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Seminar R u G March 31, 2008 Marcel Merk Nikhef and VU

Flavour Physics with LHCb “ When Beauty D ecays and Symmetries B reak ”. Seminar R u G March 31, 2008 Marcel Merk Nikhef and VU. Contents: CP violation with the CKM matrix Bs meson and “ new physics ” B-physics with the LHCb detector. CERN. LHCb. ATLAS. CMS. ALICE.

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Seminar R u G March 31, 2008 Marcel Merk Nikhef and VU

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  1. FlavourPhysicswithLHCb“When Beauty Decays and SymmetriesBreak” Seminar RuG March 31, 2008 Marcel Merk Nikhef and VU • Contents: • CP violationwith the CKM matrix • Bs meson and “newphysics” • B-physicswith the LHCb detector

  2. 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 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.

  5. 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:

  6. 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

  7. The CKM Matrix VCKM

  8. The CKM Matrix VCKM TypicalB-mesondecay diagram: Vcb 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. UnitarityTriangle: VCKM V†CKM = 1

  12. UnitarityTriangle: VCKM V†CKM = 1 Im    0 1 Re Unitaritytriangle: Individual CP violatingphases in CKM are notobservable The combinationsa,b,g are Amount of CP violation is proportional to surface of the triangle

  13. UnitarityTriangle and B-physics : Bdmixing phase : Bsmixing phase : weak decay phase Im    0 1 Re Im   + Precise determination of parameters through study of B-decays.  0 Re

  14. BenchmarkExample: Bs→Ds K

  15. 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”…..

  16. 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

  17. 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!

  18. BdvsBsmixing The top quark and itsinteractionscanbestudied without producingitdirectly! Bdmixing Bsmixing b b Bsmixing d d t t Bd Bs Bd Bs W W W W Bs → Bs Bs → Bs Bd → Bd Bd → Bd s d t b t s

  19. The CP violatingdecay: Bs→Ds K Due to mixingpossibility the decayBs→Ds K canoccur in twoquantum amplitudes: a1. Directly: Coupling constant with CP oddphaseg a2. Via mixing: In addition, mixing and gluoninteractionsadd a non-CPviolatingphase “d” betweena1 and a2 How do the phasedifferencesbetween the amplitudes lead to an observable CP violation effect…?

  20. Observing CP violation BDs− K+ A=a1+a2 A=a1+a2 BDs+ K− +g d d A -g a2 A a2 a1 a1 Compare the |amplitude| of the B decay versus that of anti-B decay; gis the CP odd phase , dis a CP even phase |A||A| Only if both g and dare not 0 Note for completeness: since the CP even phase depends on the mixing the CP violation effect becomes decay time dependent

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

  22. 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

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

  24. 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 phase g Observation of CP Violation is a consequence of quantum interference!! Nikhef-evaluation

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

  26. Searching for new virtual particles J/y Bs f Tinyweakphase in couplings! Standard Model ? New Physics  Decay time Possibleweakphase in couplings! Nikhef-evaluation

  27. 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

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

  29. 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…

  30. The LHCb experiment qb qb LHCb experiment: 700physicists 50 institutes 15countries LHCb ATLAS CMS ALICE

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

  32. b-bdetection in LHCb Background Supression Flavourtagging Decay time measurement • 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

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

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

  35. LHCbTracking: vertexregion  Vertex locator around the interaction region Silicon strip detector with ~ 30 mm impact-parameter resolution

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

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

  38. LHCb tracking: momentum measurement Silicon: ~1.41.2 m2 All tracking stations have four layers: 0,-5,+5,0 degree stereo angles. Straw tubes ~65 m2 

  39. LHCb tracking: momentum measurement Red = Measurements (hits) Blue = Reconstructed tracks Eff = 94% (p > 10 GeV) ~1.41.2 m2  • TypicalMomentumresolutiondp/p ~ 0.4% • Typical Impact Parameter resolutionsIP ~ 40 mm

  40. LHCb Hadron Identification: RICH 3 radiators to cover full momentum range: Aerogel C4F10 CF4 RICH2:100 m3 CF4 n=1.0005 • RICH1: 5 cm aerogel n=1.03 • 4 m3 C4F10 n=1.0014 Cerenkovlightemissionangle  RICH: K/p separation e.g. to distinguish Dsp and DsK events.

  41. LHCb calorimeters e h  • Calorimeter system : • Identifyelectrons, hadrons, neutrals • Level 0 trigger: high electron and hadron Et (e.g. Ds K events)

  42. LHCb muon detection m  • Muon system: • Identifymuons • Level0 trigger: High Pt muons

  43. View of LHCb in Cavern Muondet Muondet Calo’s Calo’s Magnet Magnet RICH-2 RICH-2 OT RICH-1 RICH-1 OT VELO VELO It’s full! Installation of major structures is essentially complete

  44. Hope to soon see the firsteventsfrom…

  45. Display of LHCb simulatedevent

  46. PrepareBs→DsK Reconstruction… p 144 mm ,K 47 mm K Bs K Ds  d 440 mm • Trigger : • ET Calorimeters, Vertex topology • Flavour Tag: • Lepton-ID, Kaon-ID • Background suppression: • Mass resolution, K/p ID • Decay time: • Decay distance measurement • Momentum measurement Invariant Mass

  47. … to see time dependent CP violationsignal! The amplitude of these “wiggles“ are proportional to the imaginary part of the CKM phase gamma! 5 years data: Bs→Ds-p+ Bs→ Ds-K+ Decay time (ps) →

  48. Conclusion: after 5 years of LHCb… Expectederrorsafter 5 years(10 fb-1) of LHCb: CKM UnitarityTriangle in 2007: To makethis plot only Standard Model physics is assumed.

  49. Conclusion and Outlook LHCb The collaboration has organisedanalysisgroups and identified “hot topics”: • CP Violation • Measure the Bsmixingphase(Bs→J/yf) • Measure the CKM anglegamma via treemethod (Bs → DsK) • Measure the CKM anglegamma via penguinloops (B(s) → h+h -) • Rare Decays • MeasureBranching Ratio Bs→ m+m - • Measureangular distribution B0 → K* m+m - • Measureradiativepenguinsdecays: b → s g (B → Xsg ) • OtherFlavourPhysics • Anglebeta, B-oscillations, lifetimes, D-physics, Higgs,…? • Atlas and CMS look fornewphysics via direct production of particles • LHCbtries to studyit via the (possibly complex) couplings in B decay loop diagrams

  50. Summary of SignalEfficiencies

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