Double beta decay: present status

The present status of double beta decay experiments (including the search for $2{\beta }^{+}$, EC${\beta }^{+}$ 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 $<m_{\nu }><0.75$ eV and $<g_{ee}

< 1.9 \cdot 10^{-4}$, respectively. Proposals for future double beta decay experiments with a sensitivity for the $<m_{\nu }>$ at the level of (0.01-0.1) eV are considered.