Complete structure-dependent analysis of the decay P → l+l-

We use the Mellin-Barnes representation in order to improve the theoretical estimate of mass corrections to the width of light pseudoscalar meson decays into a lepton pair, P -> l(+)l(-). The full resummation of the terms (M-2/A(2))(n), (m(2)/M-2)(n) and (m(2)/A(2))(n) to the decay amplitude is performed, where m is the lepton mass, M is the meson mass and A approximate to m(rho) is the characteristic scale of the P -> gamma*gamma* form factor. The total effect of mass corrections is quite important for eta (eta') decays. We also comment on the estimation of the hadronic light-by-light scattering contribution to the muon anomalous magnetic moment in the chiral perturbation theory. (C) 2009 Elsevier B.V. All rights reserved.