Effect of a Pion-Pion Scattering Resonance on Nucleon Structure. II

It is shown that a resonance of suitable position and width in the J=1, I=1 state of the pion-pion system can bring the dispersion-theoretic calculation of the isotopic-vector part of the nucleon electromagnetic structure into agreement with experiment. The calculation of the isotopic-vector part of the nucleon form factors involves in first approximation the pion form factor and the matrix element for the production by two pions of a nucleon-antinucleon pair. For the pion form factor we used a semiphenomenological solution based on the work of Chew and Mandelstam and involving two parameters related to the position and width of the resonance. For the ++N amplitude we used the results of the preceding paper.