Physics with bottom quarks: The LHCb experiment

1. Physics@FOM Veldhoven 2009. Focus Session F01: The start-up of the LHC at CERN Physicswithbottom quarks: The LHCb experiment Marcel Merk Nikhef and the Free University Jan 20, 2009 • Contents: • Physicswithb-quarks • CP Violation • The LHCb Experiment

2. LHCb @ LHC CERN LHCb ATLAS CMS ALICE

3. LHC: Search forphysicsbeyond Standard Model Atlas CMS LHCb • Atlas/CMS: directobservation of newparticles • LHCb: observation of newparticles in quantum loops LHCb is aiming at search for newphysics in CP violation and Rare Decays Focus of this talk

4. Flavourphysicswith 3 generations of fermions measurements LEP 1 c u t Cross section 4 neutrino’s b d s 3 neutrino’s 2 neutrino’s m e t nm nt ne Beam energy (GeV) I II III quarks 1200 ~3 176300 ~7 120 4300 (masses in MeV) 1777 0.511 leptons 106 ~0 ~0 ~0 Note: In the Standard Model 3 generations of Diracparticles is the minimum requirement to create a matter - antimatter asymmetry (CP violation).

5. Interactions between Quarks Cabibbo described “V-A” quark interactions with flavour changing charged currents:  quark mixing u Jμ+ W gweak d , s Nicola Cabibbo

6. Interactions between Quarks Cabibbo described “V-A” quark interactions with flavour changing charged currents:  quark mixing u , c , t Jμ+ W gweak d , s , b Matter →Antimatter gweak→g*weak Makoto Kobayashi Nicola Cabibbo Toshihide Maskawa Kobayashi andMaskawapredicted in 1972 the 3rd quark generation to explain CP-Violation within the Standard Model  Nobel Prize 2008 (shared with Nambu) 9 Coupling constants: gweak→g ∙ VCKM

7. The CKM Matrix VCKM d s b u c t

8. The CKM Matrix VCKM TypicalB-meson ( ) decay diagram: u W Vcb d b The B-meson has a relatively long lifetime of 1.5 ps Related to masshierarchy? d d c

9. The CKM Matrix VCKM Wolfensteinparametrization: VCKM Fromunitarity (VCKM V†CKM=1) : CKM has four free parameters: 3 real: l (0.22) , A ( 1), r 1 imaginary: ih Particle → Antiparticle: Vij→Vij* => 1 CP Violatingphase!

10. The CKM Matrix VCKM Wolfensteinparametrization: VCKM Fromunitarity (VCKM V†CKM=1) : CKM has four free parameters: 3 real: l (0.22) , A ( 1), r 1 imaginary: ih Particle → Antiparticle: Vij→Vij* => 1 CP Violatingphase!

11. BenchmarkExample: Bs→Ds K

12. BenchmarkExample: Bs→Ds K • Decay amplitudes: particles: antiparticles: • Buthowcan we observe a CP asymmetry? • Decayprobabilities are equal? No CP asymmetry?? Makeuse of the factthat B mesons “mix”…..

13. The CP violatingdecay: Bs→Ds K A B-mesoncanoscillateintoananti-B: Due to mixingpossibility the decayBs→Ds–K+canoccur in twoquantum amplitudes: A1. Via mixing: b s t Bs Bs W W Coupling constant with CP oddphaseg A2. Directly: s t b It is straighforward to show that the interference term of the two amplitudes have anoppositesignfor the particle and antiparticle cases.  The observable CP violation effect.

14. Double slit experiment withquantumwaves Ds- Bs K+ LHCb is a completely analogous interference experiment using B-mesons…

15. A Quantum Interference B-experiment Ds- Bs K+ Measure decay time pp at LHCb: 100 kHz bb “slit A”: Decay time “slit B”: Nikhef-evaluation

16. CP Violation: matter – antimatter asymmetry Ds- Bs K+ An interference pattern: Decay time  Decay time Nikhef-evaluation

17. CP Violation: matter – antimatter asymmetry CP Violation: matter – antimatter asymmetry Ds- Bs K+ Ds+ Bs K- An interference pattern: Matter Decay time CP-mirror: Antimatter Decay time  Decay time Difference between curves is proportional to the CKM phase g Observation of CP Violation is a consequence of quantum interference!! Nikhef-evaluation

