Bulletin of the American Physical Society
2005 72nd Annual Meeting of the Southeastern Section of the APS
Thursday–Saturday, November 10–12, 2005; Gainesville, FL
Session FD: Dark Matter |
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Chair: Jim Fry, University of Florida Room: Hilton Hickory |
Friday, November 11, 2005 8:30AM - 8:42AM |
FD.00001: Mixed Wino Dark Matter Eun-Kyung Park, Howard Baer, Azar Mustafayev, Stefano Profumo In the mSUGRA model, the value of the neutralino relic density is well beyond WMAP. In order to abtain the correct relic abandance of neutralinos, we examine the aspects of DM in the NUGM(Non-Universal Gaugino Mass) case which allows a mixed wino-bino lightest SUSY particle(LSP). In our study, we investigate rates for indirect detection of neutralinos via detection of muons in neutrino telescope, and detect of photons, positrons and anti-protons by balloon and space based detectors. We find the measured wino content of the LSP and reduced mass difference between the lightest neutralinos can have effects on the depletion of relic neutralino density. It means $\tilde Z_2$ two body decay modes are closed so that the mass reconstructions at LHC should be simpler. Finally, we conclude that measurement of the $\tilde Z_2-\tilde Z_1$ mass gap at the CERN LHC and various sparticle masses and cross sections as a function of the electron beam polarization at the ILC(International Linear Collider) will indicate the existence of MWDM(Mixed Wino Dark Matter). [Preview Abstract] |
Friday, November 11, 2005 8:42AM - 8:54AM |
FD.00002: Star formation and dark matter in galaxy NGC 157 Lauren Davis, Stephen Gottesman We have made high-resolution images of the atomic hydrogen in NGC 157. When combined with the radio observations of Ryder et al. (1998), these allow a more detailed look at the structure of the extended HI disk of NGC 157. In the inner part of the HI disk we found a close association between large HI density and the presence of ionized hydrogen regions. The rotation curve falls to $\sim $120 km s$^{-1}$, nearly half its peak value, a steep drop that may imply a truncated disk. The determinations of the rotation curve and flux distribution allow the calculation of total mass, HI mass, and mass--to-light ratios. We have detected a tail in the HI leading to a satellite. We believe that the more diffuse outer region has been strongly disturbed by interaction with the satellite. The absence of a corresponding optical source for the satellite galaxy suggests a high mass-to-light ratio. [Preview Abstract] |
Friday, November 11, 2005 8:54AM - 9:06AM |
FD.00003: Liquid Xenon Techniques for Dark Matter Detection. Aaron Manalaysay The XENON10 experiment will search for cold dark matter in the form of WIMPs with an expected sensitivity of $\sigma \sim 2\times 10^{-44}$cm$^{2}$ at the Gran Sasso Underground Lab in Italy. The detector measures energy deposition in liquid xenon simultaneously in the form of scintillation and ionization which allows for nuclear recoil discrimination. A dual-phase (liquid and gas) design is utilized for charge-signal amplification which is a new technique that is still under development. At UF, we have built a smaller, 1kg version of this detector to test the concept, specifically using a neutron beam to measure the ionization and scintillation yields of nuclear recoils down to 10 keV recoil energies. We present the status of XENON10, along with the initial results of our detector and expectations based on Monte Carlo simulations. [Preview Abstract] |
Friday, November 11, 2005 9:06AM - 9:18AM |
FD.00004: Results from the 2004 campaign of the Cryogenic Dark Matter Search experiment and status of the current upgrade. Samuel Leclercq The CDMS II experiment uses Z-dependent Ionization Phonon (ZIP) detectors cooled at 50 mK, confined in a lead and polyethylene shield, in the Soudan Underground Laboratory, to discriminate Weakly Interacting Massive Particles (WIMPs) against radioactive background. In 2004 CDMS II operated 6 Ge ZIPs and 6 Si ZIPs. The 74.5 live days of operation gave after cuts 34 kg-d exposure for the Ge ZIPs and 15 kg-d exposure for Si ZIPs. All criteria for identifying a signal from nuclear recoil due to WIMPs were developed 'blind' with respect to the WIMP search data. Improved techniques for the rejection of electron recoils on the detector surface were developed. The new 90{\%} C.L. upper limit on the scalar WIMP-nucleon cross section is 1.6 x 10$^{-43}$ cm$^{2}$ from Ge, and 3 x 10$^{-42}$ cm$^{2}$ from Si, for a WIMP mass of 60 GeV/c$^{2}$. The current setup reached the base temperature in August 2005, it operates 19 Ge ZIPs and 11 Si ZIPs. The goal is to increase the sensitivity by a factor 10 compared to the 2004 results. [Preview Abstract] |
Friday, November 11, 2005 9:18AM - 9:30AM |
FD.00005: Background studies for the XENON Dark Matter Project Jesse Angle The XENON Dark Matter Project uses liquid xenon as target and detector for detecting cold dark matter particles at a sensitivity more than three orders of magnitude better than current projects. Integral to the sensitivity of this detector is strong understanding of the background signal and its source. Using an ultra-pure germanium crystal detector operated in a low-level shield at the Soudan Mine in Minnesota, we are able to measure the radioactivity of the various materials that will comprise the XENON detector. I will present first results from our screening effort, as well as background expectations of the first stage of the experiment, XENON10 at the Gran Sasso Underground Lab, based on Monte Carlo simulations using GEANT4. [Preview Abstract] |
Friday, November 11, 2005 9:30AM - 9:42AM |
FD.00006: The Structure of Our Galaxy's Dark Matter Halo Leanne Duffy Incomplete thermalization of the galactic halo leads to cold flows of dark matter particles, with peaks in their velocity distribution. I discuss the expected properties of these flows under the current concordance cosmology and their impact on dark matter detection, focussing on the recent search result from the Axion Dark Matter eXperiment (ADMX) collaboration. [Preview Abstract] |
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