Interactions of 300-GeV protons with tungsten and chromium

Abstract

Targets consisting of tungsten and chromium powders imbedded in nuclear emulsion were exposed to the 300-GeV proton beam at the Fermi National Accelerator Laboratory. For each event found, the number of minimum-ionizing (shower) tracks $n_s$ and the number of heavily ionizing tracks $N_h$ were determined, and the production angles of the shower tracks were measured. For 39 chromium events, we find $〈n_s〉=13.8\mathrm{}\pm 1.2$, $〈N_h〉=7.2\mathrm{}\pm 0.7$, and $〈-\ln tan\left(\frac{{\theta }_{\mathrm{lab}}}{2}\right)〉\equiv 〈r〉=3.32\mathrm{}\pm 0.07$. For 51 events in tungsten, we find $〈n_s〉=18.6\mathrm{}\pm 1.5$, $〈N_h〉=12.9\mathrm{}\pm 1.2$, and $〈r〉=2.83\mathrm{}\pm 0.06$. The ratio $R\equiv \frac{〈n_s〉}{{〈n_s〉}_p}$, where ${〈n_s〉}_p$ is the average charged multiplicity in $p-p$ collisions, agrees with the form $R=\frac{1}{2}+\frac{\overline{\nu }}{2}$, where $\overline{\nu }$ is the mean number of intranuclear collisions. However, no single model adequately explains both the multiplicity and the angular distribution data.