On Delta resonance contribution to two-photon exchange amplitude

TL;DR

This paper investigates the impact of Delta(1232) resonance production on two-photon exchange amplitudes in elastic electron-proton scattering, revealing significant effects on electric form factors at high momentum transfer.

Contribution

It provides the first detailed calculation of Delta resonance contributions to all three TPE amplitudes, highlighting their importance in polarization measurements.

Findings

Delta resonance mainly affects electric form factor

The effect increases with Q^2

TPE corrections are significant for high Q^2 polarization experiments

Abstract

We consider two-photon exchange (TPE) in the elastic electron-proton scattering and study the contribution arising from the production of Delta(1232) resonance in the intermediate state. We calculate all three TPE amplitudes (generalized form factors), and find that the Delta contribution mainly influences generalized electric form factor (contrary to the elastic contribution, which affects magnetic form factor), and the effect grows with Q^2. If the corresponding correction is applied to the recent polarization transfer measurements of proton form factors, their results will change markedly. Thus we suggest that TPE corrections due to inelastic intermediate states are important to polarization experiments at high Q^2, and should not be neglected.