Cross sections for the production of 35 radioactive nuclides extending from ${}_{}{}^7{}_{}{}^{}\mathrm{Be}$ to ${}_{}{}^{67}{}_{}{}^{}\mathrm{Ga}$ by the interaction of 80-GeV ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ar}$ ions with Cu have been measured. These are compared with existing results for other relativistic heavy ions and for 28-GeV protons incident on Cu targets of various thicknesses. Differences in shapes of the yield distributions for products with $37\le A\le 64$ are inferred to arise primarily from increased secondary effects in the semithick targets used for the heavy-ion studies. The larger absolute cross sections (corrected to zero target thickness) for ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ar}$ ions appear to be due solely to the increased total reaction cross section, ${\sigma }_R$, over that for protons. The production of target fragments with $22\le A\le 64$ is estimated to account for ≅ 70% of ${\sigma }_R$. Calculations using realistic nuclear density distributions suggest that such products are formed in peripheral collisions (impact parameters ≳ 5 fm) in which there is no strong overlap of the cores of the ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ar}$ and Cu nuclei. Lighter products are presumed to result from more central collisions, and these are enhanced by factors larger than expected from ${\sigma }_R$ (a factor of 2 greater in the case of ${}_{}{}^7{}_{}{}^{}\mathrm{Be}$). The application of the concepts of limiting fragmentation and factorization as a framework for the interpretation of highenergy heavy-ion induced reactions with complex nuclei is discussed.

NUCLEAR REACTIONS Cu(${}_{}{}^{40}{}_{}{}^{}\mathrm{Ar}$, spallation), $E=80\mathrm{}$ GeV; measured $\sigma \mathrm{}(A,Z)\mathrm{}$, 35 products ${}_{}{}^7{}_{}{}^{}\mathrm{Be}$-${}_{}{}^{67}{}_{}{}^{}\mathrm{Ga}$; deduced mass yield and charge dispersion curves, target fragmentation cross sections. Natural targets, Ge(Li) counting, radiochemistry.

• Received 1 December 1977

DOI:https://doi.org/10.1103/PhysRevC.17.1632