Double Beta Decay: History, Present and Future

The properties of the neutrinos have been the most important issues in particle physics, astrophysics, and cosmology. After the discovery of neutrino oscillations, search for neutrinoless double beta decay (0nuBB-decay) represents the new frontiers of neutrino physics, allowing in principle to fix the neutrino mass scale, the neutrino nature (the Dirac or Majorana particles) and possible CP violation effects. Many next generation 0nuBB-decay experiments are in preparation or under consideration. In this presentation the development in the field of nuclear double beta decay is reviewed. A connection of the 0nuBB-decay to neutrino oscillations is established. The light and sterile neutrino exchange mechanisms as well as R-parity breaking mechanisms of the 0nuBB-decay are analyzed. A connection to other lepton number violating processes is also subject of interest. The problem of reliable determination of the 0nuBB-decay nuclear matrix elements is addressed. Possibilities to constrain the 0nuBB-decay nuclear matrix elements with help of charge changing, muon capture and neutrino-nucleus reactions are discussed. The perspectives of the field of the double beta decay are outlined.