Two-photon decays of pi^0, eta and eta-prime

Abstract

We investigate the decays of pi^0, eta and eta-prime into two photons in an effective U(3) chiral Lagrangian approach without employing large N_c arguments. Tree level and one-loop contributions from the anomalous Wess-Zumino-Witten Lagrangian are calculated and the importance of eta--eta-prime mixing is discussed. Unitarity corrections beyond one-loop play an important role for the decays with off-shell photons and are included by employing a coupled channel Bethe-Salpeter equation which satisfies unitarity constraints and generates vector-mesons from composed states of two pseudoscalar mesons.