Model-independent extraction of two-photon effects in elastic electron-proton scattering

TL;DR

This paper provides a model-independent estimate of two-photon exchange effects in elastic electron-proton scattering by analyzing polarization transfer and cross section data separately, addressing discrepancies in nucleon form factor measurements.

Contribution

It introduces a method to estimate two-photon corrections without relying on specific models, using dispersion relations on separate datasets to reconcile experimental discrepancies.

Findings

Estimated two-photon correction Delta^(2γ) aligns with direct calculations.

Analysis confirms negligible two-photon effects on polarization transfer data.

Results help resolve the discrepancy between Rosenbluth and polarization transfer measurements.

Abstract

We address the discrepancy between the Rosenbluth and polarization transfer data for the electromagnetic form factors of the nucleon. Assuming that the effect of two-photon corrections on the polarization transfer data is negligible, we obtain a model-independent estimate of the two-photon correction Delta^(2\gamma). We analyze the polarization transfer data and the cross section data separately using dispersion relations. A central value as well as an error estimate for Delta^(2\gamma) is then obtained from a comparison of the two analyses. The resulting values for Delta^(2\gamma) are in good agreement with direct calculations available in the literature.