Few active mechanisms of the neutrinoless double beta-decay and effective mass of Majorana neutrinos

TL;DR

This paper discusses how multiple neutrinoless double beta decay experiments across different nuclei can help determine or constrain lepton violating parameters and the effective Majorana neutrino mass, enhancing understanding of neutrino properties.

Contribution

It demonstrates that combining results from three different nuclei and three mechanisms allows for constraining lepton violating parameters and extracting the Majorana neutrino mass with minimal ambiguity.

Findings

Multiple nuclei experiments can constrain lepton violating parameters.

The effective Majorana neutrino mass can be nearly uniquely determined.

Non-observation in some isotopes is compatible with sub-eV neutrino masses.

Abstract

It is well known that there exist many mechanisms that may contribute to neutrinoless double beta decay (0nbb-decay). By exploiting the fact that the associated nuclear matrix elements are target dependent we show that, given definite experimental results on a sufficient number of targets, one can determine or sufficiently constrain all lepton violating parameters including the mass term. As a specific example we show that, assuming the observation of the 0nbb-decay in three different nuclei, e.g., 76Ge, 100Mo and 130Te, and just three lepton number violating mechanisms (light and heavy neutrino mass mechanisms as well as R-parity breaking SUSY mechanism) being active, there are only four different solutions for the lepton violating parameters, provided that they are relatively real. In particular, assuming evidence of the 0nbb-decay of 76Ge, the effective neutrino Majorana mass |m_bb| can be almost uniquely extracted by utilizing other existing constraints (cosmological observations and tritium beta-decay experiments). We also point out the possibility that the non-observation of the 0nbb-decay for some isotopes could be in agreement with a value of |m_bb| in sub eV region. We thus suggest that it is important to have at least two different 0nbb-decay experiments for a given nucleus.