18. Searching for new virtual particles Standard Model Standard Model J/y Bs f  Decay time Nikhef-evaluation

19. Searching for new virtual particles J/y Bs f TinyCP-oddphase in couplings! Standard Model ? New Physics  Decay time PossibleCP-oddphase in couplings! Nikhef-evaluation

20. Searching for new virtual particles J/y Bs f Search for a CP asymmetry: Standard Model B->J/yf B->J/yf ? New Physics  Decay time Mission: To search for new particles and interactions that affect the observed matter-antimatter asymmetry in Nature, by making precision measurements of B-meson decays. Nikhef-evaluation

21. LHCb @ LHC 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 b CERN LHCb ATLAS CMS ALICE A LargeHadronCollider Beauty Experiment forPrecisionMeasurements of CP-Violation and Rare Decays

22. b-bdetection in LHCb K Bs K Ds K  Primary vertex btag Background Supression Flavourtagging Decay time measurement ~1 cm • vertices and momenta reconstruction • effective particle identification(π, К, μ, е, γ) • triggers LHCbeventrate: 40 MHz 1 in 160 is a b-bbarevent 1012 b-bbarevents per year

23. GEANT MC simulation Used to optimise the experiment and to test measurement sensitivities

24. A walk through the LHCb detector ~ 200 mrad ~ 300 mrad (horizontal) 10 mrad p p 

25. 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 • Vertexing: • Impact parameter trigger • Decaydistance (time) measurement

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

27. 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 

28. 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

29. 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

30. LHCb calorimeters K Bs K Ds K  Primary vertex bt e h  • Calorimeter system : • Identifyelectrons, hadrons, neutrals • Level 0 trigger: high ETelectron and hadron

31. 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%

32. 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 detector is completed

33. We have seen the firsteventsfrom the LHC

34. First LHC Tracks in the Velo • linked hits • not linked hits  Talk of Ann Van Lysebetten

35. Cosmic tracks in LHCb • Detector alignment • T0 calibration • RT-relation • …

36. Events from the LHC beam injection

37. In Summary p 144 mm ,K 47 mm Bs K K Ds  d 440 mm Detect produced particles: Reconstruct and select B-events: Decay time spectra: Extract CP-Violation parameters: MC 5 years data: BsDs-K+ Decay time (ps)

38. Conclusion and Outlook • Complementary research approach: • Atlas and CMS look fornewphysicsvia direct productionof particles • LHCb studies newphysicsvia the couplingsin B-decay loop effects In LHCbmany different B-decay studies are prepared to examine CP violation and rare decays. The experiment is readyfor data in 2009!

40. Backup Slides

41. Summary of SignalEfficiencies

42. 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

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

44. Display of LHCb simulatedevent

45. First sign of New Physics in Bsmixing? ? + S.M. N.P. SM box has (to a goodapprox.) noweakphase: fSM = 0

46. First sign of New Physics in Bsmixing? ? + S.M. N.P. SM box has (to a goodapprox.) noweakphase: fSM = 0 UTfitcollab.; March 5, 2008 Combining recent results of CDF, D0 on withBabar, Belle results: March 5, 2008 3.7 sdeviation From 0 IffS ≠ 0 thennewphysicsoutside the CKM is present…

47. Quark flavourinteractions • Chargedcurrentinteractionwith quarks: u, c, t J W • Quark masseigenstates are notidentical to interactioneigenstates: gweak d, s, b • In terms of the masseigenstates the weakinteractionchangesfrom:

48. Quark flavourinteractions • Chargedcurrentinteractionwith quarks: u, c, t J W • Quark masseigenstates are notidentical to interactioneigenstates: gweak d, s, b • In terms of the masseigenstates the weakinteractionchanges to: CabibboKobayashiMaskawa quark mixing matrix

49. B meson Mixing Diagrams Dominated by top quark mass: A neutralB-mesoncanoscillateintoan anti B-mesonbeforedecaying: b u,c,t d Bd Bd W W d u,c,t b

50. B0B0Mixing: ARGUS, 1987 Integrated luminosity 1983-87: 103 pb-1 Produce a bb bound state, (4S), in e+e- collisions: e+e-(4S)  B0B0 and then observe: ~17% of B0 and B0 mesons oscillate before they decay Dm ~ 0.5/ps, tB ~ 1.5 ps First sign of a really largemtop!