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Probing the Top Mass from Leptons only: Preliminary Results

Probing the Top Mass from Leptons only: Preliminary Results. HEP2006 – April 13 th , Ioannina Victoria Giakoumopoulou. Signal. Lepton+jets 1 lepton Dilepton 2 leptons. Sources of Background. Lepton+jets W+jets Fakes Dilepton Diboson WW/WZ Z  τ + τ - Drell-Yan Fakes.

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Probing the Top Mass from Leptons only: Preliminary Results

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  1. Probing the Top Mass from Leptons only:Preliminary Results HEP2006 – April 13th , Ioannina Victoria Giakoumopoulou

  2. Signal • Lepton+jets • 1 lepton • Dilepton • 2 leptons

  3. Sources of Background • Lepton+jets • W+jets • Fakes • Dilepton • Diboson WW/WZ • Zτ+τ- • Drell-Yan • Fakes

  4. Dilepton Channel 2 leptons of opposite sign, with PT>20GeV at least 2 jets with |η|≤2.5 and ET≥15GeV Zveto for events in 76<Mll<106 GeV window MET>25GeV L-cut: MET>50GeV if Δφ(MET, lep or jet<200) H>200GeV Event Selection • Lepton+Jets Channel • 1 lepton with PT>20GeV • 4 jets with |η|≤2.5 and ET≥15GeV • MET>20GeV • H>200GeV (Sum of the Transverse Energy)

  5. Lepton+Jets: PT for Signal & BackgroundThe Fit

  6. Dilepton: PT for Signal The Fit

  7. Lepton+jets: Maximum LikelihoodMC @1fb-1 Min=175 Gev/c2  signal and background fit to PT  background fit to PT 206 Signal events of MTOP=175GeV/c + 296 Background events

  8. Lepton+jets: Linearity check 8 PseudoExperiments Mout=p0+p1Min

  9. Dilepton : Maximum LikelihoodMC @1fb-1 - Only signal Min=175 Gev/c2 50 Signal events of MTOP=175GeV/c

  10. Dilepton: Linearity check 25 PseudoExperiments Only Signal

  11. Lepton+jets: Statistical Error

  12. Lepton+jets: Statistical Error @Tevatron/LHC

  13. Systematic Uncertainties • ISR/FSR • PDF • Background • Shape • Normalization < 0.5 GeV • Generator

  14. Summary • Top Mass method using Leptons looks promising • Statistical Error • ±7 GeV by the end of RUNII (Tevatron) • <1 GeV by the end of second year (LHC) • Systematics • No jet energy scale • No b-jet energy • A small systematic error is expected (under study)

  15. BACKUP

  16. Outline • Top-antitop production and decay • Event selection • Preliminary results • PT spectrum • Fitting PT • Finding Top Mass with Maximum Likelihood Method • Statistical and Systematic errors

  17. e-e(1/81) mu-mu (1/81) tau-tau (1/81) e -mu (2/81) e -tau(2/81) mu-tau (2/81) e+jets (12/81) mu+jets(12/81) tau+jets(12/81) jets (36/81) Top Pair Production & Decay • W decays define channel: • Dilepton: 11.12% • Lepton+jets: 44.44% • All-hadronic: 44.44%

  18. PROTON g JET g q q g JET JET ¢ q q w ANTIPROTON W+jets background

  19. l p p q τ- γ*, Ζ* q p p gluon p p p p τ+ gluon jet jet Drell-Yan & Zτ+τ- backgrounds

  20. Methodology Outline Estimation of the Top Mass using the Lepton PT information • Lepton PT templates for the signal • PT is linearly dependent to the Top Mass • Herwig samples with Mtop=140-220GeV • Lepton PT templates for backgrounds • Fit the PT templates with Gamma x Fermi function • Implement Maximum Likelihood method to estimate the Top Mass

  21. Lepton+Jets: PT for Signal & Background

  22. Dilepton: PT for Signal & Background

  23. Fit Function • Parameterization of Pt where c=20GeV and b=0.1GeV • Fitting 21 PT histograms for Mtop = 140-220 GeV • Find the optimum mass dependent parameters p and q • Fitting combined background • Find the optimum parameters p and q

  24. Likelihood • N: number of data events • nbexp: expected number of background events • σnb: expected background uncertainty • ns: number of estimated signal events • nb: number of estimated background events

  25. Measurements of the Top Mass hep-ex/0507091

  26. Event Selection

  27. Systematics from other Template methods

  28. Mass from other Template Methods

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