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Results for Top and Higgs at Tevatron

Results for Top and Higgs at Tevatron. Outline. Tevatron CDF and D Ø Top quark studies Search for Higgs Summary. ICHEP 2004, August 16-22, Beijing China Dmitri Denisov, Fermilab. Top Quark Studies and Higgs Searches. Discovery of top quark at Fermilab in 1995

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Results for Top and Higgs at Tevatron

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  1. Results for Top and Higgs at Tevatron Outline Tevatron CDF and DØ Top quark studies Search for Higgs Summary ICHEP 2004, August 16-22, Beijing China Dmitri Denisov, Fermilab

  2. Top Quark Studies and Higgs Searches Discovery of top quark at Fermilab in 1995 Completed SM Quark Sector Studies of heaviest known elementary particle SM parameters, tests Beyond SM searches Higgs boson is last missing particle in SM Describes EWSM – particle masses Experimental challenges: low cross sections and substantial backgrounds Accelerator Detectors Analysis Tevatron currently is the only accelerator able to produce such heavy particles Dmitri Denisov, ICHEP04, August 21 2004

  3. Tevatron Parameters Run I Run IIa Run IIb Bunches in Turn 6  6 36  36 36 36 s (TeV) 1.8 1.96 1.96 Typical L (cm-2s-1) 1.6 1030 9 1031 3 1032  Ldt (pb-1/week) 3 17 50 Bunch crossing (ns) 3500 396 396 Interactions/ crossing 2.5 2.3 8 Run IRun IIa Run IIb 0.1 fb-1 Substantial upgrades for Run II: 2001-2009 10% energy increase: 30% higher stop integrated luminosity increase: x50 6 km long Tevatron ring Dmitri Denisov, ICHEP04, August 21 2004

  4. Tevatron Run II Performance 0.7 fb-1 1.1032 cm-2sec-1 1 week=168 hours Peak luminosity is above 1.1032 cm-2sec-1 Reliable operation  in stores ~120 hours/week Total ~0.7 fb-1 delivered in Run II  as planned Dmitri Denisov, ICHEP04, August 21 2004

  5. Tevatron Long Term Luminosity Plan To reach higher masses with the same energy  higher luminosity Increase in number of antiprotons  the key for higher luminosity Expected peak luminosity  3.1032 cm-2sec-1 by 2007 Currently expecting delivered luminosity to each experiment  4-8 fb-1 by the end of 2009 Today Dmitri Denisov, ICHEP04, August 21 2004

  6. CDF and DØ Experiments in Run II CDF DØ New Silicon Detector New Central Drift Chamber New End Plug Calorimetry Extended muon coverage New electronics Silicon Detector 2 T solenoid and central fiber tracker Substantially upgraded muon system New electronics Driven by physics goals detectors are becoming “similar”: silicon, central magnetic field, hermetic calorimetry and muon systems Dmitri Denisov, ICHEP04, August 21 2004

  7. Data Collection by Experiments CDF and D0 experiments are very complex Typical ratio of “recorded” to “delivered” luminosity is 80%-90% As of now both experiments recorded ~0.5 fb-1 Results presented correspond to ~0.2 fb-1 Analyzed data Analyzed data Dmitri Denisov, ICHEP04, August 21 2004

  8. Detection of High Pt Objects Electrons Muons Jets Top and Higgs final decay products  electrons  muons  jets (b)  missing Et (n) Detection and MC optimization using well known objects D0 Preliminary Missing Et b tagging Dmitri Denisov, ICHEP04, August 21 2004

  9. Top Quark Studies Heaviest known elementary particle: 180GeV  measure properties of least known quark  top quark mass constrains Higgs mass  sensitive to new physics  short life time: probe bare quark Dmitri Denisov, ICHEP04, August 21 2004

