First Observation of the Decay KL → π0e+e-γ

The KTeV Collaboration

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We report on the first observation of the decay KL→π0e+e-γ by the KTeV E799 experiment at Fermilab. Based upon a sample of 48 events with an estimated background of 3.6±1.1 events, we measure the KL→π0e+e-γ branching ratio to be (2.34±0.35±0.13)×10−8. Our data agree with recent O(p6) calculations in chiral perturbation theory that include contributions from vector meson exchange through the parameter aV. A fit was made to the KL→π0e+e-γ data for aV with the result −0.67±0.21±0.12, which is consistent with previous results from KTeV.

Original languageEnglish (US)
JournalPhysical review letters
Issue number2
StatePublished - Jun 25 2001

ASJC Scopus subject areas

  • Physics and Astronomy(all)


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