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Emanuela Barberis Northeastern University, Boston for the CDF and D Ø collaborations

Top Quark Measurements at the Tevatron. Emanuela Barberis Northeastern University, Boston for the CDF and D Ø collaborations. - Introduction : Top quark physics at the Tevatron - Production of Top (Run II) - Top mass and properties (Run I&II)

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Emanuela Barberis Northeastern University, Boston for the CDF and D Ø collaborations

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  1. Top Quark Measurements at the Tevatron Emanuela Barberis Northeastern University, Boston for the CDF and DØ collaborations - Introduction: Top quark physics at the Tevatron - Production of Top (Run II) - Top mass and properties (Run I&II) - Summary and outlook Emanuela Barberis - DPF2003

  2. DØ • new inner tracking in 2T • (silicon&fiber trackers, • preshowers) • upgraded m detectors • upgraded trigger, DAQ.. CDF • upgraded silicon, new drift chamber, TOF • upgraded m detectors and calorimeter • upgraded trigger, DAQ.. CDF and DØ at the Fermilab Tevatron Run II: proton antiprotons collide@, upgraded detectors, higher luminosity Triggering and reconstruction of a top event involves all aspects of the detector Run II measurement ≡ progress in operation and understanding of the new detectors Emanuela Barberis - DPF2003

  3. Top Quark Production and Decay • in proton antiproton collisions at Tevatron energies, top quarks • are primarly produced in pairs • Br(t→Wb)=100% • Both W’s decay via Wl (l=e or ; 5%) • dilepton • One W decays via Wl (l=e or ; 30%) • lepton+jets • Both W’s decay via Wqq (44%) • all hadronic EW single top production: not yet observed Emanuela Barberis - DPF2003

  4. W helicity Top Mass l+ Top Width Anomalous Couplings Production cross-section Top Spin W+ CP violation Top Charge Resonance production p n t b Production kinematics _ b X _ Top Spin Polarization _ q’ t q Rare/non SM Decays W- _ p Branching Ratios |Vtb| Top Quark Physics in Run II Run I: discovery • Run II: • with high precision • we hope to answer • questions such as: • Why is top so heavy ? • Is it or the third generation special ? • Is top involved with EWSB ? • Is it connected to new physics ? Emanuela Barberis - DPF2003

  5. Production cross section Emanuela Barberis - DPF2003

  6. - N N obs bkg s = ( t t ) CDF dilepton DØ dilepton ò A L DØ topological Integrated luminosity CDF lepton-tag Acceptance×Efficiency DØ lepton-tag CDF SVX-tag CDF hadronic DØ hadronic CDF combined DØ combined Run I cross section results ~100 events Measured in Run I in all decay channels and using different techniques: b tagging, kinematic selection, Neural Networks • Run II top cross section (1.96 TeV) • ~ 30% higher than Run I (1.8 TeV) Emanuela Barberis - DPF2003

  7. Event selection (similar to Run I): • 2 high PT isolated charged leptons (e,m) • Neutrinos: large missing ET • At least 2 jets • Large transverse energy b  Backgrounds: • Physics: WW/WZ, • Drell Yan (Z/g*→ ee,mm), Z→tt • Instrumental: fake leptons in W+jets and QCD p b p E T t(→W+b) t(→W-b)  • Smaller yield • Cleaner signal (2 high PT leptons) • Smaller systematics (fewer jets) e+,m+ e-,m- in the dilepton channel, Run II Emanuela Barberis - DPF2003

  8. , CDF Run II • Two high pT isolated  or e with opposite charge • (ET,l/j)>20o • Z mass veto • ET>25 GeV • ≥ 2 jets, raw ET>10 GeV & || < 2.0 • HT=(ET,ElT,EjetT) >200 GeV Event selection Backgrounds • WW/WZ, Z→ tt determined with MC • Z/g* from data, QCD from data 79 pb-1 Emanuela Barberis - DPF2003

