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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.

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LHCb Physics Programme

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  1. CERN TheoryInstitute: Flavour as a window to New Physics at the LHC: May 5 –June 13, 2008 LHCbPhysicsProgramme Marcel Merk For the LHCbCollaboration May 26, 2008 • Contents: • The LHCb Experiment • PhysicsProgramme: • 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 LargeHadronCollider Beauty Experiment forPrecisionMeasurements of CP-Violation and Rare Decays

  3. The LHCb Detector Muondet Muondet Calo’s Calo’s Magnet Magnet RICH-2 RICH-2 OT RICH-1 RICH-1 OT+IT 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 • Decaydistance (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 Massresolution s ~14 MeV Bs→ Ds K Bs →Dsp 

  8. Particle Identification RICH: K/pidentification 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/pidentification;eg. distinguish Dsp and DsK events. Cerenkovlightemissionangle 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 : • Identifyelectrons, hadrons, neutrals • Level 0 trigger: high ETelectron and hadron

  11. LHCb muon detection K Bs K Ds K  Primary vertex btag m  • Muon system: • Level 0 trigger: High Pt muons • Flavourtagging: 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 Bsoscillations: • ExperimentalSituation: • Idealmeasurement (nodilutions) Bs->Ds–p+ (2 fb-1)

  14. Measuring time dependent decays  Bs K Ds K  Primary vertex bt Measurement of Bsoscillations: ExperimentalSituation: Idealmeasurement (nodilutions) + Realisticflavourtaggingdilution Bs->Ds–p+ (2 fb-1)

  15. Measuring time dependent decays  Bs K Ds K  Primary vertex bt Measurement of Bsoscillations: ExperimentalSituation: Idealmeasurement (nodilutions) + Realisticflavourtaggingdilution + Realisticdecay time resolution Bs->Ds–p+ (2 fb-1)

  16. Measuring time dependent decays  Bs K Ds K  Primary vertex bt Measurement of Bsoscillations: ExperimentalSituation: Idealmeasurement (nodilutions) + Realisticflavourtagging + Realisticdecay time resolution + Background events Bs->Ds–p+ (2 fb-1)

  17. Measuring time dependent decays  Bs K Ds K  Primary vertex bt Measurement of Bsoscillations: ExperimentalSituation: Idealmeasurement (nodilutions) + Realisticflavourtaggingdilution + Realisticdecay time resolution + Background events + Trigger and selectionacceptance Bs->Ds–p+ (2 fb-1) • Twoequally important aimsfor the experiment: • Limit the dilutions: goodresolution, tagging etc. • Preciseknowledge of dilutions

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

  19. PhysicsProgramme LHCb is a heavy flavourprecision experiment searchingfornewphysics 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 Bdtriangle Bstriangle • 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 • SincesametopologyBsDsK, Bs Dsp • combine samples to fit Dms, DGs • and Wtagtogetherwith CP phaseg+fs. 10 fb-1 data: Bs→Ds-p+ Bs→ Ds-K+ (Dms = 20) • Uselifetimedifference • DGs to resolvesome • ambiguities (2 remain). s(g+fs) = 9o–12o Decay Time →

  23. B →Dpand Bs→DsK • B  D(*)pmeasuresg in similarway as BsDsK • More statistics, but smaller asymmetry • No lifetimedifference: • 8 –foldambiguityforg solutions LHCb-2005-036 InvokingU-spinsymmetry (d↔s) canresolve these ambiguities in a combinedanalysis of DsK and D(*)pi (Fleisher) Canmakeanunambiguous extraction, dependingon The value of strongphases: s(g) < 10o (in 2 fb-1) U-spinbreaking

  24. 1.bgfrom trees: B→DK • Interferedecays bc with bu • to finalstatescommon 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 • Largeeventrate; smallinterference • MeasurementrBdifficult bc favoured Cabibbosupp. D0K– fDK– B– bu suppressed Cabibboallowed. D0K– • ADS method: • Usecommonflavour state fD=(K+ p –)Note: decayD0→K+p–is double Cabibbosuppressed • Lowereventrate; largeinterference 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 observablesfor 5 unknows: g, rB, dB, dDp , dD3p s(g) = 5o to 13o dependingonstrongphases. s(g) Alsounderstudy: 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±withD → KK, Kp, pp (high background) Dalitz analyses Overall: expectprecisionof s(g) = 5owith2 fb-1 of data

