Bulletin of the American Physical Society
2007 APS April Meeting
Volume 52, Number 3
Saturday–Tuesday, April 14–17, 2007; Jacksonville, Florida
Session T12: Dark Matter III |
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Sponsoring Units: DPF Chair: Harry Nelson, University of California, Santa Barbara Room: Hyatt Regency Jacksonville Riverfront City Terrace 8 |
Monday, April 16, 2007 1:30PM - 1:42PM |
T12.00001: Dark Matter Detection rates in models with a Well-Tempered Neutralino Eun-Kyung Park, Howard Baer, Azar Mustafayev, Xerxes Tata In models with a ``well-tempered neutralino'', where the soft SUSY breaking terms are adjusted to give the measured abundance of CDM in the universe from WMAP, the neutralino is typically of the mixed bino-wino or mixed bino-higgsino state. Along with the necessary enhancement to neutralino annihilation rates, these models tend to give elevated direct detection scattering rates compared to predictions from SUSY models with universal soft breaking terms. We present neutralino direct detection cross sections from a variety of models containing a well-tempered neutralino, and find cross section asymptotia with detectable scattering rates. These asymptotic rates provide targets that various direct CDM detection experiments should aim for. [Preview Abstract] |
Monday, April 16, 2007 1:42PM - 1:54PM |
T12.00002: Nuclear Recoil Background from Neutrons in a WIMP Search Raul Hennings-Yeomans Searches for the interactions of weakly interacting massive particles (WIMPs) must be performed underground to shield from cosmic rays. Cosmic rays can produce secondary particles, such as fast neutrons, which in turn can produce nuclear recoils that are very similar to a WIMP signal. This talk will present studies of the neutron-induced background for the Cryogenic Dark Matter Search (CDMS) experiment at the Soudan Underground Laboratory, based on accumulated data and Monte Carlo simulations, with special emphasis on the discovery potential of the current CDMS run. This talk will be the third of a sequence of four from CDMS. [Preview Abstract] |
Monday, April 16, 2007 1:54PM - 2:06PM |
T12.00003: The Cryogenic Dark Matter Search Xinjie Qiu The Cryogenic Dark Matter Search (CDMS) uses low-temperature detectors to seek weakly interacting massive particles (WIMPs) via their interactions with nuclei, while discriminating against interactions of background particles. The first two runs of the CDMS II experiment at the Soudan Underground Lab provided the world's best sensitivity to WIMP dark matter. After a brief summary of theoretical and experimental evidence for WIMP dark matter, we will present an overview of the CDMS experiment and a summary of the most recent results of CDMS II experiment. This talk will be the first of a sequence of four from CDMS. [Preview Abstract] |
Monday, April 16, 2007 2:06PM - 2:18PM |
T12.00004: Muon-Induced Background Study for Double Beta Decay and Dark Matter Experiments Dongming Mei, Andrew Hime, Christina Keller Fast neutrons produced by muons traversing a detector are an important background for low energy neutrino experiments and dark matter searches. Muon-induced neutron production rates with heavy elements, such as lead and copper, are not well understood as evidenced by discrepancies between measurements and FLUKA simulations as large as about a factor of 3. Such a large discrepancy must be understood in order to optimize the detector design against muon-induced backgrounds. Muon-induced neutron production can be measured at the 300-foot level at Homestake using a detector system which consists of eight inner NaI detectors and forty outer liquid scintillators, together with the muon tracking detectors above and below the target. The inner and outer detectors in coincidence will be used to measure the neutron energy spectrum. The hit pattern of the outer detector indicates the multiplicity and angular distribution of the neutrons generated by muons. The construction of the entire detector system requires an R$\&$D program to optimize the design in the detection efficiency. This paper will present the simulation results for detector design. [Preview Abstract] |
Monday, April 16, 2007 2:18PM - 2:30PM |
T12.00005: A Background Model for MiniCLEAN Dongming Mei, Andrew Hime MiniCLEAN is aimed at the direct detection of Weakly Interacting Massive Particles (WIMPs) that as they recoil from liquid argon and liquid neon targets operating deep beneath the Earth's surface. Fast neutrons are naturally produced by the inherent radioactivity of detector construction materials and form an irreducible background to a potential WIMP signal. This paper describes our evaluation of neutron background for the proposed MiniCLEAN detector utilizing a fiducial mass of 1- ton. The neutron yield and energy spectra through ($\alpha$,n) reactions in various materials will be discussed. We will present simulation results for both liquid argon and liquid neon and emphasize our strategy for controlling background. The projected sensitivity for a WIMP search in MiniCLEAN will also be discussed. [Preview Abstract] |
Monday, April 16, 2007 2:30PM - 2:42PM |
T12.00006: Searching for Supersymmetric Dark Matter Annihilation Signals in the AMS01 Electron Spectrum Gray Rybka If dark matter is composed of supersymmetric neutralinos, some of the cosmic ray fluxes incident on earth could be the products of neutralino self-annihilation. The AMS-01 experiment flown on the space shuttle in 1998 measured cosmic ray fluxes above the atmosphere. I search the AMS-01 electron spectrum for neutralino annihilation remnants that have drifted through the galaxy to earth, and use the results to place limits on which supersymmetric models, cosmic ray propagation models, and dark matter distributions are compatible with each other. [Preview Abstract] |
Monday, April 16, 2007 2:42PM - 2:54PM |
T12.00007: Propagation uncertainties in measuring galactic SUSY dark matter in the AMS-01 electron spectrum Sa Xiao Assuming dark matter is SUSY neutralinos, its self-annihilation can give rise to anomalous features on the astrophysical background of various normal charged particles in cosmic rays, such as electrons, positrons, protons and antiprotons. We search for such features in the electron spectrum on Earth with data taken by AMS precursor flight on NASA space shuttle mission STS-91 in 1998. Propagation effects in galaxy are crucial to background estimation and understanding how the signal appears at Earth. The boron-to-carbon ratio in cosmic rays is very sensitive to propagation parameters. I study this in our data, and use it to place uncertainties on the limits we get from our dark matter search. [Preview Abstract] |
Monday, April 16, 2007 2:54PM - 3:06PM |
T12.00008: Status and WIMP Sensitivity of the Current CDMS Run Jeffrey Filippini The Cryogenic Dark Matter Search (CDMS) uses low-temperature detectors to search for interactions of weakly interacting massive particles (WIMPs). The CDMS II experiment is currently acquiring data with its full complement of 30 semiconductor detectors at Soudan Underground Laboratory, promising an order of magnitude increase in experimental reach. To do so the experiment must discriminate against background particle interactions with extremely high accuracy. This talk will describe the status and projected sensitivity of CDMS II's current run, focusing on the discrimination techniques that suppress backgrounds during long detector exposures. This talk will be the second of a sequence of four from CDMS. [Preview Abstract] |
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