1. Flavour Physics with LHCb “ When Beauty Decays and Symmetries Break” Seminar RuG March 31, 2008 Marcel Merk Nikhef and VU 31-3-20081 Contents: CP violation with the CKM matrix Bs meson and “new physics” B-physics with the LHCb detector

2. LHCb ATLAS CMS ALICE CERN

3. LHC: Search for physics beyond Standard Model 31-3-20083 Atlas/CMS: direct observation of new particles LHCb: observation of new particles in quantum loops LHCb is aiming at search for new physics in CP violation and Rare Decays Focus of this talk AtlasCMSLHCb

4. Flavour physics with 3 generations of fermions 31-3-20084 u d c s t b IIIIII e   e   quarks leptons ~0 1777 106 ~0 0.511 120 4300 176300 1200 ~7 ~3 LEP 1 2 neutrino’s 3 neutrino’s 4 neutrino’s measurements Beam energy (GeV) Cross section Note: In the Standard Model 3 generations of Dirac particles is the minimum requirement to create a matter - antimatter asymmetry.

5. Quark flavour interactions 31-3-20085 Charged current interaction with quarks: Quark mass eigenstates are not identical to interaction eigenstates: In terms of the mass eigenstates the weak interaction changes from: u, c, t d, s, b W g weak J

6. Quark flavour interactions 31-3-20086 Charged current interaction with quarks: Quark mass eigenstates are not identical to interaction eigenstates: In terms of the mass eigenstates the weak interaction changes to: Cabibbo Kobayashi Maskawa quark mixing matrix u, c, t d, s, b W g weak J

7. The CKM Matrix V CKM 31-3-20087

8. The CKM Matrix V CKM 31-3-20088 d b d c V cb Typical B-meson decay diagram: The B-meson has a relatively long lifetime of 1.5 ps Related to mass hierarchy?

9. The CKM Matrix V CKM 31-3-20089 From unitarity (V CKM V † CKM =1) : CKM has four free parameters: 3 real: A (  ),  1 imaginary: i  Particle → Antiparticle: V ij → V ij * => 1 CP Violating phase! Wolfenstein parametrization: V CKM

10. The CKM Matrix V CKM 31-3-200810 From unitarity (V CKM V † CKM =1) : CKM has four free parameters: 3 real: A (  ),  1 imaginary: i  Particle → Antiparticle: V ij → V ij * => 1 CP Violating phase! Wolfenstein parametrization: V CKM

11. Unitarity Triangle: V CKM V † CKM = 1 31-3-200811

12. Unitarity Triangle: V CKM V † CKM = 1 31-3-200812 0 1 Im    Re Unitarity triangle: Individual CP violating phases in CKM are not observable The combinations , ,  are Amount of CP violation is proportional to surface of the triangle

13. 0 ++   Re   : B d mixing phase  : B s mixing phase  : weak decay phase 0 1 Im    Re Im Precise determination of parameters through study of B-decays. Precise determination of parameters through study of B-decays. Unitarity Triangle and B-physics

14. Benchmark Example: B s →D s K 31-3-200814

15. Benchmark Example: B s →D s K 31-3-200815 But how can we observe a CP asymmetry? Decay probabilities are equal? No CP asymmetry?? Make use of the fact that B mesons “mix”….. Decay amplitudes: particles: antiparticles:

16. Sept 28-29, 200516 B meson Mixing Diagrams Dominated by top quark mass: d b bd W u,c,t W BdBd BdBd A neutral B-meson can oscillate into an anti B-meson before decaying:

17. Sept 28-29, 200517 B 0 B 0 Mixing: ARGUS, 1987 First sign of a really large m top ! Produce a b b bound state,  (4S), in e + e - collisions: e + e -   (4S)  B 0 B 0 and then observe: ~17% of B 0 and B 0 mesons oscillate before they decay   m ~ 0.5/ps,  B ~ 1.5 ps Integrated luminosity 1983-87: 103 pb -1

