Neutrinoless Double Beta Decay and Neutrino Masses

Neutrinoless double beta decay (0 nu beta beta) is a promising test for lepton number violating physics beyond the standard model (SM) of particle physics. There is a deep connection between this decay and the phenomenon of neutrino masses. In particular, we will discuss the relation between 0 nu beta beta and Majorana neutrino masses provided by the so-called Schechter-Valle theorem in a quantitative way. Furthermore, we will present an experimental cross check to discriminate 0 nu beta beta from unknown nuclear background using only one isotope, i.e., within one experiment.