Polarization transfer in the 2H(e⃗,e′p⃗)n reaction up to Q2=1.61 (GeV/c)2

Physical Review C (Impact Factor: 3.73). 06/2006; 73(6). DOI: 10.1103/PhysRevC.73.064004
Source: arXiv


The recoil proton polarization was measured in the 2H(e⃗,e′p⃗)n reaction in Hall A of the Thomas Jefferson National Accelerator Facility. The electron kinematics were centered on the quasielastic peak (xBj≈1) and included three values of the squared four-momentum transfer, Q2=0.43,1.00 and 1.61 (GeV/c)2. For Q2=0.43 and 1.61 (GeV/c)2, the missing momentum, pm, was centered at zero, whereas for Q2=1.00 (GeV/c)2 two values of pm were chosen: 0 and 174 MeV/c. At low pm, the Q2 dependence of the longitudinal polarization, Pz′, is not well described by a state-of-the-art calculation. Further, at higher pm, a 3.5σ discrepancy was observed in the transverse polarization, Px′. Understanding the origin of these discrepancies is important to confidently extract the neutron electric form factor from the analogous 2H(e⃗,e′n⃗)p experiment.

Download full-text


Available from: Sabine Jeschonnek, Dec 27, 2013
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: There has been much activity in the measurement of the elastic electromagnetic proton and neutron form factors in the last decade, and the quality of the data has been greatly improved by performing double polarization experiments, in comparison with previous unpolarized data. Here we review the experimental data base in view of the new results for the proton, and neutron, obtained at MIT-Bates, MAMI, and JLab. The rapid evolution of phenomenological models triggered by these high-precision experiments will be discussed, including the recent progress in the determination of the valence quark generalized parton distributions of the nucleon, as well as the steady rate of improvements made in the lattice QCD calculations. Comment: 71 pages, 43 figures (published version with typos corrected)
    Full-text · Article · Dec 2006 · Progress in Particle and Nuclear Physics
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: High-precision measurements of the proton elastic form-factor ratio, mupGEp/GMp, have been made at four-momentum transfer, Q2, values between 0.2 and 0.5GeV2. The new data, while consistent with previous results, clearly show a ratio less than unity and significant differences from the central values of several recent phenomenological fits. By combining the new form-factor ratio data with an existing cross-section measurement, one finds that in this Q2 range the deviation from unity is primarily due to GEp being smaller than expected.
    Full-text · Article · Jan 2007
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The new parameterization of the generalized parton distributions t-dependence is proposed. It allows one to reproduce sufficiently well the electromagnetic form factors of the proton and neutron at small and large momentum transfer. The description of the data obtained by the Rosenbluth method and the polarization method are compared. The results obtained by the latter method are shown to be compatible with the correspondent neutron data. The impact parameter dependence of the neutron charge density is examined. The quark contributions to gravitational form factors of the nucleons are obtained.
    Full-text · Article · Feb 2009 · Physical review D: Particles and fields
Show more