Vector meson exchange contributions to K → πγγ and KL → γℓ+ℓ− Original Research Article

We have studied in the framework of Chiral Perturbation Theory (χPT) the O(p6) vector meson contributions to K → πγγ and KL → γγ∗. We construct the most general χPT Lagrangian for the weak vector-pseudoscalar-photon (VPγ) vertex for K → πγγ and KL → γγ∗ and consequently we get the full structure of the O(p6) local contributions generated by vector meson exchange. We then compute new factorizable contributions to the weak VPγ vertex generated by the odd-intrinsic parity violating Lagrangian with no additional couplings. We find in fact a very nice agreement with the phenomenology of K → πγγ and KL → γγ∗, more predictive power and a deeper understanding of the O(p6) local operators. A novel interpretation of the KL → γγ∗ data is given. Also a comparison with the existing models is presented.