Bulletin of the American Physical Society
2020 Fall Meeting of the APS Division of Nuclear Physics
Volume 65, Number 12
Thursday–Sunday, October 29–November 1 2020; Time Zone: Central Time, USA
Session KG: Neutrinoless Double Beta Decay II |
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Chair: Jon Engel, UNC |
Saturday, October 31, 2020 8:30AM - 8:42AM |
KG.00001: Investigation of neutron-induced backgrounds in isotopes of Molybdenum for 0$\nu\beta\beta$ decay searches M.F. Kidd, W. Tornow, S. Finch Double-beta decay searches with bolometric crystals are extremely promising due to their excellent energy resolution, detection efficiency, and pulse-shape discrimination. Additionally, they can be constructed from a variety of materials, including many enriched double-beta decay candidates such as $^{100}$Mo. With a Q-value of 3034.40 $\pm$ 0.17 keV, and a natural abundance of 9.82\%, $^{100}$Mo is an excellent candidate nucleus for the study 0$\nu\beta\beta$ decay. One potential background for observing this transition is neutron inelastic scattering on isotopes of molybdenum. In $^{100}$Mo, a nuclear level with energy 3039.4 $\pm$ 1.0 keV cascades to the ground state. Though none of these individual gamma rays emitted in this de-excitation lie in the region of interest, if they all interact within a single bolometric crystal, they will sum to a value within the ROI. Even with an enriched $^{100}$Mo sample, other isotopes of molybdenum will be present. The isotopes $^{95}$Mo and $^{97}$Mo also have energy levels that lie within the ROI: 3037 keV and 3035 keV respectively. The decay schemes of these levels are unknown, so we can only search for decays to the ground state. We report our initial results in the investigation of $^{nat}$Mo(n,n’$\gamma$) with 4.5 MeV neutrons. [Preview Abstract] |
Saturday, October 31, 2020 8:42AM - 8:54AM |
KG.00002: ABSTRACT WITHDRAWN Danielle Speller |
Saturday, October 31, 2020 8:54AM - 9:06AM |
KG.00003: A detailed background model for the CUPID-Mo $0 \nu \beta \beta$ experiment Toby Dixon CUPID-Mo, located in the Laboratoire Souterrain de Modane (France), is a demonstrator for CUPID, a next generation search for $0 \nu \beta \beta$ in $^{100}$Mo. CUPID-Mo consists of 20 $\sim 200g$ Li$_2^{100}$MoO$_4$ scintillating bolometers with 20 Ge light detectors. It has demonstrated excellent crystal radiopurity ($^{238}$U $ ^{232}$Th chains 0.3 - 1 $\mu Bq/kg$ for relevant isotopes), $\alpha$, $\beta/\gamma$ particle discrimination ( $>99.9\%$) and energy resolution ($\sim 7 keV$ FWHM at $2615 keV$). CUPID-Mo has placed the leading limit on the half life of $0 \nu \beta \beta$ in $^{100}$Mo of $T_{1/2}^{0 \nu}>1.4 \cdot 10^{24}yr$ with $90\%$ c.i. In this talk, we present a detailed model to disentangle the various background sources using a Geant4 Monte-Carlo simulation. This enables a precision analysis of the $2\nu \beta \beta$ decay spectrum in $^{100}$Mo. This decay has a short half-life of $\sim 7\cdot 10^{18} yrs$, and CUPID-Mo will provide statistics competitive to much larger experiments but with a much better signal to noise ratio. We then apply these results to the CUPID background model which with a $\sim 100 \times$ increase in mass and significant reduction of passive material will have an unprecedented sensitivity to $0\nu \beta \beta$ in $^{100}$Mo. [Preview Abstract] |
Saturday, October 31, 2020 9:06AM - 9:18AM |
KG.00004: Alpha Background Rejection through Pulse Shape Discrimination in the MAJORANA DEMONSTRATOR Alexandru Hostiuc The MAJORANA DEMONSTRATOR is an experiment searching for neutrinoless double-beta decay in Ge-76. The experiment consists of two modular arrays with 44.8 kg of high purity Germanium detectors, 29.7 kg of which is enriched to 88{\%} in Ge-76, operating at the 4850' level of the Sanford Underground Research Facility in Lead, South Dakota. P-type point contact detector technology allows for the identification and rejection of specific background event populations through an analysis of pulse shape characteristics. The DCR (delayed charge recovery) pulse shape parameter estimates the slope of an event's waveform after the rising edge to identify alpha-like events with a characteristic delayed charge collection component. We present the performance and improvements to our alpha background rejection with the DCR parameter, its systematics, and show its influence on the sensitivity of the experiment. [Preview Abstract] |
