 for all ejectiles in this beam energy range. It was found that energy and angular dependencies of the cross sections cannot be reproduced by the microscopic model of intranuclear cascade with coalescence of nucleons and the statistical model for evaporation of particles from excited, equilibrated residual nuclei. The inclusion of nonequilibrium processes, described by a phenomenological model of the emission from fast and hot moving sources, resulting from break-up of the target nucleus by impinging proton, leads to very good reproduction of data. Cross sections of these processes are quite large, exhausting approximately half of the total production cross sections. Due to good reproduction of energy and angular dependencies of d2sigma/dOmega dE by model calculation it was possible to determine total production cross sections for all studied ejectiles. Results obtained in this work point to the analogous reaction mechanism for proton induced reactions on Ni target as that observed previously for Au target in the same beam energy range.