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Published March 1, 2019 | Published
Journal Article Open

Observation of the Decay D^0 → K^−π^+e^+e^−


We report the observation of the rare charm decay D^0 → K^−π^+e^+e^−, based on 468  fb^(−1) of e^+e^− annihilation data collected at or close to the center-of-mass energy of the Υ(4S) resonance with the BABAR detector at the SLAC National Accelerator Laboratory. We find the branching fraction in the invariant mass range 0.675 < m(e^+e^−) < 0.875  GeV/c^2 of the electron-positron pair to be B(D^0 → K^−π^+e^+e^−) = (4.0±0.5±0.2±0.1)×10^(−6), where the first uncertainty is statistical, the second systematic, and the third due to the uncertainty in the branching fraction of the decay D^0 → K^−π^+π^+π^− used as a normalization mode. The significance of the observation corresponds to 9.7 standard deviations including systematic uncertainties. This result is consistent with the recently reported D^0 → K^−π^+μ^+μ^− branching fraction, measured in the same invariant mass range, and with the value expected in the standard model. In a set of regions of m(e^+e^−), where long-distance effects are potentially small, we determine a 90% confidence level upper limit on the branching fraction B(D^0 → K^−π^+e^+e^−) < 3.1×10^(−6).

Additional Information

© 2019 Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI. Funded by SCOAP3. Received 30 August 2018; revised manuscript received 11 December 2018; published 27 February 2019. We are grateful for the excellent luminosity and machine conditions provided by our PEP-II colleagues, and for the substantial dedicated effort from the computing organizations that support BABAR. The collaborating institutions wish to thank SLAC for its support and kind hospitality. This work is supported by DOE and NSF (USA), NSERC (Canada), CEA and CNRS-IN2P3 (France), BMBF and DFG (Germany), INFN (Italy), FOM (Netherlands), NFR (Norway), MES (Russia), MINECO (Spain), STFC (United Kingdom), BSF (USA-Israel). Individuals have received support from the Marie Curie EIF (European Union) and the A. P. Sloan Foundation (USA).

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Published - PhysRevLett.122.081802.pdf


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