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Outlook: Introduction LHCb performance Radiative decays: CP violation Bs  Φ γ

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

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Outlook: Introduction LHCb performance Radiative decays: CP violation Bs  Φ γ

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  1. Outlook: • Introduction • LHCb performance • Radiative decays: CP violation BsΦγ • Backward-forward Asymmetry BK*μμ • Branching ratio of very rare Bsμμ • 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] Lake Louise Winter Institute 2008

  2. LHCb 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) P. Vazquez Lake Louise Winter Institute 2008

  3. Rare B decays V. Gligorov • LHCb Physics • CP violation in B system: using tree and penguins processes (NP) • Rare B decays: test FCNC (bs) • 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sγRadiative decays: BK*γ, BsΦγ ΛbΛγ, ΛbΛ*γ Bρ0γ, Bωγ bsll: • BK*μμ, • B+K+μμ, B+K+ee Bqll Bsμμ β(Bsμμ) LFV Bqll’ Bsμe ACP(t) (BsΦγ) AFB(BK*μμ) Lake Louise Winter Institute 2008

  4. [1]NNLO [2]HFAG BsΦγ Motivation: Inclusive BR in agreement with SM LHCb can perform exclusive measurements And test the γ polarization In SM is bsγ is predominantly (at 0(ms/mb) left handed CP violation in the mixing and decay depends on the γ polarization Measured in BK*(Ksπ0)γACP at Belle[3], BaBar (SK*γ = -0.08 ±0.31±0.05) [4] LHCb can measure time-dependent CP asymmetry of BsΦγ ACP(t) (BsΦγ) [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 Lake Louise Winter Institute 2008

  5. ACP(t) for BsΦγ MC stats: 37 M bb events Full detector simulation main 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 Lake Louise Winter Institute 2008

  6. AFB AFB(m2μμ) theory illustration BELLE ’06 Mmm2 (GeV2) m2[GeV2] AFB(BK*μμ) Motivation: BR in agreement with SM β(BK*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 μin 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 Lake Louise Winter Institute 2008

  7. AFB(BK*μμ) An example 0.1fb-1 experiment Yields Efficiency ~ 1% Background B/S  0.5+0.2 @ 90% CL bb: bμ,bμ bb: bμ,c (cμ) Issues Acceptance function a(θl,m2μμ,) Sensitivity 0.07 fb-1 competitive with BaBar & Belle AFB An example 0.5fb-1 experiment Mmm2 (GeV2) Lake Louise Winter Institute 2008

  8. β(Bsμμ) Motivation Bsμμ very rare Helicity suppress (mμ/mB)2 SM well predicted SM: β(Bsμμ) = (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] [1] arXiv:0709.0098v1 [hep-ph] [2] arXiv:0712.1708v1 [hep-ex] [3] arXiv:0705.300v1 [hep-ex] Lake Louise Winter Institute 2008

  9. Bs  μμ Bs KK Mass (MeV) β(Bsμμ) 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 (bμ,bμ, bμ , bcμ) Bhh, small compared with bμ,bμ 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: Bhh ~200 k @ 2fb-1 background (from sidebands) Normalization: B+J/Ψ K+ 2 M @ 2fb-1 Red: signal Blue: bb inc. Black: b μb μ Green: Bc+  J/Ψμν arbitrary units GL (geometry) Lake Louise Winter Institute 2008

  10. 90% CL imit on BR (only bkg is observed) Expected final CDF+D0 limit BR (x10–9) 10-7 Uncertainty in background prediction 2x10-8 (~0.05 fb-1) SM prediction 5x10-9 (~ 0.4 fb-1) Integrated luminosity (fb–1) β(Bsμμ) [1] SM agreement 2 fb–1 3 evidence 6 fb–1 5 observation Exclusion: 0.1 fb–1 BR < 10-8 0.5 fb–1 < SM [1] arXiv:0709.0098v1 Lake Louise Winter Institute 2008

  11. Conclusions 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 Bsμμ 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 Bsμμ evidence if SM 2 fb-1, observation 6 fb-1 BK*μμσ(s0) ~0.5 (0.3) GeV2 @ 2 (10) fb-1 other observables: A(2)T, FL BsΦγACP asymmetry >2 fb-1 Lake Louise Winter Institute 2008

  12. π-K separation: Kaon ID ~ 88% Pion mis-ID ~ 3% LHCb expected performance Trigger: 1MHz @ L0  2 kHz @ HLT B signature : “large” Pt and displaced tracks HLT: ~ 1.5 kHz μ + di-μ inclusive sample Mass resolution σ(Mass) Bsμμ ~20 MeV BK*μμ ~14 MeV BsΦγ ~90 MeV efficiency (L0xHLT) Bsμμ ~90 % BK*μμ ~70 % B Φγ ~40 % P. Vazquez Particle ID Vertexing σ(proper time) BsΦγ ~50-110 fs μ ID Bqhh (~0.5%)2 (mu-ID eff 95%) Lake Louise Winter Institute 2008

  13. Asymmetry AT(2) Longitudinal polarization FL 2 fb-1 SM NLO MSSM tan=5 MSSM tan=5 A(2)T ,FT (BK*μμ) Other observables [1] in BK*μμ Expresed in terms of transversity amplitudes Fit individual angular distributions (θl,Φ,θK*) vs m2μμ Sensitivity with An example 2 fb-1 experiment [1] hep-ph/0612166 Lake Louise Winter Institute 2008

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