Nuclear interactions of 660 MeV protons and the momentum distribution of nucleons in nuclei

Abstract

An investigation is carried out of the angular distributions and, by magnetic analysis, of the energy spectra of secondary charged particles (mainly protons with energies ⪆ 60 MeV )emitted at angles of 7°, 12.2°, 18°, 24° and 30° in interactions of 660 MeV protons with nuclei of Be, C, Cu and U. The cross sections for emission of such secondary charged particles increase with decrease of the angles. In the order of decreasing energy the various spectral regions of all investigated elements corresponds to diffraction scattering of protons on nuclei (in the small angle region), single quasi-elastic proton-nucleon collisions, π-mesons production on bound nucleons and nuclear cascade. The experimental energy spectra for single quasi-elastic proton-nuclear scattering are compared with the spectra computed in the impulse approximation under various assumptions regarding the momentum distributions of the nucleons in the nuclei. The Be and C data are consistent with a Gaussian nucleon momentum distribution falling to 1/e at an energy of approximately 20 MeV. This means that the mean square value of the nucleon momentum in Be and C nuclei corresponds to an energy of ≈ 30 MeV.