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LHCb Physics Programme

CERN Theory Institute: Flavour as a window to New Physics at the LHC: May 5 –June 13, 2008. LHCb Physics Programme. Marcel Merk For the LHCb Collaboration May 26, 2008. Contents: The LHCb Experiment Physics Programme: CP Violation Rare Decays. LHCb @ LHC. b. b. b. b.

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LHCb Physics Programme

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  1. CERN Theory Institute: Flavour as a window to New Physics at the LHC: May 5 –June 13, 2008 LHCb Physics Programme Marcel Merk For the LHCbCollaboration May 26, 2008 • Contents: • The LHCb Experiment • Physics Programme: • CP Violation • Rare Decays

  2. LHCb @ LHC b b b b • √s = 14 TeV • LHCb: L=2-5 x 1032 cm-2 s-1 • sbb = 500 mb • inel / sbb = 160 • => 1 “year” = 2 fb-1 CERN LHCb ATLAS CMS ALICE A Large Hadron Collider Beauty Experiment for Precision Measurements of CP-Violation and Rare Decays

  3. The LHCb Detector Muon det Muon det Calo’s Calo’s Magnet RICH-2 RICH-2 Magnet RICH-1 OT+IT OT RICH-1 VELO VELO Installation of major structures is complete

  4. A walk through the LHCb spectrometer…

  5. B-VertexMeasurement 144 mm 47 mm K K Bs K Ds  d 440 mm Example: Bs → Ds K s(t) ~40 fs Primary vertex  Decay time resolution = 40 fs Vertex Locator (Velo) Silicon strip detector with ~ 5 mm hit resolution  30 mm IP resolution • Vertexing: • Impact parameter trigger • Decay distance (time) measurement

  6. Momentum and Mass measurement Momentum meas.: Mass resolution for background suppression 

  7. Momentum and Mass measurement p+, K Bs K K Ds  Primary vertex bt Momentum meas.: Mass resolution for background suppression Mass resolution s ~14 MeV Bs→ Ds K Bs →Ds p 

  8. Particle Identification RICH: K/p identification using Cherenkov light emission angle  • RICH1: 5 cm aerogel n=1.03 • 4 m3 C4F10 n=1.0014 RICH2: 100 m3 CF4 n=1.0005

  9. Particle Identification RICH: K/p identification; eg. distinguish Dsp and DsK events. Cerenkov light emission angle Bs → Ds K ,K Bs KK : 97.29 ± 0.06% pK : 5.15 ± 0.02% K K Ds  Primary vertex bt  • RICH1: 5 cm aerogel n=1.03 • 4 m3 C4F10 n=1.0014 RICH2: 100 m3 CF4 n=1.0005

  10. LHCb calorimeters K Bs K Ds K  Primary vertex bt e h  • Calorimeter system : • Identify electrons, hadrons, neutrals • Level 0 trigger: high ET electron and hadron

  11. LHCb muon detection K Bs K Ds K  Primary vertex btag m  • Muon system: • Level 0 trigger: High Pt muons • Flavour tagging: eD2 = e (1-2w)2 6%

  12. LHCb trigger Detector 40 MHz L0: high pT (m, e, g, h) [hardware, 4ms] 1 MHz HLT: high IP, high pT tracks [software] then full reconstruction of event 2 kHz Storage (event size ~ 50 kB) L0, HLT and L0×HLT efficiency Efficiency  Note: decay time dependent efficiency: eg. Bs → Ds K K Bs K Ds K  Primary vertex bt Proper time [ps]  12

  13. Measuring time dependent decays  Bs K Ds K  Primary vertex bt Measurement of Bs oscillations: • Experimental Situation: • Ideal measurement (no dilutions) Bs->Ds–p+ (2 fb-1)

  14. Measuring time dependent decays  Bs K Ds K  Primary vertex bt Measurement of Bs oscillations: Experimental Situation: Ideal measurement (no dilutions) + Realistic flavour tagging dilution Bs->Ds–p+ (2 fb-1)

  15. Measuring time dependent decays  Bs K Ds K  Primary vertex bt Measurement of Bs oscillations: Experimental Situation: Ideal measurement (no dilutions) + Realistic flavour tagging dilution + Realistic decay time resolution Bs->Ds–p+ (2 fb-1)

  16. Measuring time dependent decays  Bs K Ds K  Primary vertex bt Measurement of Bs oscillations: Experimental Situation: Ideal measurement (no dilutions) + Realistic flavour tagging + Realistic decay time resolution + Background events Bs->Ds–p+ (2 fb-1)

  17. Measuring time dependent decays  Bs K Ds K  Primary vertex bt Measurement of Bs oscillations: Experimental Situation: Ideal measurement (no dilutions) + Realistic flavour tagging dilution + Realistic decay time resolution + Background events + Trigger and selection acceptance Bs->Ds–p+ (2 fb-1) • Two equally important aims for the experiment: • Limit the dilutions: good resolution, tagging etc. • Precise knowledge of dilutions

