Two-photon exchange in electron deuteron scattering

It is shown that the amplitude of elastic ed scattering beyond Born approximation contains six generalized form factors, but only three linearly independent combinations of them (generalized charge, quadrupole and magnetic form factors) contribute to the reaction cross section in the second order perturbation theory. We examine two-photon exchange and find that it includes two types of diagrams, when two virtual photons interact with the same nucleon and when the photons interact with different nucleons.We discuss contribution of the two-photon exchange in reaction observables, generalized \mathcal A and \mathcal B structure functions and tensor polarization of the deuteron.