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B s → mm at D Ø

B s → mm at D Ø. New result first presented by Fermilab Postdoc Masato Aoki at FPCP2010. Primary author of manuscript now submitted to Physics Letters arXiv:1006.3469v1 [hep-ex]. News from Batavia. Tevatron, detectors, collaborations all going strong Now have 9 fb -1 delivered.

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B s → mm at D Ø

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  1. Bs→mm at DØ New result first presented by Fermilab Postdoc Masato Aoki at FPCP2010 Primary author of manuscript now submitted to Physics Letters arXiv:1006.3469v1 [hep-ex]

  2. News from Batavia • Tevatron, detectors, collaborations all going strong • Now have 9 fb-1 delivered. • Expecting ~12 fb-1 per experiment • Lots of exciting results still coming out Party celebrating 9 fb-1 July 16, 2010 “The Toes of Joe Lykken” B. Casey, ICHEP2010

  3. Leptonic B decays • Standard Model rate well understood • Standard Model rate is small • New physics enhancements can be large SM BF: B(Bs→mm) = (3.6±0.3) x 10-9 Buras, arXiv:0904.4917 B. Casey, ICHEP2010

  4. Signal and Background m m c m b Bs m p p m m c b b b p p p p c K b Bs p K m m sequential Signal double B→KK B. Casey, ICHEP2010

  5. Background reduction pT (mm) MinimumpT (m) Minimum DCA Angle between momentum and direction Vertexc2 sidebands sidebands Signal MC + J/y K data and MC Signal MC + J/y K data and MC Signal MC + J/y K data and MC Signal MC + J/y K data and MC Flight length significance Signal MC + J/y K data and MC Signal MC + J/y K data and MC sidebands sidebands sidebands sidebands m m SV PV B. Casey, ICHEP2010

  6. Background reduction m pT (mm) Minimum pT (m) m Minimum DCA SV Angle between momentum and direction Vertex c2 Dave Butler PV Flight length significance B. Casey, ICHEP2010

  7. Background reduction Bayesian Neural Network B+→J/y K+ Calibration sample Expect ~3 signal events in our data with these cuts Signal region B. Casey, ICHEP2010

  8. B→h+h- 10-20lbefore outer muon layers B-→D0mn, D0→K-p+ Matching variables m K After penetration + matching cuts B. Casey, ICHEP2010

  9. Signal extraction 2D fit to m(mm) and BNN BNN sequential m(mm) double m(mm) Background shape from BNN sideband, norm from m(mm)sidebands B. Casey, ICHEP2010

  10. Comparisons Old Old: 1D just counting events in signal region New: 2D including shape in signal region ~40% improvement in expected limit New/Old m(mm) New m(mm) BNN B. Casey, ICHEP2010

  11. Results In highest sensitivity region: 51 ± 4expected bkg events, 55 data events BF < 51 x 10-9 (95% CL) 14x SM Expected limit: 38 x 10-9 11x SM arXiv:1006.3469v1 [hep-ex] CDF preliminary 2009: 43 x 10-9 observed 33 x 10-9 expected B. Casey, ICHEP2010

  12. Conclusions Present • Have a new limit based on 6.1 fb-1 • 4.6 times more data than last pub • 2.4 times sensitivity of last pub • Includes many improvements • 33% reduction in KK background at same efficiency • 40% improvement from 2D fitting • Next steps • More data • Design variables to target dominant background of gluon fusion bb production where both B mesons decay semileptonically. Future B. Casey, ICHEP2010

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