Microscopic self-energy calculations and dispersive optical-model potentials

TL;DR

This paper compares microscopic Faddeev-random-phase approximation (FRPA) nucleon self-energies with dispersive optical-model (DOM) potentials for calcium isotopes, revealing insights into their features and suggesting improvements for DOM functional forms.

Contribution

It demonstrates that ab initio FRPA calculations can explain many features of empirical DOM potentials and proposes enhancements based on non-locality and angular momentum dependence.

Findings

FRPA explains key features of DOM potentials

Orbital angular momentum dependence indicates non-locality in imaginary self-energy

Nucleon-nucleon tensor force influences asymmetry dependence

Abstract

Nucleon self-energies for 40Ca, 48Ca, 60Ca isotopes are generated with the microscopic Faddeev-random-phase approximation (FRPA). These self-energies are compared with potentials from the dispersive optical model (DOM) that were obtained from fitting elastic-scattering and bound-state data for 40Ca and 48Ca. The \textit{ab initio} FRPA is capable of explaining many features of the empirical DOM potentials including their nucleon asymmetry dependence. The comparison furthermore provides several suggestions to improve the functional form of the DOM potentials, including among others the exploration of parity and angular momentum dependence. The non-locality of the FRPA imaginary self-energy, illustrated by a substantial orbital angular momentum dependence, suggests that future DOM fits should consider this feature explicitly. The roles of the nucleon-nucleon tensor force and charge-exchange component in generating the asymmetry dependence of the FPRA self-energies are explored. The global features of the FRPA self-energies are not strongly dependent on the choice of realistic nucleon-nucleon interaction.