Two-photon exchange in electron-trinucleon elastic scattering
We discuss two-photon exchange (TPE) in elastic electron scattering off the trinucleon systems, He and H. The calculations are done in the semirelativistic approximation with the trinucleon wave functions obtained with the Paris and CD-Bonn nucleon-nucleon potentials. An applicability area of the model is wide enough and includes the main part of kinematical domain where experimental data exist. All three TPE amplitudes (generalized form factors) for electron He elastic scattering are calculated. We find that the TPE amplitudes are few times more significant in the scattring of electrons off He then in the electron proton scattering.