Two-photon exchange in elastic electron-proton scattering : QCD factorization approach
Abstract
We estimate the two-photon exchange contribution to elastic electron-proton scattering at large momentum transfer Q2. It is shown that the leading two-photon exchange amplitude behaves as 1/Q4 relative to the one-photon amplitude, and can be expressed in a model independent way in terms of the leading twist nucleon distribution amplitudes. Using several models for the nucleon distribution amplitudes, we provide estimates for existing data and for ongoing experiments.
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