Bulletin of the American Physical Society
2010 Fall Meeting of the APS Division of Nuclear Physics
Volume 55, Number 14
Tuesday–Saturday, November 2–6, 2010; Santa Fe, New Mexico
Session FE: Dark Matter and Dark Energy |
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Chair: Alexander Friedland, Los Alamos National Laboratory Room: Coronado |
Thursday, November 4, 2010 4:00PM - 4:12PM |
FE.00001: Update on the MiniCLEAN dark matter experiment Keith Rielage MiniCLEAN utilizes over 500 kg of liquid cryogen to detect nuclear recoils from WIMP dark matter with a projected sensitivity of 2$\times 10^{-45}$ cm$^{2}$ for a mass of 100 GeV. The liquid cryogen is interchangeable between argon and neon to study the A$^{2}$ dependence of the potential signal and examine backgrounds. MiniCLEAN utilizes a unique modular design with spherical geometry to maximize the light yield using cold photomultiplier tubes in a single-phase detector. Pulse shape discrimination techniques are used to separate nuclear recoil signals from electron recoil backgrounds. Assembly of the experiment has begun at SNOLAB and an update on the project will be given. [Preview Abstract] |
Thursday, November 4, 2010 4:12PM - 4:24PM |
FE.00002: Simulation of Backgrounds for the MiniCLEAN Dark Matter Experiment Stanley Seibert The MiniCLEAN dark matter experiment is an ultra-low background liquid cryogen detector slated to begin operation at SNOLAB in 2011. The detector will have a fiducial volume of 150 kg of liquid argon for 2 years of data collection, to be followed by a liquid neon run. The ability to exchange the target material gives MiniCLEAN both competitive sensitivity to WIMP dark matter and also the opportunity to demonstrate the technologies required to build multi-ton neon detectors for precision solar neutrino measurements. I will discuss the major backgrounds for the MiniCLEAN experiment and report on progress in modeling these backgrounds in a full optical simulation of the detector. In addition, I will show the effects of our projected detector response and reconstruction performance on the background distributions. [Preview Abstract] |
Thursday, November 4, 2010 4:24PM - 4:36PM |
FE.00003: The DEAP-3600 Dark Matter Search Thomas Sonley The DEAP-3600 experiment will search for dark matter particle interactions on liquid argon at SNOLAB, located 2 km underground in Sudbury, Ontario. A prototype detector (DEAP-1) with a 7-kg liquid argon target mass is currently operating underground for studies of background reduction and rejection including pulse-shape discrimination of beta/gamma events. The larger detector containing a total mass of 3600 kg of liquid argon is under construction. The target sensitivity to spin-independent scattering on nucleons of $10^{-46}$ cm$^2$ will allow an improvement in dark matter particle sensitivity by a factor of several hundred over current searches. The status of the experiment and construction at SNOLAB will be presented. [Preview Abstract] |
Thursday, November 4, 2010 4:36PM - 4:48PM |
FE.00004: Cross-Section Measurements for Elastic and Inelastic Scattering of Neutrons from Noble Gases Sean MacMullin, Mary Kidd, Werner Tornow, Calvin Howell, Michael Brown, Reyco Henning Neutron backgrounds are a significant concern to experiments that attempt to directly detect Weakly Interacting Massive Particle (WIMP) dark matter. Recoil nuclei produced by neutron elastic scattering can mimic WIMP signatures. There is insufficient experimental data available for the scattering cross-sections of neutrons with noble gases (Ne, Ar, Xe), which are candidate target materials for such experiments. Neutron elastic and inelastic scattering from neon of natural abundance was investigated at the Triangle Universities Nuclear Laboratory at neutron energies relevant to ($\alpha$,n) and low-energy spallation neutron backgrounds in these experiments. The differential cross-section was measured using a time-of-flight technique at neutron energies of 8.0 and 5.0 MeV. Details of the experimental technique and current status of measurements will be presented. [Preview Abstract] |
Thursday, November 4, 2010 4:48PM - 5:00PM |
FE.00005: Particle discrimination in PIXeY, a prototype two-phase xenon detector for use in dark matter searches N. Larsen, E. Bernard, S. Cahn, A. Curioni, A. Lyashenko, J. Nikkel, Y. Shin, A. Young, D. McKinsey, N. Destefano, W. Zimmerman, M. Gai In the past few years xenon has risen as a forerunner as a medium for dark matter detection. PIXeY (Particle Identification in Xenon at Yale) is a small-scale two-phase xenon-based detector. Its primary use is that of an R{\&}D detector for development of technologies to be used in direct dark matter detectors, as well in neutrinoless double-beta decay searches and gamma ray imaging. A major advantage of two-phase detectors is the ability to precisely measure the charge-to-light ratio of interactions within the detector. This provides an accurate method for discriminating between electron recoils (gamma rays) and nuclear recoils (neutrons, WIMPS) within the detector. Unlike similar detectors, PIXeY can operate at a very wide range of drift field strengths, up to 8kV/cm. One of PIXeY's main goals is to determine the effects of field strength on the charge-to-light ratio in order to determine the optimal field strength for discriminating between electron and nuclear interactions. In this presentation, I will discuss the physics of particle discrimination in PIXeY and in similar Xe-based detectors. In addition, I will report on the PIXeY cryogenics and purification system which maintain the stable environment and large charge yield essential for particle identification and discrimination. [Preview Abstract] |
