Bulletin of the American Physical Society
2010 Fall Meeting of the APS Division of Nuclear Physics
Volume 55, Number 14
Tuesday–Saturday, November 2–6, 2010; Santa Fe, New Mexico
Session GD: Mini-symposium on Nuclear Double Beta Experiments I |
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Chair: Martin Cooper, Los Alamos National Laboratory Room: Sweeny D |
Friday, November 5, 2010 8:30AM - 9:06AM |
GD.00001: Progress and Future Prospects in Neutrinoless Double Beta Decay Experiments Invited Speaker: Lepton number conservation, the neutrino's absolute mass and its particle-antiparticle nature can all be addressed by neutrinoless double beta decay. Double beta decay is being investigated around the world by several experiments using different candidate isotopes. A current status of these searches and their sensitivities to neutrino mass will be presented along with prospects for future neutrinoless double beta decay searches that will push the sensitivity below the 50 meV scale. [Preview Abstract] |
Friday, November 5, 2010 9:06AM - 9:18AM |
GD.00002: Shell model calculations of double-beta decay lifetimes of $^{76}$Ge and $^{82}$Se Sabin Stoica, Andrei Neacsu, Mihai Horoi The neutrinoless double beta decay is the most sensitive process to determine the absolute scale of the neutrino masses, and the only one that can distinguish whether neutrino is a Dirac or a Majorana particle. A key ingredient for extracting the absolute neutrino masses from neutrinoless double beta decay experiments is a precise knowledge of the nuclear matrix elements (NME) for this process. A newly developed shell model approaches for computing the NME and half-lifes for the two-neutrino and neutrinoless double beta decay modes of $^{48}$Ca using modern effective interactions will be presented. The implications of the new results on the experimental limits of the effective neutrino mass will be discussed, and compared with those obtained for the $^{76}$Ge and $^{82}$Se decays. [Preview Abstract] |
Friday, November 5, 2010 9:18AM - 9:30AM |
GD.00003: Double-Beta Decay of $^{150}$Nd to Excited Final States M.F. Kidd, J.H. Esterline, W. Tornow An experimental study of the two-neutrino double-beta (2$\nu\beta\beta$) decay of $^{150}$Nd to various excited final states of $^{150}$Sm was performed at Triangle Universities Nuclear Laboratory (TUNL). Such data provide important checks for theoretical models used to predict 0$\nu\beta\beta$ decay half lives. The measurement was performed at the recently established Kimballton Underground Research Facility (KURF) using the TUNL-ITEP $\beta\beta$ decay setup. In this setup, two high-purity germanium detectors were operated in coincidence to detect the deexcitation gamma rays of the daughter nucleus. This coincidence technique, along with the location underground, provides a considerable reduction in background in the regions of interest. This study yields the first results from KURF and the first detection of the coincidence gamma rays from the 0$^+_1$ excited state of $^{150}$Sm. These gamma rays have energies of 334.0 keV and 406.5 keV, and are emitted in coincidence through a 0$^+_1\rightarrow$2$^+_1\rightarrow$0$^+_{gs}$ transition. An enriched Nd$_2$O$_3$ sample obtained from Oak Ridge National Laboratory was used. After counting for 391 days, 29 raw events in the region of interest were observed. This count rate gives a half life of $T_{1/2}=(0.72^{+0.36}_{-0.18}\pm0.04(syst.))\times 10^{20}$ years, which agrees within error with another recent measurement, in which no coincidence was employed. An updated result will be given. [Preview Abstract] |
Friday, November 5, 2010 9:30AM - 9:42AM |
GD.00004: Inelastic neutron scattering as a potential background in neutrinoless double-beta decay experiments Melissa Boswell, M. Devlin, S.R. Elliott, N. Fotiades, A. Hime, R.O. Nelson, V. Guiseppe, D.