$\pi \to l\nu \gamma$ Form Factors at Two-loop

Abstract

Within Chiral Perturbation Theory (CHPT) we compute the form factors A, V and $\gamma =A/V$ in the $\pi \to \nu l\gamma$ decay to $O(p^6)$. A and $\gamma$ obtain corrections of order 25%.

Comments: Added cut-off dependence discusion, misprints corrected