{pi}NN vertex function in a meson-theoretical model

The {pi}NN vertex function is calculated within a dispersion theoretical approach, including both {pi}{rho} and {pi}{sigma} intermediate states, where the {sigma} meson is an abbreviation for a correlated pion pair in a relative {ital S} wave with isospin I=0. A strong coupling between the {pi}{sigma} and {pi}{rho} states is found. This leads to a softening of the {pi}NN form factor. In a monopole parametrization, a cutoff {Lambda}{approx}800hMeV is obtained as compared to {Lambda}{approx}1000hMeV using {pi}{rho} intermediate states only. {copyright} {ital 1999} {ital The American Physical Society}