Bulletin of the American Physical Society
APS April Meeting 2013
Volume 58, Number 4
Saturday–Tuesday, April 13–16, 2013; Denver, Colorado
Session X5: Fundamental Symmetries |
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Sponsoring Units: DNP GPMFC Chair: Seamus Riordan, University of Massachusetts Amherst Room: Governor's Square 14 |
Tuesday, April 16, 2013 10:45AM - 10:57AM |
X5.00001: Testing Lorentz invariance in $\beta$ decay Hans Wilschut, Auke Sytema, Elwin Dijck, Steven Hoekstra, Klaus Jungmann, Stefan M\"uller, Gerco Onderwater, Coen Pijpker, Lorenz Willmann, Jacob Noordmans, Rob Timmermans In theories aiming to unify the Standard Model with gravity, Lorentz invariance may be broken. Although Lorentz symmetry appears to hold well, few experiments have been performed that consider its violation in the weak interaction.We have started a theoretical and experimental research program to this effect. In particular we consider a Lorentz violating correction of the W-boson propagator, characterized by a tensor. With this Standard Model Extension the $\beta$-decay rate will depend, for example, on the spin direction of the parent nucleus and the emission direction of the $\beta$ and $\nu$ particles. Specifically, we consider allowed Fermi and Gamow-Teller transitions and explore the spin degrees of freedom in the latter. Experimentally we exploit the Gamow-Teller transition of polarized $^{20}$Na, by which we can test the dependence of the $\beta$-decay rate on the spin orientation of $^{20}$Na. A change in the $\gamma$ rate when reversing the spin is an indication of Lorentz invariance violation. In addition the decay rate should depend on sidereal time and the polarization direction relative to the earth rotation axis. The method of the measurement will be presented, together with the first results. [Preview Abstract] |
Tuesday, April 16, 2013 10:57AM - 11:09AM |
X5.00002: ABSTRACT WITHDRAWN |
Tuesday, April 16, 2013 11:09AM - 11:21AM |
X5.00003: Systematics of the SNS n-3He Experiment Christopher Crawford The $\vec{\mbox{n}} + {}^3\mbox{He} \to {}^3\mbox{H} + \mbox{p}$ reaction is sensitive to isospin zero components of the hadronic weak interaction, complementary to NPDGamma (isospin one). We are preparing an experiment to measure the PV proton asymmetry of this reaction at the SNS Fundamental Neutron Physics Beamline immediately following the NPDGamma experiment. Due to a large PC nuclear asymmetry, this experiment must be run with longitudinal neutron polarization, with the beam centerline, magnetic holding field, and detectors aligned. I will discuss our commissioning and run plan and measures to suppress all systematic effects well below our statistical sensitivity of $10^{-8}$. [Preview Abstract] |
Tuesday, April 16, 2013 11:21AM - 11:33AM |
X5.00004: Probing the Faraday Effect of Polarized $^{3}He$ Gretchen Phelps, Josh Abney, Wolfgang Korsch The Faraday Effect refers to the phenomenon in which the polarization of light transmitted through a magnetized medium is rotated. The relation $\phi=VlB$ describes the magnitude of the rotation, where V is the material dependent Verdet constant and \emph{l} is the length of the medium in an applied magnetic field B. Polarized $^{3}$He, generated in a glass cell constructed of GE-180, gives rise to a Faraday rotation via nuclear spin optical rotation (NSOR), a measure of which establishes a new technique in $^{3}$He polarization monitoring. Our set-up incorporates a triple-modulation technique with present sensitivities at the $\mu$rad level. This is accomplished through the combination of a photo-elastic modulator, an optical chopper, and a sinusoidally driven magnetic field. Several calibration samples were used to test the triple-modulation method. Good agreement between our results and the commonly accepted values for the Verdet constant was achieved. Technical challenges and progress towards the determination of $V_{^{3}He}$ will be presented. [Preview Abstract] |
Tuesday, April 16, 2013 11:33AM - 11:45AM |
