Search for New Physics through Rare B Decays

S. Uozumi for the CDF-II collaboration21th Feb 2012 Lake Louis Winter Institute

NP? NP?

CDMS II

Rouzbeh Allahverdi, Bhaskar Dutta, Yudi SantosoarXiv:0912.4329

Excluded by1)Rare B decay b → sγ2)No CDM candidate3)Muon magnetic moment

abc

Bs → µ+µ− Search

910)2.02.3(: −×±Br

SM Expectation

Br enhancementBy New Physics

JHEP 1009 (2010)106

Gaugino mass (GeV)

Sle

pton

/sqq

ark

mas

s (G

eV)

Bs/d µ+µ− Method: Relative normalization counting– Same method with previous 6.9 fb-1 results last summer (PRL 107, 191801)– This analysis updates results with whole 9.7 fb-1 of CDF Run-II data• Measure the rate of Bs/d → μ+μ- decays relative to B+ →J/ψK+ control sample1. Apply same event pre-selection to both sample2. Bs → μ+μ- sample is highly purified by Neural Network (NN) event selection3. NN takes 14 kinematic variables and output value ranging 0 (BG like)~1 (signal like)4.Bs → μ+μ- candidates are categorized into 8 different NN value bins for counting5. BG shape is determined from di-muon mass sideband fitting

Bs/BdSignalregion

Pre-selectedBs → μ+μ-

Pre-selected B+ →J/ψK+ Neural Network

Pre-selection

NN out=0.700-0.760

NN out=0.987-0.995

NN out=0.995-1.000

Original Bs → μ+μ- and B+ →J/ψK+ samples.....

Final Bs → μ+μ- sample

Typial BG fittingFor one NN outputbin

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Bs µ+µ− old result with 7 fb-1 (Aug 2011)CDF II 7 fb-1

1.1 80.9( ) 1.8 10sBr B µ µ+ − + −

−→ = ×

• Observed a >2σ excess over background only, fit for the signal branching ratioand obtain Br(Bs µ+µ−) < 4.0 (3.5) × 10−8 at 95% (90%) C.L.

•From a small excess, we have set double-sided limit

Central-Centralmuons

Central-Forwardmuons

which is ~2σ away from SM expectation.

•Now we update the result on the whole Run II data sample WITHOUT CHANGING anything in the 7 fb-1 analysis (PRL 107, 191801 ).

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Observed events are fairly consistent with background.Set Br. upper limitBr(Bd µ+µ−) < 4.6 (3.8) × 10−9 at 95% (90%) C.L.

Mµµ for Bd µ+µ- with CDF-II full dataset

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Central-Centralmuons

Central-Forwardmuons

• Excess not reinforced by new data but still there. • Best fit estimates a 2σ excess of signal over background yielding

CDF II Preliminary 9.7 fb-1

Mµµ for Bs µ+µ- with CDF-II full dataset

SM prediction

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Bs µ+µ- Double-sided Br. Limit with 9.7fb-1

p-values assuming Bs background only : 0.94%Bs SM+background : 7.1% … still ~2σ away from SM

9 (3.2 0.2) 10Br −± ×with SM prediction

Single-sided upper limit : Br(Bs µ+µ−) < 2.7 × 10−8 at 95% C.L.•From previous 7.0 fb-1 result, central value of Br. fraction shifted to lower value, however still stays around ~2σ region from the SM.

• Public note and paper preparation underway.

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Bs µ+µ- LHCb, CMS and CDF

Expected CDF single-sided limit (95%) 1.3 ×10−8

CDF double-sided limit

Observed CDF single-sided limit (95%) 2.7 ×10−8

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b→ sµ+µ− for New Physics

NP?

• Strongly suppressed in SM due to 2nd order weak interaction• New physics in a loop can change Br. Fraction and kinematics of those event

• Many channels with different spectator quark flavors available to explore b sµ+µ− decays

•Tools to go beyond SM :• Br. fraction of several B baryons into b sµ+µ− process• Direction, angle of outgoing particles … may differ depending on intermediate new physics model

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Br(Λb0→Λμ+μ-)

=[1.73±0.42(stat)±0.55(syst)]×10-6

Br(Bs0→φμ+μ-) =[1.47±0.24±0.46]×10-6

Br(B+→K+μ+μ-) =[0.46±0.04±0.02]×10-6

Br(B0→K*0μ+μ-) =[1.02±0.10±0.06]×10-6

Br(B0→K0μ+μ-) =[0.32±0.10±0.02]×10-6

Br(B+→K*+μ+μ-) =[0.95±0.32±0.08]×10-6

World’s first observation !!Other B0/+ K µ+µ− channels have comparably large statisticswith B factories & LHC.

Reconstructed b→ sµ+µ− events and Br. fractionsCDF II 6.7 fb-1, Phys. Rev. Lett 107, 201802 (2011)

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Event-shape (AFB) analysis for b sµ+µ− decay

•Current CDF result based on 6.8fb-1 (arXiv:1108.0695)

•Both CDF and LHCb results are approaching to SM prediction.

• CDF is finishing analysis usingfull 9.7fb-1 of data.Stay tuned!

• There are various event-shape parameters to access physics beyond the SM (arXiv:1108.0695.)

• Most interesting parameter is FB asymmetry as a function of q2=Mµµ2

compared with muon polar angle in B rest frame :

From LHC talk onAug ’11by P. Koppenburg

6.8 fb-1CDF

• B rare decays are excellent stage to search for New Physics effect.•Using full 9.7 fb-1 of CDF Run-II data sample, we measured :

Summary & Conclusions

• Various b sµ+µ− decay channels are observed with 6.8 fb-1 of data :

Br(Λb0→Λμ+μ-) =[1.73±0.42(stat)±0.55(syst)]×10-6

Br(Bs0→φμ+μ-) =[1.47±0.24±0.46]×10-6

Br(B+→K+μ+μ-) =[0.46±0.04±0.02]×10-6

Br(B0→K*0μ+μ-) =[1.02±0.10±0.06]×10-6

Br(B0→K0μ+μ-) =[0.32±0.10±0.02]×10-6

Br(B+→K*+μ+μ-) =[0.95±0.32±0.08]×10-6

… world’s first!!

•AFB result with full CDF Run-II data analysis will come out soon!

• Latest CDF result stays ~2σ from SM