γγ → πππ to one loop in chiral perturbation theory

The γγ → π0π0π0 and γγ → π+π−π0 amplitudes are discussed in the general context of Chiral Perturbation Theory (ChPT) to O(p6). Chiral loops are found to play a major role. This makes these processes a good test of ChPT, mainly in its anomalous sector. We correct earlier numerical results at tree level and determine the one-loop results as well.