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 D12: Dark Matter I |
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Sponsoring Units: DPF Chair: Tom Shutt, Case Western University Room: Hyatt Regency St. Louis Riverfront (formerly Adam's Mark Hotel), St. Louis C |
Saturday, April 12, 2008 1:30PM - 1:42PM |
D12.00001: Determination of the scintillation and ionization yield of nuclear recoils in liquid Xe from XENON10 neutron calibration data Peter Sorensen Neutron calibration data from the XENON10 experiment is used as a sensitive probe of the Xe scintillation yield ($\mathcal{L}_{eff}$) and ionization yield, for nuclear recoils on liquid Xe. Previous data for the ionization yield $-$ the number of ionization electrons extracted per keV recoil energy (keVr) $-$ do not extend below 25 keVr, while our method is robust to $<3$ keVr. Previous data for the scintillation yield vary by $\times1.5$ at 10 keVr, with limited data at lower energies. We show the most likely $\mathcal{L}_{eff}$ curve consistent with the XENON10 neutron calibration data, along with statistical and systematic limits on it's variation. [Preview Abstract] |
Saturday, April 12, 2008 1:42PM - 1:54PM |
D12.00002: Background Rejection in the CDMS Dark Matter Search Jeffrey Filippini The Cryogenic Dark Matter Search (CDMS) uses low-temperature semiconductor detectors to search for interactions of weakly interacting massive particles (WIMPs). The CDMS II experiment has recently completed the data analysis of the first data run with its full complement of 30 detectors at Soudan Underground Laboratory. Highly accurate background rejection techniques are required to perform an effective WIMP search at the necessary sensitivities. This talk will focus on the discrimination techniques CDMS uses to suppress backgrounds during this long detector exposure, as well as some directions for future increases in discrimination power. [Preview Abstract] |
Saturday, April 12, 2008 1:54PM - 2:06PM |
D12.00003: Measurements of the Argon and Neon Scintillation Efficiencies in microCLEAN Daniel Gastler I present recent measurements of the nuclear-recoil scintillation efficiency for liquid argon and liquid neon. The scintillation efficiency characterizes the amount of scintillation light produced in a nuclear recoil when compared to that of an electronic recoil of the same energy. These results are from argon and neon runs of the 4 kg noble liquid microCLEAN detector as a part of the DEAP/CLEAN program to detect WIMP dark matter. [Preview Abstract] |
Saturday, April 12, 2008 2:06PM - 2:18PM |
D12.00004: Pulse Shape Discrimination (PSD) in Liquid Argon Bei Cai Dark Matter Experiment using Argon Pulse-shape discrimination (DEAP) plans to search for WIMPs (Weakly Interacting Massive Particles) through elastic scattering on ${}^{40}$Ar. In this single-phase liquid argon (LAr) experiment discrimination of $\beta$ and $\gamma$ backgrounds from the WIMP-induced nuclear recoil signal is achieved by analyzing the pulse shape of scintillation light. A 7-kg low-background LAr scintillation detector was constructed and run at Queen's University in Canada. A background rejection of 6 $\times$ $10^{-8}$ at 120-240 photo-electrons was achieved. [Preview Abstract] |
Saturday, April 12, 2008 2:18PM - 2:30PM |
D12.00005: Pulse shape discrimination in liquid argon and liquid neon Hugh Lippincott I present results from microCLEAN, a 4 kg noble liquid detector built as part of the DEAP/CLEAN programme to detect dark matter in the form of WIMPs using scintillation light. The sensitivity of these detectors to dark matter is limited by the level of discrimination between electronic and nuclear recoils. Scintillation light is produced in the decay of excimers that can exist in both the singlet and triplet states. Because these states have very different lifetimes, their populations can be easily separated using timing information. Since electronic and nuclear recoils produce different ratios of singlet to triplet molecules, the relative size of the two components can determine what type of event occurred. I present the pulse shape discrimination observed in both liquid argon and liquid neon using various methods, and I predict the sensitivity of a larger liquid argon detector to WIMP dark matter. [Preview Abstract] |
Saturday, April 12, 2008 2:30PM - 2:42PM |
D12.00006: Sensitivity and backgrounds for the LUX dark matter search Peter Sorensen The LUX 300~kg two-phase Xe detector aims to detect or exclude dark matter in the form of Weakly Interacting Massive Particles (WIMPs) with scalar cross section (per nucleon) as low as $7\times10^{-46}$~cm$^2$. This is equivalent to $\sim 0.5$~events/100~kg/month in a 100~kg fiducial volume. The LUX design is set to ensure $<1$ background event / 10~months live, which could potentially be characterized as a WIMP interaction. Based on above-ground calibrations and data from the XENON10 experiment, LUX expects to reject up to 99.9\% of the dominant electron-recoil background at detector threshold ($\sim4.5$~keVr), with 50\% acceptance for nuclear recoils. This level of electron recoil rejection power requires a gamma/beta background event rate of $<8\times10^{-4}$~events/keVee/kg/day at threshold $-$ a factor of $>150$ above the requisite nuclear recoil background rate. This talk will discuss projected backgrounds and sensitivity of the LUX experiment. [Preview Abstract] |
Saturday, April 12, 2008 2:42PM - 2:54PM |
D12.00007: Scintillation Output of CF$_4$ for Dark Matter Detection Asher Kaboth Directional detection of dark matter is a powerful way to look for the galactic dark matter halo. The DMTPC collaboration has developed optical readout of time projection chambers, which allow for the direction reconstruction of dark matter nuclear recoils. However, to make this method feasible, the gas in the TPC must have a high scintillation rate. This talk presents a measurement of N$_\gamma$/N$_{e^-}$ for a potential gas, CF$_4$. [Preview Abstract] |
Saturday, April 12, 2008 2:54PM - 3:06PM |
D12.00008: Measurements of low energy nuclear recoil tracks and its implications for dark matter searches Christina Hagemann, Michael Gold, Martin Hoeferkamp, Dinesh Loomba The direction of dark matter particles passing through the solar system is expected to have an anisotropy due to our own motion through the galaxy. The directionality associated with this WIMP wind is one of the strongest signatures for dark matter detection. We show how this directional signal can be measured in our detector which uses low-pressure gas as the target material. Just how well the directionality can be measured is limited by detector resolution and by uncertainties in our knowledge of the energy-loss of low energy nuclear recoils resulting from WIMP interactions. Here we describe preliminary results from ongoing R\&D of nuclear recoil tracks in the energy range of interest for WIMP interactions. [Preview Abstract] |
Saturday, April 12, 2008 3:06PM - 3:18PM |
D12.00009: The Maximum Patch Method for Directional Dark Matter Detection Shawn Henderson Present and planned dark matter detection experiments search for WIMP-induced nuclear recoils in poorly known background conditions. In this environment, the maximum gap statistical method provides a way of setting more sensitive cross-section upper limits by incorporating known signal information. We give a recipe for the numerical calculation of maximum gap cumulative distribution functions in one dimension, and extend the method to two dimensions for planned directional dark matter detection experiments that will measure both recoil energy and angle. [Preview Abstract] |
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