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

Abstract

The nucleon spin-orbit interaction is a cornerstone of nuclear structure theory, yet its isospin dependence remains insufficiently constrained within modern nuclear energy density functional (EDF) theory. It was recently shown that, within the framework of extended Skyrme EDFs, the charge-weak form factor difference $\hat{I}”F_{\mathrm{CW}}$ in ${}^{48}$Ca exhibits remarkable sensitivity to the effective isovector spin-orbit (IVSO) interaction, whereas $\hat{I}”F_{\mathrm{CW}}$ in ${}^{208}$Pb is much less sensitive to this channel. Extending this analysis to other nuclei, we find that ${}^{90}$Zr, with its ten spin-orbit unpaired $1{\mathrm{g}}_{9/2}$ neutrons, displays a $\hat{I}”F_{\mathrm{CW}}$ 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, ${}^{62}$Ni, like ${}^{208}$Pb, remains largely insensitive to the IVSO interaction. This structure-driven distinction suggests an experimental strategy: future parity-violating electron scattering measurements, e.g., the MREX experiment at the MESA facility, on ${}^{48}$Ca and ${}^{90}$Zr would help constrain the effective IVSO strength, while measurements on ${}^{208}$Pb and ${}^{62}$Ni can provide a cleaner probe of the density dependence of the symmetry energy with reduced IVSO sensitivity.

15 pages, 3 figures, 1 table. Presentation improved and discussions added. Accepted version to appear in Particles as Selected Papers from the International Symposium Commemorating the 40th Anniversary of Halo Nuclei

References in corpus (1)

• Evidence for strong isovector nuclear spin-orbit interaction