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 LHCb Jose A. Hernando (CERN, on leave Universidade de Santiago de Compostela, Spain) [On behalf of the LHCb collaboration]
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Lake Louise Winter Institute 20081 Outlook: Introduction LHCb performance Radiative decays: CP violation Bs Φγ Backward-forward Asymmetry B
Lake Louise Winter Institute Rare B decays LHCb Physics CP violation in B system: using tree and penguins processes (NP) Rare B decays: test FCNC (b s) 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. b sγ) strongly limit extensions of SM Indirect search of new particles: “visible” via loops Experimental observables: ratios, asymmetries, branching ratios to leptons b sγ Radiative decays: B K*γ, Bs Φγ Λ b Λγ, Λ b Λ * γ B ρ 0 γ, B ωγ b sll : B K*μμ, B + K + μμ, B + K + ee B q ll Bs μμ LFV B q ll’ Bs μe A CP (t) (Bs Φ γ) A FB (B K * μμ) β(Bs μμ)
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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
Lake Louise Winter Institute 2008 3
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)
Lake Louise Winter Institute 2008 4
BsBsΦΦγγ
Motivation:Inclusive BR in agreement with SM LHCb can perform exclusive measurementsAnd 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 polarizationMeasured 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
tmStmCtAss
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)
Lake Louise Winter Institute 2008 5
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
Lake Louise Winter Institute 2008 6
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 distributionsAFB asymmetry vs m2
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
itrar
y un
its
Lake Louise Winter Institute 2008 10
10-7
2x10-8
(~0.05 fb-1)
5x10-9
(~ 0.4 fb-1)
Integrated luminosity (fb–1)
BR
(x10
–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]
Lake Louise Winter Institute 2008 11
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