Gamma*Ndelta from factors from a relativistic dynamical model of pion electroproduction

We obtain the electromagnetic form factors of the γNΔ transition by analyzing recent pion-electroproduction data using a fully relativistic dynamical model. Special care is taken to satisfy Ward-Takahashi identities for the Born term in the presence of form factors, thereby allowing the use of realistic electromagnetic form factors of the nucleon and pion. We parametrize the Q2 dependence of the bare γNΔ form factors by a three-parameter form which is consistent with the asymptotic behavior inferred from QCD. The parameters of the bare γNΔ form factors are the only free parameters of the model and are fitted to the differential cross-section and multipole-analysis data up to Q2=4(GeV∕c)2 in the Δ(1232)-resonance region. This analysis emphasizes the significance of the pion-cloud effects in the extraction of the resonance parameters