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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

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
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

search for b s d
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

search methodology
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

selection procedure

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

apply selection
Apply Selection
  • Observation in agreement with background expectation
  • Set limits

HEP 2007, Manchester

results
Results

World’s best limit

HEP 2007, Manchester

search for b h
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

search methodology1
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

selection strategy
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

observations
Observations

HEP 2007, Manchester

results1
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

summary outlook
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

backup
Backup

HEP 2007, Manchester

b s d backgrounds
Bs/d →  Backgrounds
  • Estimate backgrounds from:
  • sidebands (combinatoric)
  • branching fractions B→h+ h- and fake rates

HEP 2007, Manchester