Bulletin of the American Physical Society
APS April Meeting 2011
Volume 56, Number 4
Saturday–Tuesday, April 30–May 3 2011; Anaheim, California
Session G10: Electromagnetic Interactions II |
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Sponsoring Units: DNP Chair: Doug Higinbotham, Thomas Jefferson National Accelerator Facility Room: Garden 1 |
Sunday, May 1, 2011 8:30AM - 8:42AM |
G10.00001: Measurement of the Proton Form Factor Ratio $G_E/G_M$ from Double Spin Asymmetries Anusha Liyanage Experiment E03-109 (SANE, Spin Asymmetries of the Nucleon Experiment) was carried out in Hall C at Jefferson Lab to study the proton spin structure functions with a dynamically polarized ammonia target and longitudinally polarized electron beam. Scattered electrons were detected by the Big Electron Telescope Array (BETA), and a set of elastic data was collected by detecting the recoiling proton in the High Momentum Spectrometer (HMS) in coincidence with the electron. The measurement of the elastic double spin asymmetry allows to extract the proton electric to magnetic form factor ratio $G_E/G_M$ at high four-momentum transfers, $Q^2$ = 5.25 (GeV/c)$^2$ and $Q^2$ = 6.25 (GeV/c)$^2$. In addition to the coincidence data, inclusively scattered electrons from the polarized ammonia target were detected by HMS, which allows to extract $G_E/G_M$ from the beam-target asymmetry in the elastic region at lower four-momentum transfer, $Q^2$ = 2.2 (GeV/c)$^2$. These alternative measurements of $G_E/G_M$ will verify the dramatic discrepancy at high $Q^2$ between the Rosenbluth and the recoil polarization transfer method. The current status of the analysis will be presented. [Preview Abstract] |
Sunday, May 1, 2011 8:42AM - 8:54AM |
G10.00002: Coulomb Corrections in Deep Inelastic Scattering and the Nuclear Dependence of $R=\sigma_L/\sigma_T$ David Gaskell Measurements of Deep Inelastic structure functions from nuclei are typically performed at very high energies, hence effects from the Coulombic acceleration or deceleration of the incident and scattered lepton due to additional protons in a heavy nucleus are typically ignored. However, re-analysis of data taken at SLAC from experiments E140 and E139 indicates that the effect of including Coulomb corrections, while not large, is non-zero and impacts the extracted results non-trivially. In particular, there is a significant impact when these data are used to extrapolate the magnitude of the EMC effect to nuclear matter. In addition, the conclusion from E140 that there is no evidence for a nuclear dependence of $R=\sigma_L/\sigma_T$ is thrown into question. When combined with recent data from Jefferson Lab, $R_A-R_D$ at $x=0.5$ is found to differ from zero by two $\sigma$. [Preview Abstract] |
Sunday, May 1, 2011 8:54AM - 9:06AM |
G10.00003: GEn Extraction at Q2 = 1 (GeV/c)$^2$ from Polarized 3He(e,e') Measurements Ge Jin The neutron electric form factor, GEn, was extracted for the first time at Q2 = 1 (GeV/c)$^2$ from polarized 3He(e,e') measurements in Hall A at Jefferson Lab. By getting the ratio of longitudinal and transverse quasi-elastic 3He(e,e') scattering asymmetry, the electron and magnetic contributions can be separated. The proton and neutron contributions to the 3He quasi-elastic responses were calculated in PWIA by Salme and the neutron electric form factor can be extracted. This inclusive scattering method becomes feasible for the first time due to the falloff of the other form factors at high Q$^2$ while GEn remains almost constant. Approximately 20\% uncertainty was achieved in the measurement largely contributed by statistics from 3 days of data-taking. All aspects of the measurement will be discussed including theoretical model, experiment and analysis details. [Preview Abstract] |
Sunday, May 1, 2011 9:06AM - 9:18AM |
G10.00004: Measurement of the Target Single-Spin Asymmetry in Quasi-Elastic $^3$He$^{\uparrow}$(e,e') Yawei Zhang Nuclear and nucleon structure are often studied by measuring form factors using the Born approximation, which assumes one-photon exchange, with multiple-photon exchanges neglected, so the target single-spin asymmetry is expected to be zero in the Born approximation. The Jefferson Lab experiment E05-015 was devoted to the measurement of the neutron target single-spin asymmetry, A$^n_y$, using the inclusive quasi-elastic $^3$He$^{\uparrow}$(e,e') reaction with a vertically polarized $^3$He target and standard Hall A high resolution spectrometers at Q$^2$=0.13, 0.46 and 0.97 (GeV/c)$^2$. The non-zero results from this experiment clearly demonstrate the contribution of two-photon exchange, providing new constraints on Generalized Parton Distribution Models and new information on the dynamics of the two-photon exchange process. Details of this experiment and a very preliminary result will be presented. [Preview Abstract] |
Sunday, May 1, 2011 9:18AM - 9:30AM |
G10.00005: Photo-production of $\Sigma^{*+}(1385)$ with CLAS Gagik Gavalian, Moskov Amaryan The differential cross section of $\Sigma^{*+}(1385)$ was
measured using high statistics CLAS experiment. The angular
dependence of the cross section was measured for the
$\cos\Theta^{K^{\circ}}_{c.m.}$ for $50~MeV$ energy bins in the
photon energy. The data allowed the cross section extraction in
the energy range $1.7~$GeV$ |
Sunday, May 1, 2011 9:30AM - 9:42AM |
G10.00006: ABSTRACT WITHDRAWN |
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