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 (15)

• Global analysis of proton elastic form factor data with two-photon exchange corrections
• Two-photon exchange in elastic electron-nucleon scattering
• The two-photon exchange contribution to elastic electron-nucleon scattering at large momentum transfer
• How well do we know the electromagnetic form factors of the proton?
• Measurement of the vector analyzing power in elastic electron-proton scattering as a probe of double photon exchange amplitudes
• Measurement of the Transverse Beam Spin Asymmetry in Elastic Electron Proton Scattering and the Inelastic Contribution to the Imaginary Part of the Two-Photon Exchange Amplitude
• Proton radii and two-photon exchange
• Two-photon exchange in dispersion approach
• Box diagram in the elastic electron-proton scattering
• Experimental constraints on non-linearities induced by two-photon effects in elastic and inelastic Rosenbluth separations
• Contribution of spin 1/2 and 3/2 resonances to two-photon exchange effects in elastic electron-proton scattering
• Two-Photon-Exchange Correction to Parity-Violating 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
• On the Nucleon Distribution Amplitude: The Heterotic Solution

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• Two photon exchange amplitude with πN intermediate states: P33 channel
• An experimental program with high duty-cycle polarized and unpolarized positron beams at Jefferson Lab
• Reexamination of phenomenological two-photon exchange corrections to the proton form factors and e+-p scattering
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• Comparison of Neural Network and Hadronic Model Predictions of Two-Photon Exchange Effect
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• Demonstration of a novel technique to measure two-photon exchange effects in elastic $e^{\pm }p$ scattering
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• The ratio of $e^{\pm }p$ scattering cross sections predicted from the global fit of elastic $ep$ data
• Meson exchange effects in elastic $ep$ scattering at loop level and the electromagnetic form factors of the proton
• Two photon exchange in elastic electron scattering off hadronic systems
• Study of Two-Photon Corrections in the $p\bar{p}-->e+e-$ Process: Hard Rescattering Mechanism
• Measuring the lepton sign asymmetry in elastic electron-proton scattering with OLYMPUS
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• Gauge Invariant Two-Photon-Exchange Contributions in $e^{-}{\pi }^{+}\to e^{-}{\pi }^{+}$
• Resonances contribution to two-photon exchange effects and possible large forward-backward asymmetry in $e^{+}{e}^{-}\to p\bar{p}$
• A novel way to probe distribution amplitudes of neutral mesons in e^+e^- annihilation