Bulletin of the American Physical Society
2016 Fall Meeting of the APS Division of Nuclear Physics
Volume 61, Number 13
Thursday–Sunday, October 13–16, 2016; Vancouver, BC, Canada
Session KC: Electromagnetic Observables |
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Chair: Liping Gan, University of North Carolina, Wilmington Room: Junior Ballroom B |
Saturday, October 15, 2016 2:00PM - 2:12PM |
KC.00001: Measurement of the Low Q$^2$ Elastic Form Factor Ratio $\mu G_E / G_M$ Using Electron Scattering Double Spin Asymmetries Jessica Campbell, Moshe Friedman Using a polarized electron beam and a polarized proton target, an elastic scattering experiment was conducted at Jefferson Lab (JLab) in 2012 with the aim of studying the proton elastic form factor ratio $\mu G_E / G_M$ in the momentum transfer range of Q$^2$ = 0.01 - 0.08 GeV$^2$. This experiment will improve our understanding of the form factor ratio at very low $Q^2$ and can be used to constrain extractions the proton charge and magnetic radius. In addition, many models and calculations continue to suggest that non-Dipole $Q^2$–dependent structures might be present in the individual form factors and should reflected in this ratio. The experiment made use of Jefferson Lab's 80\% polarized electron beam incident on the University of Virginia's polarized proton target. With this setup, the experiment was able to access a lower $Q^2$ range than is inaccessible to recoil polarization measurements which require secondary scattering of the recoiling proton. The focus of this work is to report on the preliminary analysis and expected uncertainties. [Preview Abstract] |
Saturday, October 15, 2016 2:12PM - 2:24PM |
KC.00002: Analysis of the Neutron Electric Form Factor at $Q^{2}=$ 1.4 GeV$^{2}$using the reaction $^{3}\vec{{H}}e(\vec{{e}},{e}'n)pp$ Richard Obrecht The Jefferson Lab Hall A experiment E02-013 extracted the neutron electric form factor $G_{E}^{n} $ by measuring the beam-target asymmetry in quasi-elastically scattering of longitudinally polarized electrons from a polarized $^{3}He$ target via the semi-exclusive reaction$^{3}\vec{{H}}e(\vec{{e}},{e}'n)pp$. The experiment measured the electric form factor at a spacelike four-momentum transfer squared $Q^{2}=$1.4, 1.7, 2.7, and 3.4 GeV$^{2}$, but only the latter three points were published by S. Riordan et al. (Phys. Rev. Lett. 105, 262302). The goal of this talk is to present the analysis chain necessary to extract the form factor from a neutron asymmetry that arises by periodically changing the sign of the beam helicity. The analysis includes selecting quasi-elastic events in a high noise environment, and correcting for various factors that dilute the signal such as false proton asymmetries and final state interactions within the target. [Preview Abstract] |
Saturday, October 15, 2016 2:24PM - 2:36PM |
KC.00003: ABSTRACT WITHDRAWN |
Saturday, October 15, 2016 2:36PM - 2:48PM |
KC.00004: Factorization Breaking of $A^T_d$ for polarized deuteron targets in a relativistic framework Sabine Jeschonnek, J. W. Van Orden We discuss the possible factorization of the tensor asymmetry $A^T_$d measured for polarized deuteron targets within a relativistic framework. We define a reduced asymmetry and find that factorization holds only in plane wave impulse approximation and if p-waves are neglected. Our numerical results show a strong factorization breaking once final state interactions are included. We also compare the d-wave content of the wave functions with the size of the factored, reduced asymmetry and find that there is no systematic relationship of this quantity to the d-wave probability of the various wave functions. [Preview Abstract] |
Saturday, October 15, 2016 2:48PM - 3:00PM |
KC.00005: Studies of Final-State Interactions via Helicity Asymmetries in Exclusive Pseudoscalar Meson Photoproduction off Deuteron Yordanka Ilieva Exclusive meson photoproduction off deuteron is a great tool to study final-state interactions (FSI) between the hadrons produced in the scattering of the incident photon off one of the target nucleons and the spectator nucleon. FSI in the reaction $\gamma d\to K^{+}\Lambda n$ enable access the dynamics of $\Lambda n$ elastic scattering and provide a method of studying the hyperon-nucleon interaction. Also, as deuteron is often used as a neutron target, FSI in reactions such as $\gamma d\to p\pi^{+}\pi^{-}$ contribute to the reaction dynamics in addition to the quasi-free $\gamma n\to p\pi^{-}$ and their understanding is critical for the estimate of observables off the free nucleon. In this talk we will show preliminary results for beam-helicity asymmetries for the reactions $\vec{{\gamma }}d\to K^{+}\Lambda n$ , $\vec{{\gamma }}d\to pp\pi^{-}$ , and $\vec{{\gamma }}d\to p\pi^{+}\pi^{-}n$ and their evolution over the spectator-nucleon virtuality. The data were obtained with the CLAS at Jefferson Lab in experiment E06-103 where a circularly-polarized photon beam with energies between 0.5 GeV and 2.5 GeV was incident on unpolarized deuteron target. We will present an interpretation of our $K^{+}\Lambda n$ results in terms of $\Lambda n$ elastic scattering. We will also discuss the extraction of polarization observables for photoproduction off the free nucleon using our helicity asymmetries for reactions off the deuteron. [Preview Abstract] |
