HEIDELBERG-MOSCOW BETA-BETA EXPERIMENT WITH GE-76 - FULL SETUP WITH 5DETECTORS

The full setup of the Heidelberg-Moscow double beta decay experiment i s presented. This experiment gives at present the most stringent upper bound, improving the neutrino mass limit into the sub-eV range. Out o f 19.2 kg of 86% enriched Ge-76 five crystals were grown with a total mass of 11.51 kg. Since February 1995 all five detectors, correspondin g to 10.96 kg active mass, are in regular operation in the Gran Sasso underground laboratory, four of them in a common shield. No signal is observed for the neutrinoless double beta decay (0 nu beta beta). The measured data from the first three enriched detectors with a statistic al significance of 13.60 kg yr result in a new half-life limit of T-1/ 2(0(+)-->0(+))>7.4x10(24) yr (90% C.L.). With this Limit a Majorana ma ss of the neutrinos larger than 0.6 eV (90% C.L.) is excluded. From th e data taken in the previously operated setup with three enriched dete ctors in a common shielding and a statistical significance of 10.58 kg yr new results an extracted for the two neutrino double beta decay (2 nu beta beta) of Ge-76. The procedure of a quantitative and model-ind ependent description of the background via a Monte Carlo simulation is outlined in some detail. The combined result is T-1/2(2 (-0.01)(+0.01 )(stat)(-0.11)(+0.13)(sys)]X10(21)yr. Further on the results concernin g new Majoron models and the impact on SUSY parameters are briefly rev iewed. Future improvements on the background with the application of d igital pulse shape analysis are discussed and an outlook on the future of beta beta research is given.