Dirac form factors and electric charge radii of baryons in the combined chiral and1/Ncexpansions

Abstract

The baryon Dirac form factor is computed at one-loop order in large-N_c baryon chiral perturbation theory, where N_c is the number of color charges. Loop graphs with octet and decuplet intermediate states are systematically incorporated into the analysis and the effects of the decuplet-octet mass difference are accounted for. There are large-N_c cancellations between different one-loop graphs as a consequence of the large-N_c spin-flavor symmetry of QCD baryons. As a byproduct, the mean-square charge radius is also computed through a detailed numerical analysis. The predictions of large-N_c baryon chiral perturbation theory are in very good agreement both with the expectations from the 1/N_c expansion and with the experimental data.