Nucleon form factors from a covariant quark core: Limits in their description

Abstract

In treating the relativistic 3–quark problem, a dressed–quark propagator parameterization is used which is compatible with recent lattice data and pion observables. Furthermore 2–quark correlations are modeled as a series of quark loops in the scalar and axialvector channel. The resulting reduced Faddeev equations are solved for nucleon and delta. Nucleon electromagnetic form factors are calculated in a fully covariant and gauge–invariant scheme. Whereas the proton electric form factor GE and the nucleon magnetic moments are described correctly, the neutron electric form factor and the ratio GE/GM for the proton appear to be quenched. The influence of vector mesons on the form factors is investigated which amounts to a 25 % modification of the electromagnetic proton radii within this framework.