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Search for Rare b-Hadron Decays at CDF II

Search for Rare b-Hadron Decays at CDF II. Michael Milnik (University of Karlsruhe) for the CDF Collaboration. HEP 2007, Manchester. Covered in This Talk. B s/d →  B →  h B u →  K B d →  K * B s →  .

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Search for Rare b-Hadron Decays at CDF II

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  1. Search for Rare b-Hadron Decays at CDF II Michael Milnik (University of Karlsruhe) for the CDF Collaboration HEP 2007, Manchester

  2. Covered in This Talk • Bs/d→  • B →  h • Bu →  K • Bd →  K* • Bs →  Results from CDF on B0,Bs→h+h-’ covered by M. Morello later in this session HEP 2007, Manchester

  3. Search for Bs/d →  • Motivation: • In the SM, B→ heavily suppressed (need FCNC) expectation: • Bd→ further Cabbibo-suppressed • Expect to see nothing, if something seen  new physics A.J. Buras, Phys. Lett. B566, 115 (2003) HEP 2007, Manchester

  4. Search Methodology • Unbiased (blinded) selection optimisation using • signal event sample: MC simulation • background sample: data sidebands • Normalize to well-known B → J/ K decay  cancellation of many systematic effects • Apply cuts on search mode and normalization mode • Estimate Backgrounds • Unblind HEP 2007, Manchester

  5. Pmm Bs mm DR < 1 (a <57o) Da   Pm Pm y  L3D x z Selection Procedure • Form likelihood ratio from following discriminating variables: • displacement of reconstructed B vertex (long B lifetime) • isolation (expect B to be isolated) • “pointing angle” between reconstructed B momentum and direction to primary vertex (should be small) • Optimize on best limit with 90% C.L. HEP 2007, Manchester

  6. Apply Selection • Observation in agreement with background expectation • Set limits HEP 2007, Manchester

  7. Results World’s best limit HEP 2007, Manchester

  8. Search for B→h • Non-resonant decays B → h via box or penguin diagrams  new physics may be observable through interference with SM amplitudes • Already observed (BaBar, Belle): • Bu →  K • Bd →  K* • Missing: • Bs →  • prediction: BR(Bs)=1.6x10-6 PRD 73, 092001 (2006) PRL 96, 251801 (2006) C.Q. Geng and C.C. Liu, J. Phys. G 29, 1103 (2003) HEP 2007, Manchester

  9. Search Methodology • Similar method than for Bs→ • Unbiased (blinded) selection optimisation using • signal event sample: MC simulation • background sample: data sidebands • Normalize to analogous resonant B → J/ h decay • Apply cuts on search mode and normalization mode • Remove resonant  by cutting out J/ / (2S) mass ranges • Unblind HEP 2007, Manchester

  10. Selection Strategy Optimize selection based on cuts on similar quantities as used for Bs→ (decay length, isolation, pointing angle) Optimize on best value for HEP 2007, Manchester

  11. Observations HEP 2007, Manchester

  12. Results BR(B+→ K+) = [0.72 ± 0.15(stat.) ± 0.05(syst.)]x10-6 BR(B0→K*) = [0.82 ± 0.31(stat.) ± 0.10(syst.)]x10-6 HEP 2007, Manchester

  13. Summary & Outlook • CDF set limits for Bs/d→ • currently probe the 10-8 level • limits severely constrain new physics models • growing dataset will allow deeper probing in the future • CDF investigating B → h modes • results in agreement with those of b-factories • most stringent limit on Bs→ • More data – better results: watch out! HEP 2007, Manchester

  14. Backup HEP 2007, Manchester

  15. Bs/d →  Backgrounds • Estimate backgrounds from: • sidebands (combinatoric) • branching fractions B→h+ h- and fake rates HEP 2007, Manchester

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