outlook: introduction lhcb performance radiative decays: cp violation bs Φ γ
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Outlook: Introduction LHCb performance Radiative decays: CP violation Bs Φ γ Backward-forward Asymmetry B K * μμ Branching ratio of very rare Bs μμ Conclusions. Prospects for rare B decays in LHCb Jose A. Hernando - PowerPoint PPT PresentationTRANSCRIPT
Lake Louise Winter Institute 2008 1
Outlook: Introduction LHCb performance Radiative decays: CP violation BsΦγ Backward-forward Asymmetry BK*μμ Branching ratio of very rare Bsμμ Conclusions
Prospects for rare B decays in LHCbJose A. Hernando
(CERN, on leave Universidade de Santiago de Compostela, Spain)
[On behalf of the LHCb collaboration]
Lake Louise Winter Institute 2008 2
LHCb experiment and conditionsLHCb experiment and conditions
Luminosity range 2-5 1032 cm-2s-1
Nominal integrated luminosity 2 fb-1 / year (107s)
1012 bb produced/year B, Bs, B+
But large backgrounds and small BR 0(10-6)of relevant decays
10 MHz visible interaction (1% bb)
Total 10 fb-1
•P. Vazquez
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Rare B decaysRare B decays
LHCb Physics CP violation in B system: using tree and penguins processes (NP) Rare B decays: test FCNC (bs)
•V. Gligorov
Rare B decays FCNC has a pivotal roll:
• They are suppressed in SM, only realized via boxes or penguins
• NP can show up as the same level of SM
• Present results (i.e. bsγ) strongly limit extensions of SM
• Indirect search of new particles: “visible” via loops
Experimental observables: ratios, asymmetries, branching ratios to leptons
•bsγ Radiative decays:
•BK*γ, BsΦγ
•ΛbΛγ, ΛbΛ*γ
•Bρ0γ, Bωγ
bsll :
•BK*μμ,
•B+K+μμ, B+K+ee
Bqll
Bsμμ
LFV Bqll’
BsμeACP(t) (BsΦγ) AFB(BK*μμ)
β(Bsμμ)
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BsBsΦΦγγ
Motivation:
Inclusive BR in agreement with SM
LHCb can perform exclusive measurements
And test the γ polarization
In SM is bsγ is predominantly (at 0(ms/mb) left handed
CP violation in the mixing and decay depends on the γ polarization
Measured in BK*(Ksπ0)γ ACP at Belle[3], BaBar (SK*γ = -0.08 ±0.31±0.05) [4]
LHCb can measure time-dependent CP asymmetry of BsΦγ
,)2/cosh()2/sinh(
)sin()cos()(
tt
tmStmCtA
ss
ssCP
[1]NNLO
•[2]HFAG
•[1] hep-ph/0607258
•[2] arXiv/0704.3575 hep/ex
•[3] hep-ph/0507057, Phys.Rev D72,051103
•[4] arXiv/0708.1614 hep/exp
•[5] hep-ph/0410036
[5] SM: C~0, S~-0.1±0.1%, AΔ ~ sin2ψ
Ψ fraction of “wrong” polarization
ACP(t) (BsΦγ)
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AACPCP(t)(t) for B for BssΦΦγγ
Full detector simulationmain background bb (37 M)
Selection Et(γ) > 2.8 GeV,
Yields (2 fb-1):Total efficiency ~ 0.3%
Background bb inclusive: B/S ~ 0.55 @ 90 CL
Issues: Acceptance function a(t) σ(t) as function of topology
•MC stats: 37 M bb events
2 fb-1
σ(AΔ) 0.20
σ(S,C) 0.11
2 fb-1
BK*γ 72 k
BsΦγ 11 k
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AAFBFB(B(BKK**μμμμ))
Motivation:
BR in agreement with SM
β(BK*μμ) 1.22+0.38-0.3210-6
But NP can show us in angular distributions
AFB asymmetry vs m2μμ
Decay described with 3 angles (θl,Φ,θK*)
AFB of μ in θl vs m2μμ
SM zero point well predicted:SM: [1] 4.36+0.33
-031 GeV2
BaBar and Belle [2] Measurements
•[1] hep-ph/0412400
•[2] hep-ph/0603018
AF
B
M2 (GeV2)
BELLE ’06
m2
[GeV2]
AFB(m2μμ) theory illustration
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AAFBFB(B(BKK**μμμμ))
Yields Efficiency ~ 1%
