Phenomenological analysis of two-photon exchange effects in proton form factor measurements

Abstract

We perform a model-independent phenomenological analysis of experimental data on proton form factor ratio. We find that only one of the two-photon exchange amplitudes, which we call $\ensuremath{\delta}{\mathcal{G}}_{M}$, is responsible for the discrepancy between Rosenbluth and polarization methods. The linearity of Rosenbluth plots implies that $\ensuremath{\delta}{\mathcal{G}}_{M}$ is approximately linear function of \ensuremath{\varepsilon}. The slope of $\ensuremath{\delta}{\mathcal{G}}_{M}$ is extracted from experimental data and is shown to be consistent with theoretical calculations.