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Register a new userThe first result on 76Ge neutrinoless double beta decay from CDEX-1 experiment
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We report the first result on Ge-76 neutrinoless double beta decay from CDEX-1 experiment at China Jinping Underground Laboratory. A mass of 994 g p-type point-contact high purity germanium detector has been installed to search the neutrinoless double beta decay events, as well as to directly detect dark matter particles. An exposure of 304 kg*day has been analyzed. The wideband spectrum from 500 keV to 3 MeV was obtained and the average event rate at the 2.039 MeV energy range is about 0.012 count per keV per kg per day. The half-life of Ge-76 neutrinoless double beta decay has been derived based on this result as: T 1/2 > 6.4*10^22 yr (90% C.L.). An upper limit on the effective Majorana-neutrino mass of 5.0 eV has been achieved. The possible methods to further decrease the background level have been discussed and will be pursued in the next stage of CDEX experiment.
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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.
The NEMO-3 detector, which had been operating in the Modane Underground Laboratory from 2003 to 2010, was designed to search for neutrinoless double $beta$ ($0 ubetabeta$) decay. We report final results of a search for $0 ubetabeta$ decays with $6.914$ kg of $^{100}$Mo using the entire NEMO-3 data set with a detector live time of $4.96$ yr, which corresponds to an exposure of 34.3 kg$cdot$yr. We perform a detailed study of the expected background in the $0 ubetabeta$ signal region and find no evidence of $0 ubetabeta$ decays in the data. The level of observed background in the $0 ubetabeta$ signal region $[2.8-3.2]$ MeV is $0.44 pm 0.13$ counts/yr/kg, and no events are observed in the interval $[3.2-10]$ MeV. We therefore derive a lower limit on the half-life of $0 ubetabeta$ decays in $^{100}$Mo of $T_{1/2}(0 ubetabeta)> 1.1 times 10^{24}$ yr at the $90%$ Confidence Level, under the hypothesis of light Majorana neutrino exchange. Depending on the model used for calculating nuclear matrix elements, the limit for the effective Majorana neutrino mass lies in the range $langle m_{ u} rangle < 0.33$--$0.62$ eV. We also report constraints on other lepton-number violating mechanisms for $0 ubetabeta$ decays.
We propose a novel detection concept for neutrinoless double-beta decay searches. This concept is based on a Time Projection Chamber (TPC) filled with high-pressure gaseous xenon, and with separated-function capabilities for calorimetry and tracking. Thanks to its excellent energy resolution, together with its powerful background rejection provided by the distinct double-beta decay topological signature, the design discussed in this Letter Of Intent promises to be competitive and possibly out-perform existing proposals for next-generation neutrinoless double-beta decay experiments. We discuss the detection principles, design specifications, physics potential and R&D plans to construct a detector with 100 kg fiducial mass in the double-beta decay emitting isotope Xe(136), to be installed in the Canfranc Underground Laboratory.
Neutrinoless double beta decay is a process that violates lepton number conservation. It is predicted to occur in extensions of the Standard Model of particle physics. This Letter reports the results from Phase I of the GERmanium Detector Array (GERDA) experiment at the Gran Sasso Laboratory (Italy) searching for neutrinoless double beta decay of the isotope 76Ge. Data considered in the present analysis have been collected between November 2011 and May 2013 with a total exposure of 21.6 kgyr. A blind analysis is performed. The background index is about 1.10^{-2} cts/(keV kg yr) after pulse shape discrimination. No signal is observed and a lower limit is derived for the half-life of neutrinoless double beta decay of 76Ge, T_1/2 > 2.1 10^{25} yr (90% C.L.). The combination with the results from the previous experiments with 76Ge yields T_1/2 > 3.0 10^{25} yr (90% C.L.).
The Advanced Molybdenum-based Rare process Experiment (AMoRE) aims to search for neutrinoless double beta decay (0$ ubetabeta$) of $^{100}$Mo with $sim$100 kg of $^{100}$Mo-enriched molybdenum embedded in cryogenic detectors with a dual heat and light readout. At the current, pilot stage of the AMoRE project we employ six calcium molybdate crystals with a total mass of 1.9 kg, produced from $^{48}$Ca-depleted calcium and $^{100}$Mo-enriched molybdenum ($^{48textrm{depl}}$Ca$^{100}$MoO$_4$). The simultaneous detection of heat(phonon) and scintillation (photon) signals is realized with high resolution metallic magnetic calorimeter sensors that operate at milli-Kelvin temperatures. This stage of the project is carried out in the Yangyang underground laboratory at a depth of 700 m. We report first results from the AMoRE-Pilot $0 ubetabeta$ search with a 111 kg$cdot$d live exposure of $^{48textrm{depl}}$Ca$^{100}$MoO$_4$ crystals. No evidence for $0 ubetabeta$ decay of $^{100}$Mo is found, and a upper limit is set for the half-life of 0$ ubetabeta$ of $^{100}$Mo of $T^{0 u}_{1/2} > 9.5times10^{22}$ y at 90% C.L.. This limit corresponds to an effective Majorana neutrino mass limit in the range $langle m_{betabeta}ranglele(1.2-2.1)$ eV.
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