Neutrinoless double-beta decay of 76 Ge

An underground experiment where a Ge(Li) diode is used both as source and as detector of the lepton nonconserving neutrinoless ββ decay of76Ge is reported. A 68.5 cm3 active volume Ge(Li) heavily shielded against local radioactivity has been operated for about 4400 h of effective running time in a laboratory situated in the Mont Blanc tunnel (4.200 m of water equivalent). No evidence for neutrinoless decay was found with an upper limit on the lifetime of τ0v>5·1021 years at 68% confidence level. This result, together with those of other experiments on different nuclei, is discussed in connection with the present theories on lepton nonconservation, and a limit on the lepton nonconserving amplitude is obtained.