Validity of the distorted-wave impulse-approximation description of ${}^{40}$Ca$(e,e'p)^{39}$K data using only ingredients from a nonlocal dispersive optical model

TL;DR

This study demonstrates that a nonlocal dispersive optical model-based DWIA approach accurately describes the 0Ca(e,e'p) data, confirming the importance of nonlocal potentials and ground-state correlations in nuclear reaction analysis.

Contribution

The paper introduces a nonlocal dispersive optical model framework for DWIA calculations, providing a consistent description of 0Ca(e,e'p) data without fitting parameters.

Findings

Nonlocal optical potentials yield slightly larger spectroscopic factors.

Agreement with experimental data is comparable or better than local potential models.

The 100 MeV proton energy window is optimal for DWIA analysis.

Abstract

The nonlocal implementation of the dispersive optical model (DOM) provides all the ingredients for distorted-wave impulse-approximation (DWIA) calculations of the $(e,e'p)$ reaction. It provides both the overlap function, including its normalization, and the outgoing proton distorted wave. This framework is applied to describe the knockout of a proton from the $0\textrm{d}\frac{3}{2}$ and $1\textrm{s}\frac{1}{2}$ orbitals in ${}^{40}$Ca with fixed normalizations of 0.71 and 0.60, respectively. Data were obtained in parallel kinematics for three outgoing proton energies: 70, 100, and 135 MeV. Agreement with the data is as good as, or better than, previous descriptions employing local optical potentials and overlap functions from Woods-Saxon potentials - both with standard nonlocality corrections - whose normalization (spectroscopic factor) and radius were fitted to the data. The present analysis suggests that slightly larger spectroscopic factors are obtained when nonlocal optical potentials are employed than those generated with local potentials. The results further suggest that the chosen kinematical window around 100 MeV proton energy provides the best and cleanest method to employ the DWIA for the analysis of this reaction. The conclusion that substantial ground-state correlations cannot be ignored when describing a closed-shell atomic nucleus is therefore confirmed in detail. To reach these conclusions, it is essential to have a complete description of the nucleon single-particle propagator that accounts for all elastic nucleon-scattering observables in a wide energy domain up to 200 MeV. The current nonlocal implementation of the DOM fulfills this requirement.