Perturbative QCD predictions for two-photon exchange

Abstract

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. The results of existing "hadronic" calculations, taking into account just the nucleon intermediate state, can be smoothly connected with pQCD result near Q^2 = 3 GeV^2. Above this point two methods disagree, which implies that "hadronic" approach becomes inadequate at high Q^2. Other relevant observables, such as electron/positron cross section ratio, are also discussed.

References in corpus (5)

• Global analysis of proton elastic form factor data with two-photon exchange corrections
• Two-photon exchange in dispersion approach
• Contribution of spin 1/2 and 3/2 resonances to two-photon exchange effects in elastic electron-proton scattering
• Phenomenological analysis of two-photon exchange effects in proton form factor measurements
• Transverse target spin asymmetry in inclusive DIS with two-photon exchange

Cited by in corpus (1)

• Two-photon exchange in elastic electron-proton scattering : QCD factorization approach