1. Lake Louise Winter Institute 20081 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]

2. Lake Louise Winter Institute 20082 LHCb experiment and conditions Luminosity range 2-5 10 32 cm -2 s -1 Nominal integrated luminosity 2 fb -1 / year (10 7 s) 10 12 bb produced/year  B, Bs, B + But large backgrounds and small BR 0(10 -6 )of relevant decays 10 MHz visible interaction (1% bb) Total10 fb -1 P. Vazquez

3. Lake Louise Winter Institute 20083 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)

4. Lake Louise Winter Institute 20084 Bs  Φ γ 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(m s /m b ) left handed CP violation in the mixing and decay depends on the γ polarization Measured in B  K*(K s π 0 )γ A CP at Belle[3], BaBar (S K*γ = -0.08 ±0.31±0.05) [4] LHCb can measure time-dependent CP asymmetry of Bs  Φ γ [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%, A Δ ~ sin2ψ Ψ fraction of “wrong” polarization A CP (t) (Bs  Φ γ)

5. Lake Louise Winter Institute 20085 A CP (t) for B s  Φ γ 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 MC stats: 37 M bb events 2 fb -1 σ(A Δ )0.20 σ(S,C)0.11 2 fb -1 B  K*γ 72 k Bs  Φ γ 11 k

6. Lake Louise Winter Institute 20086 A FB (B  K * μμ) Motivation: BR in agreement with SM β(B  K*μμ) 1.22 +0.38 -0.32 10 -6 But NP can show us in angular distributions A FB asymmetry vs m 2 μμ Decay described with 3 angles (θ l,Φ,θ K* ) A FB of μ in θ l vs m 2 μμ SM zero point well predicted: SM: [1] 4.36 +0.33 -031 GeV 2 BaBar and Belle [2] Measurements [1] hep-ph/0412400 [2] hep-ph/0603018 A FB M  2 (GeV 2 ) BELLE ’06 m 2  [GeV 2 ] A FB (m 2 μμ ) theory illustration

7. Lake Louise Winter Institute 20087 A FB (B  K * μμ) 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(θ l,m 2 μμ, ) Sensitivity 0.07 fb -1 competitive with BaBar & Belle An example 0.5fb -1 experiment An example 0.1fb -1 experiment M  2 (GeV 2 ) A FB 2 fb -1 B  K*μμ 7.3 k 0.5 fb -1 2 fb -1 10 fb -1 σ(s0)0.8 GeV 2 0.5 GeV 2 0.3 GeV 2

8. Lake Louise Winter Institute 20088 β(Bs  μμ) Motivation Bs  μμ very rare Helicity suppress (m μ /m B ) 2 SM well predicted SM: β(Bs  μμ) = (3.55±0.33) x 10 -9 Very sensitive to (pseudo) scalar operators MSSM ~ tan 6 β/M 4 A 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]

9. Lake Louise Winter Institute 20089 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 GL (geometry) Mass (MeV) Bs  μμ Bs  KK arbitrary units

10. Lake Louise Winter Institute 200810 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 agreement 2 fb –1  3  evidence 6 fb –1  5  observation Exclusion: 0.1 fb –1  BR < 10 -8 0.5 fb –1  < SM β(Bs  μμ) [1]

11. Lake Louise Winter Institute 200811 Conclusions LHCb finishing installation, getting ready for 1 st 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 A FB (B  K*μμ) σ(s 0 ) ~0.8 GeV 2 @ 0.5 fb -1 And above 2 fb-1 Bs  μμ evidence if SM 2 fb -1, observation 6 fb -1 B  K * μμ σ(s 0 ) ~0.5 (0.3) GeV 2 @ 2 (10) fb -1 other observables: A (2) T, F L Bs  Φ γ A CP asymmetry >2 fb -1

12. Lake Louise Winter Institute 200812 Particle ID π-K separation: Kaon ID ~ 88% Pion mis-ID ~ 3% μ ID B q  hh (~0.5%) 2 (mu-ID eff 95%) LHCb expected performance Mass resolution Vertexing σ(Mass) Bs  μμ ~20 MeV B  K*μμ ~14 MeV Bs  Φ γ ~90 MeV σ(proper time) Bs  Φ γ ~50-110 fs Trigger: 1MHz @ L0  2 kHz @ HLT B signature : “large” Pt and displaced tracks HLT: ~ 1.5 kHz μ + di-μ inclusive sample efficiency (L0xHLT) Bs  μμ ~90 % B  K* μμ ~70 % B  Φγ ~40 % P. Vazquez

13. Lake Louise Winter Institute 200813 A (2) T,F T (B  K*μμ) Other observables [1] in B  K*μμ Expresed in terms of transversity amplitudes Fit individual angular distributions (θ l,Φ,θ K* ) vs m 2 μμ 2 fb -1 Asymmetry A T (2) Longitudinal polarization F L SM NLO MSSM tan  =5 2 fb –1 10 fb –1 A T (2)  0.42  0.16 FLFL  0.016  0.007 A FB  0.020  0.008 Sensitivity with [1] hep-ph/0612166 An example 2 fb -1 experiment