Thursday, November 4, 2010 5:00PM - 5:12PM |
FE.00006: Fluorescence Efficiency and Visible Re-emission Spectrum of Tetraphenyl Butadiene Films at Extreme Ultraviolet Wavelengths Victor Gehman, Stanley Seibert, Andrew Hime, Keith Rielage, Yongchen Sun, Dongming Mei, Joel Massen, Daniel Moore There are a large number of direct dark matter and neutrino detection experiments either in construction or in planning which will use the scintillation light from noble elements as a mechanism for measuring radiation deposition. This scintillation light is emitted in extreme ultraviolet (EUV, 100--200 nm) wavelengths. There are very few photon detectors directly sensitive to this wavelength that are also capable of detecting the very small number of photons expected from signal events in such detectors. The most technically feasible solution to this problem is to surround the noble element volume with a thin film of Tetraphenyl Butadiene (TPB) to act as a fluor. The TPB film shifts the EUV photons to visible photons, detectable with commercial photomultiplier tubes. Here we present a study of the fluorescence efficiency of such films as well as the shape of the visible re-emission spectral shape at several input EUV wavelengths. [Preview Abstract] |
Thursday, November 4, 2010 5:12PM - 5:24PM |
FE.00007: The DRIFT Dark Matter Search Eric Miller The DRIFT dark matter detector is a 1 cubic meter scale TPC with direction sensitivity to WIMP recoils operating in the Boulby Mine in England. Results on a spin-dependent limit from data taken underground with a 30 Torr CS2 - 10 Torr CF4 gas mixture will be presented. The primary source of backgrounds in this data are from low-energy nuclear recoil events due to radon progeny plated out on the detector's wire central cathode. Here we describe a dramatic background reduction resulting from the installation of a new thin-film central cathode. We also describe a new technique which promises to fully fiducialize the chamber, potentially eliminating this source of background entirely. [Preview Abstract] |
Thursday, November 4, 2010 5:24PM - 5:36PM |
FE.00008: Dark Energy from Interacting Dark Fermions Terrence Goldman, Bruce McKellar, Paul Alsing, Gerard Stephenson Physics is rife with interacting systems that exhibit negative pressure: atomic nuclei are very well known examples. We examine the range of parameters, for neutral fermions interacting only by exchange of an extraordinarily light scalar particle, that produce a negative pressure on the scale of the Universe over time periods where Dark Energy is or may be relevant. Of known or expected neutral Majorana fermions, active neutrinos can be ruled out but sterile neutrinos would work, as well as the LSP, to describe the recent observations of Dark Energy effects. After a phase change required by the instability responsible for the negative pressure, the resulting clouds of neutral fermions will contribute to Dark Matter. Nothing requires that this can only happen once. [Preview Abstract] |
Thursday, November 4, 2010 5:36PM - 5:48PM |
FE.00009: The mass, energy, space and time systemic theory-MEST Dayong Cao The solar system is mass-energy center, and the wave (space-time) and planet are around. Sun absorb the matter (mass-energy) and radiate the light (space-time). The dark hole system is the space-time center, and the dark matter-energy and dark planet (dark comet-asteroid) are around. Dark hole absorb the light (space-time), and radiate the dark mass-energy (mass-energy). So the dark mass-energy main make up of the negative proton and the negative neutron who can take negative density and negative pressure. The cosmological model is like ``Taiji'' model which is from Ancient China. The black hole (invisible stuff) has not a big mass and energy. The light can not leave off it, because it absorb the light. So it can cause the ``red-shift.'' Sun has a companion dark hole. When it recurrent visit solar system, it can take ``red-shift speeded up,'' and can take many dark comet-asteroids to impact near our earth. When the dark mass-energy go into the solar corona, The electron neutrinos can bombard the negative neutron and the negative proton, and take the a reaction with them. It's equation: n$^{-}$+v$_e$ $\rightarrow$ p+$\mu$, p$^{-}$+v$_e$ $\rightarrow$ n+$\mu$. Among it, n$^-$: the negative neutron, p$^-$: the negative proton, $v_e$: the electron neutrino, p: the proton, n: the neutron, $\mu$: the muon. We will use them to change the orbit of earth and dark comet for avoiding its impaction. [Preview Abstract] |
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