Speaker
Description
We studied the transition form factor involved in pseudoscalar meson ($\pi$,$\eta$,$\eta$') decays into two virtual photons by means of a chiral-invariant Lagrangian, considering the lowest-lying multiplet of vector and pseudoscalar resonances. Accounting for $U(3)$ breaking effects, we give the most general corrections of order $m_P^2$ to the form factor. Most parameters are fixed requiring short-distance constraints. The remaining ones are fitted to experimental measurements of the form factors in the space-like $(q^2<0)$ region of photon momenta. We, thus, obtain the P-pole contribution to the hadronic light-by-light scattering of the muon g-2 with an improved certainty: $(8.47 \pm 0.16)\times10^{-10}$. This is obtained neglecting BaBar data for the $\pi^0$ Transition Form Factor which, in our analysis, is in conflict with the remaining experimental inputs.
