High sensitivity GEM experiment on 2β decay of 76Ge

The GEM project is designed for the next-generation 2 beta decay experiments with Ge-76. One ton of 'naked' HP Ge detectors (natural at the first GEM-I phase and enriched in Ge-76 to 86% at the second GEM-II stage) are operating in super-high-purity liquid nitrogen contained in a Cu vacuum cryostat (sphere of diameter 5 m). The latter is placed in the water shield (of dimensions 11 X 11 m(2)). Monte Carlo simulation evidently shows that the sensitivity of the experiment (in terms of the T-1/2 limit for 0v2 beta decay) is approximate to 10(27) yr with natural HP Ge crystals and approximate to 10(28) yr with enriched ones. These bounds correspond to the restrictions on the neutrino mass m(v) less than or equal to 0.05 eV and m(v) less than or equal to 0.015 eV with natural and enriched detectors, respectively. Besides, the GEM-I set-up could advance the current best limits on the existence of neutralinos-as dark matter candidates-by three orders of magnitude, and at the same time would be able to identify unambiguously the dark matter signal by detection of its seasonal modulation. (Some figures in this article are in colour only in the electronic version).