Speaker
Description
We present an analysis of neutrinoless double beta decay (DBD) mediated by non-interfering exchange of light and heavy neutrinos, in the context of current calculations of nuclear matrix elements (NME) in different nuclear models.
We derive joint upper bounds on the light and heavy contributions to the Majorana effective mass through an updated combination of the latest data from the following experiments and isotopes: GERDA and MAJORANA (Ge), KamLAND-Zen and EXO (Xe), and CUORE (Te), for different choices of NME. We then consider three Ton-scale project which might provide possible DBD evidence at >3sigma level in the allowed parameter space: LEGEND (Ge), nEXO (Xe) and CUPID (Mo). The combinations of possible DBD signals mediated by light, heavy, and light+heavy neutrinos is studied for different choices of NME, showing the conditions under which the underlying mechanism(s) can be identified or not. In particular, the role of NME ratios in different isotopes is elucidated through appropriate graphical representations. By using different "true" and "test" NME sets as a proxy for NME uncertainties, significant bias effects may emerge, confusing the identification of light vs heavy neutrino contributions to DBD signals. These results provide further motivations for more accurate NME calculations and for multi-isotope DBD searches at the Ton scale.
| Collaboration / Activity | Neutrino Physics |
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