The East Lansing Model: a Bayesian uncertainty quantified optical potential for rare isotopes

TL;DR

The East Lansing Model offers a Bayesian, uncertainty-quantified optical potential for neutrons and protons, improving extrapolations for rare isotopes by incorporating novel asymmetry terms and experimental data.

Contribution

It introduces a new parameterization with an asymmetry-dependent term to better encode neutron skins and improve predictions for unstable nuclei.

Findings

Inclusion of (p,n) data does not significantly alter stable nucleus parameterization.

New parameterization captures neutron skin effects via asymmetry dependence.

Extrapolations toward driplines show reduced uncertainties compared to existing models.

Abstract

The East Lansing Model is a global, uncertainty-quantified optical potential for neutron and proton projectiles, with a novel form for the neutron-proton asymmetry component, with the goal to improve extrapolations away from stability. Our Bayesian calibration relies on (n,n), (p,p) and (p,n) experimental data for angular distributions on spherical targets with mass $A\geq 40$, and beam energies in the range $E = 10-100$ MeV. When considering the stable nuclei for which data is available, our results demonstrate that the inclusion of the $(p,n)$ data alone does not significantly change the parameterization. The additional information contained in (p,n) only becomes evident by introducing a new parameterization, one that gives the flexibility to encode neutron skins in the optical potential through an asymmetry dependent term. Finally, extrapolations of ELM toward the limits of stability (namely toward the proton and neutron driplines) leads to reduced uncertainties when compared to other global optical potentials in use.