Bulletin of the American Physical Society
APS April Meeting 2015
Volume 60, Number 4
Saturday–Tuesday, April 11–14, 2015; Baltimore, Maryland
Session C2: Dark Matter II |
Hide Abstracts |
Sponsoring Units: DPF DNP Chair: Marcela Carena, Fermi National Accelerator Laboratory Room: Holiday 1 |
Saturday, April 11, 2015 1:30PM - 1:42PM |
C2.00001: Study of annual modulation at Soudan Mine using a liquid scintillation detector Chao Zhang, Dongming Mei The phenomenon of annual modulation is believed to be one of signatures induced by Weakly Interacting Massive Particles(WIMPs) through elastic scattering off nucleus in the target for direct dark matter searches. Both DAMA and CoGeNT experiments have claimed the discovery of dark matter in terms of annual modulation while many other experiments have ruled out the entire claimed region. However, the sources that caused the annual modulation in DAMA and CoGeNT are till mysterious. A 12-liter liquid scintillation detector has been running at Soudan Mine (1.95 km.w.e) for several years. Using this detector, muon and muon-induced neutron fluxes at Soudan Mine are measured to be ($1.65\pm 0.02 (sta.) \pm 0.1 (sys.) ) \times10^{-7}$ cm$^{-2}$s$^{-1}$ (E$_{\mu}$ $>$ 1 GeV) and $(2.23 \pm 0.52 (sta.) \pm 0.99 (sys.) ) \times10^{-9}$ cm$^{-2}$s$^{-1}$ (E$_{n}$ $>20$ MeV), respectively. Data analysis for three years shows a clear annual modulation pattern ($E>10$ MeV) caused by cosmic-ray muons with an amplitude of $\sim$2\%. The annual modulation caused by radon has also been observed in the energy region below 10 MeV. We demonstrate the sources of annual modulation in different energy region and explain how background-induced annual modulation may mimic dark matter signature. [Preview Abstract] |
Saturday, April 11, 2015 1:42PM - 1:54PM |
C2.00002: Systematic uncertainties in the search for annual modulation in CDMS-II Danielle Speller Weakly Interacting Massive Particles (WIMPs) have long been one of the leading candidates for dark matter, the undetected mass component comprising $\sim$~27\% of the universe. The primary indicator of a WIMP signal is an excess in the nuclear-recoil event rate measured by a detector, while the revolution of the Earth about the Sun introduces a periodicity in the detector-WIMP relative velocity, resulting in an annual modulation of the WIMP rate. This combination of excess and modulation is an important hallmark for a signal of WIMP origin. The Cryogenic Dark Matter Search (CDMS) experiment uses semiconductor crystals to search for WIMPs scattering from atomic nuclei through the simultaneous measurement of ionization and athermal phonons. This technique achieved excellent discrimination between nuclear recoils (expected for WIMP interactions) and radioactively induced electron recoils, enabling a sensitive search for an annually modulating signal. I will discuss the results of this search, including possible systematic effects, and describe implications for interpretations of other experimental results such as those from the CoGeNT experiment. [Preview Abstract] |
Saturday, April 11, 2015 1:54PM - 2:06PM |
C2.00003: Status of SuperCDMS Soudan High Threshold Analysis Todd Doughty The $\Lambda$CDM model of the universe implies that $\sim$80\% of the matter in the universe is non-baryonic dark matter. A particularly well motivated candidate for this dark matter is the Weakly Interacting Massive Particle (WIMP). The SuperCDMS collaboration searches for WIMP recoils in germanium crystal detectors. A total mass of ~9 kg has been operating at the Soudan Underground Laboratory since March 2012. Previous analyses have presented results optimized for low-mass WIMPs using only a subset of the data. I present the status of the high-threshold analysis that is optimized for heavier WIMP masses ($>$10 GeV) and uses the entire $\sim$3000 kg-day dataset. [Preview Abstract] |
Saturday, April 11, 2015 2:06PM - 2:18PM |
C2.00004: Modeling Background Distributions for the SuperCDMS Soudan High Threshold Analysis Brett Cornell The SuperCDMS Soudan experiment searches for interactions of WIMP dark matter particles with germanium detectors, using ionization yield and fiducialization to reject backgrounds. An exposure of 3000 kg-day has been accumulated with 9 kg of new-generation SuperCDMS iZIP detectors, which use a sophisticated ionization electrode and phonon sensor structure to report information about the three-dimensional position of each event. We report on the development of a model for background distributions that exploits this new position information as well as improved simulations of detector physics. This model will be used to optimize nuclear recoil acceptance and background rejection for a cut-based analysis, and it may be further developed for an eventual maximum likelihood analysis. [Preview Abstract] |
Saturday, April 11, 2015 2:18PM - 2:30PM |
C2.00005: Neutron Veto Prototype for the SuperCDMS SNOLAB Experiment Abaz Kryemadhi, Ben Loer, Katrina Schrock, Matthew Bressler Both cosmology and particle physics converge on Weakly Interacting Massive Particles as good candidates for dark matter. SuperCDMS will use cryogenic germanium and silicon crystals at SNOLAB to search for WIMP interactions. Because neutrons can mimic WIMP interactions, SuperCDMS considers deploying a neutron veto detector. The veto is made of liquid scintillator doped with an agent that enhances neutron capture and produces alpha particles. Light emitted from these reactions then gets captured by wavelength-shifting fibers and routed to silicon photodetectors. We designed and built a 1/4 scale prototype in order to understand the light output, characterize the photodetectors, tune simulation parameters, and understand the process of construction. [Preview Abstract] |
Saturday, April 11, 2015 2:30PM - 2:42PM |
C2.00006: Trigger Efficiency Calculation from the Second Run of CDMSlite. Alexander Leder The Cyrogenic Dark Matter Search - Low Ionization Threshold Experiment (CDMSlite) is a dark matter direct detection experiment that utilizes Neganov-Luke phonon amplification to achieve a very low, sub-keV ionization energy threshold. In order to characterize the vital low energy response for the CDMSlite mode, we analyzed datasets corresponding to exposure from various calibration sources taken between Feburary and May 2014. Building upon our previous CDMSlite result and taking advantage of improved instrumentation in this new dataset, we measured the trigger efficiency for a larger 70 V bias voltage. This talk discusses the event selection and maximum likelihood analysis of this trigger efficiency estimate. [Preview Abstract] |
Saturday, April 11, 2015 2:42PM - 2:54PM |
C2.00007: Understanding the Energy Spectrum from the Second Run of CDMSlite Mark Pepin The first run of the CDMSlite experiment demonstrated the use of Neganov-Luke phonon amplification in a single SuperCDMS detector to achieve lower energy thresholds for the direct detection of dark matter. A longer physics run with improved noise rejection has been recorded with a larger voltage bias of -70 V applied across the same detector, yielding an amplification factor of 15 (for electron recoils) and reducing the statistical uncertainty of the measured background rate. In order to extract optimal dark-matter sensitivity with these data it is important to understand the shape and composition of the background spectrum at the lowest energies. The dominant backgrounds in this high-voltage mode are from Compton scatters, internal activation lines (primarily from $^{71}$Ge decays), and microphonic noise. This presentation will consider the contributions from these sources and how the electric field geometry in the detector can distort the spectra. Prospects for new results will also be discussed. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700