The LBL/UCSB 76Ge Double Beta Decay Experiment: First Results

A paper given at the IEEE Nuclear Science Symposium last year presented the scientific justification for this experiment and discussed the design of the detector system. At the present time two of the dual detector systems (i.e., four out of a final total of eight detectors) are operating in the complete active/ passive shield in the low background laboratory at LBL. Early results (1620 hrs) of an experiment using two detectors yield a limit of 4 × 1022 years (68% confidence) for the half life of the neutrinoless double beta decay (ßßo¿) of 76Ge. Although this experiment was carried out above ground, the result approaches those achieved by other groups in deep underground laboratories. Based on studies of the origins of background in our system, we hope to reach a limit of 3 × 1023 years (or more) in a two month/ four detector experiment to be carried out soon in an underground facility.