Physics beyond the Standard Model: experiments at the Gran Sasso Laboratory

Experiments in underground laboratories have shown strong evidence of physics beyond the Standard Model. The anomalies observed in electron neutrinos from the sun and muon neutrinos from cosmic rays interacting in the atmosphere can be explained if neutrinos are massive and oscillate. The physics program at the Gran Sasso Laboratory that we are defining will focus on the next phase of neutrino physics with a complementary set of experiments on the muon- neutrino beam from CERN (CNGS project), on solar neutrinos, on atmospheric neutrinos and on neutrinos from supernova explosions. The relevant thermonuclear cross-sections will be measured. The Majorana vs. Dirac nature of electron neutrinos will be explored with the search for neutrinoless double beta decays in different isotopes. Experiments on non-baryonic dark matter are reaching a sensitivity that brings them close to being able to detect neutralinos in certain optimistic theoretical expectations. The program at Gran Sasso for the next years will include a strong effort to increase further the sensitivity by orders of magnitude with different complementary techniques. (38 refs).