Two-photon exchange amplitudes for the elastic $ep$ scattering at Q^2=2.5 GeV^2 from the experimental data

TL;DR

This paper extracts two-photon exchange amplitudes at Q^2=2.5 GeV^2 from experimental data, providing insights into their magnitudes and agreement with theoretical models.

Contribution

It presents the first extraction of two-photon exchange amplitudes at this energy from combined unpolarized and polarization data.

Findings

Only one amplitude, δG_M, can be accurately determined (~10%).

The extracted δG_M agrees well with theoretical predictions.

Rough estimates for the other two amplitudes are provided.

Abstract

We extract two-photon exchange amplitudes for the elastic electron-proton scattering at Q^2=2.5 GeV^2 from the unpolarized cross-section and recent polarization transfer measurements. There are three independent amplitudes, but only one of them, \delta G_M, can be determined with a reasonable accuracy(about 10%). The result is in good agreement with theoretical predictions. Rough estimates for two other amplitudes are obtained.