Bulletin of the American Physical Society
2008 Annual Meeting of the Division of Nuclear Physics
Volume 53, Number 12
Thursday–Sunday, October 23–26, 2008; Oakland, California
Session BB: Mini-Symposium: 3D View of the Nucleon and Its Spin I |
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Chair: Charles Hyde, Old Dominion University and University of Blaise Pascal Room: Room 208 |
Friday, October 24, 2008 8:30AM - 9:06AM |
BB.00001: Nucleon Structure and Master Parton Distribution Invited Speaker: The most general parton distributions that one can define are 6-dimensional Wigner quantum phase-space Wigner distributions. Different projections will lead to different reduced distributions which can be probed in experiment such as generalized parton distributions and transverse-momentum dependence parton distributions. The role of these distributions in understanding the structure of the nucleon will be discussed. [Preview Abstract] |
Friday, October 24, 2008 9:06AM - 9:18AM |
BB.00002: Proton electromagnetic form factor ratio at high momentum transfer via recoil polarization in Hall C at Jefferson Lab Andrew Puckett Experiment E04-108 in Hall C at Jefferson Lab measured the ratio of the proton's electric ($G_E$) and magnetic ($G_M$) form factors using the recoil polarization technique at three different values of squared four-momentum transfer $Q^2$--5.2, 6.8, and 8.5 GeV$^2$. Data taking was completed in June 2008, and analysis of the data is underway. Two new detectors were built by the collaboration to carry out this experiment. A large solid-angle electromagnetic calorimeter was used to detect elastically scattered electrons in coincidence with scattered protons detected by the Hall C High Momentum Spectrometer (HMS). The calorimeter allowed a clean rejection of the significant inelastic backgrounds present at such high $Q^2$. A new Focal Plane Polarimeter (FPP) was installed in the HMS detector hut to measure the polarization of the scattered proton. After a brief overview of the experiment, the present status of the analysis will be discussed. [Preview Abstract] |
Friday, October 24, 2008 9:18AM - 9:30AM |
BB.00003: Deeply Virtual Compton Scattering with CLAS Francois-Xavier Girod As the lightest of all baryons, and the single stable hadron, the proton can be considered as the simplest laboratory tool to investigate the non-perturbative stucture of QCD. The interest in the nucleon structure has been renewed over the past decade, due to the development of the Generalized Parton Distribution (GPD) formalism. The cleanest process to test the GPDs is Deeply Virtual Compton Scattering, which is the electroproduction of photons in the Bjorken regime of large $Q^2$ and $\nu$, at fixed $x_B$ and small $t$. In order to access this process, the CEBAF Large Acceptance Spectrometer (CLAS) has been upgraded by the addition of a new calorimeter to detect photons at small angles. I will present an overview of the E1-DVCS experiment, starting from the conception and construction of the equipment to simulations and data taking. I will show results for the Beam Spin Asymmetry, which is linked to GPDs. I will conclude by giving perspectives on GPDs measurements at 6 and 12 GeV with CLAS. [Preview Abstract] |
Friday, October 24, 2008 9:30AM - 9:42AM |
BB.00004: Measurement of the Double Longitudinal Spin Asymmetry for Charged Pion Production in 200 GeV Polarized p+p Collisions at RHIC Bernd Surrow A primary goal of the STAR spin physics program at RHIC is the measurement of the gluon polarization, delta g, in the proton. The STAR detector, with its large-acceptance tracking and calorimetery, provides a uniquely suited environment for asymmetry measurements in a number of different final-state channels in polarized p+p collisions such as inclusive jet production [1], charged and neutral pion [2] production. These asymmetries will provide important contributions to a global analysis of delta g. We present here the most recent measurements of the double longitudinal spin asymmetry (ALL) for the production of charged pions at mid-rapidity. These asymmetries are compared to NLO pQCD calculations for different gluon polarization scenarios and are used to provide constraints on delta g. Charged pions are of particular interest as they are sensitive to the sign of delta g. Results and continuing analyses are presented from RHIC runs 5 and 6. [1] Will Jacobs, Recent Longitudinal Spin Asymmetry Measurements for Inclusive Jet Production at STAR, DNP 2008 Fall meeting. [2] Oleksandr Grebenyuk, Longitudinal Double-Spin Asymmetry and Cross Section for Inclusive Neutral Pion Production in Polarized p + p Collisions at RHIC, DNP 2008 Fall meeting. [Preview Abstract] |
Friday, October 24, 2008 9:42AM - 9:54AM |
BB.00005: Beam Spin Asymmetry Measurements from Deeply Virtual Eta Production Zhao Bo, Maurizio Ungaro, Kyungseon Joo We present for the first time measurements of the Beam Spin Asymmetry (BSA) from Deeply Virtual Eta Production. With the e1-DVCS experiment at JLAB we have access to Deep Virtual pseudo-scalar Meson Production and consequently to the properties of the polarized Generalized Parton Distributions(GPDs) and/or Regge phenomenology. The experiment was run with the CLAS detector during the spring of 2005, using a 5.7 GeV longitudinally polarized electron beam impinging on a liquid Hydrogen target. Preliminary results show a large (15\%) and constant (in Q2, t, x) BSA indicating a non zero longitudinal-transverse interference in contrast with the GPD assumptions. [Preview Abstract] |
Friday, October 24, 2008 9:54AM - 10:06AM |
BB.00006: Spin Structures of the Deuteron and the Neutron - New Results from CLAS Nevzat Guler In the EG1B experiment, carried out at Jefferson Lab using the CLAS detector, we have measured double polarization asymmetries in and above the nucleon resonance region ( 1.08 GeV $< W <$ 3.0 GeV ). We used a longitudinally polarized electron beam with energies of 1.6, 2.5, 4.2 and 5.75 GeV incident on longitudinally polarized proton and deuteron targets. The large kinematic coverage of the experiment ( 0.05 GeV$^2$ $<$ Q$^2$ $<$ 5.0 GeV$^2$ ) helps us to understand the spin structure of the nucleon, especially in the transition region between hadronic and quark-gluon degrees of freedom. We will present results on $A_1$, $g_1$ and $\Gamma_1$ using the entire data set for the deuteron and extractions of the neutron spin structure functions from the combined deuteron and proton data. [Preview Abstract] |
Friday, October 24, 2008 10:06AM - 10:18AM |
BB.00007: Spin Asymmetry on the Nucleon Experiment Hovhannes Baghdasaryan The Spin Asymmetry on the Nucleon Experiment (SANE) is a measurement of the spin structure function $g^{p}_{2}$ and $A^{p}_{1}$ over a broad range of Bjorken scaling variable \textit{x} from 0.3 to 0.8, for four-momentum transfers from 2.5 GeV$^2$ to 6.5 GeV$^2$. The experiment will measure inclusive double spin asymmetries using TJNAF polarized electron beams of about 4.8 and 6 GeV energies, scattered off UVA solid polarized NH$_{3}$ target. The experiment will take place in 2008. We will discuss the physics motivation for SANE as well as the proposed experimental arrangement, and expected results. [Preview Abstract] |
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