18. B d vs B s mixing 31-3-200818 d b b d W t t W BdBd BdBd The top quark and its interactions can be studied without producing it directly! s s b d W t t W BsBs BsBs B d → B d B d mixing B s mixing B s → B s B s mixing

19. The CP violating decay: B s →D s K 31-3-200819 Due to mixing possibility the decay B s →D s K can occur in two quantum amplitudes: a1. Directly: a2. Via mixing: Coupling constant with CP odd phase  How do the phase differences between the amplitudes lead to an observable CP violation effect…? In addition, mixing and gluon interactions add a non-CP violating phase “  ” between a1 and a2

20. Sept 28-29, 200520 Observing CP violation |A||A|  Only if both  and  are not 0 B  D s + K − B  D s − K + A=a 1 +a 2   ++ -- a1a1 a1a1 a2a2 a2a2 A A Compare the |amplitude| of the B decay versus that of anti-B decay;   is the CP odd phase,  is a CP even phase Note for completeness: since the CP even phase depends on the mixing the CP violation effect becomes decay time dependent

21. Double slit experiment with quantum waves 31-3-200821 BsBs Ds-Ds-  LHCb is a completely analogous interference experiment using B-mesons…

22. 6-sept-2007Nikhef-evaluation22 “slit A”: A Quantum Interference B-experiment pp at LHCb: 100 kHz bb Decay time BsBs Ds-Ds-  “slit B”: Measure decay time

23. 6-sept-2007Nikhef-evaluation23 CP Violation: matter – antimatter asymmetry BsBs DsDs  An interference pattern: Decay time  Decay time

24. 6-sept-2007Nikhef-evaluation24 BsBs Ds+Ds+  BsBs DsDs  Matter Antimatter CP-mirror: Difference between curves is proportional to the phase  Decay time  Decay time An interference pattern: CP Violation: matter – antimatter asymmetry Observation of CP Violation is a consequence of quantum interference!!

25. 6-sept-2007Nikhef-evaluation25 Searching for new virtual particles Standard Model BsBs J/   Standard Model  Decay time

26. 6-sept-2007Nikhef-evaluation26 Searching for new virtual particles Standard Model New Physics BsBs J/    Decay time Tiny weak phase in couplings! Possible weak phase in couplings!

27. 6-sept-2007Nikhef-evaluation27 Searching for new virtual particles Standard Model New Physics 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. B->J/  BsBs J/   Search for a CP asymmetry:  Decay time

28. 31-3-200828 + First sign of New Physics in B s mixing? SM box has (to a good approx.) no weak phase:  SM = 0 S.M.N.P.

29. 31-3-200829 + First sign of New Physics in B s mixing? SM box has (to a good approx.) no weak phase:  SM = 0 If  S ≠ 0 then new physics outside the CKM is present… S.M.N.P. UTfit collab.; March 5, 2008 Combining recent results of CDF, D0 on with Babar, Belle results: March 5, 2008 3.7  deviation From 0

30. The LHCb experimentLHCb ATLAS CMS ALICE bb bb LHCb experiment: 700 physicists 50 institutes 15 countries

31. LHCb experiment in the cavern 31-3-200831 Shielding wall (against radiation) Electronics + CPU farm Offset interaction point (to make best use of existing cavern) Detectors can be moved away from beam-line for access

32. b-b detection in LHCb 31-3-200832 LHCb event rate: 40 MHz 1 in 160 is a b-bbar event 10 12 b-bbar events per year Background Supression Flavour tagging Decay time measurement vertices and momenta reconstruction effective particle identification (π, К, μ, е, γ) triggers

33. 33 GEANT MC simulation Used to optimise the experiment and to test measurement sensitivities

34. 34 A walk through the LHCb detector  pp ~ 200 mrad ~ 300 mrad (horizontal) 10 mrad Inner acceptance ~15 mrad (10 mrad conical beryllium beampipe)

35. LHCb Tracking: vertex region 31-3-200835  Vertex locator around the interaction region Silicon strip detector with ~ 30  m impact-parameter resolution

36. 36 Pile-Up Stations Interaction Region  =5.3 cm LHCb tracking: vertex region  y x y x

