Flavoured Neutrinoless Double Beta Decay

TL;DR

This paper proposes an alternative mechanism for neutrinoless double beta decay involving flavor-violating scalar interactions, which can alter the effective neutrino mass predictions and be tested at colliders and neutrino experiments.

Contribution

It introduces a new scalar interaction mechanism affecting neutrinoless double beta decay, with detailed nuclear matrix element evaluation and a UV-complete model analysis.

Findings

Normal mass ordering neutrino mass may not vanish due to flavor contributions.

Interference effects between standard and scalar diagrams are significant.

The model can be tested at colliders and future neutrino experiments.

Abstract

We discuss a mechanism of neutrinoless double beta decay, where neutrinos of different flavours come into play. This is realized by effective flavour-violating scalar interactions. As one consequence, we find that within the normal mass ordering the neutrino effective mass may no longer vanish due to contributions from other flavours. We evaluate the necessary nuclear matrix elements, consider the interference between the standard diagram and the new scalar one, and analyze a UV-complete model that realizes the scalar interaction. Tests of the complete model are possible at colliders and future neutrino experiments. Our scenario represents an alternative mechanism for neutrinoless double beta decay, where nevertheless lepton number violation resides only in Majorana mass terms of light neutrinos.