Bulletin of the American Physical Society
APS April Meeting 2010
Volume 55, Number 1
Saturday–Tuesday, February 13–16, 2010; Washington, DC
Session P10: Dark Matter III |
Hide Abstracts |
Sponsoring Units: DPF Chair: Dan Akerib, Case Western Reserve University Room: Maryland B |
Monday, February 15, 2010 10:45AM - 10:57AM |
P10.00001: Studies of xenon gas purity for next generation detectors Attila Dobi The next generation of neutrino and dark matter detectors will require large quantities of extremely pure liquid argon and xenon. These types of experiments measure purity using dedicated devices which are capable of detecting electronegative impurities at concentrations less than one part per billion in the liquid phase. On the other hand, the purifiers used by these experiments often operate solely on the gas phase. Gas phase purity has been more difficult to monitor, because the analysis technology (Atmospheric Pressure Ionization Mass Spectroscopy) is out of reach for most researchers. We describe here our development of a new, inexpensive technique for monitoring the purity of xenon in the gas phase. Using this method we have reached sensitivities of better than one part per billion. We have begun using our device to study the performance of a common xenon gas purifier, the SAES Monotorr zirconium getter. To date gaseous xenon purification data for the SAES noble gas purifier does not exist. Our method of purity measurement is promising and would be a cost effective option for experiments using ultra high purity xenon. [Preview Abstract] |
Monday, February 15, 2010 10:57AM - 11:09AM |
P10.00002: The \textsc{Majorana} \textsc{Demonstrator} Low-Energy Program Michael Miller The \textsc{Majorana Demonstrator} is a 60 kg germanium detector array currently being constructed for operation at the 4850 ft level of the Sanford Underground Lab. The core physics program is to probe the Majorana/Dirac nature of neutrinos by searching for neutrinoless double beta decay. However, recent developments in germanium detector technology have dramatically lowered the detector energy threshold from approximately 2-4 keV to as low as 100-400 eV. Combined with the ultra-low-background design, the low-energy threshold enables additional physics opportunities for the \textsc{Majorana Demonstrator }such as searches for low-mass WIMPS and axions. We present (i) highlights from the ongoing R{\&}D towards low-background low-noise detectors, including updates on readout, digitization and trigger; (ii) sensitivity limits from prototype detectors currently operating in deep-underground locations; and (iii) sensitivity projections for the 60 kg \textsc{Majorana Demonstrator} array. [Preview Abstract] |
Monday, February 15, 2010 11:09AM - 11:21AM |
P10.00003: Design and Performance of Next Generation Cryogenic Dark Matter Detectors Jeff Yen, Matt Pyle, Bruno Serfass, Paul Brink, Blas Cabrera, Matt Cherry, Nader Mirabolfathi, Larry Novak, Bernard Sadoulet, Dennis Seitz, Kyle Sundqvist, Astrid Tomada, Betty Young To achieve the surface electron rejection required for ton scale dark matter searches with germanium, we have demonstrated an advanced interleaved charge and phonon detector. The design's large surface E-fields and small electrodes suppress leakage of surface electrons from $^{109}$Cd into the nuclear recoil band to less than 1:3000 for 69\% wimp search volume efficiency (after radial fiducial volume cuts), 2 orders of magnitude better than current designs. Assymetries in charge collection between the 4 electrodes allow for charge only z fiducial volume reconstruction, which further suppresses this surface leakage by greater than 1:1000 with 62\% total wimp search efficiency. Finally, high fidelity partition and pulse shape information from 6 phonon sensors (3 on each side) allow for full 3D event reconstruction which discriminate against electronic surface events at greater than 1:3000 independent of charge assymetry discrimination with 80\% efficiency. In summary, this design should meet the discrimination requirements for experiments probing $10^{-47}$cm$^{2}$ wimp nucleon cross section scales. [Preview Abstract] |
Monday, February 15, 2010 11:21AM - 11:33AM |
P10.00004: ABSTRACT WITHDRAWN |
Monday, February 15, 2010 11:33AM - 11:45AM |
