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Latest result of DZero@Tevatron

Latest result of DZero@Tevatron. 韩良 中国科学技术大学. Tevatron ： Fermilab Proton-Antiproton Collider. Chicago. Batavia, Illinois. DØ. DØ. Booster. p. Tevatron. p. Tevatron P-Pbar @ 1.96 TeV 2 x10 32 cm -2 s -1 CDF + D Ø. p sou rce. Main Injector & Recycler. 19 countries

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Latest result of DZero@Tevatron

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  1. Latest result of DZero@Tevatron 韩良 中国科学技术大学

  2. Tevatron：Fermilab Proton-Antiproton Collider Chicago Batavia, Illinois DØ DØ Booster p Tevatron p • Tevatron P-Pbar @ • 1.96TeV • 2x1032cm-2s-1 • CDF+DØ p source Main Injector & Recycler L.HAN@2007威海

  3. 19 countries 80 institutions 650+ physicists DØInternational Collaboration L.HAN@2007威海

  4. L.HAN@2007威海

  5. The D0 Detector • Silicon Micro-vertex Tracker (SMT) - up to |h|<3.0 - IP resolution ~ 10mm • Central Fiber Tracker (CFT) - up to |h|<1.6 - 10% at pT>40GeV • LAr+Ur EM-CAL, - e/g, up to|h|<3.0 • LAr+Cu HD-CAL - jet/met, up to|h|<4.0 • Muon in 1.8T Toroid - up to |h|<2 L.HAN@2007威海

  6. Accelerator and detector performance • Run 2a • Finished 03/2006 • Inst. lumi up to ~1.5x1032 cm-2s-1 • Delivered ~1.6 fb-1 • Run IIb • Started 06/2006 • Inst. lumi up to ~3x1032 cm-2s-1 • Delivered 3 fb-1 Run 2b Run 2a L.HAN@2007威海

  7. B physics L.HAN@2007威海

  8. B production at the Tevatron • bb cross section orders of magnitude larger than at B-factories (4S) or Z • σ(e+e-→ Z → bb) = 7nb • σ(e+e- → Υ(4S) → bb) = 1nb • (B+, pT  6 GeV, |y|<1@Tevatron)~4 mb • all kinds of b hadrons produced: • Bd, Bs, Bc, B**, b, b, … • However: • Overwhelming QCD, b-hadrons hidden in • 103 larger background • crucial for B physics program: • good vertexing & tracking • muon system w/ good coverage L.HAN@2007威海

  9. Bd oscillation frequency Bs oscillation frequency Bs Oscillation Vtd determination : CPviolation Unitarity in SM Measurement of Δms contributes to better determination of Vtd L.HAN@2007威海

  10. L.HAN@2007威海

  11. Opposite-side flavor tag (OST) Reconstructed Side X B μ(e) μ+ π- D-S f ν K- K+ Most Clean mode BsνμDs(φπ) Bs candidate (invi. mass/IP of tracks from f, Ds) at reco-side: • The sign of m Bs flavor at decay • Transverse length LT(Bs) • Transverse momentum PT(Bs) ~ PT(Dsμ) L.HAN@2007威海

  12. μD±X 7,422±281 μDsX 26,710±560 Dataset: Likelihood ration optimization on S/√B Improvement on reco-side Bs candidate Discriminator : • Helicity angle (Ds,K1) • Ds Isolation • pT(K1K2) • m(Ds) • 2 of Ds Vertex Fit • m(K1K2 or K1) L.HAN@2007威海

  13. tagging side μ- X B Initial Flavor Tagging Uncorrelated hadronization of two b-quark in PPbar interaction μ+ π- 37o D-S φ ν K- K+ Flavor discriminate variables: - muon jet charge - SV charge - event charge L.HAN@2007威海

  14. Likelihood ration from data (B+) • Single tagging variable • Calibrate with Bd Initial Initial d<0 d>0 Δmworld-average = 0.507 ± 0.004 ps-1 L.HAN@2007威海

  15. 1,519±96 5,601±102 OSTμ sample @ D0 (~1 fb-1) OST with tagging efficiency ~20% 7,422±281 26,710±560 L.HAN@2007威海

  16. X μ+ B μ(e) PV D-S π- LT(BS) φ PT(μDS) ν K- K+ Transverse Proper Decay Length • Visible Proper Decay Length (VPDL) • K factor for missing particles • Proper Decay L e.g. associated nm L.HAN@2007威海

  17. Asymmetry Amplitude Fitting Approach Dms>14.8ps-1@ 95% CL, deviation of 2.5s from A=0 at 19ps-1 L.HAN@2007威海

  18. Log Likelihood Scan Approach • PDFs: • Proper Decay L • Dilution • Mass • Systematic: • Resolution • K-factor variation • Br (BsDsX) • VPDL model -- 17<Dms<21 ps-1@90% CL assuming Gaussian error most probable value of 19 ps-1 -- CDF result as 17.33±0.42±0.07ps-1 L.HAN@2007威海

  19. Two same sign muons are detected w/ tagging legη=1.4 MKK=1.019 GeV, MKKπ=1.94 GeV PT(μBs)=3.4 GeV; PT(μtag)=3.5 GeV Tagging muon BS μ+ μ+ D-S π- K- K+ φ Oscillated BS candidate Y, cm X, cm L.HAN@2007威海