  18. Expected Performance: GEANT MC simulation • Simulation software: • Pythia+EvtGen • GEANT simulation • Detector response • Reconstruction software: • Event Reconstruction • Decay Selection • Trigger/Tagging • Physics Fitting Used to optimise the experiment and to test physics sensitivities

  19. PhysicsProgramme LHCb is a heavy flavour precision experiment searching for new physics in CP-Violation and Rare Decays • CP Violation • Rare Decays

  20. CP Violation – LHCb Program q1 b q2 W− d, s W − b u,c,t d (s) q g q Bd triangle Bs triangle • CP Program: Is CKM fully consistent for trees, boxes and penguins? • gmeasurementsfrom trees • gmeasurementfrompenguins • bsfrom the box: “Bsmixingphase” • bsin penguins V*ib Viq q u, c, t b W− W+ u, c, t q b Viq V*ib

  21. 1.a g +fsfrom trees: Bs→DsK • Time dependent CP violation in interference of bc and bu decays: Bs Bs Bs Bs Bs/Bs →Ds–K+ (10 fb-1) Time

  22. Bs→DsK • Since same topology BsDsK, Bs Dsp • combine samples to fit Dms, DGs • and Wtag together with CP phase g+fs. 10 fb-1 data: Bs→Ds-p+ Bs→ Ds-K+ (Dms = 20) • Use lifetime difference • DGs to resolve some • ambiguities (2 remain). s(g+fs) = 9o–12o Decay Time →

  23. B →Dpand Bs→DsK • B  D(*)p measures g in similar way as BsDsK • More statistics, but smaller asymmetry • No lifetime difference: • 8 –fold ambiguity for g solutions LHCb-2005-036 Invoking U-spin symmetry (d↔s) can resolve these ambiguities in a combined analysis of DsK and D(*)pi (Fleisher) Can make an unambiguous extraction, depending on The value of strong phases: s(g) < 10o (in 2 fb-1) U-spin breaking

  24. 1.bgfrom trees: B→DK • Interfere decays bc with bu • to final states common to D0 and D0 color suppression • GLW method: • fD is a CP eigenstate common to • D0 and D0: fD= K+K-, p+p-,… • Measure: B→D0K, B → D0K, B→ D1K • Large event rate; small interference • Measurement rB difficult bc favoured Cabibbo supp. D0K– fDK– B– bu suppressed Cabibbo allowed. D0K– • ADS method: • Use common flavour state fD=(K+ p –)Note: decay D0→K+p–is double Cabibbo suppressed • Lower event rate; large interference Decay time independent analysis

  25. B→D(*)K(*) See talk of AngeloCarbone GLW: D KK (2 rates) ; ADS: D Kp( 4 rates) ; ADS: DK3p(4 rates) ; Normalization is arbitrary: 7 observables for 5 unknows: g, rB, dB, dDp , dD3p s(g) = 5o to 13o depending on strong phases. s(g) Also under study: B± → DK±with D → Kspp 80-12o B± → DK±with D → KK pp 18o B0 → DK*0with D → KK, Kp, pp 6o -12o B± → D*K±with D → KK, Kp, pp (high background) Dalitz analyses Overall: expect precision of s(g) = 5owith 2 fb-1 of data

  26. 2. gfrom loops: B(s)→hh See talk of AngeloCarbone • Interfere b u tree diagram with penguins: • Strong parameters d (d’), q (q’) are • strength and phase of penguins to tree. • Weak U-spin assumption : • d=d’+-20% , q, q’ independent • Assume mixing phases known 2 fb-1 Dms=20 BsK+K- BG s ( g ) ~10o Time

  27. 3. The Bd and BsMixingPhase Time dependent CP violation in interference between mixing and decay B Bs fCP fCP B Bs “Golden mode” s(sin2b ) ~ 0.02 “Yesterday’s sensation is today’s calibration and tomorrow’s background” – Val Telegdi

  28. Bsmixingphase 1. Pure CP eigenstates Low yield, high background 2. Admixture of CP eigenstates: Bs→J/y f “Golden mode”: Large yield, nice signature However PS->VV requires angular analysis to disentagle h=+1 (CP-even) ,-1 (CP-odd)

  29. Full 3D Angularanalysis cos y = cosqf cosq f Study possible systematics of LHCb acceptance and reconstruction on distributions.