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

  27. 3. The Bd and BsMixingPhase Time dependent CP violation in interferencebetweenmixing and decay B Bs fCP fCP B Bs “Golden mode” s(sin2b ) ~ 0.02 “Yesterday’ssensation 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”: Largeyield, nice signature However PS->VV requiresangularanalysis to disentagleh=+1 (CP-even) ,-1 (CP-odd)

  29. Full 3D Angularanalysis cos y = cosqf cosq f Studypossiblesystematics of LHCbacceptance and reconstructionondistributions.

  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 • Compareobservedphases in tree decayswiththose inpenguins • Bsf frequires time dependent CP asymmetry • (PSVV angularanalysis a la J/yf ) See talk of Olivier Leroy

  32. PhysicsProgramme LHCb is a heavy flavourprecision Experiment searchingfornewphysics in CP-Violation and Rare Decays • CP Violation • Rare Decays

  33. Rare Decays – LHCb Program WeakB-decaysdescribedbyeffectiveHamiltonian: i=1,2: trees i=3-6,8: g penguin i=7: gpenguin i=9,10: EW penguin New physics shows up via new operators Oiormodification of Wilson coefficientsCicompared to SM. Studyprocessesthat are suppressed at tree level to look for NP affectingobservables: BranchingRatio’s, decay time asymmetries, angularasymmetries, 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] • Contributionsfromelectroweakpenguins • Angular distribution is sensitive to NP 3 angles: ql, f ,qK AFB Observable: Forward-BackwardAsymmetry in ql Zero crossing point (so) wellpredicted: hep-ph:0106067v2

  35. B0→K*0µ+µ- • AFB(s), fast MC, 2 fb–1 s= (m)2 [GeV2]  See talk MiteshPatel EventSelection: 2 fb-1 Afb(s)  s0 s(s0) = 0.5 GeV2 Remove resonances • Systematicstudy: • Selectionshouldnotdistort m2mm • s0 point to first order notaffected

  36. 2. Bs→fg See talk MiteshPatel • Probes the exclusive b →s radiativepenguin • Measure time dependent CP asymmetry: b   (L) + (ms/mb)  (R) In SM b→s g is predominatly (O(ms/mb)) lefthanded Observed CP violationdependson the gpolarization Eventselection: Adir 0, Amix  sin2y sin2f, AD  cos 2ycosf tan y = |b→s gR| / | b→s gL| , cos f  1 SM: Statisticalprecisionafter 2 fb-1 (1 year) s(Adir ) = 0.11 , s (Amix ) = 0.11(requirestagging) s (AD) = 0.22 (notaggingrequired) Measuresfraction “wrong” gpolarization

  37. 3. Bs →m+m- See talk MiteshPatel • 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 EventSelection: MainBackgrounds: Suppressedby: bm, bmMass & Vertexresol. B hhParticleIdentification • With 2 fb-1 (1 “year”): • Observe BR: 6 x 10-9with 5 s • Assuming SM BR: 3s observation

  38. PhysicsProgramme LHCb is a heavy flavourprecision Experiment searchingfornewphysics 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 flavourprecision experiment searchingfor New Physics in CP Violationand Rare Decays A program to do this has been developed and the methods, includingcalibrations and systematic studies, are beingworked 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 collaborationwith the theorycommunity to continue developingnewstrategies. We are excitinglylookingforward to the data from the LHC. * Expectuncertainty to scalestatistically to 10 fb-1. Beyond: see Jim Libby’s talk on Upgrade CP Violation: 2 fb-1 (1 year)* gfrom trees: 5o - 10o gfrompenguins: 10o Bsmixingphase: 0.023 bsefffrompenguins: 0.11

  41. Backup

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

  43. Display of LHCb simulatedevent

  44. FlavourTagging Performance of flavourtagging: 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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