New findings on neutrinoless double beta decay matrix elements using IBM-2

¹ Department of Physics, University of Jyväskylä, P.O. Box 35, FI-40014, Jyväskylä, Finland
² Finnish Institute for Educational Research, University of Jyväskylä, P.O. Box 35, FI-40014, Jyväskylä, Finland

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Published online: 21 November 2025

Abstract

Although the study of double beta decay has come a long way since the beginning, there is still much to research. The recent discovery of the ab­sence of a short-range component in the light neutrino exchange mechanism of the nuclear matrix element (NME) for neutrinoless double beta decay shows that the theoretical assessment of the decay is not yet complete. This new com­ponent appears crucial in calculating the total NME, as it can account for up to 50% of the long-range NME, even though the parameters affecting the size of the NME are not precisely known and require further study. We have calcu­lated the short-range NME of neutrinoless double-beta decay using the widely adopted microscopic interacting boson model (IBM-2) and compared the results with those obtained using other nuclear models. We also demonstrate the effect of the new total NME on decay half-life predictions. For example, for ¹³⁰Te, the estimated half-life using the total NME could be as low as 0.54 × 10²⁶ years, compared to 1.08 × 10²⁶ years using only the long-range NME.