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Register a new userImproved limits on $beta^+$EC and ECEC processes in $^{74}$Se
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New limits on $beta^+$EC and ECEC processes in $^{74}$Se have been obtained using a 600 cm$^3$ HPGe detector and an external source consisting of 1600 g of a natural selenium powder. For different $beta^+$EC and ECEC transitions (to the ground and excited states) obtained limits are on the level $sim (0.2-4.8)times10^{19}$ yr at 90% C.L. In particular, for the potentially resonant transition into the 1204.2 keV excited state of $^{74}$Ge a lower half-life limit of $1.1times10^{19}$ yr at 90% C.L. has been obtained. Possibility to increase the sensitivity of such measurements is discussed.
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A radiopure cadmium tungstate crystal scintillator, enriched in 106-Cd to 66%, with mass of 216 g (106-CdWO4) was used in coincidence with four ultra-low background HPGe detectors contained in a single cryostat to search for double beta decay processes in 106-Cd. New improved half-life limits on the double beta processes in 106-Cd have been set on the level of 1e20-1e21 yr after 13085 h of data taking deep underground (3600 m w.e.) at the Gran Sasso National Laboratories of INFN (Italy). In particular, the limit on the two neutrino electron capture with positron emission T1/2 >1.1e21 yr, has reached the region of theoretical predictions. The resonant neutrinoless double electron captures to the 2718, 2741 and 2748 keV excited states of 106-Pd are restricted on the level of T1/2 > 8.5e20 - 1.4e21 yr.
We present a search for beta plus/EC double beta decay of 120Te performed with the CUORICINO experiment, an array of TeO2 cryogenic bolometers. After collecting 0.0573 kg y of 120Te, we see no evidence of a signal and therefore set the following limits on the half-life: T1/2 (0nu) > 1.9 10^{21} y at 90% C.L. for the 0 neutrino mode and T1/2 (2nu) > 7.6 10^{19} y at 90% C.L. for the two neutrino mode. These results improve the existing limits by almost three orders of magnitude (four in the case of 0 neutrino mode).
Double-beta processes in $^{184}$Os and $^{192}$Os were searched for over 15851 h at the Gran Sasso National Laboratory (LNGS) of the I.N.F.N. by using a 118 g ultra-pure osmium sample installed on the endcap of a 112 cm$^3$ ultra-low-background broad-energy germanium detector. New limits on double-electron capture and electron capture with positron emission in $^{184}$Os were set at the level of $lim T_{1/2} sim 10^{16}-10^{17}$ yr. In particular the $2 u$2K and $2 u$KL decays of $^{184}$Os to the ground state of $^{184}$W are restricted as $T_{1/2}geq3.0times 10^{16}$ yr and $T_{1/2}geq2.0times 10^{16}$ yr, respectively. A lower limit on the half-life for the double-beta decay of $^{192}$Os to the first excited level of $^{192}$Pt was set as $lim T_{1/2}=2.0times 10^{20}$ yr at 90% C.L.
We report new results from the search for neutrinoless double-beta decay in $^{130}$Te with the CUORE detector. This search benefits from a four-fold increase in exposure, lower trigger thresholds and analysis improvements relative to our previous results. We observe a background of $(1.38pm0.07)cdot10^{-2}$ counts$/($keV$cdot$kg$cdot$yr$)$ in the $0 ubetabeta$ decay region of interest and, with a total exposure of 372.5 kg$cdot$yr, we attain a median exclusion sensitivity of $1.7cdot10^{25}$ yr. We find no evidence for $0 ubetabeta$ decay and set a $90%$ CI Bayesian lower limit of $3.2cdot10^{25}$ yr on the $^{130}$Te half-life for this process. In the hypothesis that $0 ubetabeta$ decay is mediated by light Majorana neutrinos, this results in an upper limit on the effective Majorana mass of 75-350 meV, depending on the nuclear matrix elements used.
We report the first direct measurement of the $^{14}text{O}$ superallowed Fermi $beta$-decay $Q_{EC}$-value, the last of the so-called traditional nine superallowed Fermi $beta$-decays to be measured with Penning trap mass spectrometry. $^{14}$O, along with the other low-$Z$ superallowed $beta$-emitter, $^{10}$C, is crucial for setting limits on the existence of possible scalar currents. The new ground state $Q_{EC}$ value, 5144.364(25) keV, when combined with the energy of the $0^+$ daughter state, $E_x(0^+)=2312.798(11)$~keV [Nucl. Phys. A {bf{523}}, 1 (1991)], provides a new determination of the superallowed $beta$-decay $Q_{EC}$ value, $Q_{EC}(text{sa}) = 2831.566(28)$ keV, with an order of magnitude improvement in precision, and a similar improvement to the calculated statistical rate function $f$. This is used to calculate an improved $mathcal{F}t$-value of 3073.8(2.8) s.
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