Nonresonantπ−πContributions to Electromagnetic Form Factors

Abstract

The effect of the exchange of two nonresonant pions on the electromagnetic structure of the pion and the nucleon is investigated. The results show that such an exchange is not negligible. By taking it into account, the value of the $\rho$ mass needed to fit the nucleon isovector form factor may be changed from its previous anomalously low value to its experimental value. In addition, the coupling constant $g_{\rho \mathrm{NN}}$, as deduced from the nucleon electromagnetic structure, is affected significantly.