Arbitrary mass Majorana neutrinos in neutrinoless double beta decay

TL;DR

This paper updates the constraints on heavy Majorana neutrinos mediating neutrinoless double beta decay, incorporating recent nuclear matrix element calculations and experimental bounds, providing a simplified formula for arbitrary neutrino masses.

Contribution

It introduces a simplified explicit formula for the nuclear matrix element dependence on neutrino mass, enabling easy half-life calculations across isotopes and updating existing exclusion plots.

Findings

Updated NLDBD-decay exclusion plots with recent data.

Derived a simple formula for nuclear matrix element dependence on neutrino mass.

Provided parameters for quick half-life estimations for various isotopes.

Abstract

We revisit the mechanism of neutrinoless double beta (NLDBD) decay mediated by the exchange with the heavy Majorana neutrino N of arbitrary mass mN, slightly mixed with the electron neutrino. By assuming the dominance of this mechanism, we update the well-known NLDBD-decay exclusion plot in the mass-mixing angle plane taking into account recent progress in the calculation of nuclear matrix elements within quasiparticle random phase approximation and improved experimental bounds on the NLDBD-decay half-life of Ge-76 and Xe-136. We also consider the known formula approximating the mN dependence of the NLDBD-decay nuclear matrix element in a simple explicit form. We analyze its accuracy and specify the corresponding parameters, allowing one to easily calculate the NLDBD-decay half-life for arbitrary mN for all the experimentally interesting isotopes without resorting to real nuclear structure calculations.