37. 37 LHCb tracking: momentum measurement  B y [T] Bfield: B dl = 4 Tm Tracking: Mass resolution for background suppression in eg. D s K

38. 38 LHCb tracking: momentum measurement  All tracking stations have four layers: 0,-5,+5,0 degree stereo angles. Silicon: ~1.4  1.2 m 2 Straw tubes ~6  5 m 2

39. 39  ~1.4  1.2 m 2 Red = Measurements (hits) Blue = Reconstructed tracks Eff = 94% (p > 10 GeV) Typical Momentum resolution  p/p ~ 0.4% Typical Impact Parameter resolution  IP ~ 40  m LHCb tracking: momentum measurement

40. 40 LHCb Hadron Identification: RICH  3 radiators to cover full momentum range:  Aerogel  C 4 F 10 CF 4  RICH2: 100 m3 CF4 n=1.0005 RICH: K/  separation e.g. to distinguish D s  and D s K events. RICH1: 5 cm aerogel n=1.03 4 m 3 C 4 F 10 n=1.0014 Cerenkov light emission angle

41. 41 LHCb calorimeters  e h Calorimeter system : Identify electrons, hadrons, neutrals Level 0 trigger: high electron and hadron E t (e.g. Ds K events)

42. 42 LHCb muon detection   Muon system: Identify muons Level0 trigger: High Pt muons

43. View of LHCb in Cavern 31-3-200843 VELO Muon det Calo’s RICH-2Magnet OTRICH-1 VELO Muon det Calo’s RICH-2Magnet OTRICH-1 It’s full! Installation of major structures is essentially complete

44. Hope to soon see the first events from… 31-3-200844

45. 31-3-200845 Display of LHCb simulated event

46. 46 Prepare B s →D s K Reconstruction… Trigger : – E T Calorimeters, Vertex topology Flavour Tag: – Lepton-ID, Kaon-ID Background suppression: – Mass resolution, K/  ID Decay time: – Decay distance measurement – Momentum measurement DsDs BsBs KK KK  ,K   d p 47  m 144  m 440  m Invariant Mass

47. … to see time dependent CP violation signal! 31-3-200847 5 years data: B s → D s -   B s → D s - K + The amplitude of these “wiggles“ are proportional to the imaginary part of the CKM phase gamma! Decay time (ps) →

48. Conclusion: after 5 years of LHCb… 31-3-200848 To make this plot only Standard Model physics is assumed. CKM Unitarity Triangle in 2007: Expected errors after 5 years (10 fb -1 ) of LHCb:

49. Conclusion and Outlook LHCb 31-3-200849 CP Violation Measure the Bs mixing phase (B s →J /   ) Measure the CKM angle gamma via tree method ( B s → D s K ) Measure the CKM angle gamma via penguin loops ( B (s) → h  h  ) Rare Decays Measure Branching Ratio B s →  +  - Measure angular distribution B 0 → K*  +  - Measure radiative penguins decays: b → s  → X s  Other Flavour Physics Angle beta, B-oscillations, lifetimes, D-physics, Higgs,…? The collaboration has organised analysis groups and identified “hot topics”: Atlas and CMS look for new physics via direct production of particles LHCb tries to study it via the (possibly complex) couplings in B decay loop diagrams

50. Summary of Signal Efficiencies 31-3-200850

51. Thank you for the attention. 31-3-200851

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55. Research Questions Is flavour physics fully described by the CKM mechanism Is CP violation in CKM sufficient to describe baryogenesis Many models beyond the SM include a rich flavour physics structure Are the penguin, box and tree diagrams governed by the same physics? Search for CP violation where SM predicts none Measure Branching Ratio for processes which are forbidden in SM For the hypothesis that neutrinos are not massless the lepton system has a similar flavour strcture V CKM → V PMNS 31-3-200855