  10. Top Quark Production and Decays Decay Production In SM top decays 100% to Wb Classification of top decays is based on Ws decays Top quarks at Tevatron are (mainly) produced in pairs via strong interaction 85% 15% Top pair cross section at 1.96 TeV is 6.7 pb Top decays classification: di-lepton, lepton+jets, all jets Dmitri Denisov, ICHEP04, August 21 2004

  11. Selection of Top Quark Events “Di-lepton” mode has  low backgrounds: di-bosons, Drell-Yan, ...  but low statistics: ~5% for e, m decays “Lepton+jets” very productive mode  6 times more decays then di-lepton mode  main background W+jets  good purity after b tagging “All jets” mode  ~50% branching  high QCD backgrounds, jets combinatoric In triggering and analysis select events with  high Pt leptons  high Et multiple jets  large missing Et (n)  displaced vertex for b jets Dmitri Denisov, ICHEP04, August 21 2004

  12. DØ Top Cross Section in di-lepton Channel Topological selection  isolated (not in jet) high Pt ee(156 pb-1), mm(140 pb-1), em(143 pb-1) pair  2 or more jets  large missing Et Backgrounds: WW, Z+jets, W+jets, fakes D0 Run II Preliminary Ultra-pure sample of top events: S/N>50 Cross Section em only Extra b tag Dmitri Denisov, ICHEP04, August 21 2004

  13. CDF Top Cross Section in di-lepton Channel 197 pb-1 data sample for all channels  topological selection Combine ee, mm and em channels for best precision pb Dmitri Denisov, ICHEP04, August 21 2004

  14. CDF Top Cross Section in lepton+jets Channel l+jets topological l+jets with vertex b tagging l+jets with soft lepton tagging Exploit different strategies  higher statistics – topological  b-jets tagging  displaced vertex  soft lepton (m) Dmitri Denisov, ICHEP04, August 21 2004

  15. DØ Top Cross Section in lepton+jets Channel Selection of events (topological method)  high Pt lepton  large missing Et  4 or more jets (no b tagging) Form topological discriminant to optimize top events selection Single b tag Double b tag Tagging jets from b decays using displaced vertex algorithms reduces backgrounds substantially Dmitri Denisov, ICHEP04, August 21 2004

  16. Run II Top Quark Cross Section: Summary Errors between different channels are correlated Measurements demonstrate success of multiple top detection techniques Results within errors consistent with NNLO SM predictions for 1.96TeV of 6.7pb Dmitri Denisov, ICHEP04, August 21 2004

  17. Top Quark Mass Measurement Fundamental SM parameter Top mass together with EW data constrain Higgs mass Using Run I l+jets events (125 pb-1) DØ developed “matrix element method” Detailed knowledge of top quark decay and detector response is required  event by event likelihood calculated vs mt Phase space x LO ME Probability for observable x when y was produced (Ex: quark ET jet ET) PDFs Currently single most precise top mass measurement mt= 180.13.6(stat)3.9(syst) GeV Dmitri Denisov, ICHEP04, August 21 2004

  18. Run II Top Mass Measurement at CDF Run I style “template” method is efficiently used di-leptons l+jets, b tagged l+jets, multivariate Dynamical Likelihood Method is similar to D0 “matrix element method” Single most precise Run II measurement Dmitri Denisov, ICHEP04, August 21 2004

  19. Top Quark Mass Measurement at DØ in Run II Measurements in l+jets channel (~150 pb-1) template method uses templates for signal and background mass spectra ideogram method uses analytical likelihood for event to be signal or background Template Ideogram Template method mt= 1706.5(stat)+10.2/-5.7(syst) GeV Ideogram method mt= 177.55.8(stat)7.1(syst) GeV Dmitri Denisov, ICHEP04, August 21 2004

  20. Tevatron Top Quark Mass Measurement New combined Run I result  (Was mt= 174.35.1 GeV) mt= 178.04.3 GeV Run II top quark mass results from both detectors are available Systematic error (mainly jet energy scale) is becoming limiting accuracy factor TeV EWWG is working on combining Run II top mass measurement from CDF and DØ Dmitri Denisov, ICHEP04, August 21 2004

