Resonance estimates of $\mathcal{O}(p^6)$ low-energy constants and QCD short-distance constraints

• DOI: 10.1007/s100520100755
• Publication Date: 2007-10-09T19:58:07Z
• Authors: M. Knecht; A. Nyffeler
• Keywords: Vector meson dominance; Form factor (electronics); Photon energy; Low energy

Starting from the study of the low-energy and high-energy behaviours of the QCD three-point functions , and , several O(p^6) low-energy constants of the chiral Lagrangian are evaluated within the framework of the lowest meson dominance (LMD) approximation to the large-N_C limit of QCD. In certain cases, values that differ substantially from estimates based on a resonance Lagrangian are obtained. It is pointed out that the differences arise through the fact that QCD short-distance constraints are in general not correctly taken into account in the approaches using resonance Lagrangians. We discuss the implications of our results for the O(p^6) counterterm contributions to the vector form factor of the pion and to the decay ��-> e ��_e ��, and for the pion-photon-photon transition form factor.<br/>39 pages, Latex. v2: some typos corrected, references updated, version to appear in Eur. Phys. J. C<br/>