56. Bd meson vs Bs meson 31-3-200856 These B bbar oscillations allow for a beautiful CP experiment

57. 57 Result of track finding Typical event display: Red = measurements (hits) Blue = all reconstructed tracks Efficiency vs p :Ghost rate vs p T : Eff = 94% (p > 10 GeV) Ghost rate = 3% (for p T > 0.5 GeV) VELO TT T1 T2 T3 On average: 26 long tracks 11 upstream tracks 4 downstream tracks 5 T tracks 26 VELO tracks 20  50 hits assigned to a long track: 98.7% correctly assigned Ghosts: Negligible effect on b decay reconstruction

58. 58 Experimental Resolution  p/p = 0.35% – 0.55% p spectrum B tracks  IP = 14  + 35  /p T 1/p T spectrum B tracks Momentum resolution parameter resolution Impact parameter resolution

59. 59 Particle ID RICH 1 RICH 2  (K->K) = 88%  (p->K) = 3% Example: Bs->Dsh KK  BsBs KK  ,K  DsDs Prim vtx

60. Event in the Simulation 31-3-200860

61. Zoom in on the Velo detector 31-3-200861

62. Roger FortyPhysics challenges of the LHC (III)62 4. Expected results Example of an early physics measurement that is expected from LHCb: Measurement of B s –B s oscillations Use channel B s  D s   + Plot made for one year of data  80,000 selected events for  m s = 20 ps -1 (SM preferred) Proper time distribution for events produced as B s (rather than B s ) Need to take care of flavour tagging, proper-time resolution, background rejection and acceptance correction Can measure frequency accurately cf recent result  m s = 17.8 ± 0.1 ps -1 [CDF] Next step: measure the phase of the oscillation, using B s  J/   decays (B s counterpart of B 0  J/  K S ), cleanly predicted in the SM:  s =  0.04

63. Roger FortyPhysics challenges of the LHC (III)63 Penguin decays These are another category of decays involving loop diagrams New particles might appear in those loops Some indication from the B factory experiments that their results for penguin decays do not agree with expectations  might be a hint of new physics? LHCb should reach a precision of ± 0.04 on the asymmetry of B s   Experiment Theory

64. Roger FortyPhysics challenges of the LHC (III)64 Rare decays Profit from the enormous statistics to search for very rare decays such as B s      Branching ratio ~ 3  10 -9 in the Standard Model BR can be strongly enhanced in SUSY [G. Kane et al, hep-ph/0310042] LHCb can reach the SM prediction in a few years Integrated Luminosity (fb -1 ) BR (x10 -9 ) 55 33 SM prediction SUSY models LHCb

65. b q1q1 d, s q2q2 W−W− Topologies in B decays g d (s) q q W − bu,c,t b q q b W+W+ W−W− V* ib V iq V* ib Trees Penguins Boxes m b γ L +m q γ R b q W–W– u, c, t Z, γ d (s) l+l+ l−l− W − bu, c, t

66. Search for NP comparing observables measured in tree and loop topologies  (tree+box) in B  J/  K s  (tree) in many channels  (tree+box) in B s  J/    (peng+tree) in B  , ,   (peng+box) in B   K s  (peng+box) in Bs    New heavy particles, which may contribute to d- and s- penguins, could lead to some phase shifts in all three angles:  (NP) =  (peng+tree) -  (tree)  (NP) =  (B   Ks) -  (B  J/  Ks ) ≠ 0  (NP) =  (B s   ) -  (B s  J/  )

67. b  s  exclusive b   (L) + (m s /m b )   (R) Measurement of the photon helicity is very sensitive test of SM Methods: - mixing induced CP asymmetries in B s  , B  K s  0  -  b   : asymmetries in the final states angular distributions are sensitive to the photon and  b polarizations. - Photon helicity can be measured directly using parity-odd triple correlation (P(  ),[ P(h 1 )  P(h 2 )]) between photon and 2 out of 3 final state hadrons. Good examples are B   K  and B  K  decays

68. B → K* μμ ? A very important property is forward-backward asymmetry....and position of its zero, which is robust in SM: A FB (s), fast MC, 2 fb –1 s = (m  ) 2 [GeV 2 ]