Bulletin of the American Physical Society
APS April Meeting 2012
Volume 57, Number 3
Saturday–Tuesday, March 31–April 3 2012; Atlanta, Georgia
Session X11: Underground Neutrino Physics and Background Studies |
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Sponsoring Units: DNP Chair: Lisa Kaufman, Indiana University Room: Embassy F |
Tuesday, April 3, 2012 1:30PM - 1:42PM |
X11.00001: Kimballton Underground Research Facility S. Derek Rountree, R. Bruce Vogelaar A new deep underground research facility is open and operating only 30 minutes from the Virginia Tech campus. It is located in an operating limestone mine, and has drive-in access (eg: roll-back truck, motor coach), over 50 miles of drifts (all 40' x 20+'; the current lab is 35' x 22' x 100'), and is located where there is a 1700' overburden. The laboratory was built in 2007 and offers fiber optic internet, LN2, 480/220/110 V power, ample water, filtered air, 55 F constant temp, low Rn levels, low rock background activity, and a muon flux of only $\sim $0.004 muons per square meter, per second, per steradian. There are currently six projects using the facility: mini-LENS - Low Energy Neutrino Spectroscopy (Virginia Tech, Louisiana State University, BNL); Neutron Spectrometer (University of Maryland, NIST); Double Beta Decay to Excited States (Duke University); HPGe Low-Background Screening (North Carolina State University, University of North Carolina, Virginia Tech); MALBEK - Majorana neutrinoless double beta decay (University of North Carolina); Ar-39 Depleted Argon (Princeton University). I will summarize the current program and exciting potential for the future. [Preview Abstract] |
Tuesday, April 3, 2012 1:42PM - 1:54PM |
X11.00002: Prototyping for LENS B.C. Rasco The Low-Energy Neutrino Spectroscopy (LENS) experiment will precisely measure the energy spectrum of low-energy solar neutrinos via charged-current neutrino reactions on indium. The LENS detector concept applies indium-loaded scintillator in an optically-segmented lattice geometry to achieve precise time and spatial resolution with unprecedented sensitivity for low-energy neutrino events. The LENS collaboration is currently developing prototypes that aim to demonstrate the performance and selectivity of the technology and to benchmark Monte Carlo simulations that will guide scaling to the full LENS instrument. Currently a 120 liter prototype, microLENS, is operating with pure scintillator (no indium loading) in the Kimballton Underground Research Facility (KURF). We will present results from initial measurements with microLENS and plans for a 400 liter prototype, miniLENS, using indium loaded scintillator that will be installed this summer. [Preview Abstract] |
Tuesday, April 3, 2012 1:54PM - 2:06PM |
X11.00003: A measurement of underground neutral particle fluxes with the SciBath detector Lance Garrison, Rex Tayloe, Robert Cooper, Lori Rebenitsch, Remmington Thornton, Hans-Otto Meyer The SciBath detector is an 80 liter liquid scintillator detector read out by a three dimensional grid of 768 wavelength-shifting fibers. Initially conceived as a charged particle detector for neutrino studies that could image charge particle tracks in all directions, it is also sensitive to fast neutrons (1-100 MeV) with high efficiency and good energy resolution. Across the neutron spectrum of interest, the detection efficiency and energy resolution are expected to be nearly 30\%. Furthermore, tracking algorithms are being developed to not only measure the neutron energy spectrum with high resolution but to image the neutron angular flux distribution. At the end of December the apparatus finished a two month run to measure neutrinos and neutrons 100 meters underground in the Fermilab MINOS near-detector area. An overview of the detector performance during this run will be presented as well as the latest results from the deployment. These results can be extrapolated to future measurements of fast-neutron backgrounds at other underground facilities. [Preview Abstract] |
Tuesday, April 3, 2012 2:06PM - 2:18PM |
X11.00004: The {\sc Majorana Demonstrator} Neutrinoless Double-beta Decay Experiment V.E. Guiseppe Neutrinoless double-beta decay searches play a major role in determining the nature of neutrinos, the existence of a lepton violating process, and the effective Majorana neutrino mass. The M{\sc ajorana} Collaboration is assembling an array of HPGe detectors to search for neutrinoless double-beta decay in $^{76}$Ge. Our proposed method uses the well-established technique of searching for neutrinoless double-beta decay in high purity Ge-diode radiation detectors that play both roles of source and detector. The use of p-type point contact Ge detectors present advances in background rejection and a significantly lower energy threshold than conventional Ge detectors. The lower energy threshold opens up a broader and exciting physics program including searches for dark matter and axions concurrent with the double-beta decay search. Initially, M{\sc ajorana} is constructing a prototype module to demonstrate the potential of a future 1-tonne experiment. The status and potential physics reach of the M{\sc ajorana Demonstrator} module will be presented. [Preview Abstract] |
