Momentum dependence of the rho - omega mixing amplitude in a hadronic model.

We calculate the momentum dependence of the [rho]-[omega] mixing amplitude in a purely hadronic model. The basic assumption of the model is that the mixing amplitude is generated by [ital N[bar N]] loops and thus driven entirely by the neutron-proton mass difference. The value of the amplitude at the [omega]-meson point is expressed in terms of only the [ital NN][omega] and [ital NN][rho] coupling constants. Using values for these couplings constrained by empirical two-nucleon data we obtain a value for the mixing amplitude in agreement with experiment. Extending these results to the spacelike region, we find a [rho]-[omega] contribution to the [ital NN] interaction that is strongly suppressed and opposite in sign relative to the conventional contribution obtained from using the constant on-shell value for the mixing amplitude.