A search for double beta decay in 76Ge

Abstract

A search for neutrinoless double beta (0 vββ) decay in 76Ge has been carried out using an array of eight 140 cm 3 (fiducial volume of 1095 cm 3) high purity germanium semiconductor crystals situated in the St. Gotthard underground laboratory. Operation of the detector array for a total of 5848 h (3.93 kg yr) yields no evidence for 0 vββ decay and gives an upper limit of T 1 2 0v(0 +→0 +) > 2.7 (1.6)×10 23 yr and T 1 2 0v(0 +→2 +) > 1.0 (0.6) × 10 23 yr at the 68%(90%) confidence level. Majorana neutrino mass limits are deduced. Limits for the double beta decay with majoron emission ( Σ 0 ββ) and two-neutrino double beta decay (2v ββ) have also been obtained and are T 1 2 Σ0 >1.7 (1.0) × 10 21 yr nd T 1 2 2v > 1.2 (1.0) × 10 20 yr , at 68%(90%) CL.