Bulletin of the American Physical Society
2008 APS April Meeting and HEDP/HEDLA Meeting
Volume 53, Number 5
Friday–Tuesday, April 11–15, 2008; St. Louis, Missouri
Session M13: Neutrinos I |
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Sponsoring Units: DNP Chair: Steve Elliott, Los Alamos National Laboratory Room: Hyatt Regency St. Louis Riverfront (formerly Adam's Mark Hotel), St. Louis F |
Sunday, April 13, 2008 3:30PM - 3:42PM |
M13.00001: Solar neutrino flux results measured with the Neutral Current Detector array in the Sudbury Neutrino Observatory (SNO) Keith Rielage In 2004, the Sudbury Neutrino Observatory (SNO) added an array of $^{3}$He proportional counters to the 1000 tonnes of heavy water. The Neutral Current Detector (NCD) array detects the neutrons liberated in the neutral current reaction of neutrinos on deuterium. The NCD measurement of the total flux of active solar neutrinos above 2.22 MeV is decoupled from the PMT-based measurements of the electron solar neutrino flux resulting in a smaller correlation between these fluxes in this phase than in the previous SNO results. The operation of the NCD array will be discussed. The solar neutrino flux results from this 385-live-day phase and the latest global combined fits for the solar neutrino mixing angle and mass difference will be discussed. This work was supported in part by the US Department of Energy Office of Science - Nuclear Physics. [Preview Abstract] |
Sunday, April 13, 2008 3:42PM - 3:54PM |
M13.00002: A Monte Carlo Simulation of the SNO Neutral Current Detector Array Jocelyn Monroe The third phase of the Sudbury Neutrino Observatory is designed to make a systematically independent measurement of the total boron-8 solar neutrino flux, above the deuteron break-up threshold. A neutral current detector (NCD) array of 40 gas-filled proportional counters was deployed in the heavy water target. The dominant background to the neutron capture signal is from alphas produced in the uranium and thorium decay chains inside NCD constituent materials. We have developed a full Monte Carlo of the signal and background processes that accurately simulates pulse shape characteristics in the NCD array. This detailed model is of general interest to experiments using pulse shape analysis with proportional counters. [Preview Abstract] |
Sunday, April 13, 2008 3:54PM - 4:06PM |
M13.00003: Low Background Phase of KamLAND Gregory Keefer The KamLAND collaboration operates a 1 kton liquid scintillation detector in the Kamioka mine in Japan. KamLAND's main scientific results are the precision measurement of the solar $\Delta$m$^{2}$ utilizing reactor anti-neutrinos and first evidence for the observation of geologically produced anti-neutrinos. The KamLAND collaboration has been working toward upgrading the detector for a low background phase. During the spring of 2007, we performed the first phase of purification by circulating 1.3 ktons of KamLAND liquid scintillator through a newly developed distillation and purging system. The ultimate goal of purification is to allow for a direct measurement of the 862 keV, $^{7}$Be neutrinos originating from the Sun. A description of the purification process, liquid scintillator quality control measures, and detector monitoring will be presented. The achieved background reduction after this first phase of purification and planned future work on KamLAND will be discussed. [Preview Abstract] |
Sunday, April 13, 2008 4:06PM - 4:18PM |
M13.00004: Probing the Mystery of Neutrino Mass with CUORE Larissa Ejzak Understanding the nature of neutrino masses will require physics beyond the long-standing Standard Model of particle physics. CUORE, the Cryogenic Underground Observatory for Rare Events, will be a next-generation experiment at Gran Sasso National Laboratory investigating neutrino masses through the mechanism of double beta decay. It will operate on the principle of bolometric calorimetry; the detector will consist of an array of 988 TeO$_{2}$ crystals with a total mass of 207 kg of $^{130}$Te, maintained at 10 mK. CUORE's particular focus is the search for neutrinoless double beta decay, which, if observed, would indicate that neutrinos have Majorana masses -- meaning that they are their own antiparticles, and in turn implying that lepton number, which so far has appeared to be a good symmetry of the Standard Model, is violated. CUORE will also be able to place improved limits on the absolute neutrino mass scale and possibly to determine the mass hierarchy of the three neutrino mass eigenstates. We will discuss the status of the CUORE project and present the latest results from CUORICINO, a prototype experiment currently running at Gran Sasso. [Preview Abstract] |
Sunday, April 13, 2008 4:18PM - 4:30PM |
