Axial-vector form factors for Kl2γ and πl2γ at O(p6) in chiral perturbation theory Original Research Article

We present two-loop calculations on the axial-vector form factors FA of semileptonic radiative kaon and pion decays in chiral perturbation theory. The relevant dimension-6 terms of the Lagrangian are evaluated from the resonance contribution and the results of the irreducible two-loop graphs of the sunset topology are given in detail. We also explicitly show that the divergent parts in FA are cancelled exactly as required.