WORLD STATUS OF DOUBLE BETA DECAY

After neutrino oscillation discovery, search for Neutrinoless Double Beta Decay (0ν–DBD) represents the new frontier of neutrino physics, allowing in principle to fix the neutrino mass scale, the neutrino nature (Dirac or Majorana particle) and to reveal CP violation effects. In this paper, we introduce the main experimental approaches to this search and review the most sensitive present experiments, able to constrain the effective neutrino Majorana mass (〈m_ν〉) to a value lower than a few tenths of eV. Next-generation experiments are then overviewed, with a critical comparison between the claimed performance and the real results achieved so far in the corresponding smaller-scale searches. A positive result in case of inverse-hierarchy neutrino-mass spectrum looks within the reach of the most promising future detectors.