  9. , CDF Run II Run I Run II Emanuela Barberis - DPF2003

  10. Tracking view µ2 µ1 Jet1 Jet2 3 meters pT(1) = 57 GeV/c2 pT(2) = 53 GeV/c2 M = 69 GeV/c ETj= 32, 15 GeV ET=54 GeV HT=212 GeV Secondary vertex Lxy/xy= 14.6 dilepton candidate, CDF Run II +- + 2 jets Lego view µ2 µ1 Jet1 Jet2 • muon • electron • photon µ1 Primary vertex µ2 • muon • electron • hadron Jet1 Emanuela Barberis - DPF2003 Vertex view

  11. , DØ Run II • Two high pT isolated  or e • ET (Z mass) cut • ≥ 2 jets, ET>20 GeV & || < 2.5 • HT=(ElT,EjetT) cut em+jets Sum of jet, electron PT (GeV) em+jets Jet Multiplicity DØ Run II preliminary Event selection Backgrounds • WW, Z→ tt determined with MC • Z/g*, W+jets and QCD from data DØ Run II preliminary mm+jets ET (GeV) candidates Mmm (GeV) Emanuela Barberis - DPF2003

  12. and candidate, DØ Run II em mm ee Z→tt→ll WW→ll 0.02 ± 0.01 0.001± 0.001 0.02 ± 0.02 0.00 ± 0.00 0.02 ± 0.02 0.001 ± 0.001 Z→ll DY→ll QCD, W+jets -- -- 0.05 ± 0.01 0.20 ± 0.12 0.20 ± 0.21 0.18 ± 0.18 0.98 ± 0.48 All BG 0.07 ± 0.01 0.60 ± 0.30 1.00 ± 0.48 Expected Signal 0.50 ±0.01 0.3 ± 0.04 0.25 ± 0.02 Observed 1 2 4 pT(e) = 20.3 GeV/c2 pT() = 58.1 GeV/c2 ETj= 141.0, 55.2 GeV ET=91 GeV HT (e)= 216 GeV 33pb-1 42pb-1 48.2pb-1 Jet1 Tracking view Jet2 e+- + 2 jets Emanuela Barberis - DPF2003

  13. in the lepton+jets channel, Run II b p E T • Larger yield, and still relatively clean jet Event preselection: • 1 high PT isolated charged lepton (e,m). • Neutrinos: large missing ET • Large jet multiplicity • dilepton veto  Backgrounds: p b • W+jets and fake leptons in QCD jet Further selection & techniques: jet • from kinematic: ≥ 4 jets (DØ) • tag b jets with displaced VTX ≥ 3 jets, ≥ 1 b tag (CDF) • tag b jets with Soft Lepton Tag ≥ 3 jets, ≥ 1 SLT tag (DØ) jet t(→W±b) t(→W±b) e±,m± qq Emanuela Barberis - DPF2003

  14. One e or m with PT>20 GeV • Veto Z’s, cosmics, and conversions • ET>20 GeV • ≥ 3 jets with ET>15 GeV • ≥ 1 jet with secondary vertex tag (SVX) , CDF Run II Event selection jet Method Secondary vtx • Look for displaced vertices • (≥ 2 tracks), jet is tagged as • b jet if Lxy/xy >3 displaced tracks Lxy Primary vtx do • Efficiency of b tagging a tt event measure in tt MC, apply Data/MC scale factor prompt tracks (event tag) = 45  1  5 % Emanuela Barberis - DPF2003

  15. , CDF Run II , CDF Run II Backgrounds • Mistags: • from # tagged jets with • Lxy<0 in inclusive jet data • W+heavy flavor: • from W+jets data, b tag • rate, and Run I flavor • composition • Non W: • from data • WW, WZ, Z→tt: • from MC Emanuela Barberis - DPF2003

  16. , CDF Run II 57.5 pb-1 Emanuela Barberis - DPF2003

  17. Primary vertex Jet1 µ Lxy/xy= 10.8 µ Jet1 Secondary vertex Jet4 Lxy/xy= 21.9 3 meters Jet4 pT() = 54.4 GeV/c2 ETj= 96.7, 65,8, 54.8, 33.8 GeV ET= 40.8 GeV Jet3 Jet3 Jet2 Jet2 Vertex view Tracking view lepton+jets candidate, CDF Run II Jet3 Jet2 + 4 jets Jet1 Jet4 µ • muon • electron • photon Lego view • muon • electron • hadron Emanuela Barberis - DPF2003

