Eur. Phys. J. A 16, 95-109 (2003)
DOI: 10.1140/epja/i2002-10070-4

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

M. Oettel¹ and R. Alkofer<sup>2

1</sup>  Special Research Centre for the Subatomic Structure of Matter, University of Adelaide, Adelaide SA 5005, Australia
²  Institute for Theoretical Physics, Tübingen University, Auf der Morgenstelle 14, D-72076 Tübingen, Germany

Reinhard.Alkofer@uni-tuebingen.de

(Received: 16 April 2002 / Published online: 17 January 2003)

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 and the nucleon magnetic moments are described correctly, the neutron electric form factor and the ratio 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.

PACS
11.10.St - Bound and unstable states; Bethe-Salpeter equations.
12.39.Ki - Relativistic quark model.
13.40.Gp - Electromagnetic form factors.
14.20.Dh - Protons and neutrons.

© Società Italiana di Fisica, Springer-Verlag 2003