Upper Limit on the eta to gamma gamma gamma Branching Ratio with the   KLOE Detector
  We have searched for the C-violating decay eta to gamma gamma gamma in a sample of ~ 18 million eta mesons produced in phi to eta gamma decays, collected with the KLOE detector at the Frascati phi-factory DAFNE. No signal is observed and we obtain the upper limit BR(eta to gamma gamma gamma) less equal than 1.6x10^(-5) at 90 % C.L. 
The KLOE Collaboration: A. Aloisio, et al