Abstract
We analyze the electromagnetic pion and koan form factors by including sofr and higher-twist effects within the framework of resumed perturbative QCD (pQCD) for both the space and time-like regions. 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 vector Ward Identity at Q2=0. The soft contributions are obtained via local quark-hadron duality while the hard contributions rest on the well known factorization ansatz with intrinsic transverse momentum dependence of the distribution amplitudes modeled via the Brodsky-Huang-Lepage ansatz. Our analysis shows that while the perturbative twist-2 hard part prevails for large Q2 beyond 100-150 GeV2 or so, for low and moderate momentum transfers, say, below 10-16 GeV2, the soft contributions dominate in the space-like region and the twist-3 contributions dominate in the time-like region. Thus, we demonstrate the importance of including the genuine non-perturbative soft and power suppressed twist-3 contributions for simultaneously explaining the space and time-like experimental form factor data to a reasonable good accuracy.
