Bulletin of the American Physical Society
2015 Fall Meeting of the APS Division of Nuclear Physics
Volume 60, Number 13
Wednesday–Saturday, October 28–31, 2015; Santa Fe, New Mexico
Session HD: Mini-Symposium on Experimental Challenges for Double Beta Decay Experiments II |
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Chair: Matthew Green, North Carolina State University, Oak Ridge National Laboratory Room: Sweeney Ballroom C |
Friday, October 30, 2015 8:30AM - 8:42AM |
HD.00001: CUORE: Cryogenic challenges and prospects for a future upgrade Vivek Singh The Cryogenic Underground Observatory for Rare Events (CUORE) is a ton-scale bolometric experiment searching for the $0\nu\beta\beta$ decay in $^{130}$Te. It consists of a closely packed array of 988 TeO$_2$ crystals (5 x 5 x 5 cm$^3$ each) and will be hosted in one of the largest cryostats ever constructed to reach a base temperature of $\sim$10 mK. With a background goal of 10 c/keV/ton/y and an expected energy resolution of $\sim$5 keV in the region of interest, CUORE has the potential to probe the effective Majorana neutrino mass down to 50-130 meV (90$\%$ C.L). A natural follow-up to CUORE would be a ton-scale bolometric experiment which can be sensitive to the effective mass of $\sim$10 meV, covering the entire inverted hierarchy region of the mass spectrum. CUPID (CUORE Upgrade with Particle ID) is a proposed next-generation bolometric experiment which aims to use the CUORE cryogenic infrastructure in conjunction with new detector technologies and novel background mitigation techniques. After briefly outlining the design of CUORE with a focus on its novel cryogenic system, an overview of the current status of CUORE commissioning effort would be presented. The talk will then delve on some of the R\&D activities which are being actively pursued under the CUPID framework. [Preview Abstract] |
Friday, October 30, 2015 8:42AM - 8:54AM |
HD.00002: Research and Development Supporting a Next Generation Germanium Double Beta Decay Experiment Keith Rielage, Steve Elliott, Pinghan Chu, Johnny Goett, Ralph Massarczyk, Wenqin Xu To improve the search for neutrinoless double beta decay, the next-generation experiments will increase in source mass and continue to reduce backgrounds in the region of interest. A promising technology for the next generation experiment is large arrays of Germanium p-type point contact detectors enriched in 76-Ge. The experience, expertise and lessons learned from the MAJORANA DEMONSTRATOR and GERDA experiments naturally lead to a number of research and development activities that will be useful in guiding a future experiment utilizing Germanium. We will discuss some R\&D activities including a hybrid cryostat design, background reduction in cabling, connectors and electronics, and modifications to reduce assembly time. [Preview Abstract] |
Friday, October 30, 2015 8:54AM - 9:06AM |
HD.00003: The next generation neutrinoless double-beta decay experiment nEXO Michael Jewell The nEXO Collaboration is designing a very large detector for neutrinoless double beta decay of Xe$^{136}$. The nEXO detector is rooted in the the current EXO-200 program, which has reached a sensitivity for the half-life of the decay of $1.9\times10^{25}$\,y with an exposure of 99.8 kg-y. The baseline nEXO design assumes 5 tonnes of liquid xenon, enriched in the mass 136 isotope, within a time projection chamber. The detector is being designed to reach a half-life sensitivity of $>5\times10^{27}$\,y, covering the inverted neutrino mass hierarchy, with 5 years of data. We present the nEXO detector design, the current status of R\&D efforts, and the physics case for the experiment. [Preview Abstract] |
Friday, October 30, 2015 9:06AM - 9:18AM |