M13.00005: Systematic Effects on Pulse Shape Analysis in HPGe Detectors for 0$\nu\beta\beta$ Searches Victor M. Gehman The M{\sc ajorana} Project will endeavor to provide direct limits on the effective Majorana mass of the electron neutrino through the measurement of neutrinoless double-beta decay in $^{76}$Ge. One of the techniques that the M{\sc ajorana} experiment will implement to separate single-site energy depositions (such as 0$\nu\beta\beta$ or 2$\nu\beta\beta$ events) from multi-site events (such as multiply scattering $\gamma$ rays) is pulse shape analysis. We present work performed at Los Alamos National Laboratory using a ``CLOVER'' detector (a close-packed array of four 800g, two-fold segmented natural germanium detectors) to characterize systematic uncertainties in the survival probabilities of double-escape, Compton continuum and full-energy $\gamma$ ray events under two-moment parametric pulse shape cuts. [Preview Abstract] |
Sunday, April 13, 2008 4:30PM - 4:42PM |
M13.00006: P-type Modified Electrode Germanium Detector Impurity Profiles Jeremy Kephart Germanium detectors with unprecedented capabilities are needed for detecting ultra-rare events in future neutrinoless double-beta decay experiments, searches for dark matter, environmental monitoring programs, national security applications, and potentially neutrino astrophysics. An ideal detector would combine ultra-low background capabilities, minimal electronic instrumentation, extremely low energy threshold, and the ability to perform event reconstruction to determine the interaction type or the spatial distribution of ionization following an interaction. A germanium detector with a special, very low capacitance, contact geometry and presumably a deliberately contrived impurity profile could provide all these capabilities. We present an analysis of the detector impurity concentration profiles and their impact on the depletion voltage, capacitance and charge collection times for such detectors. [Preview Abstract] |
Sunday, April 13, 2008 4:42PM - 4:54PM |
M13.00007: The COBRA Neutrinoless Double Beta Experiment. Qiang Li The COBRA is a proposed experiment to detect neutrinoless double beta decays of the isotope 116Cd. The COBRA design is based on CZT room temperature solid state detectors. A prototype of the experiment made of 64 1cm$^3$ detectors is running in the Gran Sasso underground laboratory. In this talk, I will discuss the design of the COBRA prototype experiment and possible designs of a large-scale experiment made of 410 kg of CZT detectors. We are currently evaluating the option to use CZT detector units with 200 micron spatial resolution. Such detectors would make it possible to track the electrons from double beta decays and to distinguish them from certain types of background events. [Preview Abstract] |
Sunday, April 13, 2008 4:54PM - 5:06PM |
M13.00008: $^{112}$Sn Double-Electron Capture to Excited States - A Possible Alternative to Neutrinoless Double-Beta Decay Mary Kidd, James Esterline, Werner Tornow As first suggested by Winter in 1955 and re-emphasized by Georgi, Glashow and Nussinov in 1981 the double-electron capture (EEC) process on a nucleus with an excited state of the daughter at an energy that coincides with the mass difference between the parent and daughter atoms may play a decisive role in determining the properties of neutrinos. For perfect degeneracy, a substantial resonance enhancement in the capture probability is predicted, and there is no phase space left for the two-neutrino double electron capture. Here we concentrate on $^{112}$Sn. Using the TUNL apparatus designed for double-beta decay studies to excited states we placed a 3.9 g foil of enriched (99.5\%) $^{112}$Sn between our two HPGe detectors. In addition, we surrounded the detectors with rods of natural tin (0.97\% of $^{112}$Sn), thus providing a total mass of 15.7 g of $^{112}$Sn for our search for the coincident detection of 1253.4 keV and 617.6 keV $\gamma$ rays (0$^+\rightarrow$2$^+\rightarrow$0$_{gs}^+$ sequence). After 60 days of counting we obtained no events in the energy region of interest. This null result corresponds to T$_{1/2}$ $>$ 1.4 $\times$ 10$^{19}$ years (90\% CL) for the 0$\nu$EEC process. Analysis of the singles spectra, gives a half-life of T$_{1/2}$ $>$ 4.8 $\times$ 10$^{19}$ years (90\% CL) for the 0$\nu$EEC process. [Preview Abstract] |
Sunday, April 13, 2008 5:06PM - 5:18PM |
M13.00009: CLEAR: Prospects for a Low Threshold Neutrino Experiment at the Spallation Neutron Source Kate Scholberg A low-threshold neutrino scattering experiment at a high intensity stopped-pion neutrino source has the potential to measure coherent neutral current neutrino-nucleus elastic scattering. A promising prospect for the measurement of this process is a proposed noble-liquid-based experiment, dubbed CLEAR (Coherent Low Energy A(Nuclear) Recoils), at the Spallation Neutron Source. This talk will describe the CLEAR proposal and its physics reach. [Preview Abstract] |
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