Electromagnetic nucleon form factors in the extended vector meson dominance model

Abstract

An extended vector meson dominance model is developed to describe electromagnetic nucleon form factors. The model includes families of the $\rho$- and $\omega$-mesons with the associated radial excitations. The free parameters of the model are determined using a global statistical analysis of experimental data on the electromagnetic nucleon form factors in space- and timelike regions of transferred momenta. The vector meson masses and widths are equal to their empirical values, while the residues of form factors at the poles corresponding to the ground states of the $\rho$- and $\omega$-mesons are consistent with the findings of both the Frazer-Fulco unitarity relations and the Bonn potential for coupling constants of the $\rho$- and $\omega$-mesons with nucleons. Theoretical constraints imposed on the model include the quark counting rules, the Okubo-Zweig-Iizuka rule, the scaling law of Sachs form factors at moderate momentum transfers, and the suppression of Sachs form factors near the nucleon-antinucleon threshold. A reasonable description of the nucleon form factors in the experimentally accessible range of transferred momenta, as well as the electric and magnetic nucleon radii and Zemach radii, is obtained.