Progress in the Development of Global Medium-Energy Nucleon-Nucleus Optical Model Potentials

TL;DR

This paper compares two global medium-energy nucleon-nucleus optical model potentials, one based on a Dirac approach and the other on a relativistic Schrödinger equivalent, analyzing their experimental agreement and predictive capabilities.

Contribution

It introduces and compares two relativistic optical model potentials, extending existing models with isovector components and analyzing their scattering predictions.

Findings

Both models successfully describe experimental scattering data.

The isovector extension improves the models' accuracy for neutron and proton scattering.

Sensitivity of scattering observables to absorptive potential components is analyzed.

Abstract

Two existing global medium-energy nucleon-nucleus phenomenological optical model potentials are described and compared with experiment and with each other. The first of these employs a Dirac approach (second-order reduction) that is global in projectile energy and projectile isospin and applies to the target nucleus 208-Pb. Here the standard S-V (isoscalar-scalar, isoscalar-vector) model has been extended to include the corresponding isovector components by introduction of a relativistic Lane model. The second of these employs a relativistic equivalent to the Schroedinger equation and is global in projectile energy, projectile isospin, and target (Z,A). Here, particular attention is given to predictions for the integrated scattering observables - neutron total cross sections and proton total reaction cross sections - and their sensitivity to the absorptive parts of the potential. Finally, current work is described and the influence of the nuclear bound state problem (treated in relativistic mean field theory) on the Dirac scattering problem is mentioned.