  21. Search for Single Top Quark Production EW production of top quark  direct probe of |Vtb|  search for new physics Events selection: is similar to top pairs in l+jets mode, but with lower jets multiplicity  backgrounds (W+jets, tt, di-bosons) are substantial Need above 1 fb-1 for observation Dmitri Denisov, ICHEP04, August 21 2004

  22. Unexpected Top Quark Decay Modes? Assuming three-generation CKM matrix unitarity, |Vtb|~1.0 R = BR(tWb)/BR(tWq) ~1.0 Can measure ratio by checking the b quark content of the top sample decay products If efficiency to tag a b quark is eb (~0.45 at CDF), then e2=(beb)2 e1=2beb(1-beb) e0=(1-beb)2 “double tag” “single tag” “no tag” R(eb-elight) BR(tWb)/BR(tWq) >0.62 at 95% C.L. Does top decays into something besides SM Wb?  Like Xb, where X  qq (100%) or Yb, where Y  ln (100%)? Estimate branching limits using ratio of top cross sections sll/slj Br(t  Xb) <0.46 at 95% C.L. Br(t  Yb) <0.47 at 95% C.L. (CDF) Dmitri Denisov, ICHEP04, August 21 2004

  23. Is Top to Wb vertex SM? W Helicity Test of V-A coupling in top decays: in SM W couples only to LH particles This together with angular momentum conservation allows top to decay into LH (negative helicity) or longitudinally-polarized (0 helicity) W bosons In SM F-=0.30, F0 =0.70, F+ =0 Helicity of W manifests itself in decay product kinematics CDF (l+jets and di-lepton) DØ (l+jets, 160 pb-1) F+ < 0.24 at 90% C.L. topological F+ < 0.24 at 90% C.L. b tagging No deviations from SM predictions Dmitri Denisov, ICHEP04, August 21 2004

  24. Experimental Limits on Higgs Mass • Available experimental limits • direct searches at LEP MH >114 GeV at 95% C.L. • precision EW fits Light Higgs favored LEP at 95% C.L. Tevatron provides: Precision mt and Mw measurements Direct searches  SM Higgs  non-SM Higgs Dmitri Denisov, ICHEP04, August 21 2004

  25. SM Higgs Production and Decays at Tevatron Decays Production Production cross section  in the 1 pb range for gg  H  in the 0.1 pb range for associated vector boson production Decays  bb for MH < 130 GeV  WW for MH > 130 GeV Search strategy: MH <130 GeV associated production and bb decay W(Z)H  ln(l) bb Backgrounds: top, Wbb, Zbb… MH >130 GeV gg H production with decay to WW Backgrounds: electroweak WW production… Dmitri Denisov, ICHEP04, August 21 2004

  26. SM Higgs Search: WH  lnbb (MH<130 GeV) DØ uses sample of W(en)+2 b tagged jets  Require exactly 2 jets to suppress top background 2.5 events expected and 2 events observed s(WH)xBR(Hbb) < 12.4 pb at 95% C.L. For MH =115 GeV CDF uses e and m channels Requires at least 1 jet b tagged Future improvements Extend b-tagging acceptance, efficiency Additional kinematic variables Better Mbb resolution Add bb channel Dmitri Denisov, ICHEP04, August 21 2004

  27. SM Higgs Search: H  WW  lnln (MH >130 GeV) e+ n W+ n W- e- DØ Run II Preliminary Search strategy:  2 high Pt leptons and missing Et  WW comes from spin 0 Higgs: leptons prefer to point in the same direction H Higgs of 160 GeV Dmitri Denisov, ICHEP04, August 21 2004

  28. Current Limits on SM Higgs Search Both experiments set 95% C.L. on SM Higgs cross section x Br Limits already exceeding Run I results DØ light (115 GeV) Higgs search limit s(WH)xBR(Hbb) < 12.4 pb-1 at 95% C.L. Dmitri Denisov, ICHEP04, August 21 2004