  20. CKM fit without new D0 result CKM fit with new D0 result -- First direct double sided precise measurement on the Bs oscillation frequency 17 < Dms< 21 ps-1 @ 90% CL -- Impact on the CKM Unitarity Triangle L.HAN@2007威海

  21. Sbdiscovery @ CDF L.HAN@2007威海

  22. Heavy Baryon spectrum L.HAN@2007威海

  23. Be able to observe: L.HAN@2007威海

  24. L.HAN@2007威海

  25. 1) 4 track decay of Lb 2) Determine background of data/PYTHIA , L.HAN@2007威海

  26. 3) Signal region observation: L.HAN@2007威海

  27. L.HAN@2007威海

  28. Xbdiscovery @ D0 L.HAN@2007威海

  29. Signal feature E. Jenkins, PRD 55 , R10-R12, (1997) Ξ-b→J/ψ + Ξ- -- Mass hierarchy M(Λb)< M(b-) < M(b), with CDF result as 5.624 < M(b) < 5.8 J/ -- 3 vertexes + 4 particles fully reconstructed -- PV lifetime: b ~ 0.1cm, - ~ 5cm,  ~ 5cm L.HAN@2007威海

  30. -- Cascade B baryon discovery: with signal significance ~ 5s -- Production ratio : L.HAN@2007威海

  31. 31 L.HAN@2007威海

  32. 1.3fb-1 2fb-1 L.HAN@2007威海

  33. Top studies L.HAN@2007威海

  34. W helicity Mass Charge CP violation Width Spin Anomalous coupling Production kinematics Production cross section Polarization Heavy resonance decay Branching ratios CKM :|Vtb| Rare decays L.HAN@2007威海

  35. Top Quark Production at Tevatron QCD pair production NLO = 6.7 pb (for mTop= 175 GeV) First observed at Tevatron in 1995 • EWK single-top production • s-channel: NLO = 0.9 pb • t-channel: NLO = 2.0 pb (Both for mTop= 175 GeV) • First evidence in Dec. 2006 • Other: ~85% ~15% s-channel t-channel ??? L.HAN@2007威海

  36. Lepton + Jets: Relatively clean with manageable backgrounds Dilepton: Cleanest but lowest statistics All Hadronic: Large branching fraction but formidable backgrounds Br(tWb) ~ 100% Top quark pair production xsection L.HAN@2007威海

  37. Important indirect test of many top quark properties  NLO calculation: 6.8 pb with ~13% uncertainty Lepton + Jets Dilepton HT>250 GeV Missing ET>30 GeV ≥1 tight tag L.HAN@2007威海

  38. CDF D0 Cross section measurement SM prediction @2TeV PPbar sNNLO ~ 6.8 ± 0.8 pb • Similar experimental and theoretical uncertainty • Working on Tevatron combination L.HAN@2007威海

  39. Top mass measurement -- Affect W boson mass at NLO -- Decide Higgs mass with W L.HAN@2007威海

  40. b combination resolution P/Pbar pdf Probability em-channel • #28 in 835pb-1 with high pT unlike signed e/m + 2 jets (wo b-tagging) • underconstrained for mt • Hypothesized mt  4 solutions with assigned weight maximize for the estimator of mt per event peak mass (missing information eg ISR/FSR shift) L.HAN@2007威海

  41. Peak mass • M.C. templates: signal tt(13 templates in 140-230GeV) + WW(ll) + Z(tt) etc • binned maximum likelihood fit L.HAN@2007威海

  42. Measure jets, not partons -- Calibrate the energy scale -- Associating jet with correct parton -- Extra jets add confusion Lepton + 4Jets Channel • What a theorist sees: • What an experimentalist sees: -- In-situ calibration using hadronic W decays -- Sophisticated analysis methods: matrix element, kinematic fit, etc. L.HAN@2007威海

  43. Event select in 370pb-1: high pT 1l + 4j, MET>20GeV, kinematic constrianed fit • Combined fit for 0,1,2 b-tagged jets, then event weighted for 24 possible j/n solutions • Full kinematic information + weighted solution  Likelihood where -- ftop, fraction of signal events in sample -- JES, jet energy calibration in situ Wqq, to reduce dominant systematic by fitting mt and JES simultaneously L.HAN@2007威海

  44. (Fit JES with maximum likelihood) L.HAN@2007威海

  45. -- Full Run2a large statistic sample : 170.9±2.2(stat+JES)±1.4(syst)GeV/c2 170.5±2.4(stat+JES)±1.2(syst)GeV/c2 L.HAN@2007威海

  46. Latest Tevatron Combination 170.9 ± 1.1(stat) ± 1.5(syst) GeV/c2 Run I result: 4.3 GeV uncertainty Latest Run II result: 1.8 GeV uncertainty -- Exceed original Run2 expectations due to in-situ jet energy scale calibration, namely statistic works on systematic L.HAN@2007威海

  47. First measurement on single top L.HAN@2007威海

  48. -- SM : direct access to |Vtb| -- Sensitive to NSM : L.HAN@2007威海

  49. -- Event selection L.HAN@2007威海

  50. -- Signal v.s. background : L.HAN@2007威海

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