Nuclear-structure aspects of double beta decay

Abstract

Neutrinoless double beta (0νββ) decay of nuclei is a process that requires the neutrino to be a massive Majorana particle and thus cannot proceed in the standard model of electro‐weak interactions. Recent results of the neutrino‐oscillation experiments have produced accurate information on the mixing of neutrinos and their squared mass differences. The 0νββ decay takes place in atomic nuclei where it can be observed, at least in principle, by underground neutrino experiments. The need of nuclei in observation of the 0νββ decay bears two facets: The nucleus serves as laboratory for detection but at the same time its complicated many‐nucleon structure interferes strongly with the analysis of the experimetal data. The information about the weak‐interaction observables, like the neutrino mass, has to be filtered from the data through the nuclear matrix elements (NMEs). Hence, exact knowledge about the NMEs is of paramount importance in the analysis of the data provided by the expensive and time‐consuming underground experiments.