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The BaBarians are coming

The BaBarians are coming. CP Results from BaBar. Neil Geddes. Standard Model CP violation BaBar Sin2 b The future.   CP. J/ Y K 0 s. B 0. B 0. B 0. The Aims. Standard Model CP Asymmetry:. CP violation in B mesons:. c. b. c. s. d. d.  = CP of final state

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The BaBarians are coming

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  1. The BaBarians are coming CP Results from BaBar Neil Geddes • Standard Model CP violation • BaBar • Sin2b • The future

  2.  CP J/YK0s B0 B0 B0 The Aims Standard Model CP Asymmetry: CP violation in B mesons: c b c s d d  = CP of final state = -1 forJ/YK0s, +1 for J/YK0L b = arg[-VcdVcb * /VtdVtb*] J/YK0s B0 uct d b Complex phase in CKM matrix produces different phases for B0anti-B0 and anti-B0B0 w w b d uct

  3. Bdp+p-,r±p ,... (r,h) a V*tbVtd V*ubVud g b (1,0) (0,0) V*cbVcd BdJ/y Ks,D*±D,.. B D±K (rescale sides by 1/|V*cbVcd| and choose V*cbVcd real ) Unitarity Triangle Quark mixing described bycomplex Cabibbo-Kobayashi-Maskawamatrix VCKM unitary  V†V = 1 V*i1V1j+V*i2V2j+V*i3V3j = 0/1

  4. Constraining The Triangle sin2b = (0.5, 0.8)

  5. Asymmetric B-factories e+e- (4s)  B0B0 (50%) B+B- (50%) e+ e- J/ B0 p+ Y(4s) 9GeV e- + 3.1GeVe+ U boosted in lab K0 _ B0 p- e, m K tag measure Dz~Dt PEP-II design luminosity 3x1033 cm-2sec-1 Small branching ratio for fCP + Continuous high precision running

  6. PEP-II and BaBar Canada China France Germany Italy Norway Russia UK USA ~600 Collaborators 9 Countries ~70 Institutions

  7. (5) 1.5 T Solenoid (4) Electromagnetic Calorimeter (6) Instrumented Iron Yoke (3) Cerenkov- Detector e+ e- (1) Silicon Vertex Detector (2) Drift Chamber The BaBar Detector

  8. Chronology • 1995 - Approval • 1998 - Construction completed • 1999 - Started taking data - events !! • 2000 - Taking data • 2,000,000 events per day,20,000 Bs per day • 2001 - Taking data • 20,000,000 events per day100,000 Bs per day • 2002 - “Results” • 120,000,000 Bs • 2002-2005 - Detailed results • 1,000,000 Bs per day first measurements first results

  9. The Method • Reconstruct CP eigenstates, J/YK0 • “tag” other B flavour • Measure Dz  Dt • Fit A(t) for sin(2b) B0 fCP (f+) • Complicated by: • Mistags • Finite time (vertex) resolution • Also need • B mass difference DM(B0) • B0 lifetime B0 fCP(f-)

  10. K0, p0 and J/Y Reconstruction K0sp+p-- K0sp0p0-

  11. Flavour Sample B Reconstruction Completely reconstruct many (anti-)B0’s B0  J/K*0(K+p-),D(*)-p+,D(*)- r+,D(*)- a1+ & c.c. Total sample ~6000 From this sample determine. A) Tagging efficiency B) Mistag fraction

  12. B Mixing Semi-leptonic decays di-lepton events Mistags Ameasured = Datrue Dilution D = 1-2w A = (Nu-Nm)/(Nu+Nm) DMB

  13. B0  (2s)K0s EMC IFR B0  J/K0s All K0smodes all CP B Reconstruction • For KL: • We do not know KL momentum. • We know direction • Impose MB constraint • Imply momentum • Measure DE B0  J/K0L

  14. e,m n c s b Tagging • Non CP vertex “tagged” as B or anti-B by: • Presence of charged lepton • Electron Pcm >1.0 GeV/c; Muon Pcm >1.1 GeV/c • Presence of charged Kaons •  Kaon Charge  0 • Overall event properties (l,K,slow-p...) Neural Network

  15. Bflavor eigenstates Bcharmonium Time Resolution • Dominated by vertex resolution for Tagging B • Common parameterisation for CP and flavour samples • Sum of three Gaussians: Core (88%), Tail (11%), and Outliers (1%) • Parameters determined from likelihood fit and other consistency checks Dz = 180 mm for tagging vertex,Dz = 70 mm for fully reconstructed vertex

  16. preliminary Mistags and s(t) Dm(B0) = (0.519 ± 0.020 ± 0.016)  ps-1 Flavour Sample Determines Mistag and Dt Resolution parameters Quality factor Q =e (1-2w)2. s(sin2b) a 1 / QNrec if no background

  17. Fit for sin2b sin2b is measured with a 35 parameter simultaneous fit to data flavour and CP samples: DmB and tB are fixed at the PDG world average values: DmB = 0.472 ps-1 tB = 1.548 ps

  18. Fit Parameters • Sin2b • 4 signal dilutions (D=1-2w) • 4 values of DD for the 4 signal categories • 9 parameters for the signal Dt resolution function • 8 background dilutions • 3 parameters describing the background resolution function • 1 parameter for the fraction of CP background • 5 parameters for the fractions and lifetime of the Bflav background

  19. 2b = 2b = Measured Asymmetries CP -1 CP +1 • sin2 = 0.34  0.20  0.05

  20. Cross Checks

  21. Systematic Errors

  22. BaBar, Belle and the Rest Feb 2001 Belle (~10 fb-1) sin(2b) = 0.58 ±0.33±0.1 BaBar (~22fb-1) sin(2b) = 0.34 ±0.20±0.05 Allowed region (blue) is determined using theoretical inputs and fitting many experimental measurements

  23. What if sin(2) is < 0.5 ? Standard model bound ~ 0.59  sin2 0.82 SM constraints are wrong because: • SM valid but: • |Vub|smaller than theoretically favoured range • SU(3) breaking in Bd0 /Bs0 mixing larger than favoured range • BK larger than theoretically favoured range • SM incomplete; new flavour violating and/or CP violating physics: • New contributions to Bd0 mixing and Bs0 mixing • New CP violating contribution to B0 mixing • New CP violating contribution to K0 mixing (and K) Eyal, Nir and Perezhep-ph/008009

  24. Covering the Angles B0d a B.R. ~ few 10- 6 Theoretically uncertain BABAR can measure the phase angles B0dDK B0dJ/K0S g b Very clean, Eff B.R. ~ 10- 4 Eff B.R ~10- 7; tough!!

  25. (fb-1) 18 12 6 ‘80 ‘90 ‘00 ‘80 ‘90 ‘00 Prospects CESR/CLEO (from CESR Web page) PEPII/BABAR 30 fb-1 ‘05

  26. Conclusions • PEP-II and BaBar collected/analysed ~25 fb-1 in 2000 • More than double our data by the end of the run in August • By 2005, we should accumulate ~ 500 fb-1 • Measure sin 2, compare sin 2 in individual modes • Measurements of direct CP violation and rare decays. • sin 2 = 0.34  0.20 0.05 The BaBarians have already arrived !

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