Tuesday, April 3, 2012 2:18PM - 2:30PM |
X11.00005: Surface alpha backgrounds from plate-out of radon progeny Gopakumar Perumpilly, Vincente Guiseppe Low-background detectors operating underground aim for unprecedented low levels of radioactive backgrounds. Although the radioactive decays of airborne radon (particularly Rn-222) and its subsequent daughters present in an experiment are potential backgrounds, more troublesome is the deposition of radon daughters on detector materials. Exposure to radon at any stage of assembly of an experiment can result in surface contamination by daughters supported by the long half life (22 y) of Pb-210 on sensitive locations of a detector. We have developed a model of the radon progeny implantation using Geant4 simulations based on the low energy nuclear recoil process. We explore the alpha decays from implanted progeny on a Ge crystal as potential backgrounds for a neutrinoless double-beta decay experiment. Results of the simulations validated with alpha spectrum measurement of plate-out samples will be presented. [Preview Abstract] |
Tuesday, April 3, 2012 2:30PM - 2:42PM |
X11.00006: Experimental limit of the atmospheric concentration of $^{42}$Ar Jeremy Kephart, Rosara Kephart, Judah Friese Any small amount of radioactivity can have significant implications for many large scale physics experiments that are searching for unique signals such as those from double beta decay and the hunt for dark matter. These ultra-low background measurements have a need to understand all possible sources of background present in the system. $^{42}$Ar has been identified as a possible small source of background due to its presence in the atmosphere and in liquid argon. This work combines ultra-sensitive separations with ultra-low background detection techniques to experimentally determine a new quantitative upper limit of $^{42}$Ar in the atmosphere [Preview Abstract] |
Tuesday, April 3, 2012 2:42PM - 2:54PM |
X11.00007: Double-Beta-Decay as a Possible Indicator of Change in the Strong Force Eugene Chaffin When the half-lives of Te-130 and Se-82 for two-neutrino double-beta decay are measured using modern techniques, the results are different from values obtained, for geologically old samples, by measuring the radiogenic decay products and the parent concentrations. The reason for this discrepancy is not known, but we examine the systematics of the available data to determine if this could be due to a change in the strength of the strong force or the weak force. The available geologic data are limited to these samples for which the decay products are noble gases. A graph of the available data shows a change in the half-life between Precambrian and Phanerozoic samples. Alternate hypotheses, such as catastrophic xenon and krypton loss from the samples suffer from a lack of plausibility. There is no apparent geologic reason why there should be catastrophic xenon loss from Precambrian rocks compared to Phanerozoic rocks, or similarly why the leakage of xenon should be greater for Precambrian rocks than Phanerozoic rocks. If there had been continuous leakage there shouldn't be such a disparity around a specific transition shown in the graph. Possible mechanisms, such as a change in the vacuum expectation value of the Higgs field or a change in the neutrino rest mass, are discussed. [Preview Abstract] |
Tuesday, April 3, 2012 2:54PM - 3:06PM |
X11.00008: Compact Cosmic Ray Detector for On-orbit Testing of Shielding Materials Stephen Berkebile, James R. Gaier It is widely recognized that radiation poses an exposure risk to astronauts on long term missions in deep space. For deep space missions longer than six months, the principal risk to astronauts is due to galactic cosmic rays (GCRs). New shielding materials must be developed if this risk is to be mitigated. A high fidelity materials testbed, which will be integrated into the MISSE-X suite of experiments slated to fly on the International Space Station, is being developed to validate the GCR shielding effectiveness of candidate materials. A compact detector design will be presented which is intended to determine through which of nine candidate materials a particle has passed, identify the type of particle, and estimate its linear energy transfer. These tasks will be accomplished by using solid-state photomultipliers attached to two sets of polystyrene scintillating fiber arrays and a Tl-doped CsI crystal scintillator. [Preview Abstract] |
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