Abstract
We report on a search for double beta decay of ^{130}hbox {Te} to the first 0^{+} excited state of ^{130}hbox {Xe} using a 9.8,hbox {kg}cdot hbox {yr} exposure of ^{130}hbox {Te} collected with the CUORE-0 experiment. In this work we exploit different topologies of coincident events to search for both the neutrinoless and two-neutrino double beta decay modes. We find no evidence for either mode and place lower bounds on the half-lives: T^{0nu }_{0^+_1}>7.9cdot 10^{23}hbox {yr} and T^{2nu }_{0^+_1}>2.4cdot 10^{23}hbox {yr} (90%,hbox {CL}). Combining our results with those obtained by the CUORICINO experiment, we achieve the most stringent constraints available for these processes: T^{0nu }_{0^+_1}>1.4cdot 10^{24}hbox {yr} and T^{2nu }_{0^+_1}>2.5cdot 10^{23}hbox {yr} (90%,hbox {CL}).
Highlights
Two-neutrino (2νββ) [1] and neutrinoless (0νββ) [2] double beta decay are among the rarest decay processes studied
The CUORE experiment (Cryogenic Underground Observatory for Rare Events) [6,7,8,9], which is currently running at Laboratori Nazionali del Gran Sasso (LNGS), is designed to perform a high-sensitivity search for 0νββ decay of 130Te to the ground state of 130Xe[10]
The soughtafter experimental signature of 0νββ decay is a monochromatic peak in the summed energy spectrum of the final state electrons at 2527.518 ± 0.013 keV [11,12,13], which is the transition energy of the decay
Summary
Two-neutrino (2νββ) [1] and neutrinoless (0νββ) [2] double beta decay are among the rarest decay processes studied. The active isotope is contained in TeO2 crystals, which are operated as thermal detectors in a cryostat capable of reaching temperatures below 10 mK At this temperature, the crystal heat capacity becomes very small and a release of energy within a crystal results in a detectable increase of its temperature. Two more patterns are possible, namely the emission of three gamma rays with energies of 536.1 keV, 586.0 keV and 671.3 keV (branching ratio of 12.2%) and the emission of two gamma rays with energies of 671.3 keV and 1122.1 keV (branching ratio of 1.8%) These gamma lines result in multi-detector coincidence signatures which we exploit in our analysis to achieve very powerful background rejection. Prior to the current work, the most stringent constraints on these decays came from the CUORICINO [19] experiment, a predecessor to CUORE-0, which reported the following limits on the decay half-lives [20]: T001+ν > 9.4 · 1023 yr , T021+ν > 1.3 · 1023 yr
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