First observation of KL→π±eνe+e-

E. Abouzaid, M. Arenton, A. R. Barker, L. Bellantoni, E. Blucher, G. J. Bock, E. Cheu, R. Coleman, M. D. Corcoran, B. Cox, A. R. Erwin, C. O. Escobar, A. Glazov, A. Golossanov, R. A. Gomes, P. Gouffon, Y. B. Hsiung, D. A. Jensen, R. Kessler, K. KoteraA. Ledovskoy, P. L. McBride, E. Monnier, K. S. Nelson, H. Nguyen, R. Niclasen, D. G. Phillips, H. Ping, E. J. Ramberg, R. E. Ray, M. Ronquest, E. Santos, W. Slater, D. Smith, N. Solomey, E. C. Swallow, P. A. Toale, R. Tschirhart, C. Velissaris, Y. W. Wah, J. Wang, H. B. White, J. Whitmore, M. J. Wilking, B. Winstein, R. Winston, E. T. Worcester, M. Worcester, T. Yamanaka, E. D. Zimmerman, R. F. Zukanovich

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3 Scopus citations


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.

Original languageEnglish (US)
Article number081803
JournalPhysical review letters
Issue number8
StatePublished - Aug 25 2007

ASJC Scopus subject areas

  • General Physics and Astronomy


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