Measurement of the decay KL→e+e−γγ

Abstract The full data set of the NA31 experiment at CERN has been used to analyse the decay mode K 0 L → e + e − γγ . A signal of 47 events has been observed with an estimated background of 6.9 events. The total number of kaon decays in the decay volume was determined to be (2.1±0.1 stat )·10 9 . This corresponds to a branching ratio of 8.0±1.5 +1.4 −1.2 ·10 −7 .