Search for neutrinoless double beta decay with enriched 76Ge in Gran Sasso 1990-2003

The results of the HEIDELBERG-MOSCOW experiment which searches with 11 kg of enriched 76Ge for double beta decay in the Gran Sasso underground laboratory are presented for the full running period August 1990-May 2003. The duty cycle of the experiment was ~80%, the collected statistics is 71.7 kg yr. The background achieved in the energy region of the Q value for double beta decay is 0.11 events kg-1 yr -1 keV-1 . The two-neutrino accompanied half-life is determined on the basis of more than 100 000 events. The confidence level for the neutrinoless signal has been improved to 4.2σ