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arXiv · 0809.1359

Electromagnetic pion and kaon form factors in light-cone resummed perturbative QCD

Udit Raha·Andreas Aste
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Abstract

We analyze the electromagnetic pion and kaon form factor by including radiative and higher-twist effects within the framework of resummed pQCD in the space-like region. We focus on the transition from the perturbative to non-perturbative behavior in the phenomenological intermediate energy regime. Using a modified k_T factorization scheme with transverse degrees of freedom, we evaluate the non-perturbative soft contributions as distinct from the hard contributions, ensuring no double counting via the Ward identity at Q^2=0. The soft contributions are obtained via local quark-hadron duality while the hard contributions rest on the well known collinear factorization theorem using model wave functions with modified Brodsky-Huang-Lepage type ansatz and distribution amplitudes derived from light-cone QCD sum rules. Our analysis shows that the perturbative hard part prevails for large Q^2 beyond 50-100 GeV^2, while for low and moderate momentum transfers below 10-16 GeV^2 the soft contributions dominate over the hard part. Thus, we demonstrate the importance of including the soft contributions for explaining the experimental form-factor data.

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Udit Raha, Andreas Aste. 2009-03-01. Electromagnetic pion and kaon form factors in light-cone resummed perturbative QCD. https://doi.org/10.1103/physrevd.79.034015

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