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University of Chicago

Heavy Quarks, Bosons, & Photons. University of Chicago. Lecture 2: Things I would Like to See Measured at the Tevatron. Rick Field University of Florida. Enrico Fermi Institute, University of Chicago. CDF Run 2. Heavy Quark & Boson Production at the Tevatron.

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  1. Heavy Quarks, Bosons, & Photons University of Chicago Lecture 2: Things I would Like to See Measured at the Tevatron Rick Field University of Florida Enrico Fermi Institute, University of Chicago CDF Run 2 Rick Field – Florida/CDF

  2. Heavy Quark & Boson Production at the Tevatron • Total inelastic stot ~ 100 mb which is 103-104 larger than the cross section for D-meson or a B-meson. • However there are lots of heavy quark events in 1 fb-1! • Want to study the production of charmed mesons and baryons: D+, D0, Ds , lc , cc , Xc, etc. • Want to studey the production of B-mesons and baryons: Bu , Bd , Bs , Bc , lb , Xb, etc. with 1 fb-1 ~1.4 x 1014 ~1 x 1011 ~6 x 106 ~6 x 105 ~14,000 ~5,000 • Two Heavy Quark Triggers at CDF: • For semileptonic decays we trigger on m and e. • For hadronic decays we trigger on one or more displaced tracks (i.e. large impact parameter). CDF-SVT Rick Field – Florida/CDF

  3. Lxy ~ 1 mm B/D decay Primary Vertex Secondary Vertex CDF Impact Parameter( ~100mm) D0 K Selecting Heavy Flavor Decays • To select charm and beauty in an hadronic environment requires: • High resolution tracking • A way to trigger on the hadronic decays (i.e. a way to trigger on tracks) • At CDF we have a “Secondary Vertex Trigger” (the SVT). The CDFSecondary Vertex Trigger (SVT) • Online (L2) selection of displaced tracks based on Silicon detector hits. Collision Point Rick Field – Florida/CDF

  4. Selecting Prompt Charm Production Collision Point • Separate prompt (i.e. direct) and secondary charm based on their transverse impact parameter distribution. Prompt D Secondary D from B • Prompt D-meson decays point back to primary vertex (i.e. the collision point). • Secondary D-meson decays do not point back to the primary vertex. Prompt peak Direct Charm Meson Fractions: D0: fD=86.4±0.4±3.5% D*+: fD=88.1±1.1±3.9% D+: fD=89.1±0.4±2.8% D+s: fD=77.3±3.8±2.1% BD tail D impact parameter Most of reconstructed D mesons are prompt! Rick Field – Florida/CDF

  5. Prompt Charm Meson Production Charm Meson PT Distributions • Theory calculation from M. Cacciari and P. Nason: Resummed perturbative QCD (FONLL), JHEP 0309,006 (2003). Fragmentation: ALEPH measurement, CTEQ6M PDF. CDF prompt charm cross section result published in PRL (hep-ex/0307080) Data collected by SVT trigger from 2/2002-3/2002 L = 5.8±0.3 pb-1. Rick Field – Florida/CDF

  6. Comparisons with Theory Next step is to study charm-anticharm correlations to learn about the contributions from different production mechanisms: “flavor creation” “flavor Excitation” “gluon splitting” Ratio of Data to Theory • NLO calculations compatible within errors? • The pT shapes are consistent with the theory for the D mesons, but the measured cross section are a factor of about ~1.5 higher! Rick Field – Florida/CDF

  7. Bottom Quark Production at the Tevatron CDF Run 1 1999 Tevatron Run 1 b-Quark Cross Section • Important to have good leading (or leading-log) order QCD Monte-Carlo model predictions of collider observables. • The leading-log QCD Monte-Carlo model estimates are the “base line” from which all other calculations can be compared. • If the leading-log order estimates are within a factor of two of the data, higher order calculations might be expected to improve the agreement. • If a leading-log order estimate is off by more than a factor of two, it usually means that one has overlooked something. • I see no reason why the QCD Monte-Carlo models should not qualitatively describe heavy quark production (in the same way they qualitatively describe light quark and gluon production). QCD Monte-Carlo leading order “Flavor Creation” is a factor of four below the data! Extrapolation of what is measured (i.e. B-mesons) to the parton level (i.e. b-quark)! • “Something is goofy” (Rick Field, CDF B Group Talk, December 3, 1999). Rick Field – Florida/CDF

