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Calculated cross-sections of pion production by 450-mev protons on various nuclei. McMillin, Douglas John


We construct a model to explain the production of pions in the bombardment by protons of various nuclei and we use the model to calculate relative cross-sections for the process. The model assumes that the incident proton interacts with the target nucleons individually and that the proton-nucleon cross-section can be used as a free parameter. The model accounts for many important nuclear effects, some for the first time in explaining the A-dependence of the pion yield. The effects included are those due to proton and pion absorption, to the background nuclear potentials and to the struck-nucleon momentum and density distributions. We compute differential cross-sections in several special cases and compare them with experimental data at 450 MeV. Agreement is only moderate, but it is as good as any previously obtained and, unlike the earlier results, it does not depend on the assumption of an absorbing neutron blanket. Our agreement depends instead on the use of a modern nuclear radius and a reasonable treatment of pion absorption. In this respect our results confirm what earlier workers had assumed, that absorption is the dominant factor controlling the proton-nucleus production of pions. Also important is the proton-nucleon production rate, a reasonable value of which we assume. Potential effects are important because the basic production rate and pion absorption are both very energy dependent. The effects of struck-nucleon momentum and density distribution, as we calculate them, are small at the energy considered.

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