  30. Bs→ J/y f signal backg sum • Simultaneouslikelihoodanalysis in time, mass, full 3d-angular distribution • Includemasssidebands to model the time spectrum and angular distribution of the background • Model the tresolution •  s (fs)=0.02 s(t)= 35 fs time s(M)= 14 MeV See talk of Olivier Leroy mass cosqf cos qtr ftr

  31. 4. b & bsfromPenguins • Compare observed phases in tree decays with those in penguins • Bs f f requires time dependent CP asymmetry • (PSVV angular analysis a la J/yf ) See talk of Olivier Leroy

  32. PhysicsProgramme LHCb is a heavy flavour precision Experiment searching for new physics in CP-Violation and Rare Decays • CP Violation • Rare Decays

  33. Rare Decays – LHCb Program Weak B-decays described by effective Hamiltonian: i=1,2: trees i=3-6,8: g penguin i=7: g penguin i=9,10: EW penguin New physics shows up via new operators Oior modification of Wilson coefficients Ci compared to SM. Study processes that are suppressed at tree level to look for NP affecting observables: Branching Ratio’s, decay time asymmetries, angular asymmetries, polarizations, … LHCb Program: Look fordeviations of the SM picture in the decays: b sl+l- ; Afb(BK*mm) ,B+→K+ll (RK), Bs→fmm b  s g ; Acp(t) Bs fg, B→K*g, Lb→Lγ, Lb→ L*γ,B →r0g, B→wγ Bq l+l- ; BR (Bs mm) LFV Bq l l‘ (notreportedhere)

  34. 1. B0→K*0µ+µ- AFB(m2μμ) theory illustration m2[GeV2] • Contributions from electroweak penguins • Angular distribution is sensitive to NP 3 angles: ql, f ,qK AFB Observable: Forward-Backward Asymmetry in ql Zero crossing point (so) well predicted: hep-ph:0106067v2

  35. B0→K*0µ+µ- • AFB(s), fast MC, 2 fb–1 s = (m)2 [GeV2]  See talk Mitesh Patel Event Selection: 2 fb-1 Afb(s)  s0 s(s0) = 0.5 GeV2 Remove resonances • Systematic study: • Selection should not distort m2mm • s0 point to first order not affected

  36. 2. Bs→fg See talk Mitesh Patel • Probes the exclusive b →s radiative penguin • Measure time dependent CP asymmetry: b   (L) + (ms/mb)  (R) In SM b→s g is predominatly (O(ms/mb)) left handed Observed CP violation depends on the g polarization Event selection: Adir 0, Amix  sin2y sin2f, AD  cos 2ycosf tan y = |b→s gR| / | b→s gL| , cos f  1 SM: Statistical precision after 2 fb-1 (1 year) s(Adir ) = 0.11 , s (Amix ) = 0.11(requires tagging) s (AD) = 0.22 (no tagging required) Measures fraction “wrong” g polarization

  37. 3. Bs →m+m- See talk Mitesh Patel • Bs mm is helicity suppressed • SM Branching Ratio: (3.35 ± 0.32) x 10 -9 • Sensitive to NP with S or P coupling hep-ph/0604057v5 Event Selection: Main Backgrounds: Suppressed by: bm, bm Mass & Vertex resol. B hh Particle Identification • With 2 fb-1 (1 “year”): • Observe BR: 6 x 10-9 with 5 s • Assuming SM BR: 3s observation

  38. PhysicsProgramme LHCb is a heavy flavour precision Experiment searching for new physics in CP-Violation and Rare Decays • CP Violation • Rare Decays • + “Other” Physics

  39. “Other” Physics See the followingtalksforanoverview: RalucaMuresan: • CharmPhysics: Mixing and CP Violation Michael Schmelling: • Non CP ViolationPhysics: • B production, multiparticleproduction, deepinelasticscattering, …

  40. Conclusions LHCb is a heavy flavour precision experiment searching for New Physics in CP Violation and Rare Decays CP Violation: 2 fb-1 (1 year)* • gfrom trees: 5o - 10o • gfrompenguins: 10o • Bsmixingphase: 0.023 • bsefffrompenguins: 0.11 A program to do this has been developed and the methods, including calibrations and systematic studies, are being worked out.. • Rare Decays: 2 fb-1 (1 year)* • BsK*mm s0 : 0.5 GeV2 • Bs gAdir , Amix : 0.11 • AD : 0.22 • Bsmm BR.: 6 x 10-9 at 5s We appreciate the collaboration with the theory community to continue developing new strategies. We are excitingly looking forward to the data from the LHC. * Expect uncertainty to scale statistically to 10 fb-1. Beyond: see Jim Libby’s talk on Upgrade

  41. Backup

  42. LHCb Detector RICH-2 PID MUON ECAL HCAL RICH-1 PID vertexing Tracking (momentum)

  43. Display of LHCb simulated event

  44. FlavourTagging Performance of flavour tagging: Tagging power:

  45. Full table of selections Nominal year = 1012 bb pairs produced (107 s at L=21032 cm2s1 with bb=500 b) Yields include factor 2 from CP-conjugated decays Branching ratios from PDG or SM predictions

  46. BsDsK5 years data BsDs-K+ BsDs+K- BsbDs+K- BsbDs-K+

  47. Angleg in Summary

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