  8. Sources of Heavy Quarks Leading-Log Order QCD Monte-Carlo Model (LLMC) • We do not observe c or b quarks directly. We measure D-mesons (which contain a c-quark) or we measure B-mesons (which contain a b-quark) or we measure c-jets (jets containing a D-meson) or we measure b-jets (jets containing a B-meson). Leading Order Matrix Elements (structure functions) × (matrix elements) × (Fragmentation) + (initial and final-state radiation: LLA) Rick Field – Florida/CDF

  9. Amp(gg→QQg) = s(gg→QQg) = Other Sources of Heavy Quarks • In the leading-log order Monte-Carlo models (LLMC) the separation into “flavor creation”, “flavor excitation”, and “gluon splitting” is unambiguous, however at next to leading order the same amplitudes contribute to all three processes! “Flavor Excitation” (LLMC) corresponds to the scattering of a b-quark (or bbar-quark) out of the initial-state into the final-state by a gluon or by a light quark or antiquark. “Gluon-Splitting” (LLMC) is where a b-bbar pair is created within a parton shower or during the the fragmentation process of a gluon or a light quark or antiquark. Here the QCD hard 2-to-2 subprocess involves only gluons and light quarks and antiquarks. and there are interference terms! Next to Leading Order Matrix Elements 2 + + Rick Field – Florida/CDF

  10. Inclusive b-quark Cross Section Tevatron Run 1 b-Quark Cross Section • Data on the integrated b-quark total cross section (PT > PTmin, |y| < 1) for proton-antiproton collisions at 1.8 TeV compared with the QCD Monte-Carlo model predictions of PYTHIA 6.158 (CTEQ3L, PARP(67)=4). The four curves correspond to the contribution from “flavor creation”, “flavor excitation”, “gluon splitting”, and the resulting total. Total “Flavor Excitation” “Flavor Creation” “Gluon Splitting” Rick Field – Florida/CDF

  11. Conclusions from Run 1 • All three sources are important at the Tevatron and the QCD leading-log Monte-Carlo models do a fairly good job in describing the majority of the b-quark data at the Tevatron. • We should be able experimentally to isolate the individual contributions to b-quark production by studying b-bbar correlationsfind out in much greater detail how well the QCD Monte-Carlo models actually describe the data. • One has to be very careful when the experimenters extrapolate to the parton level and publish parton level results. The parton level is not an observable! Experiments measure hadrons! To extrapolate to the parton level requires making additional assumptions that may or may not be correct (and often the assumptions are not clearly stated or are very complicated). It is important that the experimenters always publish the corresponding hadron level result along with their parton level extrapolation. • One also has to be very careful when theorists attempt to compare parton level calculations with experimental data. Hadronization and initial/final-state radiation effects are almost always important and theorists should embed their parton level results within a parton-shower/hadronization framework (e.g. HERWIG or PYTHIA). “Nothing is goofy” Rick Field, Cambridge Workshop, July 18, 2002 All three sources are important at the Tevatron! MC@NLO! Rick Field – Florida/CDF

  12. J/   B K The Run 2 J/Y Cross Section • The J/y inclusive cross-section includes contribution from the direct production of J/y and from decays from excited charmonium, Y(2S), and from the decays of b-hadrons, B→ J/y + X. J/y coming from b-hadrons will be displaced from primary vertex! Down to PT = 0! 39.7 pb-1 Primary vertex (i.e. interaction point) Rick Field – Florida/CDF

  13. CDF Run 2 B-hadron Cross Section PRD 71, 032001 (2005) • Run 2 B-hadron PT distribution compared with FONLL (CTEQ6M). Cacciari, Frixone, Mangano, Nason, Ridolfi • Good agreement between theory and experiment! 39.7 pb-1 |Y| < 1.0 B-hadron pT Rick Field – Florida/CDF

  14. CDF Run 2 b-Jet Cross Section Collision point • b-quark tag based on displaced vertices. Secondary vertex mass discriminates flavor. • Require one secondary vertex tagged b-jet within 0.1 < |y|< 0.7 and plot the inclusive jet PT distribution (MidPoint, R = 0.7). Rick Field – Florida/CDF

