Resonance estimates of O(p(6)) low-energy constants and QCD short-distanceconstraints

Starting from the study of the low-energy and high-energy behaviors of the QCD three-point functions <VAP>, <VVP> and <AAP>, several O(p(6)) low-energ y constants of the chiral Lagrangian are evaluated within the framework of the lowest meson dominance (LMD) approximation to the large-NC limit of QCD . In certain cases, values that differ substantially from estimates based o n a resonance Lagrangian are obtained. It is pointed out that the differenc es arise through the fact that QCD short-distance constraints are in genera l not correctly taken into account in the approaches using resonance Lagran gians. We discuss the implications of our results for the O(p(6)) counterte rm contributions to the vector form factor of the pion and to the decay pi --> ev(e)gamma, and for the pion-photon-photon transition form factor.