Updated Partial Cross Sections of Proton‐Nucleus Reactions

Abstract

We have updated our 1973È1990 cross section calculations by using the measured partial cross sections of the hydrogen target of the transport collaboration for beams of nuclei 10 ¹ Z ¹ 28, of the hydrogen-carbon targets of Webber et al. for beams of 5 ¹ Z ¹ 28, and of the University of MinnesotaÈ Washington UniversityÈCaltech collaboration for beams of Fe, Kr, Ag, La, Ho, and Au nuclei. We have developed 18 modiÐcations of equations of cross section parameters. Exact values of partial cross sections are important for evaluating the source composition of cosmic rays that have small relative abundances relative to the secondary spallation products, e.g., 13C, 14N, 18O, 25Mg, 26Mg, and 31P. The isotopic ratios 13C/12C, 18O/16O, 22Ne/20Ne, and (25Mg ] 26Mg)/24Mg are a †ected by the Wolf-Rayet star contributions to cosmic rays, while 14N and particularly H and He are a †ected by the suppression of light nuclei in cosmic rays. The abundance of P is crucial in distinguishing between the two models : (1) stellar Ñare versus (2) enhanced nonvolatile grain-sputtering material contribution to cosmic rays. The earlier S and T cross sections of 20Ne and 24Mg into 14N and 15N are increased by a factor of 1.5, which reduces the calculated source component of N. The earlier calculated S and T cross sections of Au (and presumably of the Pt to Pb group), into elements with *Z \ 23 have to be reduced by about 15%, while the even-odd Rudstam parameters are eliminated for the heaviest nuclei. As a result, the calculated secondary components of 61 \ Z \ 74 are reduced and the calculated primary components are enhanced. This reinforces the need for an enhancement of r-process elements with Z [ 60 above the solar system abundances.