Orateur
Description
The recent PREX-2 and CREX data on the model-independent extraction of the charge-weak form factor difference ΔF in Pb208 and Ca48 challenge modern nuclear energy density functionals (EDFs) as well as our present understanding on the neutron skin and nuclear symmetry energy. Within the Skyrme-like EDFs, we demonstrate that the isovector spin-orbit interaction can strongly change the ΔF in Ca48 while it has essentially no influence on the ΔF in Pb208, mainly due to the eight spin-orbit unpaired 1f7/2 neutrons in Ca48. To simultaneously describe PREX-2 and CREX data in 1σ error, we find the strength of isovector spin-orbit interaction should be larger than about four times of that in the conventional Skyrme-like EDFs, implying the neutrons and protons have significantly different spin-orbit interaction. To further reconcile the data on electric dipole polarizability in Pb208 and Ca48, we obtain L≈55 MeV for the slope parameter of the symmetry energy, Δr(Pb208)≈ 0.19 and Δr(Ca48)≈0.12 fm for the neutron skin thickness. The implications of the strong isovector spin-orbit interaction are discussed.
