Considering non-locality in the optical potentials within eikonal models

TL;DR

This paper investigates the impact of non-local optical potentials on high-energy nuclear reactions within eikonal models, revealing significant effects on transfer observables and exploring methods to incorporate non-locality, which challenges the model's simplicity.

Contribution

It assesses the influence of non-local optical potentials on high-energy reactions and proposes approaches to extend the eikonal method to include non-local interactions.

Findings

Non-locality significantly affects transfer observables at high energies.

Existing extensions of the eikonal model do not accurately describe elastic scattering with non-local potentials.

Incorporating non-locality complicates the simplicity of the traditional eikonal approach.

Abstract

Background: For its simplicity, the eikonal method is the tool of choice to analyze nuclear reactions at high energies ($E>100$ MeV/nucleon), including knockout reactions. However, so far, the effective interactions used in this method are assumed to be fully local. Purpose: Given the recent studies on non-local optical potentials, in this work we assess whether non-locality in the optical potentials is expected to impact reactions at high energies and then explore different avenues for extending the eikonal method to include non-local interactions. Method: We compare angular distributions obtained for non-local interactions (using the exact R-matrix approach for elastic scattering and the adiabatic distorted wave approximation for transfer) with those obtained using their local-equivalent interactions. Results: Our results show that transfer observables are significantly impacted by non-locality in the high-energy regime. Because knockout reactions are dominated by stripping (transfer to inelastic channels), non-locality is expected to have a large effect on knockout observables too. Three approaches are explored for extending the eikonal method to non-local interactions, including an iterative method and a perturbation theory. Conclusions: None of the derived extensions of the eikonal model provide a good description of elastic scattering. This work suggests that non-locality removes the formal simplicity associated with the eikonal model.