NEW RESULTS IN THE ITEP/YePI DOUBLE BETA-DECAY EXPERIMENT WITH ENRICHED GERMANIUM DETECTORS

Abstract

The search for double beta-decay of 76 Ge was carried out with a detector fabricated of enriched material (85% abundance of 76 Ge compared with 7.8% natural abundance). Measurements have been performed by the ITEP/YePI team in the Avan salt mine, 245 meters underground, situated in Yerevan, Armenia. Evidence for two-neutrino double beta-decay of 76 Ge with half-life of T1/2(2v)=(9±1) · 1020 y was obtained. New limits for neutrinoless double beta-decay, T1/2(0v)>1.3×1024 y, and double beta-decay with majoron emission T1/2(0v, B)>1×1022 y were obtained at 68% CL from mean background fluctuations. Limit for 0v-decay derived by the maximum likelihood method was T1/2>2.0×1024 y.