  15. CDF Run 2 b-Jet Cross Section • Shows the CDF inclusive b-jet cross section (MidPoint, R = 0.7, fmerge = 0.75) at 1.96 TeV with L = 300 pb-1. • Shows data/theory for NLO (with large scale uncertainties). • Shows data/theory for PYTHIA Tune A. Rick Field – Florida/CDF

  16. The b-bbar DiJet Cross-Section • ET(b-jet#1) > 30 GeV, ET(b-jet#2) > 20 GeV, |h(b-jets)| < 1.2. Systematic Uncertainty Preliminary CDF Results: sbb = 34.5  1.8  10.5nb QCD Monte-Carlo Predictions: Differential Cross Section as a function of the b-bbar DiJet invariant mass! • Large Systematic Uncertainty: • Jet Energy Scale (~20%). • b-tagging Efficiency (~8%) Predominately Flavor creation! Rick Field – Florida/CDF

  17. “Flavor Creation” b-quark Initial - State Radiation Proton AntiProton Underlying Event Underlying Event Final - State b-quark Radiation The b-bbar DiJet Cross-Section • ET(b-jet#1) > 30 GeV, ET(b-jet#2) > 20 GeV, |h(b-jets)| < 1.2. Preliminary CDF Results: sbb = 34.5  1.8 10.5 nb QCD Monte-Carlo Predictions: Differential Cross Section as a function of the b-bbar DiJet invariant mass! JIMMY Runs with HERWIG and adds multiple parton interactions! JIMMY: MPI J. M. Butterworth J. R. Forshaw M. H. Seymour Adding multiple parton interactions (i.e. JIMMY) to enhance the “underlying event” increases the b-bbar jet cross section! Rick Field – Florida/CDF

  18. Top Decay Channels • mt>mW+mb so dominant decay tWb. • The top decays before it hadronizes. • B(W  qq) ~ 67%. • B(W ln) ~ 11% l = e, m, t. Rick Field – Florida/CDF

  19. s(tt) =  8.3 ± 1.5 (stat) ± 1.0 (syst) + 0.5 (lumi) pb Dilepton Channel • Selection: • 2 leptons ET > 20 GeV with opposite sign. • >=2 jets ET > 15 GeV. • Missing ET > 25 GeV (and away from any jet). • HT=pTlep+ETjet+MET > 200 GeV. • Z rejection. • Backgrounds: • Physics: Drell-Yan, WW/WZ/ZZ, Z tt • Instrumental: fake lepton 65 events 20 events background Rick Field – Florida/CDF

  20. s(tt) =  6.0 ± 0.6 (stat) ± 0.9 (syst) pb Lepton+Jets Channel Kinematics • Backgrounds: • W+jets • QCD • Selection: • 1 lepton with pT > 20 GeV/c. • >= 3 jets with pT > 15GeV/c. • Missing ET > 20 GeV. central • Use 7 kinematic variables in neural net to discriminate signal from background! One of the 7 variables! spherical binned likelihood fit Neural net output! Rick Field – Florida/CDF

  21. s(tt) =  8.2 ± 0.6 (stat) ± 1.1 (syst) pb Lepton+Jets Channel b-Tagging • Require b-jet to be tagged for discrimination. 1 b tag Tagging efficiency for b jets~50% for c jets~10% for light q jets < 0.1% 2 b tags HT>200GeV ~150 events ~45 events Small background! Rick Field – Florida/CDF

  22. Tevatron Top-Pair Cross-Section CDF Run 2 Preliminary Theory Bonciani et al., Nucl. Phys. B529, 424 (1998) Kidonakis and Vogt, Phys. Rev. D68, 114014 (2003) Rick Field – Florida/CDF

  23. CDF Mtop Results Transverse decay length! CDF Lepton+jets: Mtop (template) = 173.4 ± 2.5 (stat. + jet E) ± 1.3 (syst.) GeV Mtop (matrix element) = 174.1 ± 2.5 (stat. + jet E) ± 1.4 (syst.) GeV Mtop (Lxy) = 183.9 +15.7-13.9 (stat.) ± 5.6 (syst.) GeV CDF Dilepton: Mtop (matrix element) = 164.5 ± 4.5 (stat.) ± 3.1 (jet E. + syst.) GeV Rick Field – Florida/CDF

