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Top Production Measurements with the D0 Detector

Top Production Measurements with the D0 Detector. Mike Arov (Louisiana Tech University) for D0 Collaboration. Outline. D0 Detector Top Production Cross Section Combination Search for Charged Higgs boson Measurement of the Forward-Backward Charge Asymmetry in Top-Antitop Production

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Top Production Measurements with the D0 Detector

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  1. Top Production Measurements with the D0 Detector Mike Arov (Louisiana Tech University) for D0 Collaboration

  2. Outline D0 Detector Top Production Cross Section Combination Search for Charged Higgs boson Measurement of the Forward-Backward Charge Asymmetry in Top-Antitop Production Search for ttbar Resonances in the Lepton+JetsFinal State

  3. muon system shielding electronics D0 Detector • One of the two detectors on the Tevatron • Run II at collision energy of 2 TeV since 2001 • 6.0 fb-1collected

  4. TAU ID TYPES Type 1 Type 2 Type 3 Top Production Cross Section with the D0 Detector • Dilepton channel • 2 jets • Topological cuts ee: • Two isolated electrons mm: • Two isolated muons • Lepton+tau channel • 2 jets • One  candidate with high Neural Network output (3 t types) • Jets matched to a  removed • One b-tagged jet et : • One isolated electron mt: • One isolated muon • Lepton+jets channel • 3 jets • One b-tagged jet • Missing ET e+jets: • One isolated electron m+jets: • One isolated muon

  5. Top Production Cross Section Results excellent agreement All included channels have with theory Top signal here is normalized to 7.9 pb

  6. Dominant uncertainties Top Production Cross Section Combination

  7. Top Production Cross Section Summary The combined result has mass dependence in agreement with SM theory And is the most precise measurement of top pair cross section so far

  8. Search for Charged Higgs boson • If H+ is lighter than top we can have the following scenarios:

  9. Tauonic model Leptophobic model Search for Charged Higgs boson

  10. Search for Charged Higgs boson

  11. Measurement of the Forward-Backward Charge Asymmetry in Top-Antitop Production • N+ is the number of events where top has larger rapidity then antitop, while N- is the number of events where it is smaller • In LO QCD it is 0, but in NLO it isn't due to interference between diagrams like these

  12. Measurement of the Forward-Backward Charge Asymmetry in Top-Antitop Production • The theoretical prediction is strongly shaped by acceptance and geometrical dilution due to incorrect charge reconstruction. • The dilution was measured and fitted in MC • Dilution can be used to compare any • theoretical model to measured result

  13. Asymmetry Fit and Results Phys. Rev. Lett. 100 , 142002 (2008 )

  14. Search for ttbar Resonances in the Lepton+JetsFinal State • Z' appears in many theories included topcolor-assisted technicolor • Narrow resonance can be discovered by looking at the invariant mass of top pairs • At the plots we can observe how the peak changes from SM 3 jets 4 jets

  15. Search for ttbar Resonances in the Lepton+JetsFinal State • Invariant mass was plotted for l+jets candidate events • Good agreement was observed and no resonant production signal 3 jets 4 jets

  16. Search for ttbar Resonances in the Lepton+JetsFinal State Using Mtt distributions the limit is set Less then 2s at 650 GeV For topcolor-assisted technicolor MZ' > 820 GeV

  17. Summary • Top physics at D0 is diverse research field covering both SM and beyond SM physics. • In this talk I presented our last combined and most precise measurements of top pair cross section. And I also showed H+ search, first top pair asymmetry measurement and search for resonant top pair production. • More exciting measurements and searches are to come as the full collected 6 pb-1 data set is analyzed.

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