THE HEIDELBERG-MOSCOW EXPERIMENT - IMPROVED SENSITIVITY FOR GE-76 NEUTRINOLESS DOUBLE-BETA DECAY

The Heidelberg-Moscow experiment operates five enriched Ge-76 detector s with 10.96 kg active mass in the Gran Sasso underground laboratory. After 28.7 kg y of measurement with a counting rate between 2000 keV a nd 2080 keV of 0.20+/-0.01 cts/kg y keV we receive a lower limit on th e neutrinoless double beta decay of Ge-76 of T-1/2(0(+) --> 0(+)) > 1. 1 x 10(25) y (90% C.L.). This restricts the Majorana neutrino mass to 0.46 eV. Recently we achieved a reduction in the background counting r ate by a factor of 3-5 within the energy region of the neutrinoless do uble beta decay by recording the differentiated preamplifier pulse sha pes and doing an off-line analysis to distinguish between pointlike an d multiple scattered interactions. (C) 1997 Elsevier Science B.V.