Two-neutrino double-weak decays of ${}^{126}$Xe and ${}^{134}$Xe from different many-body methods

Abstract

We calculate the nuclear matrix elements and corresponding half-lives for the two-neutrino double-electron capture of ${}^{126}$Xe and the two-neutrino double-beta decay of ${}^{134}$Xe. We use different many-body methods: the proton-neutron quasiparticle random-phase approximation, the nuclear shell model, the microscopic interacting boson model, and an effective field theory for heavy nuclei. For both nuclei, all our half-life predictions are generally consistent with each other when including theoretical uncertainties for each method. Interestingly, for all calculations the lower range of the predicted ${}^{134}$Xe half-life is shorter than $T_{1/2}^{2\nu }\approx 2\times 10^{24}$\,y, which may be within the reach of next-generation experiments. For ${}^{126}$Xe, our results typically predict one order of magnitude longer half-lives than those for ${}^{134}$Xe.

Comments: 15 pages, 9 figures, appendix included