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Observation of B 0 s – B 0 s Oscillations

Observation of B 0 s – B 0 s Oscillations. The CDF Collaboration. DPF Waikiki, HI 2 Nov 2006. Joseph Kroll University of Pennsylvania. 1 st St. Ocean City, NJ, Feb. 7, 2003, H 2 O 35 0 F. Results presented today are contained in two papers:. Abulencia et al. (CDF Collaboration)

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Observation of B 0 s – B 0 s Oscillations

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  1. Observation of B0s – B0s Oscillations The CDF Collaboration DPF Waikiki, HI 2 Nov 2006 Joseph Kroll University of Pennsylvania 1st St. Ocean City, NJ, Feb. 7, 2003, H2O 350 F

  2. Results presented today are contained in two papers: • Abulencia et al. (CDF Collaboration) • hep-ex/0609040, accepted by PRL • Abulencia et al. (CDF Collaboration) • Phys. Rev. Lett. 97 062003 (2006) Parallel session presentations: V. Tiwari (CMU) , J. Miles (MIT) J. Kroll (Penn)

  3. Two-State Quantum Mechanical System • Produce flavor states: M. Gell-Mann & A. Pais, Phys. Rev.,97, 1387 (1955) • Common decay modes ! 2-state QM system • States with mass & lifetime (neglecting CP violation) “Light” (CP-even) “Heavy” (CP-odd) J. Kroll (Penn)

  4. Antiparticle exists a time t! Form asymmetry A(t) = cos(mst) ms is oscillation frequency J. Kroll (Penn)

  5. Measure Amplitude versus Oscillation Frequency Time Domain Frequency Domain 2G Units: [m] = ~ ps-1. We use ~=1 and quote m in ps-1 To convert to eV multiply by 6.582£ 10-4 J. Kroll (Penn)

  6. Start 2006: Published Results on ms ms > 14.4 ps-1 95% CL Results from LEP, SLD, CDF I Amplitude method: H-G. Moser, A. Roussarie, NIM A384 p. 491 (1997) see http://www.slac.stanford.edu/xorg/hfag/osc/PDG_2006/index.html J. Kroll (Penn)

  7. April 2006: Result from the CDF Collaboration V. M. Abulencia et al., Phys. Rev. Lett. Vol. 97, 062003 (2006) Probability “Signal” is random fluctuation is 0.2% Under signal hypothesis: measure ms J. Kroll (Penn)

  8. Since then CDF has focused on turning evidence (3) into an observation (>5) Tevatron has delivered 2 fb-1 CDF has collected 1.6 fb-1 this analysis Use the same 1 fb-1 data set with improved analysis J. Kroll (Penn)

  9. Why is this Interesting? Flavor oscillations occur through 2nd order weak interactions e.g. C. Gay,Annu. Rev. Nucl. Part. Sci. 50, 577 (2000) From measurement of ms derive |V*tbVts|2 All factors known well except “bag factor” £ “decay constant” Calculated on lattice, uncertainty ~ 10% J. Kroll (Penn)

  10. B Meson Flavor Oscillations (cont) Well measured: md = 0.507 § 0.005 ps-1 (1%) (PDG 2006) Measure ms!ms/md Theoretical uncertainties reduced Ratio measures |Vtd/Vts| This is why ms is high priority in Run II from Lattice QCD calculations – see Okamoto, hep-lat/0510113 J. Kroll (Penn)

  11. Slide giving example of new physics J. Kroll (Penn)

  12. Experimental Steps for Measuring Bs Mixing 1. Extract B0s signal – decay mode must identify b-flavor at decay (TTT) Examples: 2. Measure decay time (t) in B rest frame (L = distance travelled) (L00) 3. Determine b-flavor at production “flavor tagging” (TOF) “unmixed” means production and decay flavor are the same “mixed” means flavor at production opposite flavor at decay Flavor tag quantified by dilution D = 1 – 2w, w = mistag probability J. Kroll (Penn)

  13. Schematic of Oscillation Event opposite-side K– jet charge J. Kroll (Penn)

  14. Key Experimental Issues flavor tagging power, background displacement resolution momentum resolution (L) ~ 50 m mis-tag rate 40% (p)/p = 5% J. Kroll (Penn)

