Speaker
Description
Neutrinoless double beta decay (0νββ-decay) is an important probe to study fundamental neutrino properties, e.g., Majorana nature, neutrino masses, CP phases, and non-standard neutrino interactions. The 0νββ-decay nuclear matrix elements (NMEs) are crucial for extracting the neutrino properties from the experimental transition rate. They can not be measured separately but must be evaluated theoretically. The present-day results obtained in a wide variety of nuclear models are discussed. The subjects of interest are many-body approximations, transition operator’s form, and uncertainty in calculated NMEs. The attention is paid mainly to NMEs associated with light and heavy neutrino mass mechanisms of the 0νββ-decay. A connection between the two-neutrino double beta decay (2νββ-decay) and 0νββ-decay NMEs is addressed. An impact of the quenching of the axial-vector coupling constant on double-beta decay processes is analyzed. The related experimental and theoretical studies of single -decay, 2νββ-decay, muon capture processes, and double-charge exchange nuclear reactions are also addressed.