  24. Top Quark Mass Summer 2005 New since Summer 2005 Dilepton: CDF-II MtopME = 164.5 ± 5.5 GeV Lepton+Jets: CDF-II MtopTemp = 174.1 ± 2.8 GeV CDF-II MtopME = 173.4 ± 2.9 GeV CDF Combined: MtopCDF = 172.0 ± 1.6 ± 2.2 GeV = 172.0 ± 2.7 GeV Rick Field – Florida/CDF

  25. Top Cross-Section vs Mass Tevatron Summer 2005 CDF Winter 2006 CDF combined Updated CDF+DØ combined result is coming soon! Rick Field – Florida/CDF

  26. Is Anything “Goofy”? • Possible discrepancy between l + jets and the dilepton channel measurements of the top mass?? • Is it statistical? • Unlikely! • Is there a missing systematic? • This is probably nothing, but we should keep an eye on it! Rick Field – Florida/CDF

  27. Future Top Mass Measurements • Expect significant reduction in jet energy scale uncertainty with more data. • Today we have CDF-II Mtop(Temp) = 174.1 ± 2.8 GeV (~0.7 fb-1). • CDF should be able to achieve 1.5 GeV uncertainty on top mass! Rick Field – Florida/CDF

  28. Tevatron Run I + LEP2 Spring 2006 Constraining the Higgs Mass • Top quark mass is a fundamental parameter of SM. • Radiative corrections to SM predictions dominated by top mass. • Top mass together with W mass places a constraint on Higgs mass! Summer 05 Light Higgs very interesting for the Tevatron! Rick Field – Florida/CDF

  29. Top: Charge, Branching, Lifetime, W Helicity Top Lifetime Top Charge Everything consistent with the Standard Model (so far)! CDF Prelim. 318 pb-1 DØ Prelim. 365 pb-1 top< 1.75x10-13s ctop< 52.5m at 95%CL Exclude |Q| = 4/3 at 94% CL Reconstructed Top Charge (e) Impact Parameter (m) 370 pb-1 f+ (DØ combined) = 0.04 ± 0.11(stat) ± 0.06(syst) f+ (SM pred.) = 0 SM signal signal+bgrnd hep-ex/0603002 bgrnd Rick Field – Florida/CDF

  30. Strongly Produced tt Pairs g g Other Sources of Top Quarks • Dominant production mode NLO+NLL = 6.7  1.2 pb • Relatively clean signature • Discovery in 1995 ~85% ~15% ElectroWeak Production: Single Top • Larger background • Smaller cross section s≈ 2 pb • Not yet observed! Rick Field – Florida/CDF

  31. Single Top Production tW associated production s-channel t-channel (mtop=175 GeV/c2) Run I 95% C.L. B.W. Harris et al.:Phys.Rev.D66,054024 T.Tait: hep-ph/9909352 Z.Sullivan Phys.Rev.D70:114012 Belyaev,Boos: hep-ph/0003260 Rick Field – Florida/CDF

  32. Single Top Results from CDF • To the network 2D output, CDF applies a maximum likelihood fit and the best fits for t and s-channels are: The CDF limits! t-channel:  < 3.1 pb @ 95% C.L. s-channel:  < 3.2 pb @ 95% C.L. Rick Field – Florida/CDF

  33. Single Top at the Tevatron 95% C.L. limits on single top cross-section (2.9 pb) (0.9 pb) (2 pb) • The current CDF and DØ analyses not only provide drastically improved limits on the single top cross-section, but set all necessary tools and methods toward a possible discovery with a larger data sample! • Both collaborations are aggressively working on improving the results! Theory! We should see single top soon !!! Rick Field – Florida/CDF

  34. Top-AntiTop Resonances CDF Run 1 Excess is reduced! Phys.Rev.Lett. 85, 2062 (2000) • CDF observed an intriguing excess of events with top-antitop invariant mass around 500 GeV! Rick Field – Florida/CDF

  35. q g q  Direct Photon Cross-Section • DØ uses a neural network (NN) with track isolation and calorimeter shower shape variables to separate direct photons from background photons and p0’s! Note rise at low pT! Highest pT(g) is 442 GeV/c (3 events above 300 GeV/c not displayed)! Rick Field – Florida/CDF

  36. g + b/c Cross Sections L = 67 pb-1 • b/c-quark tag based on displaced vertices. Secondary vertex mass discriminates flavor. Rick Field – Florida/CDF

