Two-photon exchange in elastic electron-proton scattering: a QCD factorization approach.
We estimate the two-photon exchange contribution to elastic electron-proton scattering at large momentum transfer Q(2). It is shown that the leading two-photon exchange amplitude behaves as 1/Q(4), 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.
Institute für Theoretische Physik II, Ruhr-Universität Bochum, D-44780 Bochum, Germany.
Nikolai
N
Kivel
Marc
M
Vanderhaeghen