This Letter is the first report of the KL→π±eνe+e- decay. Based on 19208±144 events, we determine the branching fraction, B(KL→π±eνe+e-;Me+e->5MeV/c2,Ee+e-*>30MeV)=(1. 285±0.041)×10-5, and Γ(Ke3ee;Me+e->5MeV/c2)/Γ(Ke3)= [4.57±0.04(stat)±0.14(syst)]×10-5. This ratio agrees with a theoretical prediction based on chiral perturbation theory (ChPT) calculated to O(p4). The measured kinematical distributions agree with those predicted by just ChPT O(p4), but show significant disagreement with ones predicted by leading-order ChPT.
ASJC Scopus subject areas
- Physics and Astronomy(all)