Double beta decay-present and future

The best lifetime limit (1.2*10²⁴ years at the 90% C.L.) for neutrinoless double beta decay, beta beta _{0 nu} , comes from the UCSB/LBL experiment. This corresponds to a Majorana neutrino mass of about 1-3 eV/c², which can now be stated as an upper limit, since the possible cancellations due to mixed neutrinos of opposite CP eigenstates have been severely restricted by laboratory and cosmological constraints. Significant mass limit improvements should become possible with superconducting detectors, but if recent results from the solar neutrino experiments are confirmed, beta beta _{0 nu} may not be detectable in the laboratory.