P10.00005: High Energy Lepton Production Underground Alexander Bulmahn, Mary Hall Reno The differential cross section for lepton pair production from muons in transit is reevaluated in a manner such that it is valid beyond low lepton mass and low momentum transfer regions. Our results are more broadly applicable than the approximate formulas in the literature. Given the high fluxes of atmospheric muons, we evaluate the high energy underground electron and tau fluxes associated with muons in transit. We also present a new analytic approximation to the charge current differential neutrino cross section useful over a large range of incident neutrino energies, and we compare the underground lepton fluxes from incident atmospheric muon and neutrino fluxes. We also compare the contributions from incident conventional and prompt fluxes for production of electrons and taus in underground detectors. [Preview Abstract] |
Monday, February 15, 2010 11:45AM - 11:57AM |
P10.00006: External Background Characterization of Homestake Mine for DUSEL Keenan Thomas, Dongming Mei, Frederick Gray, Chao Zhang The Homestake Mine in Lead, South Dakota has been selected as the site for the Deep Underground Science and Engineering Laboratory (DUSEL). The former gold mine will provide underground facilities for low background experiments such as the detection of neutrinos and dark matter. Although the earth overburden provides shielding of cosmic rays, there are still sources of external background underground that are of concern to early experiments. The goal of this project is to measure sources of external background underground including muons, neutrons, gamma-rays, and airborne radon concentrations. The information produced by these measurements is of use for future experiments in the design of shielding and infrastructure such as ventilation systems for radon removal. This will present updates regarding muon flux, neutron flux, gamma-ray flux, as well as radon measurements underground. [Preview Abstract] |
Monday, February 15, 2010 11:57AM - 12:09PM |
P10.00007: Discrimination of events in superheated liquid Simon Archambault PICASSO is a Dark Matter search experiment using superheated droplets of C$_{4}$F$_{10}$ as the active detector material, suspended in an elastic polymer. If a WIMP (Weakly Interacting Massive Particle) hits a nucleus inside a droplet, the recoiling nucleus will deposit its energy in a heat spike, triggering a phase transition. The setup, installed at SNOLab, 2 km underground, consists of 32 cylindrical detectors of 4.5L. The acoustic signals emitted during a phase transition are recorded by nine piezo-electric transducers mounted on the detector walls and the waveforms are analysed offline. In this way, different types of events can be identified using different variables. One of these variables, which is proportional to the total energy of the acoustic signal, allows discrimination among neutron or WIMP-induced events, background alpha particle induced events and electronic noise; another discrimination variable is constructed from the Fast Fourier Transform of the signal and allows the discrimination of other classes of backgrounds. [Preview Abstract] |
Monday, February 15, 2010 12:09PM - 12:21PM |
P10.00008: Calibration of the LUX Dark Matter Detector Louis Kastens Calibration strategies for LUX (Large Underground Xenon), a liquid xenon time projection chamber designed to directly detect dark matter, will be explored. The introduction of external gamma and neutron sources into a water tank containing the detector will be discussed. Large liquid noble detectors achieve very low backgrounds through self-shielding of the fiducial volume, however this same shielding inhibits the use of external gamma ray sources to calibrate the fiducial volume detector. To mitigate this effect, research on novel calibration strategies using radioactive $^{83m}$Kr and $^{3}$He doped into the detector to efficiently calibrate the fiducial volume of these detectors will be reported upon. LUX will be deploying to Davis Cavern at SUSEL (Sanford Underground Science and Engineering Laboratory), future site of DUSEL (Deep Underground Science and Engineering Laboratory), in the first half of 2010. [Preview Abstract] |
Monday, February 15, 2010 12:21PM - 12:33PM |
P10.00009: IceCube update on point-source searches Jon Dumm, Mike Baker, Juan A Aguilar, Chad Finley, Teresa Montaruli During 2008-9, the IceCube Neutrino Observatory was operational with 40 strings of optical modules deployed in the ice. We present the results of searches for neutrino point sources based on unbinned maximum likelihood analyses of the data collected in this configuration. This data sample provides the best sensitivity to high energy neutrino point sources to date. We characterize the angular resolution, effective area, and sensitivity, and discuss how the performance is expected to improve as the detector moves toward the planned final 80-string configuration. [Preview Abstract] |
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