Characterizing the nuclear models informed by PREX and CREX: A view from Bayesian inference

Measurements from the weak charge radius experiments on Ca 48 (CREX) and Pb 208 (PREX) challenge existing nuclear models. In the post-PREX-CREX era, it is unclear if current models can simultaneously describe weak charge distributions along with accurate measurements of binding energy and charge radii. In this work, we explore the parameter space of relativistic and nonrelativistic models to study the differences between the electric and weak form factors, Δ F = F ch − F W , in Ca 48 and Pb 208 . We show, for the first time, which aspects of mean-field models are the most important in determining the relative magnitude of the neutron skin in lead and calcium nuclei. We carefully disentangle the tension between the PREX-2/CREX constraints and the ability of the relativistic mean field and Skyrme models to accurately describe binding energies and charge radii. We find that the nuclear symmetry energy coefficient S V and the isovector spin-orbit coefficient b 4 ′ play different roles in determining Δ F of Ca 48 and Pb 208 . Consequently, adjusting S V or b 4 ′ shifts predicted Δ F values toward or away from PREX-2/CREX measurements. Additionally, S V and the slope L are marginally correlated given the prior constraints of our Bayesian inference, allowing us to infer them separately from PREX-2/CREX data.