Effect of spin-spin interactions on nucleon-nucleus scattering

Abstract

In this thesis we investigate the interactions between nucleons, which have spin-1/2, and nuclei, which may also have intrinsic spin. The dependence of the nucleon-nucleon interaction on the relative orientations of the spin of the two particles is well known and suggests a similar dependence may be present in the interactions of nucleons with nuclei. The effect of the spin of the nucleus on the nucleon-nucleus potential has been the subject of much theoretical and experimental interest. Previous work has found that in many cases spin-spin interactions cannot be ignored, especially for high spin exotic nuclei such as those likely to be produced in the next generation of radioactive beam facilities. In this work a model has been developed for determining spin-spin terms in the nucleon-nucleus optical potential. These terms are constructed by folding a realistic effective nucleon-nucleon interaction, which includes both direct and exchange parts, over the nuclear wavefunction. The target is assumed, for our purposes, to have a simple two valence-particle structure, with the total spins of the two valence nucleons coupling to give the total spin of the nucleus. The resulting spin-spin tensors are evaluated within Distorted Wave Born Approximation to obtain the spin-spin amplitudes. This general model has been used for the specific calculation of the elastic scattering of protons by 10B, for which relevant experimental data exist. New spin-spin interactions that have higher order couplings of the target and projectile spins are included. In addition, where previous work on spin-spin interactions has only included exchange corrections for the central parts of the nucleon-nucleon interaction, we have included the non-local exchange contribution from the tensor parts of the nucleon-nucleon interaction. The effect of these spin-spin interactions on observables sensitive to the spin polarisation of the incident beam, specifically the polarisation transfer coefficient -DNN, has been investigated. We have found that the spin-spin interactions derived from this model have a significant effect on DNN when used to examine the elastic scattering of protons from 10B. The calculation of DNN has also been shown to be particularly sensitive to the parameters of the model used to describe the nuclear structure.