Bulletin of the American Physical Society
2009 APS April Meeting
Volume 54, Number 4
Saturday–Tuesday, May 2–5, 2009; Denver, Colorado
Session J10: Electroweak Interactions |
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Sponsoring Units: DNP Chair: Willem T.H. van Oers, TRIUMF Room: Governor's Square 10 |
Sunday, May 3, 2009 1:30PM - 1:42PM |
J10.00001: Search for a Higgs Boson Produced in Association with $W$ Boson using a Neural Network Approach at CDF Yoshikazu Nagai We present a search for a standard model Higgs boson produced in association with a $W$ boson using data collected with the CDF~II detector from $p\overline{p}$ collisions at a $\sqrt{s} = 1.96$~TeV. The search is performed in the $WH \rightarrow \ell \nu b\overline{b}$ channel using a data sample corresponding to an integrated luminosity of 2.7~fb$^{-1}$. An artificial neural network is used to improve separation of signal and background. In the absence of an observed excess in data, we set an upper limit on the production rate times branching ratio. [Preview Abstract] |
Sunday, May 3, 2009 1:42PM - 1:54PM |
J10.00002: Precision Measurement of $a$ and $b$ in Neutron Beta Decay L. Peter Alonzi III Using a novel $4\pi$ detector the Nab collaboration intends to measure $a$, the electron-neutrino correlation parameter, and $b$, the Fierz interference term, in neutron beta decay. Our target accuracy is $10^{-3}$ for $\Delta a/a$ and $10^{-3}$ for $\Delta b$. The Nab experiment will be conducted in the Fundamental Neutron Physics Beamline at the Spallation Neutron Source in Oak Ridge, TN. The ultimate goal is to combine the results of the Nab experiment with measurements of the neutron lifetime to resolve discrepancies regarding $\lambda =G_{A}/G_{V}$ and the CKM matrix element $V_{ud}$. We will present a design of the Electro-Magnetic Spectrometer which will be used to confine the decay products and guide them to the detector. [Preview Abstract] |
Sunday, May 3, 2009 1:54PM - 2:06PM |
J10.00003: Muon Capture on the Deuteron Frederick Gray The MuSun Collaboration is preparing to measure the rate of nuclear muon capture by the deuteron ($\mu^- + d \rightarrow \nu_\mu + n + n$) from the doublet spin state of the $\mu^- + d$ atom, with better than 1.5\% precision. It will determine this rate by observing the difference between the disappearance rates of positive and negative muons in a purified deuterium gas target. It is built upon the success of the MuCap experiment, which has measured the rate of muon capture in protium using a similar technique. The MuSun experiment will provide the most precise determination to date of the rate for any two-nucleon weak-interaction process. Using effective field theories (including chiral perturbation theory), $\mu^- + d$ capture can be related to similar processes, including proton-proton fusion and charged- and neutral-current deuteron breakup reactions. A measurement of its rate will therefore also serve as a calibration of other processes that are of fundamental importance to nuclear astrophysics. This presentation will describe the current status of the experiment, including some results from a first beam test conducted at the Paul Scherrer Institute in fall 2008. [Preview Abstract] |
Sunday, May 3, 2009 2:06PM - 2:18PM |
J10.00004: Parity-Violating Asymmetry in the Nucleon to Delta Transition C.L. Capuano The G$^0$ collaboration at Jefferson Lab has measured the
parity-violating asymmetry of polarized electrons scattered
inelastically from the proton. Data were obtained for inclusive
pion electroproduction at a beam energy of 687 MeV, with the
scattered electrons detected at backward angle (${\theta_e}$
${\sim}$ 110$^{\circ}$). These data will be used to extract the
axial vector transition form factor G$^A_{N\Delta}$ for $Q^2$ in
the range 0.3 GeV/c$^2 |
Sunday, May 3, 2009 2:18PM - 2:30PM |
J10.00005: Status of the Qweak Main Detector Construction David Mack Precision measurements of Standard Model-suppressed, weak-scale observables provide a window on potential new physics at the TeV scale. An attractive observable is the proton neutral weak charge, $Q_{Weak}^p$, which measures the coupling of the Standard Model Z boson to the proton and is proportional to the relatively small quantitity $1 - 4\sin^2\theta_W$. The proton weak charge can now be calculated to very high precision in the Standard Model but has never been directly measured. Its value could be significantly shifted by new, parity-violating electron-quark interactions such as those found in leptoquark models or RPV SUSY models. The existence of new $Z'$s could also shift the observed value. By measuring the parity-violating asymmetry in elastic $e+p$ scattering at low momentum transfer, the proton weak charge can be determined with hadronic ambiguities smaller than our projected error bar. After briefly overviewing the physics and our plans for a 4\% measurement, the status of the detector construction effort will be summarized. [Preview Abstract] |
Sunday, May 3, 2009 2:30PM - 2:42PM |
J10.00006: The 2500 W liquid hydrogen target for the Qweak experiment Silviu Covrig The precision measurement of the proton's weak charge through parity violation in the Qweak experiment in Hall C at Jefferson Lab requires a liquid hydrogen target system capable of sustaining a beam power of 2500 W. This will be the highest power LH2 target in the world, even though it must also satisfy very stringent requirements for target related systematic uncertainties. For the first time the use of computational fluid dynamics (cfd) simulations have been used to design such a target. I will describe how \emph{Fluent}, a cfd package, was used in designing the Qweak target. Cfd simulations have also been used in assessing the safety of the target system. Testing of the Qweak target will begin in the summer of 2009, with the first physics run starting in the summer of 2010. [Preview Abstract] |
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