Resonance Contributions to the Electromagnetic Low Energy Constants of Chiral Perturbation Theory

Nucl.Phys. B499 (1997) 319-348 The effective chiral Lagrangian of the strong and electromagnetic interactions of the pseudoscalar mesons at low energies depends on a set of low energy constants. We determine the contributions to the electromagnetic coupling constants at order $O(e^2 p^2)$, which arise from resonances within a photon loop. We give some implications of our results, in particular we discuss in detail the effects on the corrections to Dashen's theorem.