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QCD sum rules and soft-hard interplay for hadronic form factors

A. V. Radyushkin
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Abstract

We discuss two types of contributions to hadronic form factors in QCD: hard gluon exchange and soft wave function overlap. Within the QCD sum rule approach, the hard contribution has strong numeric suppression by factor (α_s/π) ~ 0.1 for each exchange. For this reason, the soft contribution dominates at accessible momentum transfers. The ``humpy'' distribution amplitudes used to enhance hard terms cannot be derived from QCD sum rules in a self-consistent way. The estimates of soft terms obtained within the local quark-hadronic duality approach in all cases are close to existing data, providing an experimental evidence that hard terms are small.

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A. V. Radyushkin. 1998-11-02. QCD sum rules and soft-hard interplay for hadronic form factors. https://arxiv.org/abs/hep-ph/9811225

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