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

Tianqi Zhao1,2,3,*, Zidu Lin4,†, Bharat Kumar5,‡, Andrew W. Steiner4,6,§, and Madappa Prakash3,∥

  • *Contact author: tianqi.zhao@berkeley.edu
  • †Contact author: zlin23@utk.edu
  • ‡Contact author: kumarbh@nitrkl.ac.in
  • §Contact author: awsteiner@utk.edu
  • ∥Contact author: prakash@ohio.edu
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Phys. Rev. Research 7, 043335 – Published 26 December, 2025

DOI: https://doi.org/10.1103/472x-9cxj

Abstract

Measurements from the weak charge radius experiments on Ca48 (CREX) and Pb208 (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, ΔF=Fch−FW, in Ca48 and Pb208. 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 SV and the isovector spin-orbit coefficient b4′ play different roles in determining ΔF of Ca48 and Pb208. Consequently, adjusting SV or b4′ shifts predicted ΔF values toward or away from PREX-2/CREX measurements. Additionally, SV 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.

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Phys. Rev. Research 7, 043335– Published 26 December, 2025
  • Received 14 June 2024
  • Revised 2 May 2025
  • Accepted 13 November 2025
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