Transverse momentum and Sudakov effects in exclusive QCD processes: {gamma}{sup {asterisk}}{gamma}{pi}{sup 0} form factor

Journal Article · Mon Sep 01 04:00:00 EDT 1997 · Physical Review, D

DOI:https://doi.org/10.1103/PhysRevD.56.2713· OSTI ID:538702

Musatov, I V; Radyushkin, A V ^[1]

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1. Department of Physics, Old Dominion University, Norfolk, Virginia 23529 (United States)

We analyze effects due to transverse degrees of freedom in QCD calculations of the fundamental hard exclusive amplitude of a {gamma}{sup {asterisk}}{gamma}{r_arrow}{pi}{sup 0} transition. A detailed discussion is given of the relation between the modified factorization approach (MFA) of Sterman {ital et al.} and standard factorization (SFA). Working in the Feynman gauge, we construct basic building blocks of the MFA from the one-loop coefficient function of the SFA, demonstrating that Sudakov effects are distinctly different from higher-twist corrections. We show also that the handbag-type diagram, contrary to naive expectations, does not contain an infinite chain of (M{sup 2}/Q{sup 2}){sup n} corrections: they come only from diagrams with transverse gluons emitted from the hard propagator. A simpler picture emerges within the QCD sum rule approach: the sum over soft {bar q}G{center_dot}{center_dot}{center_dot}Gq Fock components is dual to {bar q}q states generated by the local axial vector current. We combine the results based on QCD sum rules with perturbative QCD radiative corrections and observe that the gap between our curves for the asymptotic and CZ distribution amplitudes is sufficiently large for an experimental discrimination between them. {copyright} {ital 1997} {ital The American Physical Society}

• Research Organization: Thomas Jefferson National Accelerator Facility
• DOE Contract Number: AC05-84ER40150; FG05-94ER40832
• OSTI ID: 538702
• Journal Information: Physical Review, D, Journal Name: Physical Review, D Journal Issue: 5 Vol. 56; ISSN PRVDAQ; ISSN 0556-2821
• Country of Publication: United States
• Language: English

Related Subjects

66 PHYSICS
EXCLUSIVE INTERACTIONS
FACTORIZATION
FORM FACTORS
GLUONS
PERTURBATION THEORY
PHOTON-PHOTON INTERACTIONS
PIONS NEUTRAL
PROPAGATOR
QUANTUM CHROMODYNAMICS
RADIATIVE CORRECTIONS
SUM RULES
TRANSVERSE MOMENTUM