Validity of the relativistic impulse approximation for elastic proton-nucleus scattering at energies lower than 200 MeV

TL;DR

This study evaluates the relativistic impulse approximation's effectiveness in modeling elastic proton-nucleus scattering below 200 MeV, incorporating nuclear structure and medium effects for improved accuracy.

Contribution

It introduces a comprehensive analysis of RIA validity at low energies, including the effects of Pauli blocking and density-dependent corrections, with detailed microscopic optical potentials.

Findings

RIA describes elastic scattering observables well when including medium effects.

Pauli blocking effects are more significant below 200 MeV.

Density-dependent corrections become crucial below 100 MeV.

Abstract

We present the first study to examine the validity of the relativistic impulse approximation (RIA) for describing elastic proton-nucleus scattering at incident laboratory kinetic energies lower than 200 MeV. For simplicity we choose a $^{208}$Pb target, which is a spin-saturated spherical nucleus for which reliable nuclear structure models exist. Microscopic scalar and vector optical potentials are generated by folding invariant scalar and vector scattering nucleon-nucleon (NN) amplitudes, based on our recently developed relativistic meson-exchange model, with Lorentz scalar and vector densities resulting from the accurately calibrated PK1 relativistic mean field model of nuclear structure. It is seen that phenomenological Pauli blocking (PB) effects and density-dependent corrections to $\sigma$N and $\omega$N meson-nucleon coupling constants modify the RIA microscopic scalar and vector optical potentials so as to provide a consistent and quantitative description of all elastic scattering observables, namely total reaction cross sections, differential cross sections, analyzing powers and spin rotation functions. In particular, the effect of PB becomes more significant at energies lower than 200 MeV, whereas phenomenological density-dependent corrections to the NN interaction {\it also} play an increasingly important role at energies lower than 100 MeV.