A renormalized approach to neutrinoless double-beta decay

Understand

The process at the heart of neutrinoless double-beta decay, $nn \rightarrow p p\, e^- e^-$ induced by a light Majorana neutrino, is investigated in pionless and chiral effective field theory.

• We show in various regularization schemes the need to introduce a short-range lepton-number-violating operator at leading order, confirming earlier findings.
• We demonstrate that such a short-range operator is only needed in spin-singlet $S$-wave transitions, while leading-order transitions involving higher partial waves depend solely on long-range currents.
• Calculations are extended to include next-to-leading corrections in perturbation theory, where to this order no additional undetermined parameters appear.