The eta-prime -> eta pi pi decay in U(3) chiral perturbation theory
  The dominant decay mode of the eta-prime, eta-prime -> eta pi pi, is investigated within the framework of infrared regularized U(3) chiral perturbation theory up to fourth chiral order and including one-loop corrections. We find reasonable agreement with experimental data and observe convergence of the chiral series. 
N. Beisert, B. Borasoy