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Structure of the nucleon from electromagnetic form factors

  • F. Iachello
The structure of hadrons

Abstract.

Recent experimental data on the ratio of electric to magnetic elastic form factors are reviewed in light of a model of the nucleon with an intrinsic (quark-like) structure and a meson cloud. The analysis points to the astonishing result that the proton electric form factor vanishes at Q 2~ 8 (GeV/c)2 and becomes negative beyond that point. The intrinsic structure is estimated to have a r.m.s. radius of ~ 0.34 fm, much smaller than the proton r.m.s. radius ~ 0.87 fm. The calculations are in perfect agreement with the proton data, but deviate drastically from neutron data at Q 2>1 (GeV/c)2. Relativistic invariance is a crucial ingredient responsible for the vanishing of \(G_{E_{p}}\). Symmetry, rather than detailed dynamics, appears to be a determining factor in the structure of the nucleon. Scaling appears to occur at much larger values, Q 2≥ 30 (GeV/c)2, than previously thought.

PACS codes.

25.30.Bf - Elastic electron scattering 13.40.Gp - Electromagnetic form factors 14.20.Dh - Protons and neutrons 24.85.+p - Quarks, gluons, and QCD in nuclei and nuclear processes 

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Copyright information

© Società Italiana di Fisica, Springer-Verlag 2004

Authors and Affiliations

  • F. Iachello
    • 1
    • 2
  1. 1.ECT*, I-38050 Villazzano (Trento), Italy
  2. 2.Center for Theoretical Physics, Sloane Physics Laboratory, Yale University, New Haven, Connecticut 06520-8120, USA

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