Relativistic treatment of spin-transfer observables in quasielastic $(\vec{\bf p},\vec{\bf n})$ scattering

Abstract

We calculate all spin-transfer observables for the quasielastic $(\vec{p},\vec{n})$ reaction in a relativistic plane-wave impulse approximation. The nuclear-structure information is contained in a large set of nuclear-response functions that are computed in nuclear matter using a relativistic random-phase approximation to the Walecka model. A reduced value of the nucleon mass in the medium induces important dynamical changes in the residual isovector interaction relative to its nonrelativistic counterpart. As a result, good agreement is found for all spin observables --- including the spin-longitudinal to spin-transverse ratio --- when compared to the original ($q=1.72$~fm$^{-1}$) NTOF experiment. In contrast, the spin-longitudinal to spin-transverse ratio is underpredicted at $q=1.2$~fm$^{-1}$ and overpredicted at $q=2.5$~fm$^{-1}$. We comment on the role of distortions as a possible solution to this discrepancy.