Nuclear observables relevant to neutrinoless double-beta decay

Observation of 0νββ would allow the absolute neutrino masses to be determined if the associated matrix elements can be determined. No other physical process samples these directly and so complex calculations must be used to determine them. Different methods (QRPA, shell models, IBM etc.) have yet to reach satisfactory consistency. It is clear that the initial/final nuclear wave functions are important and transfer reactions are able to provide useful tests by benchmarking the relative occupation of valence orbitals. Some calculations use the BCS approximation, the validity of which can be assessed by pair transfer.