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Register a new userPrecise measurement of $2 ubetabeta$ decay of $^{100}$Mo with the CUPID-Mo detection technology
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We report the measurement of the two-neutrino double-beta ($2 ubetabeta$) decay of $^{100}$Mo to the ground state of $^{100}$Ru using lithium molybdate (crystal) scintillating bolometers. The detectors were developed for the CUPID-Mo program and operated at the EDELWEISS-III low background facility in the Modane underground laboratory. From a total exposure of $42.235$ kg$times$d, the half-life of $^{100}$Mo is determined to be $T_{1/2}^{2 u}=[7.12^{+0.18}_{-0.14},mathrm{(stat.)}pm0.10,mathrm{(syst.)}]times10^{18}$ years. This is the most accurate determination of the $2 ubetabeta$ half-life of $^{100}$Mo to date. We also confirm, with the statistical significance of $>3sigma$, that the single-state dominance model of the $2 ubetabeta$ decay of $^{100}$Mo is favored over the high-state dominance model.
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The CUPID-Mo experiment at the Laboratoire Souterrain de Modane (France) is a demonstrator for CUPID, the next-generation ton-scale cryogenic $0 ubetabeta$ experiment. It consists of a 4.2 kg array of 20 enriched Li$_{2}$$^{100}$MoO$_4$ scintillating bolometers to search for the lepton number violating process of $0 ubetabeta$ decay in $^{100}$Mo. With more than one year of operation (2.16 kg$times$yr of physics data), no event in the region of interest and hence no evidence for $0 ubetabeta$ is observed. We report a new limit on the half-life of $0 ubetabeta$ decay in $^{100}$Mo of $T_{1/2} > 1.5 times 10^{24},$yr at 90 % C.I. The limit corresponds to an effective Majorana neutrino mass $langle m_{betabeta} rangle$ $<$ (0.31--0.54)$,$eV, dependent on the nuclear matrix element in the light Majorana neutrino exchange interpretation.
The NEMO-3 experiment measured the half-life of the $2 ubetabeta$ decay and searched for the $0 ubetabeta$ decay of $^{116}$Cd. Using $410$ g of $^{116}$Cd installed in the detector with an exposure of $5.26$ y, ($4968pm74$) events corresponding to the $2 ubetabeta$ decay of $^{116}$Cd to the ground state of $^{116}$Sn have been observed with a signal to background ratio of about $12$. The half-life of the $2 ubetabeta$ decay has been measured to be $ T_{1/2}^{2 u}=[2.74pm0.04mbox{(stat.)}pm0.18mbox{(syst.)}]times10^{19}$ y. No events have been observed above the expected background while searching for $0 ubetabeta$ decay. The corresponding limit on the half-life is determined to be $T_{1/2}^{0 u} ge 1.0 times 10^{23}$ y at the $90$ % C.L. which corresponds to an upper limit on the effective Majorana neutrino mass of $langle m_{ u} rangle le 1.4-2.5$ eV depending on the nuclear matrix elements considered. Limits on other mechanisms generating $0 ubetabeta$ decay such as the exchange of R-parity violating supersymmetric particles, right-handed currents and majoron emission are also obtained.
Energy resolution, alpha/beta ratio, pulse-shape discrimination for gamma rays and alpha particles, temperature dependence of scintillation properties, and radioactive contamination were studied with CaMoO4 crystal scintillators. A high sensitivity experiment to search for neutrinoless double beta decay of 100-Mo by using CaMoO4 scintillators is discussed.
Rare event physics demands very detailed background control, high-performance detectors, and custom analysis strategies. Cryogenic calorimeters combine all these ingredients very effectively, representing a promising tool for next-generation experiments. CUPID-0 is one of the most advanced examples of such a technique, having demonstrated its potential with several results obtained with limited exposure. In this paper, we present a further application. Exploiting the analysis of delayed coincidence, we can identify the signals caused by the $^{220}$Rn-$^{216}$Po decay sequence on an event-by-event basis. The analysis of these events allows us to extract the time differences between the two decays, leading to a new evaluation of $^{216}$ half-life, estimated as (143.3 $pm$ 2.8) ms.
The CUPID-Mo experiment is searching for neutrinoless double beta decay in $^{100}$Mo, evaluating the technology of cryogenic scintillating Li$_{2}^{100}$MoO$_4$ detectors for CUPID (CUORE Upgrade with Particle ID). CUPID-Mo detectors feature background suppression using a dual-readout scheme with Li$_{2}$MoO$_4$ crystals complemented by Ge bolometers for light detection. The detection of both heat and scintillation light signals allows the efficient discrimination of $alpha$ from $gamma$&$beta$ events. In this proceedings, we discuss results from the first 2 months of data taking in spring 2019. In addition to an excellent bolometric performance of 6.7$,$keV (FWHM) at 2615$,$keV and an $alpha$ separation of better than 99.9% for all detectors, we report on bulk radiopurity for Th and U. Finally, we interpret the accumulated physics data in terms of a limit of $T_{1/2}^{0 u},> 3times10^{23},$yr for $^{100}$Mo and discuss the sensitivity of CUPID-Mo until the expected end of physics data taking in early 2020.
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