  15. What’s Special About CDF & Tevatron Tevatron delivered required luminosity Unique trigger (SVT) large sample of completely reconstructed Bs Crucial for lifetime resolution & background reduction Inner layer of silicon (L00) provided decay distance resolution Detector for particle identification (TOF) made kaon identification possible high efficiency, high purity flavor tag J. Kroll (Penn)

  16. Hadronic { • } { } • B0s Decay Modes • Fully reconstructed (, 0) • better decay time resolution • Lower statistics • Signal 8,700 Semileptonic • Not fully reconstructed • poorer decay time resolution • Higher statistics • Signal 61,500 Majority of signal collected with displaced track trigger J. Kroll (Penn)

  17. Example: Fully Reconstructed Signal Cleanest decay sequence Four charged particles in final state: K+ K-+- Also use 6 body modes: J. Kroll (Penn)

  18. Semileptonic Signals J. Kroll (Penn)

  19. Decay position production vertex 25m £ 25 m Decay time in B rest frame Proper Time & Lifetime Measurement (B0s) = 1.??? § 0.0?? ps (statistical error only) PDG 2006: 1.466 § 0.059 ps J. Kroll (Penn)

  20. <t> = 86 £ 10-15 s ¼ period for ms = 18 ps-1 Oscillation period for ms = 18 ps-1 Decay Time Resolution: Hadronic Decays Maximize sensitivity: use candidate specific decay time resolution Superior decay time resolution gives CDF sensitivity at much larger values of ms than previous experiments J. Kroll (Penn)

  21. Correction Factor (MC) Decay Time Reconstructed quantity Semileptonics: Correction for Missing Momentum J. Kroll (Penn)

  22. Same Side Flavor Tags Charge of K tags flavor of Bs at production Need particle id TOF Critical (dE/dx too) Our most powerful flavor tag: D2 = 4-5% Opposite-side tags: D2 = 1.8% J. Kroll (Penn)

  23. Results: Amplitude Scan Sensitivity 31.3 ps-1 A/A = 6.1 Hadronic & semileptonic decays combined J. Kroll (Penn)

  24. Measured Value of ms Hypothesis of A=1 compared to A=0 - log(Likelihood) J. Kroll (Penn)

  25. Significance: Probability of Fluctuation Probability of random fluctuation determined from data 28 of 350 million random trials have L < -17.26 Probability = 8 £ 10-8(5.4) Have exceeded standard threshold to claim observation -17.26 J. Kroll (Penn)

  26. Asymmetry (Oscillations) in Time Domain J. Kroll (Penn)

  27. Determination of |Vtd/Vts| D. Mohapatra et al. (Belle Collaboration) PRL 96 221601 (2006) Previous best result: CDF J. Kroll (Penn)

  28. Summary of CDF Results on B0s Mixing A. Abulencia et al., hep-ex/0609040, accepted by Phys. Rev. Lett. Observation of Bs Oscillations and precise measurement of ms Precision: 0.7% Probability of random fluctuation: 8£10-8 ( 2.83 THz, 0.012 eV) Most precise measurement of |Vtd/Vts| J. Kroll (Penn)

  29. Backup & Alternate Slides J. Kroll (Penn)

  30. Weakly Decaying Neutral Mesons Flavor states (produced mainly by strong interaction at Tevatron) J. Kroll (Penn)

  31. Key Features of CDF for B Physics • “Deadtime-less” trigger system • 3 level system with great flexibility • First two levels have pipelines to reduce deadtime • Silicon Vertex Tracker: trigger on displaced tracks at 2nd level • Charged particle reconstruction – Drift Chamber and Silicon • excellent momentum resolution: R = 1.4m, B = 1.4T • lots of redundancy for pattern recognition in busy environment • excellent impact parameter resolution (L00 at 1.5cm, 25m £ 25m beam) • Particle identification • specific ionization in central drift chamber (dE/dx) • Time of Flight measurement at R = 1.4 m • electron & muon identification J. Kroll (Penn)

  32. candidate Example of Candidate Zoom in on collision pt. Same-side Kaon tag Opposite-side Muon tag J. Kroll (Penn)

  33. Measuring Resolution in Data Use large prompt D meson sample CDF II, D. Acosta et al., PRL 91, 241804 (2003) Real prompt D+ from interaction point pair with random track from interaction point Compare reconstructed decay point to interaction point J. Kroll (Penn)

  34. Time integrated oscillation probability J. Kroll (Penn) must measure proper time dependent oscillation to measure ms

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