Observation of the rare eta->e+e-e+e- decay with the KLOE experiment
  We report the first observation of the rare eta->e+e-e+e- decay based on 1.7 fb^{-1} collected by the KLOE experiment at the DAFNE phi-factory. The selection of the e+e-e+e- final state is fully inclusive of radiation. We have identified 362 +- 29 events resulting in a branching ratio of (2.4 +- 0.2_stat+bckg +- 0.1_syst) x 10^{-5}. 
The KLOE Collaboration: F.Ambrosino, A.Antonelli, M.Antonelli,   F.Archilli, I.Balwierz, G.Bencivenni, C.Bini, C.Bloise, S.B...
hep-ex