The asymptotics of the transition form factor γγ* -> pi^o and QCD sum rules

1997/06/26 by Anatoly Radyushkin, A. V. Radyushkin, Radyushkin, A. V. +3
Physics and Astronomy · #FOS: Physical sciences #High Energy Physics - Phenomenology (hep-ph) #High-Energy Particle Collisions Research #Particle physics theoretical and experimental studies #Quantum Chromodynamics and Particle Interactions #hep-ph

paper · pdf · doi:10.48550/arxiv.hep-ph/9706518

6 pages, LaTeX (sprocl.sty, 1 eps figure incl.), Talk presented by R. Ruskov at the International Conference on the Structure and the Interactions of the Photon, Egmond aan Zee, The Netherlands, 10-15 May, 1997; to be published in the proceedings

arxiv created 1997/06/26 · openalex publication_date 1997/06/26 · arxiv updated 2009/11/30 · openalex created_date 2024/04/11 · openalex updated_date 2026/07/28

Abstract

In this paper we present the result of a direct QCD sum rule calculation of the transition form factor γγ* -> pi^o in the region of moderately large invariant momentum Q² > 1GeV² of the virtual photon. In contrast to pQCD, we make no assumptions about the shape of the pion distribution amplitude ϕ_π(x). Our results agree with the Brodsky-Lepage proposal that the Q²-dependence of this form factor is given by an interpolation between its Q²=0 value fixed by the axial anomaly and 1/Q² pQCD behaviour for large Q², with normalization corresponding to the asymptotic form ϕ_π^as (x)=6 f_πx (1-x) of the pion distribution amplitude. Our prediction for the from factor F_{γ^*γ^*π^∘}(q₁² = 0,q₂² = -Q²) is in good agreement with new CLEO data.

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