Nucleon-Nucleus Scattering and Dirac Phenomenology: What We Have Learned and What Remains

摘要

It is now generally recognized that the Dirac equation is a viable alternative to the usual Schr?dinger equation approach for analyzing nucleon-nucleus scattering data. This paper reviews the development of Dirac phenomenology, stressing how closely this development has been tied to experiment. In addition we discuss a new method for extracting neutron densities from intermediate energy elastic proton-nucleus scattering observables uses a global Dirac phenomenological (DP) approach based on the Relativistic Impulse Approximation (RIA). Data sets for 40Ca, 48Ca and 208Pb in the energy range from 500 MeV to 1040 MeV are used. The global fits reproducing the data well and this allows one to obtain the proton and neutron densities, their root-mean-square radii, Rp and Rn, and the neutron skin thickness, S_n = R_n–R_p.