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QCD sum rules: form factors and wave functions

A. V. Radyushkin
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Abstract

The shape of hadronic distribution amplitudes (DAs) is a critical issue for the perturbative QCD of hard exclusive processes. Recent CLEO data on gamma gamma* -> pi^0 form factor clearly favor a pion DA close to the asymptotic form. We argue that QCD sum rules for the moments of the pion DA φ_π(x) are unreliable, so that the humpy shape of φ_π(x) obtained by Chernyak and Zhitnitsky is a result of model assumptions rather than an unambigous consequence of QCD sum rules. This conclusion is also supported by a direct QCD sum rule calculation of the gamma gamma* -> pi^0 form factor which gives a result very close to the CLEO data.

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A. V. Radyushkin. 1997-07-12. QCD sum rules: form factors and wave functions. https://arxiv.org/abs/hep-ph/9707335

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