Elastic nucleon-nucleus scattering as a direct probe of correlations beyond the independent-particle model

TL;DR

This paper demonstrates that elastic nucleon-nucleus scattering data, analyzed through a dispersive optical model, can directly probe correlations beyond the independent-particle model, revealing the depletion of bound orbits.

Contribution

It introduces a method using the dispersive optical model to directly connect scattering data with correlations beyond the independent-particle approximation.

Findings

Elastic scattering data constrain spectral strength in the continuum.

Surface-absorption properties influence orbit depletion sensitivity.

Ab initio calculations predict a 4% depletion, aligning with empirical data.

Abstract

Employing a recently-developed dispersive optical model (DOM) which allows a complete description of experimental data both above (up to 200 MeV) and below the Fermi energy in $^{40}$Ca, we demonstrate that elastic nucleon-nucleus scattering data constrain the spectral strength in the continuum of orbits that are nominally bound in the independent-particle model. In the energy domain between 0 and 200 MeV, the integrated strength or depletion number is highly sensitive to the separation of the IPM orbit to the scattering continuum. This sensitivity is determined by the influence of the surface-absorption properties of the DOM self-energy. For an ab initio calculation employing the self-energy of the charge-dependent Bonn (CDBonn) interaction which only includes the effect of short-range correlations, no such sensitivity is obtained and a depletion of 4% is predicted between 0 and 200 MeV irrespective of the orbit. The ab initio spectral strength generated with the CDBonn interaction approaches the empirical DOM spectral strength at 200 MeV. Both spectral distributions allow for an additional 3-5% of the strength at even higher energies which is associated with the influence of short-range correlations. We suggest that the non-local form of the DOM allows for an analysis of elastic-nucleon-scattering data that directly determines the depletion of bound orbits. While obviously relevant for the analysis of elastic nucleon scattering on stable targets, this conclusion holds equally well for experiments involving rare isotopes in inverse kinematics as well as experiments with electrons on atoms or molecules.