Electromagnetic pion and kaon form factors in light-cone resummed perturbative QCD
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 kT 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 Q2=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 Q2 beyond 50-100 GeV2, while for low and moderate momentum transfers below 10-16 GeV2 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.