Updated dispersion-theoretical analysis of the nucleon electromagnetic form factors
Helmholtz-Institut für Strahlen- und Kernhysik (Theorie), Universität Bonn, 53115, Bonn, Germany
2 Institut für Kernphysik (Theorie), Forschungszentrum Jülich, 52425, Jülich, Germany
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In the light of the new data on the various neutron and proton electromagnetic form factors taken in recent years, we update the dispersion-theoretical analysis of the nucleon electromagnetic form factors from the mid-nineties. The parametrization of the spectral functions includes constraints from unitarity, perturbative QCD, and recent measurements of the neutron charge radius. We obtain a good description of most modern form factor data, with the exception of the Jefferson Lab data on G E p /G M p in the four-momentum transfer range GeV2. For the magnetic radii of the proton and the neutron we find r M p = 0.857 fm and r M n = 0.879 fm, which is consistent with the recent determinations using continued-fraction expansions.
© Società Italiana di Fisica and Springer-Verlag, 2004