The Igex 76ge Neutrinoless Double-Beta Decay Experiment: Prospects for Next Generation Experiments

The International Germanium Experiment (IGEX) has analyzed 117 mole yr of 76Ge data from its isotopically enriched (86% 76Ge) germanium detectors. Applying pulse-shape discrimination (PSD) to the more recent data, the lower bound on the half-life for neutrinoless double-beta decay of 76Ge is: $T_{1/2}(0\nu)> 1.57 \times 10^{25}$ yr (90% C.L.). This corresponds to an upper bound in the Majorana neutrino mass parameter,$$, between 0.33 eV and 1.35 eV, depending on the choice of theoretical nuclear matrix elements used in the analysis.