Saturday, October 15, 2016 3:00PM - 3:12PM |
KC.00006: Deep Exclusive $\mathrm\pi^-$ Production using a Transversely Polarized $\mathrm{^{3}He}$ Target and the SoLID Spectrometer Garth Huber The $\sin(\phi-\phi_S)$ and $\sin(\phi_S)$ Fourier amplitudes of the single-spin azimuthal asymmetry in exclusive electroproduction of charged pions from transversely polarized nucleons have been noted as providing unique views of nucleon structure. The $\sin(\phi-\phi_S)$ amplitude is expected to be particularly sensitive to the spin-flip generalized parton distribution (GPD) $\tilde{E}$, yielding structure information unlikely to be obtained from any other source. The $\sin(\phi_S)$ amplitude is also extremely important, as it provides powerful constraints on the transversity GPDs. The only measurements to date of these quantities were published by the HERMES Collaboration in 2010. The high luminosity and large acceptance capabilities of the proposed Solenoidal Large Intensity Detector (SoLID) at Jefferson Lab would allow an improved measurement with broader kinematic coverage and significantly reduced errors. I will present projections using a transversely polarized $^3$He target and the $\vec{n}(e,e'\pi^-p)$ reaction. [Preview Abstract] |
Saturday, October 15, 2016 3:12PM - 3:24PM |
KC.00007: Determination of the Hyperon Induced Polarization and Polarization--Transfer Coefficients for Quasi-Free Hyperon Photoproduction off the Bound Neutron Colin Gleason Measurement of the excited nucleon ($N^*$) spectrum provides key information on the relevant degrees of freedom within the nucleon and requires an extensive set of experimental observables over a broad kinematic range for many nuclear reactions. Polarization observables from kaon-hyperon (KY) channels are needed as many resonances predicted by quark models, but not observed in $\pi N$ channels, are expected to couple strongly to KY channels. While in the last decade data has been published for KY off the proton, data off the neutron are scarce. In this talk we will show preliminary results for $P$, $C_X$, and $C_Z$ for the reaction $\gamma d\to K^{0}\Lambda(p)$ for $E_{\gamma}$ between 0.9--2.6 GeV and cos$\theta_{K^{0}}^{CM}$ between -0.9--1. The data was collected in experiment E06-103 (g13) with the CLAS detector at Thomas Jefferson National Accelerator Facility using a circularly polarized photon beam and an unpolarized LD2 target. We will discuss the effect of neutron binding on the observables and the comparison of our results with theoretical predictions. Our study is part of a larger effort by the g13 group to provide cross--sections and polarization observables for meson photoproduction off the neutron and is expected to have a large impact on the $N^{*}$ research. [Preview Abstract] |
Saturday, October 15, 2016 3:24PM - 3:36PM |
KC.00008: New Measurements of the EMC Effect and Short Range Correlations at JLab Hall C at 11 GeV Kayla Craycraft The nuclear dependence of the Deep Inelastic Scattering (DIS) cross section (known as the EMC effect) has shown conclusively that the distribution of quarks in a nucleus is modified when compared to the deuteron. On the other hand, Short Range Correlations, which arise from hard interactions between nucleons inside the nucleus give rise to high momentum tails in nucleon momentum distributions. The observation that the size of the EMC effect is correlated with the number of SRC NN pairs in a nucleus suggests a possible origin of the EMC effect. While the observed relationship is compelling, more investigation using adding additional nuclei and improving the precision on existing measurements is necessary. Jefferson Lab experiments E12-06-105 and E12-10-008 aim to do just that, making measurements of electron scattering cross section ratios in the DIS regime and at $x>1$ for a large body of nuclei. These experiments will attempt to disentangle whether the EMC-SRC correlation is driven only by the size/atomic number of the nucleus, or if it also depends on the neutron to proton ratio. [Preview Abstract] |
Saturday, October 15, 2016 3:36PM - 3:48PM |
KC.00009: ABSTRACT WITHDRAWN |
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