Effect of recent Rp and Rn measurements on extended Gari-Krümpelmann model fits to nucleon electromagnetic form factors

The Gari-Krümpelmann (GK) models of nucleon electromagnetic form factors, in which the ρ, ω, and φ vector meson pole contributions evolve at high momentum transfer to conform to the predictions of perturbative QCD, was recently extended to include the width of the ρ meson by substituting the result of dispersion relations for the pole and the addition of the ρ' (1450) isovector vector meson pole. This extended model was shown to produce a good overall fit to all the available nucleon electromagnetic form-factor data. Since then new polarization data shows that the electric to magnetic ratios R_p and R_n obtained are not consistent with the older G_Ep and G_En data in their range of momentum transfer. The model is further extended to include the ω' (1419) isoscalar vector meson pole. It is found that while this GKex cannot simultaneously fit the new R_p and the old G_En data, it can fit the new R_p and R_n well simultaneously. An excellent fit to all the remaining data is obtained when the inconsistent G_Ep and G_En is omitted. The model predictions are extended beyond the data, if needed, to momentum transfer squared, Q², of 8 GeV²/c².