  37. g + b/c Cross Sections PYTHIA Tune A! L = 67 pb-1 g + b g + c • PYTHIA Tune A correctly predicts the relative amount of u, d, s, c, b quarks within the photon events. ET(g) > 25 GeV Rick Field – Florida/CDF

  38. g + g Cross Section L = 207 pb-1 QCD g + g g + gDf g + g mass • Di-Photon cross section with 207 pb-1 of Run 2 data compared with next-to-leading order QCD predictions from DIPHOX and ResBos. Rick Field – Florida/CDF

  39. Z-boson Cross Section L = 72 pb-1 QCDDrell-Yan • Impressive agreement between experiment and NNLO theory (Stirling, van Neerven)! Rick Field – Florida/CDF

  40. Z-boson Cross Section L = 337 pb-1 • Impressive agreement between experiment and NNLO theory (Stirling, van Neerven)! Rick Field – Florida/CDF

  41. Channel for Z→ττ: electron + isolated track One t decays to an electron: τ→e+X (ET(e)> 10 GeV) . One t decays to hadrons: τ → h+X (pT > 15GeV/c). Remove Drell-Yan e+e- and apply event topology cuts for non-Z background. Signal cone Isolation cone The Z→tt Cross Section • Taus are difficult to reconstruct at hadron colliders • Exploit event topology to suppress backgrounds (QCD & W+jet). • Measurement of cross section important for Higgs and SUSY analyses. • CDF strategy of hadronic τ reconstruction: • Study charged tracks define signal and isolation cone (isolation = require no tracks in isolation cone). • Use hadronic calorimeter clusters (to suppress electron background). • π0 detected by the CES detector and required to be in the signal cone. • CES: resolution 2-3mm, proportional strip/wire drift chamber at 6X0 of EM calorimeter. New Rick Field – Florida/CDF

  42. 1 and 3 tracks, opposite sign same sign, opposite sign The Z→tt Cross Section • CDF Z→ττ (350 pb-1): 316 Z→ττ candidates. • Novel method for background estimation: main contribution QCD. • τ identification efficiency ~60% with uncertainty about 3%! Rick Field – Florida/CDF

  43. Higgs → tt Search Let’s find the Higgs! events 140 GeV Higgs Signal! 1 event • Data mass distribution agrees with SM expectation: • MH > 120 GeV: 8.4±0.9 expected, 11 observed. • Fit mass distribution for Higgs Signal (MSSM scenario): • Exclude 140 GeV Higgs at 95% C.L. • Upper limit on cross section times branching ratio. Rick Field – Florida/CDF

  44. W-boson Cross Section • Extend electron coverage to the forward region (1.2 < |h| < 2.8)! W Acceptance 48,144 W candidates ~4.5% background overall efficiency of signal ~7% Rick Field – Florida/CDF

  45. 20 Years of Measuring W & Z Rick Field – Florida/CDF

  46. Z + b-Jet Production • Important background for new physics! • Leptonic decays for the Z. • Z associated with jets. • CDF: JETCLU, D0: MidPoint: • R = 0.7, |hjet| < 1.5, ET >20 GeV • Look for tagged jets in Z events. L = 335 pb-1 L = 180 pb-1 Extract fraction of b-tagged jets from secondary vertex mass distribution: NO assumption on the charm content. CDF DØ Assumption on the charm content from theoretical prediction: Nc=1.69Nb. Agreement with NLO prediction: Rick Field – Florida/CDF

  47. W + g Cross Sections ET(g) > 7 GeV R(lg) > 0.7 Rick Field – Florida/CDF

  48. Z + g Cross Sections Note: (W)/(Z) ≈ 4 while (W)/(Z) ≈ 11 ET(g) > 7 GeV R(lg) > 0.7 Rick Field – Florida/CDF

  49. W+W Cross-Section Campbell & Ellis 1999 Rick Field – Florida/CDF

  50. W+W Cross-Section L = 825 pb-1 We are beginning to study the details of Di-Boson production at the Tevatron! • WW→dileptons + MET • Two leptons pT > 20 GeV/c. • Z veto. • MET > 20 GeV. • Zero jets with ET>15 GeV and |h|<2.5. New Observe 95 events with 37.2 background! Missing ET! Lepton-Pair Mass! ET Sum! Rick Field – Florida/CDF

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