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Cano Ay , Johannes Gutenberg Universität , ayc@uni-mainz.de

B mixing and flavor oscillations at D Ø. Cano Ay University Mainz for the D Ø Collaboration 23 may 2005 Frontiers in Contemporary Physics III Vanderbilt University Nashville, Tennesse. Cano Ay , Johannes Gutenberg Universität , ayc@uni-mainz.de. Outline. Motivation

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Cano Ay , Johannes Gutenberg Universität , ayc@uni-mainz.de

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  1. B mixing and flavor oscillations at DØ Cano Ay University Mainz for the DØ Collaboration 23 may 2005 Frontiers in Contemporary Physics III Vanderbilt University Nashville, Tennesse Cano Ay , Johannes Gutenberg Universität , ayc@uni-mainz.de

  2. Outline • Motivation • Mixing and Oscillation • Tevatron and DØ Detector • Flavor tagging • Bd Mixing Limit • Bs Mixing Limit • Prospects and plans • Summary FCP III , Cano Ay

  3. Motivation The ratio Dms/Dmd constrains one side of the unitarity triangle also study CP violation in Bs system studied in Kaon and Bd system Belle and Babar not sensitiv LHCB not running Tevatron currently only place to study Bs Mixing FCP III , Cano Ay

  4. Mixing Particle  Antiparticle The transition of a neutral particle into its antiparticle is called Mixing. FCP III , Cano Ay

  5. Unitarity triangle Standard Model expectation: Δms= 14 ....28ps-1 Δmd= 0.5ps-1 measurement of Δms/Δmd  Vts/Vtd constrain unitarity triangle FCP III , Cano Ay

  6. Mixing (2) high uncertainties f(QCD) reduce uncertainties by taking ratio Measure Dm  asymmetry FCP III , Cano Ay

  7. Mixing (3) • Mixing limit obtained using „Amplitude“ Method • Fit data to • Fit for A as a function of Dms • A peaks at 1 for a measurement • Sensitivity given by 1.645sA = 1 (95% CL) • Limit given by A<1-1.645sA (95% CL) • From the CKM fit:Dms~ 18 ps-1 • Heavy Flavor Averaging group: • combined LEP, SLD, CDF1 results • Dms > 14.5 ps-1 flavor tagging performanceresolutionselection FCP III , Cano Ay

  8. Tevatron Big advantage for B physics : Bs meson production FCP III , Cano Ay

  9. Luminosity 460pb-1 200pb-1 FCP III , Cano Ay

  10. D0 Detector SMT H-disks SMT F-disks SMT barrels • Semileptonic decays: • trigger on muon • good muon system • reconstruct tracks and vertex • good tracking system FCP III , Cano Ay

  11. Silicon Microstrip Tracker (SMT) • Silicon Microstrip Tracker • ~800.000 channels • point resolution: 10m • Secondary vertex resolution • 40m (r-) • 80m (r-z) • Trackers • Silicon Tracker: |η|<3 • Fiber Tracker: |η|<2 • Magnetic field 2T FCP III , Cano Ay

  12. Muon Sytem • 2 Tesla toroid magnet between A und • BC Layer  Muon momentum • propotional drift tubes • pixel scintillators • Muon system coverage ||<2 and • good shielding A minidrift tube with cover partially removed FCP III , Cano Ay

  13. B production and decay B production Fermilab: σ ≈ O(100μb) L1 Trigger acceptance (DØ: Muon) : σ ≈ O(3-5μb) Used Decays: B0s → D-s μnμ D-s → (K+K-)- B0d → D*(2010)-µ+nµ D*(2010)-D0(K+-)- B+ → D0µ+nµ D0 K-+ FCP III , Cano Ay

  14. Flavor tagging Flavor tagging : determine b-flavor at production time! opposite side reconstructed side oscillated not oscillated • Soft Lepton Tag (SLT) • Opposite Jet charge (Jetq) • Same Side Tag (currently only used for Bd) FCP III , Cano Ay

  15. Bd Sample • angle and distance : • distance PV  D Vertex (xy-plane) • D Vertex not before B Vertex • Angle between PV  B Vertex and PV  D Vertex • Charged tracks: • pT > 0.65 GeV/c • impact parameter significance: Single µ data – 200pb-1 FCP III , Cano Ay

  16. Bd Mixing Limit SLT : D0 = (44.85.1)% Jetq+SST: D0 = (14.91.5)% Jetq+SST: D = 27.9% Asymmetry Asymmetry Dmd=0.4560.034ps-1(stat) 0.025ps-1(syst) consistent with Dmd=0.5020.007ps-1 (world average) FCP III , Cano Ay

  17. Currently only using a single semileptonic decay of the Bs Bs Ds X (Ds  p) ( K K) Using  + SV vertex tag (Opposite side tag, independent of reconstructed side) The goal was to develop tools and to allow a baseline to build on for the future Bs Mixing analysis procedure FCP III , Cano Ay

  18. Bs Sample • Charged tracks: • pT > 0.7 GeV/c • impact parameter significance • Invariant KK mass • 1.006 < M(KK) < 1.30 • angle and distance : • distance PV  D Vertex (xy-plane) • D Vertex not before B Vertex • Angle between PV  B Vertex and PV  D Vertex • Angle between PV  D Vertex and D momentum • … FCP III , Cano Ay

  19. Inputs to the fitting procedure MC Sample composition K-factor to take non-reconstructed particles into account Efficiencies Visible Proper Decay Length (VPDL) resolution VPDL resolution has been tuned using data Dilution from B0d and B+u semileptonic samples Bs Mixing fitting procedure FCP III , Cano Ay

  20. Sample Composition and efficiency cc estimated at ~ 3.5 ± 2.5 % VPDL (cm) Efficiency drop at low VPDL due to impact parameter cuts on tracks from Ds decay FCP III , Cano Ay

  21. K-factors K K xVPDL FCP III , Cano Ay

  22. VPDL resolution parametrized with three Gaussians Track by track smearing dependant on track momentum and polar angle Tuning results with one scale factor 1.095 VPDL Resolution: MC tuned with data no smearing after smearing VPDLrec – VPDLgen [cm] FCP III , Cano Ay

  23. Dilution DØ Run II preliminary DØ Run II preliminary • SLT + SV Jetq : D0 = (39.03.2)% D = (47.62.0)% • use mean : Davr=(45.41.7)% for Bs asymmetry FCP III , Cano Ay

  24. Bs Mixing Limit No obvious oscillations in the μDssample Dms > 5.0 ps-1 at 95% CL using “Amplitude” method FCP III , Cano Ay

  25. Sensitivity vs. Luminosity Semileptonic channels • Scaling of the current sensitivity with luminosity • if analysis remains • unchanged • with expected • improvements FCP III , Cano Ay

  26. Use both semileptonic and hadronic Bs samples More statistics in semileptonics Better proper decay time resolution in hadronics (no n) DZero has access to hadronic Bs sample triggering on opposite side muon Muon is used as high purity tag Detector addition in fall: “Layer 0” Silicon detector Proposal to increase rate to tape from 50 to 100 Hz in fall sample limited by L3 trigger and offline CPU – expect large gain in yield thanks to dedicated B-physics bandwidth Bs Mixing Projections FCP III , Cano Ay

  27. Summary measured, which is in agreement with world average Dmd=0.4560.034ps-1(stat) 0.025ps-1(syst) developed a procedure to measure Dms using semileptonic channel BsDs() Dms > 5.0ps-1 at 95% CL will add more semileptonic channels and hadronic channels „Layer 0“ Silicon detector and increasing L3 rate will improve resolution and increase statistics FCP III , Cano Ay

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