High sensitivity GEM experiment on 2β decay of76Ge

The GEM project is designed for the next-generation 2β decay experiments with 76Ge. One ton of `naked' HP Ge detectors (natural at the first GEM-I phase and enriched in 76Ge 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 11×11 m2). Monte Carlo simulation evidently shows that the sensitivity of the experiment (in terms of the T1/2 limit for 0ν2β decay) is ≈1027 yr with natural HP Ge crystals and ≈1028 yr with enriched ones. These bounds correspond to the restrictions on the neutrino mass mν≤0.05 eV and mν≤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.