HD.00004: Barium Tagging for nEXO Daniel Fudenberg, Thomas Brunner, Victor Varentsov, Ralph DeVoe, Jens Dilling, Giorgio Gratta nEXO is a next-generation experiment designed to search for $0\nu\beta\beta$-decay of Xe-136 in a liquid xenon time projection chamber. Positive observation of this decay would determine the neutrino to be a Majorana particle In order to greatly reduce background contributions to this search, the collaboration is developing several ``barium tagging'' techniques to recover and identify the decay daughter, Ba-136. ``Tagging'' may be available for a 2nd phase of nEXO and will push the sensitivity beyond the inverted neutrino-mass hierarchy. Tagging methods in testing for this phase include Ba-ion capture on a probe with identification by resonance ionization laser spectroscopy, and Ba capture in solid xenon on a cold probe with identification by fluorescence. In addition, Ba tagging for a gas-phase detector, appropriate for a later stage, is being tested. Here efficient ion extraction from heavy carrier gases is key. Detailed gas-dynamic and ion transport calculations have been performed to optimize for ion extraction. An apparatus to extract Ba ions from up to 10 bar xenon gas into vacuum using an RF-only funnel has been constructed and demonstrates extraction of ions from noble gases. We will present this system's status along with results of this R\&D program. [Preview Abstract] |
Friday, October 30, 2015 9:18AM - 9:30AM |
HD.00005: Progress in Barium Tagging on a Cryogenic Probe for the nEXO Neutrinoless Double Beta Decay Experiment Adam Craycraft, Timothy Walton, Christopher Chambers, William Fairbank nEXO is a next-generation experiment designed to search for neutrinoless double beta decay of the isotope Xe-136 in a liquid xenon time projection chamber. Positive observation of this decay would determine the nature of the neutrino to be a Majorana particle. Detecting the presence of the daughter Ba-136 at a decay site (called ``barium tagging'') provides strong rejection of backgrounds. Barium tagging may be available for a second phase of nEXO operation, allowing neutrino mass sensitivity beyond the inverted mass hierarchy. Here we present progress on a barium tagging method that involves trapping the barium ion/atom in solid xenon (SXe) at the end of a cold probe, and then detecting the ion/atom by its fluorescence in the SXe. Recent results on imaging small numbers of Ba atoms in SXe on a sapphire window, and progress toward capture of Ba atoms/ions on a cold probe and extraction from LXe, will be presented. [Preview Abstract] |
Friday, October 30, 2015 9:30AM - 9:42AM |
HD.00006: Detection of the barium daughter in $^{136}$Xe $\to ^{136}$Ba $+$ 2e$^{-}$ by \textit{in situ} single-molecule fluorescence imaging David Nygren To proceed toward effective ``discovery class'' ton-scale detectors in the search for neutrino-less double beta decay, a robust technique for rejection of all radioactivity-induced backgrounds is urgently needed. An efficient technique for detection of the barium daughter in the decay $^{136}$Xe $\to ^{136}$Ba $+$ 2e$^{-}$ would provide a long-sought pathway toward this goal. Single-molecule fluorescent imaging appears to offer a new way to detect the barium daughter atom, which emerges naturally in an ionized state in pure xenon. A doubly charged barium ion can initiate a chelation process with a non-fluorescent precursor molecule, leading to a highly fluorescent complex. Repeated photo-excitation of the complex can reveal both presence and location of a single ionized atom with high precision and selectivity. Detection within the active volume of a xenon gas Time Projection Chamber operating at high pressure would be automatic, and with a capability for redundant confirmation. [Preview Abstract] |
Friday, October 30, 2015 9:42AM - 9:54AM |
HD.00007: A Search for Lorentz-Violation in Double Beta Decay with EXO-200 Tessa Johnson The Standard-Model Extension (SME) framework assumes Lorentz-violation at the Planck scale, a result of certain theories uniting quantum mechanics to General Relativity. Lorentz-violating operators are added to the current Standard Model, potentially producing effects that could be observed on a macroscopic scale, for instance altering the standard spectrum of double beta decay. The EXO-200 experiment uses 175 kg of enriched liquid xenon to search for neutrinoless double beta decay in $^{136}$Xe, and the low background and high precision of the experiment create a good platform to search for other phenomena in double beta decay. The results of a search for deviations to the two-neutrino double beta decay spectrum of $^{136}$Xe that would indicate neutrino coupling to a Lorentz-violating operator in the SME are presented. [Preview Abstract] |
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