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B + K + νν

B + K + νν. David Doll, Ilya Narsky, David Hitlin. Theory. These FCNC (Flavor Changing Neutral Current) decays proceed via Z-penguin or W-box diagrams within the Standard Model, and are consequently quite suppressed. SM predicts a Branching Fraction of 3.8 x 10 -6 .

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B + K + νν

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  1. B+ K+νν David Doll, Ilya Narsky, David Hitlin

  2. Theory • These FCNC (Flavor Changing Neutral Current) decays proceed via Z-penguin or W-box diagrams within the Standard Model, and are consequently quite suppressed. • SM predicts a Branching Fraction of 3.8 x 10-6. • Several other theories (multi-Higgs doublet model, minimal super-symmetry (SUSY), etc.) imply an increase in b svv, which invites an investigation of this channel.

  3. Previous Analyses For This Mode Previous BaBar results Semileptonic tag: B(K+νν)<7.0*10-5 Hadronic tag :B(K+νν)<6.7*10-5 Combined: B(K+νν)<5.2*10-5 Most Recent Belle results, presented at FPCP 2007:

  4. Tag Selection • We are using Runs 1 through 5 data (319 fb-1) • We are using the semileptonic tagged events, with the D0 decaying via K-π+, K-π+π-π+, K-π+π0 B+ B+ l+ ν ν K+ ν D0

  5. Signal Selection • We use a Random Forest (Bagged Decision tree) multivariate classifier to separate signal from background. • We use a ‘double tag’ sample (both B mesons decay semileptonically) to evaluate the systematic uncertainty on the signal region. Different background processes signal

  6. Results (Journal Draft under review) • We predict 30.7 ± 10.7 events in the signal box with a signal efficiency of . • Within the signal box we see 38 events, allowing us to set an upper limit of at 90% confidence level. Signal Region

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