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Register a new userChange of nuclear configurations in the neutrinoless double-$beta$ decay of $^{130}$Te $rightarrow$ $^{130}$Xe and $^{136}$Xe $rightarrow$ $^{136}$Ba
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The change in the configuration of valence protons between the initial and final states in the neutrinoless double-$beta$ decay of $^{130}$Te $rightarrow$ $^{130}$Xe and of $^{136}$Xe $rightarrow$ $^{136}$Ba has been determined by measuring the cross sections of the ($d$,$^3$He) reaction with 101-MeV deuterons. Together with our recent determination of the relevant neutron configurations involved in the process, a quantitative comparison with the latest shell-model and interacting-boson-model calculations reveals significant discrepancies. These are the same calculations used to determine the nuclear matrix elements governing the rate of neutrinoless double-$beta$ decay in these systems.
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A quantitative description of the change in ground-state neutron occupancies between $^{136}$Xe and $^{136}$Ba, the initial and final state in the neutrinoless double-$beta$ decay of $^{136}$Xe, has been extracted from precision measurements of the cross sections of single-neutron adding and -removing reactions. Comparisons are made to recent theoretical calculations of the same properties using various nuclear-structure models. These are the same calculations used to determine the magnitude of the nuclear matrix elements for the process, which at present disagree with each other by factors of 2 or 3. The experimental neutron occupancies show some disagreement with the theoretical calculations.
We report on a search for neutrinoless double-beta decay of $^{136}$Xe with EXO-200. No signal is observed for an exposure of 32.5 kg-yr, with a background of ~1.5 x 10^{-3} /(kg yr keV) in the $pm 1sigma$ region of interest. This sets a lower limit on the half-life of the neutrinoless double-beta decay $T_{1/2}^{0 ubetabeta}$($^{136}$Xe) > 1.6 x 10$^{25}$ yr (90% CL), corresponding to effective Majorana masses of less than 140-380 meV, depending on the matrix element calculation.
The CUORICINO experiment was an array of 62 TeO$_{2}$ single-crystal bolometers with a total $^{130}$Te mass of $11.3,$kg. The experiment finished in 2008 after more than 3 years of active operating time. Searches for both $0 u$ and $2 u$ double-beta decay to the first excited $0^{+}$ state in $^{130}$Xe were performed by studying different coincidence scenarios. The analysis was based on data representing a total exposure of N($^{130}$Te)$cdot$t=$9.5times10^{25},$y. No evidence for a signal was found. The resulting lower limits on the half lives are $T^{2 u}_{1/2}(^{130} Terightarrow^{130} Xe^{*})>1.3times10^{23},$y (90% C.L.), and $T^{0 u}_{1/2}(^{130} Terightarrow^{130} Xe^{*})>9.4times10^{23},$y (90% C.L.).
We report on a search for double beta decay of $^{130}$Te to the first $0^{+}$ excited state of $^{130}$Xe using a 9.8 kg$cdot$yr exposure of $^{130}$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-decay modes. We find no evidence for either mode and place lower bounds on the half-lives: $tau^{0 u}_{0^+}>7.9cdot 10^{23}$ yr and $tau^{2 u}_{0^+}>2.4cdot 10^{23}$ yr. Combining our results with those obtained by the CUORICINO experiment, we achieve the most stringent constraints available for these processes: $tau^{0 u}_{0^+}>1.4cdot 10^{24}$ yr and $tau^{2 u}_{0^+}>2.5cdot 10^{23}$ yr.
The CUORE experiment is a large bolometric array searching for the lepton number violating neutrino-less double beta decay ($0 ubetabeta$) in the isotope $mathrm{^{130}Te}$. In this work we present the latest results on two searches for the double beta decay (DBD) of $mathrm{^{130}Te}$ to the first $0^{+}_2$ excited state of $mathrm{^{130}Xe}$: the $0 ubetabeta$ decay and the Standard Model-allowed two-neutrinos double beta decay ($2 ubetabeta$). Both searches are based on a 372.5 kg$times$yr TeO$_2$ exposure. The de-excitation gamma rays emitted by the excited Xe nucleus in the final state yield a unique signature, which can be searched for with low background by studying coincident events in two or more bolometers. The closely packed arrangement of the CUORE crystals constitutes a significant advantage in this regard. The median limit setting sensitivities at 90% Credible Interval (C.I.) of the given searches were estimated as $mathrm{S^{0 u}_{1/2} = 5.6 times 10^{24} : mathrm{yr}}$ for the ${0 ubetabeta}$ decay and $mathrm{S^{2 u}_{1/2} = 2.1 times 10^{24} : mathrm{yr}}$ for the ${2 ubetabeta}$ decay. No significant evidence for either of the decay modes was observed and a Bayesian lower bound at $90%$ C.I. on the decay half lives is obtained as: $mathrm{(T_{1/2})^{0 u}_{0^+_2} > 5.9 times 10^{24} : mathrm{yr}}$ for the $0 ubetabeta$ mode and $mathrm{(T_{1/2})^{2 u}_{0^+_2} > 1.3 times 10^{24} : mathrm{yr}}$ for the $2 ubetabeta$ mode. These represent the most stringent limits on the DBD of $^{130}$Te to excited states and improve by a factor $sim5$ the previous results on this process.
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