X5.00005: Potential use of a Kerr Cell in polarized electron accelerator sources for experiments in parity-violation Mark Dalton Measurement of parity-violation in electron scattering has evolved to measuring sub-part-per-million asymmetries with a precision better than 10 parts-per-billion. Future experiments will be significantly more demanding, the MOLLER experiment will measure a 35.6 ppb asymmetry to 0.73 ppb. Currently, the laser beam that produces the electron beam, has its helicity reversed using a Pockels Cell. This device is a birefringent crystal to which an opposite high voltage is applied for each polarization state. The time that it takes the crystal to admit the voltage change and stabilize thereafter is too long for future experiments and the cell induces unacceptably large changes in the beam correlated with the polarization, due to piezo-electric and piezo-optical phenomena. A potential solution is the use of a Kerr Cell instead. Such a device, containing a Kerr liquid, should allow the polarization to be reversed more rapidly and with significantly reduced correlation between the polarization and other changes to the beam. The Kerr effect is weak and a useful cell would likely require significantly higher voltages and unsavory chemicals. In this presentation the Kerr Cell will be introduced, barriers to using this technology will be discussed and first data available will be presented. [Preview Abstract] |
Tuesday, April 16, 2013 11:45AM - 11:57AM |
X5.00006: Linear Regression Systematics of the Q-weak Main Detector Asymmetry David Mack The Q-weak collaboration has made the first direct measurement of the proton's weak charge at Jefferson Lab to tightly constrain new, parity-violating electron-quark interactions at the multi-TeV scale. Our experiment measured the $\sim$200 ppb parity-violating asymmetry in the scattering of longitudinally polarized electrons from an unpolarized liquid hydrogen target at a luminosity of 1.8x10$^{39}$. Careful setup of the injector helped to suppress helicity correlated differences in beam position, angle, and energy which create false asymmetries due to changes in detector acceptance and the kinematic dependences of the e+p cross section. Measured differences in beam position were consistent among all 6 beam position monitors in front of the target, with a precision of $\sim$1 nanometer. The size of corrections depends on the helicity correlated beam parameter differences, and averaged about 35 ppb per shift of data. The data were regressed using 10 different sets of Independent Variables. These were expected to give similar corrections yet showed differences at the +-10 ppb level. In this presentation I'll summarize how these different schemes have not only been helpful in understanding the sensitivities of the main detector but in assigning errors to the corrections. [Preview Abstract] |
Tuesday, April 16, 2013 11:57AM - 12:09PM |
X5.00007: Measuring Muon Capture on the Deuteron Frederick Gray The MuSun experiment will measure the rate of nuclear muon capture on the deuteron with a precision of 1.5\%. This rate will be used to fix the low-energy constant that describes the two-nucleon weak axial current in effective field theory models. It will therefore calibrate evaluations of proton-proton fusion and neutrino-deuteron scattering. The experiment uses many of the techniques and much of the apparatus that were developed for the successful MuCap measurement of the rate of muon capture on the proton. However, to optimize the molecular kinetics, the deuterium gas is cooled to 30 K in a cryogenic time project chamber (TPC). In preparation for an upcoming high-statistics production run, a new in-vacuum cryo-preamplifier has been developed to improve the energy resolution of the TPC, and x-ray detectors to monitor the elemental purity of the target gas have been tested. These upgrades will be described, as will the significant progress that has been made in the analysis of data from the initial fall 2011 production run. [Preview Abstract] |
Tuesday, April 16, 2013 12:09PM - 12:21PM |
X5.00008: The Mu2e Experiment Bertrand Echenard While Charged Lepton Flavor Violating processes are heavily suppressed in the Standard Model, the rate of these reactions are enhanced to levels accessible to the next generation of experiments in many scenarios of New Physics. The Mu2e experiment is designed to search for neutrinoless muon-to-electron conversion in the Coulomb field of a nucleus with expected sensitivity of 6x10$^{\mathrm{-17}}$ at 90{\%} confidence level. Such sensitivity, about four orders of magnitude below the current limits, will allow Mu2e to probe mass scales of New Physics up to 1000-10000 TeV, far above the range directly accessible at the LHC. We briefly describe the Mu2e experiment and its physics goals. [Preview Abstract] |
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