Combined Constraints on Majorana Masses from Neutrinoless Double Beta Decay Experiments

TL;DR

This paper combines results from multiple neutrinoless double beta decay experiments across various isotopes to derive stronger, more consistent bounds on Majorana neutrino masses, and proposes a visual comparison method.

Contribution

It introduces a self-consistent approach to combine experimental bounds across isotopes and models, improving the robustness of Majorana mass constraints.

Findings

Combined bounds are stronger than individual experiments.

Results show less variation across different nuclear models.

Projections suggest near-term experiments can probe the inverted hierarchy.

Abstract

Combined bounds on the Majorana neutrino mass for light and heavy neutrino exchange mechanisms are derived from current neutrinoless double beta decay (0{\nu}\b{eta}\b{eta}) search results for a variety of nuclear matrix element (NME) models. The approach requires self-consistency of a given model to predict NMEs across different isotopes. The derived bounds are notably stronger than those from any single experiment and show less model-to-model variation, highlighting the advantages of using multiple isotopes in such searches. Projections indicate that the combination of near-term experiments should be able to probe well into the inverted mass hierarchy region. A method to visually represent 0{\nu}\b{eta}\b{eta} experimental results is also suggested to more transparently compare across different isotopes and explicitly track model dependencies.