-M. Mei, D.V. Perepelitsa I will present an overview of the {\sc{Majo\-ra\-na}} experiment, with particular emphasis on our work studying neutron interactions in shielding and detector materials. The {\sc{Majo\-ra\-na}} experiment is studying neutrinoless double-beta decay in $^{76}$Ge using an array of HPGe detectors. As with similar double beta decay experiments, the success of the experiment relies on reducing the intrinsic radioactive background to unprecedented levels, while adequately shielding the detectors from external sources of radioactivity. An understanding of the potential for neutron excitation of the shielding and detector materials is important for obtaining this level of sensitivity. Using the broad-spectrum neutron beam at LANSCE, we have measured the inelastic neutron scattering from $^{nat}$Cu, $^{enr}$Ge, and $^{nat}$Pb. The goal of this work is focused on measuring the background rates from these materials in regions around the Q-values of many candidate $0\nu\beta\beta$ decay isotopes, as well as providing data for benchmarking Monte Carlo simulations of background events. I will present some preliminary results from our analysis, and discuss the implications of our findings for {\sc{Majo\-ra\-na}} as well as other neutrinoless double beta decay experiments. [Preview Abstract] |
Friday, November 5, 2010 9:42AM - 9:54AM |
GD.00005: \textsc{Majorana}: An Ultra-Low Background Enriched-Germanium Detector Array for Fundamental Physics Measurements Michael Miller The \textsc{Majorana} collaboration will search for neutrinoless double-beta decay (0$\nu \beta \beta )$ by fielding an array of high-purity germanium (HPGe) detectors in ultra-clean electroformed-copper cryostats deep underground. Recent advances in HPGe detector technology, in particular P-type Point-Contact (PPC) detectors, present exciting new techniques for identifying and reducing backgrounds to the 0$\nu \beta \beta $. This should result in greatly improved sensitivity over previous generation experiments. The exceptionally low energy threshold attainable with PPC detectors also enables a broad physics program including searches for dark matter and axions. The \textsc{Majorana Demonstrator} is an R{\&}D program that will field two $\sim $20 kg modules of PPC detectors at Sanford Underground Laboratory. Approximatly half of the detectors will be enriched to 86{\%} in $^{76}$Ge. Here, we will cover the motivation, design, recent progress and current status of this effort, with special attention to its physics reach. [Preview Abstract] |
Friday, November 5, 2010 9:54AM - 10:06AM |
GD.00006: A background model for the {\sc{Majo\-ra\-na}} neutrinoless double-beta decay experiment Alexis Schubert The {\sc{Majorana}} Collaboration\footnote{F.T. Avignone III (2007) arXiv:0711.4808v1} will search for neutrinoless double-beta decay ($0\nu\beta\beta$) of $^{76}$Ge in an array of germanium detectors. Observation of $0\nu\beta\beta$ would determine whether the neutrino is a Majorana particle and could provide information about neutrino mass. {\sc{Majorana}} will require an extremely low background rate to acheive high sensitivity to the $0\nu\beta\beta$ rate. Radioactive decays and cosmogenically-induced radiation create backgrounds to the potential signal. Understanding and minimization of backgrounds is critical to the sensitivity of the experiment. The {\sc{Majorana}} background model uses material radiopurity information and Monte Carlo simulation results to describe the expected background energy spectrum. This model can be validated through comparison with low-background energy spectra collected from prototype detectors. {\sc{Majorana}} collaborators installed a low-background germanium detector in the Kimbalton Underground Research Facility (KURF) in Ripplemeade, Virginia. Results of the {\sc{Majorana}} Low-background BEGe at KURF (MALBEK) validation study are used to inform the {\sc{Majorana}} background model. [Preview Abstract] |
Friday, November 5, 2010 10:06AM - 10:18AM |
GD.00007: Wavelet Analysis in Point Contact HPGe Detectors Ryan Martin The low-noise and pulse-shape discrimination characteristics of point-contact High-Purity Germanium (HPGe) detectors have made them a promising detector technology for neutrinoless double-beta (0$\nu\beta\beta$) decay experiments and direct dark matter searches. In 0$\nu\beta\beta$ searches, substantial background rejection can be achieved if one can identify and reject multiple site interactions. Dark matter searches require low energy thresholds and noise reduction in the events is thus highly desirable. This talk will introduce some of the techniques of wavelet analysis that can be used to de-noise pulse shapes from point contact HPGe detectors, and to separate multi-site interactions from single-site interactions. The work presented here was done in the context of the {\sc Majorana Demonstrator} project, which will search for neutrinoless double beta decay as well as direct dark matter interactions using an array of point contact HPGe detectors. [Preview Abstract] |
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