  29. Tevatron SM Higgs Search: Outlook LEP Ldt, fb-1 Updated in 2003 in the low Higgs mass region W(Z)Hln(nn,ll)bb to include  better detector understanding  optimization of analysis Tevatron Sensitivity in the mass region above LEP limit starts at ~2 fb-1 Meanwhile  optimizing analysis techniques  understanding detectors better  searching for non-SM Higgs with higher production cross sections or enhanced branching into modes with lower backgrounds Dmitri Denisov, ICHEP04, August 21 2004

  30. Search for MSSM Higgs MSSM predicts larger Higgs cross sections for some values of parameter space then SM Using NLO cross section calculations and assuming no difference between A and h/H DØ performs search for MSSM Higgs  multi-jet high Et sample 3 or more jets b tagged Dmitri Denisov, ICHEP04, August 21 2004

  31. Search for MSSM Higgs CDF searches for With A decaying into tt pair  ~8% branching at high tanb  lower backgrounds then bb pairs No excess seen over backgrounds Dmitri Denisov, ICHEP04, August 21 2004

  32. Search for H++/H-- l + q H++ l + */Z l - H-- q l - Predicted by some beyond SM models like Left-Right Symmetric Models If short lived:  prominent signature – multiple high Pt leptons, like sign di-lepton mass peak  backgrounds: WZ, W+jets, conversions (e) If long lived (ct > 3 m):  two high ionization tracks D0 (113 pb-1) M(HL) > 118 GeV (mm) at 95% C.L. CDF (240 pb-1) M(HL) > 136 GeV (mm) at 95% C.L. Background < 10-5 MH>134GeV Dmitri Denisov, ICHEP04, August 21 2004

  33. Tevatron Top and Higgs: Summary Many excellent talks about top and Higgs studies at Tevatron are presented at ICHEP04 EW, Beyond SM, Heavy Quarks sessions Top studies are actively progressing:  updated stt, mt , limits on single top production  studies of SM predictions and beyond SM models  W helicity studies  decay modes: Wq, WX, Xq...  tt resonances,… No deviations from SM observed (yet) Higgs search is in progress:  SM Higgs  sensitivity (mH >114 GeV) starts at ~2 fb-1  non-SM Higgs  many different models tested  already see reduction in allowed phase space (Run I, LEP) Expect substantial improvements in top studies, Higgs hunting with ~0.5 fb-1 already on tapes ~8 fb-1 expected in Run II Dmitri Denisov, ICHEP04, August 21 2004

  34. Expected Run II Top Quark Studies Accuracy Dmitri Denisov, ICHEP04, August 21 2004

  35. Search for H gg • In the SM Higgs gg has Br~10-3 •  search for SM Higgs decaying to gamma pair is not practical at Tevatron • Many SM extensions allow enhanced gamma pair decay rate largely due to suppressed coupling to fermions •  Fermiphobic Higgs • Topcolor Higgs • Search strategy: • Look for peaks in gg mass spectrum for high Pt isolated g’s Dmitri Denisov, ICHEP04, August 21 2004

  36. Experimental Challenges Collecting data at energy frontier is non-trivial Large particle fluxes  irradiation issues Small bunch spacing and large number of interactions per crossing  event synhronization  complex event topology Unexpected… Not new physics, just welding induced noise resolved CDF central tracking chamber aging resolved Dmitri Denisov, ICHEP04, August 21 2004

  37. Resonances in tt system? No resonance production in tt system is expected in SM Some models predict tt bound states, example: topcolor-assisted technicolor  predicts leptophobic Z’ with strong 3rd generation coupling Experimental check: search for bumps in tt effective mass spectrum DØ, 125 pb-1 Total Top MX > 560 GeV Background Dmitri Denisov, ICHEP04, August 21 2004

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