ABSTRACT
A further nuclear decay which is extremely important for neutrino physics is neutrinoless double β-decay. This lepton-number-violating process requires, in addition to a nonvanishing neutrino mass, that neutrinos are Majorana particles. It is, therefore, often regarded as the gold-plated process for probing the fundamental character of neutrinos. For additional literature see [Doi83, Hax84, Doi85, Gro90, Boe92,Moe94,Kla95,Kla95a,Fae99,Eji00,Vog00,Kla01a,Ell02,Ell04,Zub06,Avi08, Bar08a].
