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 heavier resonances are included as intermediate states in the two-photon exchange diagrams: $D13,D33,P11,S11$, and $S31$. We show that the corrections due to the heavier resonances are smaller than 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.

• Received 10 December 2006

DOI:https://doi.org/10.1103/PhysRevC.75.038201