Subprocess Size in Hard Exclusive Scattering

Abstract

The interaction region of hard exclusive hadron scattering can have a large transverse size due to endpoint contributions, where one parton carries most of the hadron momentum. The endpoint region is enhanced and can dominate in processes involving multiple scattering and quark helicity flip. The endpoint Fock states have perturbatively short lifetimes and scatter softly in the target. We give plausible arguments that endpoint contributions can explain the apparent absence of color transparency in fixed angle exclusive scattering and the dimensional scaling of transverse rho photoproduction at high momentum transfer, which requires quark helicity flip. We also present a quantitative estimate of Sudakov effects.

16 pages, 4 figures, JHEP style; v2: quantitative estimate of Sudakov effects and more detailed discussion of endpoint behaviour of meson distribution amplitude added, few other clarifications, version to appear in Phys. Rev. D

References in corpus (4)

• Hadrons in the Nuclear Medium
• Measurement of proton-dissociative diffractive photoproduction of vector mesons at large momentum transfer at HERA
• The Q^2-Dependence of Nuclear Transparency for Exclusive ${\rho }^0$ Production
• Evidence for Quark-Hadron Duality in the Proton Spin Asymmetry $A_1$

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• Vector Meson Photoproduction from the BFKL Equation I: Theory
• Generalized Parton Distributions and Color Transparency
• A Study of the Gluon Ladder in Diffractive Processes
• Comments on the Relativity of Shape
• Generalized Parton Distributions and Transversity in Nucleons and Nuclei
• Semi-exclusive DVCS