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Experimental Overview of B Physics

Experimental Overview of B Physics. Paoti Chang National Taiwan University 2004/11/19 Mini-workshop on Flavor Physics. Introduction. • Bottom quark was discovered in 1977.

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Experimental Overview of B Physics

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  1. Experimental Overview of B Physics Paoti Chang National Taiwan University 2004/11/19 Mini-workshop on Flavor Physics 1

  2. Introduction • Bottom quark was discovered in 1977. • Experiments tried to study B physics in the 80s/90s. − Fixed Target Experiments  Hard to trigger and dirty env. − e+ e-  U(4S)  BB Productive (CLEO and ARGUS ) −e+e-  Z/WW  bb  Good but limited by statistics − pp  bb  Leptons, secondary vertices (CDF) Need luminosity; no p0, h  LHC, LHCb and BTeV in 21 centry 2

  3. CP Violation • CP: Ccharge conjugate; Pparity CPV diff. prop. for matter and anti-matt. • Atiny CP Violation was observed in the Kaon system (1964). Obs. another CPV evidence 35 years later. • In 1973, Kobayashi & Masakawa proposed six quark flavor. 3

  4. KM Mechanism • CPV arises from a complex phase in the quark mixing matrix. = 4

  5. Motivation • CPV may be large in the B meson system. (B  J/y KS) • Is CP violation only due to a single weak phase? • Is there any new interaction beyond the standard model? • Measure the three angels • and size of the triangle. • Measure B meson property. • Rare B decays provide a • rich ground to understand • B decays. • It’s useful to search for • new physics. h r 5

  6. CP Violation in B Meson Decays Indirect CP Violation (Mixing + Tree interference) 6

  7. Mixing induced CPV Asymmetry  In Hadron collider experiments, Dt is the B0 decay time.  Measure the primary vertex (collision point) and decay vertex • In U(4S) experiments, Dt is the decay time differences between B0 and B0. How to measure Dt? 7

  8. Asymmetric e+e- Collider Piermaria Oddone 8

  9. Indirect CPV illustration • The difference in the t distributions indicates ICPV. • sin21 corresponds to the amplitude of ACP. • If the area of the red and blue are different  DCPV. • Search for DCPV in B decays to flavor specific states. 9

  10. Requirements to do B physics • Lots of Bs B factory • Able to reconstruct B vertices  Silicon D. • Good Particle identification • Able to detect photons and electrons  CsI(Tl) detector • Good m coverage and able to measure KL • Fast DAQ and lots of CPU and storages. 10

  11. The PEPII Collider (magnetic separation) On resonance: 221 fb-1 Int(L dt)= 244 fb-1 9 x 3.0 GeV; L=(9.2 x 1033)/cm2/sec 11

  12. The KEKB Collider (8 x 3.5 GeV, X angle) World record: L=(1.4 x1034)/cm2/sec Int(L dt)= 323 fb-1 On-resonance 295 fb-1 12

  13. Belle Collaboration Masashi Hazumi (KEK) Masashi Hazumi (KEK) ~54 Institutes ~300 members 13

  14. Superconducting Coil (1.5T) Silicon Vertex Tracker (SVT)[5 layers] e+ (3 GeV) e- (9 GeV) Drift Chamber [40 stereo lyrs](DCH) CsI(Tl) Calorimeter (EMC) [6580 crystals]. Cherenkov Detector (DIRC) [144 quartz bars, 11000 PMTs] Instrumented Flux Return (IFR) [Iron interleaved with RPCs]. BaBar Detector 14

  15. Belle Detector Aerogel Cherenkov cnt. n=1.015~1.030 SC solenoid 1.5T 3.5GeV e+ CsI(Tl) 16X0 TOF counter 8GeV e- EFC m / KL detection 14/15 lyr. RPC+Fe Si vtx. det. 3 lyr. DSSD 15

  16. B Meson Reconstruction • B candidates are identified by the beam constrained mass(Mb) 16

  17. Flavor Tagging Algorithm r =(1-2w)MC q = +1 Btag q =   Btag 17

  18. Vertex Reconstruction BD*ln Validated by B lifetimes tB0 = 1.55  0.02ps tB+ = 1.64  0.03ps PDG: 1.55  0.03ps PDG: 1.65  0.03ps 18

  19. Event by Event Likelihood b-flavor tag PDG wrong-tag frac. f= ±1 for CP=1 resolution function B-lifetime studies 19

  20. Results • Measurements on the unitarity triangle – sin(2f1/b) from b  ccs –sin(2f1/b)eff from b sss – f2/a and f3/g • Rare B decays: PP and VV • New particle states • Size of the triangle (Kim’s talk), theoretical interpretations (Li and Cheng), new physics (He) 20

  21. sin(21) Measurement from bccs • 2911 xf = -1 events included in the fit. • J/y KL: 2332 with a purity of 60%; xf = +1 140 fb-1 21

  22. Measurement of sin2f1 (Belle 2003) 140 fb-1 sin2f1=0.733±0.057±0.028 Poor tags |lccs| =1.007±0.041(stat) i.e., consistent with no direct CPV. Good tags 22

  23. Compare CP odd and CP even (Belle 2003) CP = -1 sample sin2f1 = 0.73±0.06 CP = +1 sample (B0gJ/y KL) sin2f1 = 0.80±0.13 23

