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

• Received 29 October 2001

DOI:https://doi.org/10.1103/PhysRevD.65.092007