Two-neutrino double electron capture on $^{124}$Xe based on an effective theory and the nuclear shell model

Understand

We study the two-neutrino double electron capture on $^{124}$Xe based on an effective theory (ET) and large-scale shell model calculations, two modern nuclear structure approaches that have been tested against Gamow-Teller and double-beta decay data.

• In the ET, the low-energy constants are fit to electron capture and $\beta^{-}$ transitions around xenon.
• For the nuclear shell model, we use an interaction in a large configuration space that reproduces the spectroscopy of nuclei in this mass region.
• For the dominant transition to the $^{124}$Te ground state, we find half-lives $T^{2\nu{\rm ECEC}}_{1/2}=(1.3-18)\times 10^{22}$ y for the ET and $T^{2\nu{\rm ECEC}}_{1/2} = (0.43-2.9)\times 10^{22}$ y for the shell model.