Saturday, October 31, 2020 9:18AM - 9:30AM |
KG.00005: Searching for Neutrinoless Double Beta Decay in CUORE using Multi-Site events Sachinthya Wagaarachchi The Cryogenic Underground Observatory for Rare Events (CUORE) is a ton-scale experimental search for 0$\nu\beta\beta$ decay on ${}^{130}$Te. The CUORE detector consists of 988 TeO$_2$ crystals operating as cryogenic bolometers at the Gran Sasso National Laboratory (LNGS) in Italy. Currently our results come from selecting events that have total energy deposited in one crystal, while simulations suggest that about 11\% of 0$\nu\beta\beta$ decay events will have multi-site energy deposition. In this talk we present the preliminary results of 0$\nu\beta\beta$ decay search results using a combination of multi-site and single-site events. We will also discuss the projected sensitivity enhancement due to this novel method and our techniques for estimating the correct background shapes and systematic effects. [Preview Abstract] |
Saturday, October 31, 2020 9:30AM - 9:42AM |
KG.00006: Recent Results from EXO-200 Tim Daniels The detection of neutrinoless double-beta decay (0$\nu \beta \beta )$ would confirm the Majorana nature of neutrinos and shed light on the neutrino mass scale. The EXO-200 experiment employs 110 kg of active xenon enriched to 80.6% in isotope 136 in a liquid-phase time-projection chamber (TPC) in a 0$\nu \beta \beta $ search. Located underground at the Waste Isolation Pilot Plant (WIPP) outside Carlsbad, NM, the experiment collected data in two phases between May 2011 and December 2018. Analysis of the resulting 234.1 kg-yr dataset results in a lower limit on the 0$\nu \beta \beta $ half-life of 3.5x10$^{\mathrm{25}}$ yr at the 90% confidence level. The sensitivity of this low-background experiment is enhanced by the TPC technique, which exploits the anticorrelation of the ionization and scintillation signals and uses topological information to discriminate between beta-like signal events and gamma-ray backgrounds. Additional recent results, including measurements of$^{\mathrm{ 137}}$Xe beta-decay and liquid-xenon scintillation and ionization yields, will also be discussed [Preview Abstract] |
Saturday, October 31, 2020 9:42AM - 9:54AM |
KG.00007: Performance Estimation of Liquid Argon Veto in LEGEND-200 and LEGEND-1000 Rushabh Gala Neutrinoless double-beta decay is a hypothesized lepton-number-violating process. LEGEND-200 and LEGEND-1000 are the two phasses of the planned experiment by the LEGEND Collaboration to search for this process with 200 and 1000 kilograms of germanium detectors enriched in $^{76}$Ge respectively. To achieve the 0$\nu \beta \beta$ half-life sensitivities in excess of $10^{27}$ yrs (LEGEND-200) and $10^{28}$ years (LEGEND-1000), the detectors need to be operated with backgrounds at or below the level of 0.6 counts / (FWHM tn yr) for LEGEND-200 and 0.03 counts / (FWHM tn yr) for LEGEND-1000. For the LEGEND experiment, liquid argon(LAr) is used primarily for two purposes; It serves as a cooling medium for the Ge detectors, and also as a veto medium due to its scintillating properties in the VUV region. When gamma rays produced by the radioactive isotopes interact with the LAr volume, scintillation light is produced. As LAr is transparent to its own light, it can be wavelength shifted and collected by the photodetectors placed in the array and used as an active veto for compton-scattering-induced backgrounds. In this talk, I will discuss the performance of the LAr veto in the LEGEND-200 and LEGEND-1000 detectors. [Preview Abstract] |
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