Perturbative QCD predictions for two-photon exchange

Understand

We study two-photon exchange (TPE) in the elastic electron-nucleon scattering at high Q^2 in the framework of pQCD.

• The obtained TPE amplitude is of order alpha/alpha_s with respect to Born approximation.
• Its shape and value are sensitive to the choice of nucleon wavefunction, thus study of TPE effects can provide important information about nucleon structure.
• With the wavefunctions based on QCD sum rules, TPE correction to the electron-proton cross section has negative sign, is almost linear in epsilon and grows logarithmically with Q^2 up to 7% at Q^2 = 30 GeV^2.