Eur. Phys. J. A (2004) 20: 469-473
https://doi.org/10.1140/epja/i2003-10223-y

Updated dispersion-theoretical analysis of the nucleon electromagnetic form factors

¹ Helmholtz-Institut für Strahlen- und Kernhysik (Theorie), Universität Bonn, 53115, Bonn, Germany
² Institut für Kernphysik (Theorie), Forschungszentrum Jülich, 52425, Jülich, Germany

^* e-mail: hammer@phys.washington.edu

Abstract

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.