eta->pi(0)gamma gamma to O(p(6)) in chiral perturbation theory

The decay eta --> pi(0) gamma gamma is discussed in the framework of SU(3) chiral perturbation theory. The process is dominated by the O(p(6)) in the momentum expansion where tree-level amplitudes from the effective Lagrangian L(6) enter together with one-loop contributions from L(4) and two-loop contributions from L(2). We estimate the six independent L(6) coupling constants by resonance saturation consistent with the pion production process gamma gamma --> pi(0) pi(0) and calculate the pion-loop part of the one- and two-loop amplitude. Predictions for the total rate and spectrum of eta --> pi(0) gamma gamma are given together with a discussion of the uncertainties involved.