  24. Measurement of f1(b) from BaBar J/ψ KL signal J/ψ X background Non-J/ψ background ΔE [MeV] 24

  25. (cc) KS (CP odd) modes BaBar Results with 205 fb-1 J/ψ KL (CP even) mode sin2β = 0.722  0.040 (stat)  0.023 (sys) 25

  26. 250 fb-1 Belle Update with 253 fb-1 S = 0.722  0.040 ± 0.023 A = 0.950  0.031  0.013 26

  27. Dream of New Physics with CPV in Rare Decays • In the SM for the pure bs transition, • sin(2 1)eff (bsss) = sin(2 1)(bccs) • Any deviation may mean new physics. • Decay Modes: B  KS ; B KS ; B KKKS;KsKsKs B f0 KS, wKS • NTU is involved in this search. 27

  28. Hunting for new phases in bs penguins dominant • Large exclusive and inclusive BRs. • New physics comes from the penguin loop. 28

  29. 274M BB pB* CPV in the B f KSdecay fKS fKL purity 0.63 purity 0.17 Nsig= 36 15 Nsig=139 14 fKS+fKL:S(fK0) = +0.06 0.330.09 A(fK0) = +0.080.220.09 ~2.2s away from SM Belle 29

  30. BaBar Result onB f KS 30

  31. S = 0.736 fit B0h’KS& K+K-KS high statistics modes K+K-KS (fexcluded) h’KS Belle Nsig=399 28 Nsig=512 27 h’rg, hp+p- (hgg, p+p-p0) purity 0.56 purity 0.61 CP=+1: 1.03 0.15 0.05 Raw Asymmetry Raw Asymmetry Good tags Good tags (~0.5s @SM) (~1.0s @SM) S = +0.65 0.18 0.04 -S = +0.490.18 0.04 ( ) A = -0.19 0.11 0.05 A = -0.08 0.12 0.07 0.17 0.0 0.17 0.00 31

  32. BaBar Results on KKKs 32

  33. BaBar Results on h′KS/ f0 Ks 33

  34. 274M BB S = 0.736 fit B0wKS& f0(980)KS additional modes Nsig=31 7 Nsig=102 18 purity 0.58 Belle purity 0.56 Raw Asymmetry Good tags Good tags (~0s @SM) (~2.9s @SM) S = +0.75 0.64 -S = -0.470.41 0.08 A = +0.26 0.48 0.15 A = -0.39 0.27 0.08 0.13 0.16 34

  35. S = 0.736 fit Another penguin modeB p0Ks Nsig=168 18 purity 0.55 Raw Asymmetry Good tags 35

  36. TCPV in B0gKsKsKs from Belle (~2.8s @SM) “sin2f1” = -1.26 0.68 0.18 A = +0.54 0.34 0.08 Poor tags Good tags 36

  37. sin2f1(bgsqq) = 0.39  0.11 (Belle) 0.42  0.10 (BABAR) sin2f1(bgsqq)= 0.41  0.07 sin2f1(bgccs) = 0.726  0.037 Summary of f1(b) Measurements World Average (WA) CL = 1.2 10-4 (3.8s) 37

  38. +Loops (penguins) f2 or a Extraction •  measure eff • need to bound |eff-| (shift from loops) • different |Penguin/Tree| for different decays 38

  39. B0p+p- Results 227×106 B pairs 152×106 B pairs 372 signal events 467 signal events LR preliminary S= 1.00 0.21 0.07 -A= -0.58 0.15 0.07 = C 39

  40. B0p+p- Continue • Belle has observed CPV • in B at a level of 5.2 • 3.2 evidence for direct • CPV from Belle • Not supported by BaBar • measurement >3 difference between BABAR and Belle results Average with care! 40

  41. ACP = 0.43  0.51  0.17 0.16 6.0s Observation ofB0p0p0 (227e6 B Pairs) 4.9s (274e6 B Pairs) Signal: 82  16 (6.0s) B = (2.32  ) x 10-6 0.44 0.48 0.22 0.18 First measurements of C00 41

  42. 42

  43. Isospin Correction for 2/ 43

  44. r0p0 r+p- r-p+ • +- is not a CP eigenstate • Cut on Dalitz plot to analyse  bands • Analyse Dalitz plot 44

  45. related to a Low Quality Tag High Quality Tag Quasi two-body Approach Belle Gronau & Zupan hep-ph/0407002 45

  46. CP Violating Observables: Non-CP Observables: Time dependent Dalitz Analysis Constraint on strong phase difference Between Convert measured parameters into CPV observables 46

  47. BABAR a From time-dependent Dalitz Analysis All strong phases And amplitudes extracted from DP [Theoretically Clean: SU(2)] BABAR CONF-04/038 47

  48. Summary on 2/ Measurement 48

  49. 3 () Extraction 49

  50. Gronau London Wyler method • B- D0CPK(*)-, where D0CP is a CP-eigenstate decay (CP+: D0 π+π-, K+K- CP-: D0 Ksπ0) • We have the following observables: • 4 observables (RCP+, RCP-,ACP+, ACP-)  determine 3 unknowns (rB,δB,) 50

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