Contribution of spin 1/2 and 3/2 resonances to two-photon exchange effects in elastic electron-proton scattering

摘要

We calculate contributions of hadron resonances to two-photon exchange effects in electron-proton scattering. In addition to the nucleon and $P33$ resonance, the following resonances are included as intermediate states in the two-photon exchange diagrams: $D13$, $D33$, $P11$, $S11$ and $S31$. We show that the contributions of these resonances are generally smaller that the dominant nucleon and $P33$ contributions. We also find that there is a partial cancellation between the contributions from the spin 1/2 and spin 3/2 resonances, which results in a further suppression of their aggregate two-photon exchange effect.