A Calorimetric Search on Double Beta Decay of 130Te

TL;DR

This paper reports the final results of a cryogenic detector experiment searching for neutrinoless double beta decay of 130Te, setting the most restrictive direct limit on its lifetime and discussing implications for neutrino physics.

Contribution

It presents the largest cryogenic detector array for double beta decay search and provides the most restrictive direct limit on 130Te neutrinoless decay to date.

Findings

Lower limit of 2.1×10^23 years on 130Te neutrinoless double beta decay lifetime

Most restrictive limit on effective neutrino mass among direct experiments

Evidence for two-neutrino double beta decay of 130Te

Abstract

We report on the final results of a series of experiments on double decay of 130Te 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 128Te and two others in 130Te. The remaining ones are made with natural tellurium, which contains 31.7 % and 33.8 % 128Te and 130Te, 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 2.1E23 years has been obtained at the 90 % C.L. on the lifetime for neutrinoless double beta decay of 130Te. 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 130Te and on the neutrinoless double beta decay of 128Te to the ground state of 128Xe are also reported and discussed. An indication is presented for the two neutrino double beta decay of 130Te. Some consequences of the present results in the interpretation of geochemical experiments are discussed.