Scattering of polarized and unpolarized nucleons from 28Si.

Abstract

Measurements of the differential cross sections and analyzing powers have been made for $^{28}$Si(n,${n}_{0}$) and $^{28}$Si(n,${n}_{1}$) for incident neutron energies between 8 and 17 MeV. These data have been combined with previous differential and total cross-section data to obtain the most complete data set for neutron scattering from $^{28}\mathrm{Si}$ over the 8--40 MeV energy range. The data have been described within the framework of a symmetric rotational model using phenomenological coupled-channels calculations. Nuclear moments were deduced and they are in good agreement with those obtained from electron scattering and Coulomb excitation measurements. Various calculations were performed to determine the sensitivity of the data and calculations to the signs of the potential deformation parameters ${\ensuremath{\beta}}_{2}$ and ${\ensuremath{\beta}}_{4}$. The systematic analysis of the analyzing power data enabled the determination of the deformation length for the spin-orbit potential. Comparisons between neutron- and proton-scattering data and calculations were made to test the sensitivity of this type of data to charge symmetry breaking in the nuclear force and to investigate the isospin dependence of the absorptive part of the nucleon-nucleus scattering potential for $^{28}\mathrm{Si}$. The results of these comparisons suggest that the differences between $^{28}$Si+n and $^{28}$Si+p scattering can be attributed solely to Coulomb effects.