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

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 delta G(M), is responsible for the discrepancy between Rosenbluth and polarization methods. The linearity of Rosenbluth plots implies that delta G(M) is approximately linear function of epsilon. The slope of delta G(M) is extracted from experimental data and is shown to be consistent with theoretical calculations.