The light neutrino exchange mechanism of the $0\nu\beta\beta$-decay with left- and right-handed leptonic and hadronic currents revisited

TL;DR

This paper revisits the light neutrino exchange mechanism of neutrinoless double-beta decay, incorporating right-handed currents, recoil corrections, and improved electron wave function calculations to refine decay rate predictions and explore mechanisms.

Contribution

It introduces an extended theoretical framework for $0 uetaeta$ decay including right-handed currents and pseudoscalar terms, with improved numerical phase-space calculations and detailed decay rate analysis.

Findings

Updated phase-space factors with exact Dirac wave functions

Constraints on neutrino mass and right-handed current parameters from experimental data

Analysis of angular correlations and energy distributions to distinguish mechanisms

Abstract

The extension of Majorana neutrino mass mechanism of the neutrinoless double-beta decay ($0\nu\beta\beta$) with the inclusion of right-handed leptonic and hadronic currents is revisited. While only the exchange of light neutrinos is assumed, the $s_{1/2}$ and $p_{1/2}$-states of emitted electrons as well as recoil corrections to the nucleon currents are taken into account. Within the standard approximations the decay rate is factorized into a sum of products of kinematical phase-space factors, nuclear matrix elements and the fundamental parameters that characterize the lepton number violation. Unlike in the previous treatments the induced pseudoscalar term of hadron current is included, resulting in additional nuclear matrix elements. An improved numerical computation of the phase-space factors is presented, based on the exact Dirac wave functions of the $s_{1/2}$ and $p_{1/2}$ electrons with finite nuclear size and electron screening taken into account. The dependence of values of these phase-space factors on the different approximation schemes used in evaluation of electron wave functions is discussed. The upper limits for effective neutrino mass and the parameters $\langle\lambda\rangle$ and $\langle\eta\rangle$ characterizing the right-handed current mechanism are deduced from data on the $0\nu\beta\beta$-decay of $^{76}$Ge and $^{136}$Xe using nuclear matrix elements calculated within the nuclear shell model and quasiparticle random phase approximation. The differential decay rates, i.e. the angular correlations and the single electron energy distributions for various combinations of the total lepton number violating parameters that can help to disentangle the possible mechanism are described and discussed.