Background B/S 0.5+0.2 @ 90% CL
bb: bμ,bμ
bb: bμ,c (cμ)
Issues Acceptance function a(θl,m2
μμ,)
Sensitivity 0.07 fb-1 competitive with BaBar & Belle
An example 0.5fb-1 experiment
An example 0.1fb-1 experiment
M2 (GeV2)
AF
B2 fb-1
BK*μμ 7.3 k
0.5 fb-1 2 fb-1 10 fb-1
σ(s0) 0.8 GeV2 0.5 GeV2 0.3 GeV2
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ββ((BsBsμμμμ))
Motivation
Bsμμ very rare
Helicity suppress (mμ/mB)2
SM well predicted
SM: β(Bsμμ) = (3.55±0.33) x 10-9
Very sensitive to (pseudo) scalar operators
MSSM ~ tan6β/M4A
MSSM (NUHM) fit favor large tanβ ~ 30
μ g-2 results (deviate from SM 3.4 σ)
Current limits
[2] CDF BR < 4.7 10-8 90% CL @ 2fb-1
[3] D0 BR < 7.5 10-8 90% CL
•[1] arXiv:0709.0098v1 [hep-ph] •[2] arXiv:0712.1708v1 [hep-ex]
•[3] arXiv:0705.300v1 [hep-ex]
•[1]
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ββ((BsBsμμμμ))
Small signal and large background, but Efficient trigger: ~1.5 kHz inclusive μ. Di-μ Mass resolution: σ ~20 MeV Vertexing: GL: Combine geometrical variables
Background: Main background (bμ,bμ, bμ , bcμ ) Bhh, small compared with bμ,bμ Bc+J/Ψμν dominant of exclusive, but still small
Analysis: Divide (GL, Mass) space in N bins Expected events/bin for signal, signal+bkg
Yield : Total efficiency ~10% (all GL values) S ~30 events, Bkg ~ 83 @ 2fb-1 (GL>0.5)
Control channels: Signal description: Bhh ~200 k @ 2fb-1
background (from sidebands)Normalization: B+J/Ψ K+ 2 M @ 2fb-1
Red: signalBlue: bb inc.Black: b μb μGreen: Bc+ J/Ψμν
•GL (geometry)
•Mass (MeV)
Bs μμ
Bs KK
• arb
itra
ry u
nit
s
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10-7
2x10-8
(~0.05 fb-1)
5x10-9
(~ 0.4 fb-1)
Integrated luminosity (fb–1)
BR
(x1
0–9)
Uncertainty in background prediction
Expected final CDF+D0 limit
SM prediction
90% CL imit on BR (only bkg is observed)
[1] arXiv:0709.0098v1
SM agreement2 fb–1 3 evidence6 fb–1 5 observation
Exclusion:0.1 fb–1 BR < 10-8 0.5 fb–1 < SM
ββ((BsBsμμμμ))
•[1]
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ConclusionsConclusions
LHCb finishing installation, getting ready for 1st collisions
Rare B decays in LHCb will constrain extensions of SM or find NP
Already with first “year” data 0.1, 0.5 fb-1
Bsμμ excluded at SM value with 0.5 fb-1
AFB(B K*μμ) σ(s0) ~0.8 GeV2 @ 0.5 fb-1
And above 2 fb-1 Bsμμ evidence if SM 2 fb-1, observation 6 fb-1
BK*μμ σ(s0) ~0.5 (0.3) GeV2 @ 2 (10) fb-1
other observables: A(2)T, FL
BsΦγ ACP asymmetry >2 fb-1
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Particle ID
π-K separation:Kaon ID ~ 88%Pion mis-ID ~ 3%
μ ID
Bqhh (~0.5%)2
(mu-ID eff 95%)
LHCb expected performanceLHCb expected performance
Mass resolution
Vertexing
σ(Mass)
Bsμμ ~20 MeV
BK*μμ ~14 MeV
BsΦγ ~90 MeV
σ(proper time)
BsΦγ ~50-110 fs
Trigger: 1MHz @ L0 2 kHz @ HLTB signature : “large” Pt and displaced tracks
HLT: ~ 1.5 kHz μ + di-μ inclusive sample
efficiency (L0xHLT)
Bsμμ ~90 %
BK*μμ ~70 %
B Φγ ~40 %•P. Vazquez
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AA(2)(2)T T ,F,FTT (B (BK*K*μμμμ))
Other observables [1] in BK*μμExpresed in terms of transversity amplitudes
Fit individual angular distributions (θl,Φ,θK*) vs m2μμ
2
0
2
||
2
2
02 )(AAA
AqFL
2
||
2
2
||
2
2)2( )(AA
AAqAT
2 fb-1
Asymmetry AT(2) Longitudinal polarization FL
SM NLOMSSM tan=5MSSM tan=5
2 fb–1 10 fb–1
AT(2) 0.42 0.16
FL 0.016 0.007
AFB 0.020 0.008
Sensitivity with
•[1] hep-ph/0612166
An example 2 fb-1 experiment