Effects of isovector spin-orbit interaction on the charge-weak form factor difference in $^{48}$Ca, $^{208}$Pb, $^{90}$Zr and $^{62}$Ni

Effects of isovector spin-orbit interaction on the charge-weak form factor difference in $^{48}$Ca, $^{208}$Pb, $^{90}$Zr and $^{62}$Ni
Tong-Gang Yue, Zhen Zhang, Lie-Wen Chen
arXiv:2603.03044v1 Announce Type: cross
Abstract: The nucleon spin-orbit interaction is a cornerstone of modern nuclear theory, yet its isospin dependence remains elusive due to the lack of clean experimental probes. It has been recently demonstrated that within Skyrme-like energy density functionals, the charge-weak form factor difference $Delta F_{rm CW}$ in $^{48}$Ca exhibits remarkable sensitivity to the isovector spin-orbit (IVSO) interaction, and that a significantly enhanced IVSO strength can resolve the PREX-CREX puzzle. Extending this analysis to other nuclei, we identify that $^{90}$Zr, with its ten spin-orbit unpaired $1mathrm{g}_{9/2}$ neutrons, displays a $Delta F_{text{CW}}$ sensitivity to the IVSO strength similar to that of $^{48}$Ca, arising from modifications to the central mean-field potential rather than the one-body spin-orbit potential. In contrast, $^{208}$Pb and $^{62}$Ni remain largely insensitive to the IVSO interaction. Furthermore, this structure-driven distinction suggests a distinct experimental strategy: future parity-violating electron scattering measurements on $^{48}$Ca and $^{90}$Zr would enable a more precise determination of the IVSO strength, while measurements on $^{208}$Pb and $^{62}$Ni can serve as purer constraints on the symmetry energy slope.arXiv:2603.03044v1 Announce Type: cross
Abstract: The nucleon spin-orbit interaction is a cornerstone of modern nuclear theory, yet its isospin dependence remains elusive due to the lack of clean experimental probes. It has been recently demonstrated that within Skyrme-like energy density functionals, the charge-weak form factor difference $Delta F_{rm CW}$ in $^{48}$Ca exhibits remarkable sensitivity to the isovector spin-orbit (IVSO) interaction, and that a significantly enhanced IVSO strength can resolve the PREX-CREX puzzle. Extending this analysis to other nuclei, we identify that $^{90}$Zr, with its ten spin-orbit unpaired $1mathrm{g}_{9/2}$ neutrons, displays a $Delta F_{text{CW}}$ sensitivity to the IVSO strength similar to that of $^{48}$Ca, arising from modifications to the central mean-field potential rather than the one-body spin-orbit potential. In contrast, $^{208}$Pb and $^{62}$Ni remain largely insensitive to the IVSO interaction. Furthermore, this structure-driven distinction suggests a distinct experimental strategy: future parity-violating electron scattering measurements on $^{48}$Ca and $^{90}$Zr would enable a more precise determination of the IVSO strength, while measurements on $^{208}$Pb and $^{62}$Ni can serve as purer constraints on the symmetry energy slope.