Observation of the Decay D^{0}→K^{-}π^{+}e^{+}e^{-}

Area of Science:

• Particle Physics
• High-Energy Physics
• Quantum Chromodynamics

Background:

• The Standard Model of particle physics predicts certain decay modes for charm mesons.
• Rare decays provide sensitive probes of fundamental interactions and potential new physics.
• Previous observations of similar decays, like D0→K-π+μ+μ-, offer comparative data.

Purpose of the Study:

• To report the first observation of the rare charm decay D0→K-π+e+e-.
• To measure the branching fraction of this decay within a specific invariant mass range for the dilepton pair.
• To compare the measured branching fraction with theoretical predictions from the Standard Model and with related muon decay modes.

Main Methods:

• Analysis of 468 fb^-1 of e+e- annihilation data collected by the BABAR detector at the ϒ(4S) resonance.
• Selection criteria applied to identify the D0→K-π+e+e- decay signature.
• Use of the D0→K-π+π+π- decay as a normalization channel to determine the branching fraction.

Main Results:

• Observation of the D0→K-π+e+e- decay with a significance of 9.7 standard deviations.
• Measured branching fraction B(D0→K-π+e+e-) = (4.0±0.5±0.2±0.1)×10^-6 for 0.675
• A 90% confidence level upper limit of B(D0→K-π+e+e-)<3.1×10^-6 was determined in regions where long-distance effects are potentially small.

Conclusions:

• The observed branching fraction is consistent with the Standard Model expectations.
• The result aligns with the previously measured branching fraction for the corresponding muon decay channel.
• This observation contributes to the understanding of rare charm decays and provides constraints on theoretical models.