Nuclear reactions ofAu197with 11.5- and 300-GeV protons

Abstract

The formation cross sections of more than 60 nuclides produced in the reaction of 11.5- and 300-GeV protons with ${}_{}{}^{197}{}_{}{}^{}\mathrm{Au}$ were measured. Most of the measurements were done by direct counting of the target with calibrated Ge(Li) $\gamma$-ray spectrometers and spectral analysis with computer programs. In addition, chemical separations of osmium and gold fractions permitted the assay of nuclides which could not be resolved in the unseparated targets. The cross-section ratio at the two energies $\frac{{\sigma }_{300}}{{\sigma }_{11.5}}$ was within 20% of unity for all nuclides studied, which ranged in mass from ${}_{}{}^{22}{}_{}{}^{}\mathrm{Na}$ to ${}_{}{}^{196}{}_{}{}^{}\mathrm{Au}$. This is interpreted as showing that the spectrum of excitation energies left in the nucleus is nearly independent of bombarding energy above ∼ 10 GeV. The small cross-section changes observed are shown to be continuations of trends seen previously at lower energies. Charge dispersion curves were estimated with the aid of an empirical formula, and a mass-yield curve was constructed.