Ja n 20 03 A Calorimetric Search on Double Beta Decay of 130

We report on the final results of a series of experiments on double decay of Te carried out with an array of twenty cryogenic detectors. The set-up is made with crystals of TeO2 with a total mass of 6.8 kg, the largest operating one for a cryogenic experiment. Four crystals are made with isotopically enriched materials: two in Te and two others in Te . The remaining ones are made with natural tellurium, which contains 31.7 % and 33.8 % Te and Te, respectively. The array was run under a heavy shield in the Gran Sasso Underground Laboratory at a depth of about 3500 m.w.e. By recording the pulses of each detector in anticoincidence with the others a 90 % C.L. lower limit of 2.1 × 10 years has been obtained at the 90 % C.L. on the lifetime for neutrinoless double beta decay of Te . In terms of effective neutrino mass this is the most restrictive limit in direct experiments, after those obtained with Ge diodes. Limits on other lepton violating decays of Te and on the neutrinoless double beta decay of Te to the ground state of Xe are also reported and discussed. An indication is presented for the two neutrino double beta decay of Te . Some consequences of the present results in the interpretation of geochemical experiments are discussed.