Bulletin of the American Physical Society
2009 APS April Meeting
Volume 54, Number 4
Saturday–Tuesday, May 2–5, 2009; Denver, Colorado
Session T12: Dark Matter Searches II |
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Sponsoring Units: DAP DPF GPMFC Chair: Uwe Oberlack, Rice University Room: Plaza Court 2 |
Monday, May 4, 2009 3:30PM - 3:42PM |
T12.00001: Results from and Future Prospects for the Axion Dark Matter eXperiment S. Asztalos, R. Bradley, G. Carosi, M. Hotz, J. Hwang, D. Kinion, L. Rosenberg, G. Rybka, P. Sikivie, D. Tanner, K. van Bibber The Axion Dark Matter eXperiment (ADMX) at LLNL searches for dark-matter axions through their Primakoff conversion to microwave photons, resonantly enhanced in a high-Q cavity permeated by a strong magnetic field. ADMX remains the world's quietest spectral receiver in the GHz regime, capable of detecting a single RF photon per minute above cavity blackbody and amplifier noise. ADMX has previously covered a frequency range of 460 to 812 MHz (1.9 $-$ 3.4 micro-eV); over that octave of mass range axions were excluded as the Milky Way halo dark matter for well-motivated models of the coupling of the axion to two photons. An upgrade of ADMX has since been completed, which replaced the previous HFET amplifiers with SQUID amplifiers. This talk will describe the upgrade, including SQUID amplifier technology, recent results, and discuss plans for a second-phase upgrade to further reduce the systems noise temperature to $\sim$ 100 mK. [Preview Abstract] |
Monday, May 4, 2009 3:42PM - 3:54PM |
T12.00002: Dark Matter Searches using a Free-Electron Laser (FEL) James R. Boyce, A. Afanasev, O.K. Baker, K.B. Beard, G. Biallas, M. Minarni, R. Ramdon, M. Shinn, P. Slocum Photon coupling to light neutral bosons in the meV mass range has been predicted and searched for by several international collaborations. Using the ``light shining through a wall'' technique, light from Jefferson Lab's high average power Free-Electron Laser (FEL) was passed through a strong magnetic field upstream of an optical beam dump; regenerated photons were then searched for downstream of a second magnetic field region optically shielded from the former. While our initial results show no evidence for scalar coupling in this region of parameter space, the results establish new coupling boundaries. New constraints on the hypothetical para-photon particles were also obtained. We describe the experimental setup, the initial scalar boson results, and proposed experiments that include searching for para-photons and chameleon particles. Notice: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. The U.S. Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce this manuscript for U.S. Government purposes. [Preview Abstract] |
Monday, May 4, 2009 3:54PM - 4:06PM |
T12.00003: Dark matter search at SNOLAB with DEAP-1 and DEAP-3600 Mark Boulay, Bei Cai The DEAP/CLEAN experiment will search for WIMPs (Weakly Interacting Massive Particles) through elastic scattering on liquid argon. The first generation detector (DEAP-1) with a 7-kg liquid argon target mass is currently operating underground at SNOLAB. An overview of that experiment, including pulse-shape discrimination (PSD) results for reducing $\gamma/\beta$ backgrounds, will be presented. A larger detector (DEAP-3600) containing a total of 3600 kg of liquid argon will allow a sensitivity to spin-independent scattering on nucleons of $10^{-46}\ \rm cm^{2}$, several hundred times more sensitive than current dark matter experiments. Construction activities are planned for SNOLAB in 2009, with data taking planned to commence in 2011. The design and construction status of DEAP-3600 will be outlined. [Preview Abstract] |
Monday, May 4, 2009 4:06PM - 4:18PM |
T12.00004: Depleted Argon as a Dark Matter Detector at DUSEL Jason Spaans, Dongming Mei, Christina Keller, Yongchen Sun, Andrew Hime, Richard Ford, Cristiano Galbiati The purpose of this project is to provide argon depleted from $^{39}$Ar either by collection from underground sources or by isotopic separation. The depleted argon can then be used as a target material for next generation dark matter detectors at DUSEL. The Princeton group has demonstrated the existence of depleted argon in underground gas fields. This project aims at the characterization of $^{39}$Ar in underground water sources, kept in isolation from the atmosphere for thousands of years. To do so, we have built a gas extracting system and extracted gas from a water well at Wall, SD. This paper will present the preliminary results of our research. A second approach under investigation relies on isotopic separation by hot-wire thermal diffusion. We built a hot-wire thermal diffusion column, composed of a tungsten wire, a copper column, and a water cooling bath at USD. This paper will illustrate the current status of the effort. [Preview Abstract] |
Monday, May 4, 2009 4:18PM - 4:30PM |
