Recalculation of Proton Compton Scattering in Perturbative QCD
arXiv:hep-ph/0004143 · doi:10.1103/PhysRevD.62.114021
Abstract
At very high energy and wide angles, Compton scattering on the proton (gamma p -> gamma p) is described by perturbative QCD. The perturbative QCD calculation has been performed several times previously, at leading twist and at leading order in alpha_s, with mutually inconsistent results, even when the same light-cone distribution amplitudes have been employed. We have recalculated the helicity amplitudes for this process, using contour deformations to evaluate the singular integrals over the light-cone momentum fractions. We do not obtain complete agreement with any previous result. Our results are closest to those of the most recent previous computation, differing significantly for just one of the three independent helicity amplitudes, and only for backward scattering angles. We present results for the unpolarized cross section, and for three different polarization asymmetries. We compare the perturbative QCD predictions for these observables with those of the handbag and diquark models. In order to reduce uncertainties associated with alpha_s and the three-quark wave function normalization, we have normalized the Compton cross section using the proton elastic form factor. The theoretical predictions for this ratio are about an order of magnitude below existing experimental data.
Latex, 23 pages, 13 figures. Checked numerical integration one more way; added results for one more proton distribution amplitude; a few other minor changes. Version to appear in Phys. Rev. D
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Cited by in corpus (21)
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- Local Two-Photon Couplings and the J=0 Fixed Pole in Real and Virtual Compton Scattering
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- Transition distribution amplitudes and hard exclusive reactions with baryon number transfer
- Polarization Transfer in Proton Compton Scattering at High Momentum Transfer
- Handling the Handbag Diagram in Compton Scattering on the Proton
- Hard Photodisintegration of a Proton Pair in 3He
- Polarization Observables in Hard Rescattering Mechanism of Deuteron Photodisintegration
- The process p + pbar --> gamma + pi^0 within the handbag approch
- Real and Virtual Nucleon Compton Scattering in the Perturbative Limit
- Polarization Transfer in Wide-Angle Compton Scattering and Single-Pion Photoproduction from the Proton
- Physics Opportunities at a Photon-Photon Collider
- Hard Break-Up of Two-Nucleons from the 3He Nucleus
- High Energy Photon-Photon Collisions at a Linear Collider
- QCD radiative corrections to the soft spectator contribution in the wide angle Compton scattering
- Real Compton Scattering via Color Dipoles
- Wide-angle photo- and electroproduction of pions to twist-3 accuracy
- Shadowing in Compton scattering on nuclei
- Recalculation of Pion Compton Scattering in Perturbative QCD
- Some comments on the handbag approach to wide-angle exclusive scattering