Bulletin of the American Physical Society
APS April Meeting 2012
Volume 57, Number 3
Saturday–Tuesday, March 31–April 3 2012; Atlanta, Georgia
Session R14: High Energy Physics and Dark Matter Search |
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Sponsoring Units: GPMFC Room: Grand Hall East C |
Monday, April 2, 2012 1:30PM - 1:42PM |
R14.00001: Magnetic Resonances at Short Distances Horace Crater, Cheuk-Yin Wong The magnetic interaction at short distances between two opposite electric or color charges in the $^{3}P_{0}$ state $(J=0,L=1,S=1,P=1$ and $C=1)$ is very attractive and can overwhelm the centrifugal barrier at short distances (of about $10^{-2}$-$10^{-3}$ fermis), with a barrier between the short-distance region and the long-distance region. In the two body Dirac equations formulated in constraint dynamics, the short-distance attraction for this ${}^{3}P_{0}$ state admits a peculiar solution for the radial part of the relative wave function $u=r\psi $ that grows with distance as $r^{(1-\sqrt{1-4\alpha^{2}})/2}$, in addition to the usual solution that behaves as $r^{(1+\sqrt{1-4\alpha^{2}})/2}$. Both solutions have admissible behaviors at short distances and the usual solution leads to no resonant behavior. However, for the peculiar solution we find a resonance at about 28 MeV for $e^{+}e^{-}$ and a width of about 15 KeV. [Preview Abstract] |
Monday, April 2, 2012 1:42PM - 1:54PM |
R14.00002: Mu2e: A High-Sensitivity Charged Lepton Flavor-Violating Search at Fermilab James Miller The Mu2e Experiment at Fermilab will search for coherent, neutrino-less conversion of a muon into an electron in the field of a nucleus, $\mu^-+A\rightarrow A+e^-$, with a sensitivity improvement of a factor of 10,000 over existing limits. Such a charged lepton flavor-violating reaction probes new physics complementary to the LHC and can reach a scale unavailable by direct searches at either present or planned high energy colliders. The physics motivation for Mu2e will be presented, as well as the design of the muon beamline and spectrometer. The beamline employs a new design consisting of superconducting solenoids that will produce muons at high efficiency. A scheme by which the experiment can be mounted in the present Fermilab accelerator complex will be described. Prospects for increased sensitivity at future very high intensity sources, such as the Project X linac that is being proposed by Fermilab, will be discussed. [Preview Abstract] |
Monday, April 2, 2012 1:54PM - 2:06PM |
R14.00003: Measurement of the inclusive isolated prompt photon cross section in $pp$ collisions at $\sqrt{s}= 7~TeV$ with the ATLAS detector using 4.9 $fb^{-1}$ Scarlet Norberg A measurement of the cross section for the inclusive production of isolated prompt photons in $pp$ collisions at a center-of-mass energy $\sqrt{s} = 7~TeV$ is presented. The measurement covers the pseudorapidity ranges $|\eta^\gamma|<1.37$ and $1.52\leq|\eta^\gamma|<2.37$, in the transverse energy range $100\leq \eta^{\gamma}<1000~GeV$. The results are based on an integrated luminosity of 4.9~$fb^{-1}$, collected with the ATLAS detector at the LHC. Photon candidates are identified by exploiting the fine granularity of the electromagnetic calorimeter, which provides event-by-event rejection of the dominant background from photons produced by $\pi^0$ decays, and of the inner detector, which allows the reconstruction of photons that convert to electron-positron pairs. Residual background in the selected sample is estimated using data-driven techniques based on the observed distribution of the isolation energy in a narrow cone around the photon candidate. The results are compared with next-to-leading order perturbative QCD calculations. [Preview Abstract] |
Monday, April 2, 2012 2:06PM - 2:18PM |
R14.00004: Status of the DEAP-3600 Detector Thomas Sonley The DEAP-3600 dark matter experiment, part of the DEAP/CLEAN program, is a single-phase liquid argon detector currently under construction at SNOLAB. The detector will contain 3600 kg of argon, giving it a target sensitivity of 10$^{-46}$ cm$^2$ for spin-independent dark matter scattering on nucleons. I will discuss the highlights of our research and development efforts as well as the design and construction status of the full detector. [Preview Abstract] |
Monday, April 2, 2012 2:18PM - 2:30PM |
R14.00005: Status of the Large Underground Xenon (LUX) Detector Nicole Larsen The LUX (Large Underground Xenon) experiment is a 350-kg xenon-based direct dark matter detection experiment consisting of a two-phase (liquid/gas) xenon time projection chamber with a 100-kg fiducial mass. This technology has many advantages, including scalability, self-shielding, the absence of any long-lived isotopes, high gamma ray stopping power, and the ability to precisely measure the charge-to-light ratio of interactions within the detector, which provides an accurate method for discriminating between electron recoils (gamma rays, beta decays) and nuclear recoils (neutrons, WIMPS) within the detector. LUX's projected sensitivity for 300 days of acquisition is a cross-section of $7 \times 10^{-46}$ cm$^2$ for a WIMP mass of 100 GeV, representing an increase of nearly an order of magnitude over previous WIMP cross-section limits. From November 2011 through February 2012, LUX was deployed in a surface laboratory at the Homestake Mine in South Dakota for its second surface run. This talk will provide an overview of the LUX design and a report on the status of the experiment after the surface run and before underground deployment. [Preview Abstract] |
Monday, April 2, 2012 2:30PM - 2:42PM |
R14.00006: Simulation of Cosmogenic and Radioactive Backgrounds for the CoGeNT Dark Matter Detector Mark Kos We have completed a comprehensive list of simulations of the cosmogenic and radioactive backgrounds for the CoGeNT detector. For the cosmogenic backgrounds we include muon-induced neutrons produced in the shielding material and muon-induced neutrons from the surrounding cavern rock. We also include electrons, positrons, and gammas produced by the through-going muons. For the radioactive backgrounds we include (alpha,n) neutrons from the cavern, (alpha,n) and fission neutrons from the HDPE shielding, fission neutrons from the lead shielding, and uranium and thorium chain backgrounds in materials near the detector. The energy distributions derived from the simulations are normalized to the expected flux for the cosmogenic backgrounds, and to the measured uranium and thorium contamination for the radioactive backgrounds. We then compared the background distributions to the data and the results of these comparisons are presented. We also present results from simulations of the same background sources for the next generation of CoGeNT, C4. [Preview Abstract] |
Monday, April 2, 2012 2:42PM - 2:54PM |
R14.00007: Germanium Detector Response to Nuclear Recoils in Searching for Dark Matter D'Ann Barker, Dongming Mei The discrepancies in claims from the experiments that are searching for weakly interacting massive particle (WIMP) dark matter necessitate a model for ionization efficiency at energies below 10 keV. The focus of this work is on the construction of a model for the ionization efficiency in germanium by analyzing the components of stopping power, specifically that of nuclear stopping power, at low energies. To determine the validity of the proposed model, it will be compared to previous measurements of ionization efficiency in germanium as well as that of other theoretical models. The thresholds of both CDMS and CoGeNT will be analyzed and compared in terms of the nuclear recoil energy. [Preview Abstract] |
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