DOUBLE BETA DECAY: PRESENT STATUS

Abstract

The present status of double-beta-decay experiments (including the search for 2β+, ECβ+, and ECEC processes) are reviewed. The results of the most sensitive experiments are discussed. Average and recommended half-life values for two-neutrino double-beta decay are presented. Conservative upper limits on effective Majorana neutrino mass and the coupling constant of the Majoron to the neutrino are established as 〈mν 〉 < 0.75 eV and 〈gee〉 < 1.9 × 10−4, respectively. Proposals for future double-betadecay experiments with a sensitivity for the 〈mν〉 at the level of 0.01–0.1 eV are considered.