Internal Pairs in the Capture ofπ−by Protons

The contribution from nucleon structure to the process ${\pi }^{-}+p\to n+e+e^{+}$ is calculated. The dispersion relations for photoproduction of $\pi$ mesons by virtual photons together with crossing symmetry are used. The nucleon structure contribution is found to be of the order of 2% and of the same size as the contribution from longitudinal polarization. The effect cannot be detected from present data. A 25% discrepancy between theory and experiment, which results from using the more reliable Panofsky ratio 1.8, still persists.