A calorimetric search on double beta decay of 130Te

We report on the final results of a series of experiments on double beta decay of Te-130 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-128 and two others in Te-130. The remaining ones are made with natural tellurium, which contains 31.7% and 33.8% Te-128 and Te-130, 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 lower limit of 2.1 x 10(23) years has been obtained at the 90% C.L. on the lifetime for neutrinoless double beta decay of Te-130. In terms of effective neutrino mass this leads to the most restrictive limit in direct experiments, after those obtained with Ge diodes. Limits on other lepton violating decays of Te-130 and on the neutrinoless double beta decay of Te-128 to the ground state of Xe-128 are also reported and discussed. An indication is presented for the two neutrino double beta decay of Te-130. Some consequences of the present results in the interpretation of geochemical experiments are discussed. (C) 2003 Elsevier Science B.V. All fights reserved.