Bayesian Inference of the Symmetry Energy and the Neutron Skin in 48Ca and 208Pb from CREX and PREX-2

Zhen Zhang, Lie-Wen Chen

Submitted on 7 July 2022


Using the recent model-independent determination of the charge-weak form factor difference ΔFCW in 48Ca and 208Pb by the CREX and PREX-2 collaborations, we perform Bayesian inference of the symmetry energy Esym(ρ) and the neutron skin thickness Δrnp of 48Ca and 208Pb within the Skyrme energy density functional (EDF). We find the inferred Esym(ρ) and Δrnp separately from CREX and PREX-2 are compatible with each other at 90% C.L., although they exhibit strong tension at 68.3% C.L. with CREX (PREX-2) favoring a very soft (stiff) Esym(ρ) and rather small (large) Δrnp. By combining the CREX and PREX-2 data, we obtain Esym(ρ0)=30.23.0+4.1 MeV, the symmetry energy slope parameter L=15.341.5+46.8 MeV at saturation density ρ0, Δrnp(48Ca)=0.1490.032+0.035 fm and Δrnp(208Pb)=0.1390.063+0.070 fm at 90% C.L.. The Esym(ρ) and Δrnp from combining CREX and PREX-2 are closer to the corresponding results from CREX alone, implying the PREX-2 is less effective to constrain the Esym(ρ) and Δrnp due to its lower precision of ΔFCW. Furthermore, we find the Skyrme EDF results inferred by combining the CREX and PREX-2 data at 90% C.L. nicely agree with the measured dipole polarizabilities αD in 48Ca and 208Pb as well as the neutron matter equation of state from microscopic calculations.


Comment: 6 pages, 4 figures, 2 tables

Subjects: Nuclear Theory; Astrophysics - High Energy Astrophysical Phenomena; High Energy Physics - Phenomenology; Nuclear Experiment