Ab initio short-range nuclear matrix elements for neutrinoless double-beta decay

TL;DR

This paper provides converged ab initio calculations of short-range neutrinoless double-beta decay nuclear matrix elements for key isotopes, using chiral effective field theory and the in-medium similarity renormalization group.

Contribution

It introduces a consistent ab initio approach to compute nuclear matrix elements for neutrinoless double-beta decay, incorporating different nuclear forces and effective operators.

Findings

Calculated matrix elements are consistent with but generally smaller than phenomenological estimates.

Results enable new constraints on sterile-neutrino mixing parameters.

Methodology can be applied to other isotopes and decay modes.

Abstract

We present converged ab initio calculations of short-range neutrinoless double-beta ($0\nu\beta\beta$) decay nuclear matrix elements for the key experimental isotopes $^{76}$Ge, $^{82}$Se, $^{130}$Te and $^{136}$Xe. Starting from different nuclear forces derived from chiral effective field theory, we apply the in-medium similarity renormalization group to obtain an effective valence-space Hamiltonian along with consistently transformed $0\nu\beta\beta$-decay operators. We then obtain a range of values for the matrix elements that is consistent with, but generally smaller than, those from phenomenology. Finally, we combine our results with current limits from $0\nu\beta\beta$-decay searches to obtain constraints for the sterile-neutrino mixing-mass parameter space when considering the inclusion of a fourth sterile neutrino.