Speaker
Description
Mirror charge radii provide a promising route to neutron-skin information, but their interpretation requires control of nuclear isospin-symmetry breaking beyond the Coulomb interaction. We present a differential Skyrme energy-density-functional analysis that treats mirror displacement energies (MDEs) and mirror charge-radius differences within the same class-III charge-symmetry breaking (CSB) framework. Coulomb-subtracted MDE residuals are mapped onto an effective CSB functional containing volume and surface-gradient terms, and the resulting response is propagated to radii without additional radius-sector parameters. For the measured anchor set $^{34}$Ar-$^{34}$S, $^{36}$Ca-$^{36}$S, $^{38}$Ca-$^{38}$Ar, and $^{54}$Ni-$^{54}$Fe, the MDE response ratios form a compact surface-like class rather than the volume and surface couplings separately. In SLy4, a joint volume-plus-surface fit gives RMS residuals of 0.0529 MeV in MDEs and 0.00312 fm in mirror charge radii; SkM$^{*}$ confirms the same response class and effective-coupling degeneracy, but shows a larger mass–radius residual, which we use as an EDF systematic. The MDE-calibrated CSB response shifts proton-rich mirror skins at the 10-2 fm level.
Applying the same response class to unmeasured proton-rich partners, we predict R$_{ch}$($^{40}$Ti) = 3.5736(56) fm, R$_{ch}$($^{42}$Ti) = 3.5809(54) fm, R$_{ch}$($^{46}$Cr) = 3.6917(55) fm, and R$_{ch}$($^{50}$Fe) = 3.7180(82) fm. The quoted parentheses include the experimental uncertainty of the known mirror partner and a numerical radius floor, while the SLy4–SkM${*}$ differences provide an additional EDF systematic of up to 0.020 fm. These results identify a surface-sensitive CSB response that must be quantified before mirror charge radii are used as clean neutron-skin or symmetry-energy probes.
These results identify a surface-sensitive CSB response that must be quantified before mirror charge radii are used as clean neutron-skin or symmetry-energy probes.