T12.00005: Measurements of liquid neon scintillation properties for use in current and future dark matter detectors Hugh Lippincott The DEAP/CLEAN program is a series of detectors designed to search for WIMP dark matter and pp solar neutrinos using liquid argon and liquid neon as target materials. The sensitivity of these detectors is limited by the energy threshold and the ability to discriminate between electronic and nuclear recoils in the detector, a discrimination that is possible due to the different scintillation timing signatures of the two classes of events. The energy threshold is set by the scintillation light yield of each target material. I present measurements of discrimination power and scintillation light yields for neon using the microCLEAN detector, a 4 kg prototype detector operating at Yale. In addition, I discuss simulations of a 40 tonne scale detector based on the measured scintillation parameters. [Preview Abstract] |
Monday, May 4, 2009 4:30PM - 4:42PM |
T12.00006: Temperature-Controled Cooling Tests of Photomultiplier Tubes for the miniCLEAN Dark Matter Search Victor Gehman The miniCLEAN experiment will search for WIMP dark matter with a WIMP-neucleon cross section sensitivity of $10^{-45}\mbox{cm}^{2}$. The detector has a fiducial volume of over 100 kg of liquid argon with the capability to be changed to liquid neon for background studies. The miniCLEAN experiment will be located at SNOLAB in Sudbury, Canada in late 2009. It will use position reconstruction and the time structure of scintillation light pulses to distinguish signals from backgrounds on an event-by-event basis. Because of the use of the time structure of scintillation light for background discrimination, careful understanding of the performance of photomultiplier tubes deployed in the experiment is important for successful operation. We have undertaken a program at Los Alamos National Laboratory aimed at characterizing miniCLEAN photomultipliers as a function of bias voltage at a variety of temperatures ranging from room temperature down to near the boiling point of neon (27 K). Specifically our efforts have centered on: gain, efficiency, dark current, and linearity. Recent progress and future plans for this test bench as well as its place in the overall miniCLEAN photomultiplier tube characterization program will be presented. [Preview Abstract] |
Monday, May 4, 2009 4:42PM - 4:54PM |
T12.00007: Gamma-ray Flux at Different Levels in the Homestake Mine Measured with NaI detectors Dongming Mei, Keenan Thomas, Chao Zhang, Frederick Gray, Jonathan Totushek, Christopher Ruybal Characterization of various backgrounds is an important step to the design of DUSEL in which the low background experiments are being planned. The gamma-ray flux at the different levels in the Homestake has been measured using three identical NaI detectors arranged as an array. We report the gamma-ray flux in four categories: 1) below 3 MeV, the spectrum is expected to be dominated by radioactivities from the rocks; 2) between 3 and 5.5 MeV, the shape of the spectrum should be well explained by U, Th and daughters, which are internal contamination in the NaI crystals; 3) between 5.5 to 10 MeV, the gamma-rays flux is dominated by neutron capture on surrounding materials; and 4) the gamma-ray flux above 10 MeV is induced by muon bremsstrahlung. The measured flux will be compared to the prediction by the Monte Carlo simulation. [Preview Abstract] |
Monday, May 4, 2009 4:54PM - 5:06PM |
T12.00008: Measured Muon and Neutron Flux at Different Levels in the Homestake Mine Jonathan Totushek, Frederick Gray, Christopher Ruybal, Dongming Mei, Keenan Thomas, Chao Zhang External sources of background, particularly fast neutrons and cosmogenic radioactivity from muon-induced processes, are background matter that must be eliminated for underground experiments in pursuit of double beta decay, WIMPs, and oscillations of low-energy neutrinos. We report preliminary results about muon flux and the integrated neutron flux at different levels in Homestake Mine. These results can be sued as the guidance for the design of the shielding. [Preview Abstract] |
Monday, May 4, 2009 5:06PM - 5:18PM |
T12.00009: Monte Carlo Simulation of Homestake Background Chao Zhang, Dongming Mei Background characterization is critical to the shielding design for the incoming DUSEL experiments. A simulation is performed by applying the composition of Homestake rock samples. Then the neutron and gamma ray fluxes as a function of energy induced by natural radioactivity at Homestake mine are calculated. In particular, utilizing the rock radioactivity counted by Al Smith at LBL, the neutron flux and gamma-ray flux at the 4850-level and 7400-level are predicted. The results can be used as a reference for the shielding design for low background experiments planned at DUSEL. [Preview Abstract] |
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