  18. , DØ Run II Event selection Preselect a sample enriched in W events (loose e,m PT>20 GeV, ET>20 GeV, veto soft m) DØ Run II preliminary Backgrounds (analysis I, topology) • QCD multijet evaluated from data vs. Njets • e+jets: due to fake jets (po and g) • m+jets: due to heavy flavor decays • Estimate real W+4 jets with scaling law Scaling: # of W for N jets≥ 4 jets DØ Run II preliminary Emanuela Barberis - DPF2003

  19. 49.5pb-1 40pb-1 , DØ Run II Topological cuts • ≥ 4 jets • HT>180 GeV (e) • Aplanarity>0.06 • HT(jets,pWT)>220GeV (m) Missing ET Missing E T e+jets candidate (with lifetime tag) e e e e e 5 jets, ET = 32.1 GeV, HT = 422.6 GeV Aplanarity = 0.17, pT(e) = 34.2 GeV 40-49.5 pb-1 b-tag jet SV Emanuela Barberis - DPF2003

  20. 49.5pb-1 40pb-1 , DØ Run II SLT • Event selection • same preselection as kinematic analysis • ≥ 3 jets • softer topological cuts: • HT>110 GeV • Aplanarity>0.04 • soft muon within jet (b→m, b→c→m) Backgrounds: QCD and W+jets determined from data DØ Run II preliminary DØ Run II preliminary e+jets m+jets Emanuela Barberis - DPF2003

  21. , DØ Run II combined DØ Run II preliminary lepton+jets channels only all combined Emanuela Barberis - DPF2003

  22. Mass and properties Emanuela Barberis - DPF2003

  23. The top quark mass The top quark mass, mt, enters as a parameter in the calculation of radiative corrections to other Standard Model observables • mt can be related, with • mW, to the Higgs mass • mt is roughly ½ the vacuum expectation value of the Higgs field • better understanding • of EWSB mechanism? • to perform more precise tests we need: more data • and improved techniques Emanuela Barberis - DPF2003

  24. Top quark mass, CDF Run II • 33 candidates after event selection • (same as for cross section, no b tags). • 2C fit, 24 permutation, mass constraints • Maximum likelihood fit Will improve with detector understanding mfit (GeV) Emanuela Barberis - DPF2003

  25. b-tagged Top quark mass, CDF Run II • Cleaner sample: smaller • combinatorics, smaller • background • relaxed 4th jet requirement • 11 candidates Work in progress Emanuela Barberis - DPF2003

  26. Optimized techniques, DØ Run I mt Likelihood method using most available information resolutions, reconstruction effects Measured to be estimated Acceptance Matrix Element PDF’s LO ME used, 4 jets required exclusively, additional cut on background probability (to improve purity) → 22 events Likelihood definition: estimate signal and background fractions and mt Emanuela Barberis - DPF2003

  27. Optimized techniques, DØ Run I mt mtop (5.6 GeV from PRD 58 052001,1998) large improvement on the statistical uncertainty (~2.4 stats) mW Expect a substantial improvement in the JES systematic, and the application of this technique to many measurements Emanuela Barberis - DPF2003

  28. CDF Run I Preliminary n b t W y* l Top properties, W-helicity, CDF Run I • Measurements of top properties test the • Standard Model nature of top • CDF new Run I W helicity measurement: • dilepton and lepton+jets events with 1 and 2 SVX b tagged jets, fit to • of data to V+A and models • Preliminary (fV+A=0 in SM; fV+A=1 if all V+A) expect ± 0.1stat± 0.1sys for Run IIa M2lb = ½ (M2T – M2W)(1 + cos y* ) Emanuela Barberis - DPF2003

  29. Conclusions Cross section from Run II (CDF), dilepton and l+jets Cross section from Run II (DØ), combined Mass from Run II (CDF) Improved mass from Run I (DØ) W helicity from Run I (CDF) • Run II has started, we re-establishing signals and preparing for the top physics of large datasets: • Precise knowledge of mt (~1 GeV) to constrain Higgs/SM extensions. • EW single top production, top width • Couplings to W,g,g,Z, new physics Emanuela Barberis - DPF2003

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