Double beta decay and dark matter in the Gotthard germanium experiment

An array of eight high purity Germanium crystals is operated in the Gotthard road tunnel. Based on a data sample of 6.2 kg years, limits on different modes of double beta decay in Ge-76 are obtained. In particular, the half-life for the neutrinoless double beta decay to the ground state of Se-76 is greater than 2.0 . 10(23) (3.4 . 10(23)) years at the 90% (68%) confidence level. A low energy sample of 51.6 kg days was used to set limits on cold dark matter. In particular, Dirac neutrinos with masses between 10 and 2400 GeV are ruled out. A new lower limit on the half-life for the decay of the electron into weakly interacting particles of 1.9 . 10(23) years at 68% confidence level was also derived.