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Lepton Fakes in ~ 840 /nb

Lepton Fakes in ~ 840 /nb. 26 August 2010. Intro & Selections. Reference current ttbar selections New: Mt < 25 Electrons: endcap alignment correction for data, no Δη Data & Monte Carlo samples listed at the end . W contribution to QCD Fake Rates.

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Lepton Fakes in ~ 840 /nb

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  1. Lepton Fakes in ~ 840 /nb 26 August 2010

  2. Intro & Selections • Reference current ttbar selections • New: Mt < 25 • Electrons: endcap alignment correction for data, no Δη • Data & Monte Carlo samples listed at the end

  3. W contribution to QCD Fake Rates • We want to measure the rate of fake leptons from QCD in data • Leptonic W decays will contribute to some extent • We have so far required low MET ( tcmet < 20 GeV ) to reduce the contribution from W • We now require low transverse mass also ( Mt < 25 ) • What effect does the presence of W have on the fake rate?

  4. Electron Fake Rates in Monte Carlo V1 Fake Rate V2 Fake Rate V3 Fake Rate QCD_Pt30 Only QCD_Pt30 + Weν ( No cuts on MET or Mt ) Presence of W does not dominate Fake Rate - W contribution introduces some bias - QCD prevails

  5. Muon Fake Rates in Monte Carlo Fake Rate Dominated by W InclusiveMu15 + Wmunu InclusiveMu15 + Wmunu - tcmet< 20 AND Mt < 25 InclusiveMu15 InclusiveMu15 - tcmet< 20 AND Mt < 25 W contribution suppressed by requiring low MET and Mt - We have been requiring tcmet < 20, we now require Mt < 25 also - W domination delayed by ~10 GeV in Pt - underlying QCD Fake Rate unaffected

  6. Muon Fake Rates – Comparison of Data and Monte Carlo Luminosity ~ 840 / nb Data ( HLT_Mu9 AND 15 GeV Offline Jet ) MC InclusiveMu15 + Wmunu MC InclusiveMu15 W evident in Data also - Good data / MC agreement - W starts to dominate above ~ 35 GeV How do we estimate the fake rate for Pt > 35 where W is irreducible? - Simply use the fake rate from the 30-35 GeV Pt bin for Pt > 35 GeV - QCD background peaks at low Pt and QCD FR is somewhat flat - Alternatively, use fake rate from b tagged jets

  7. Fake Rates - Jet vs. Lepton Triggered • Lepton fake rates have so far been determined from jet triggered ( HLT_Jet15U ) samples • Then require offline lepton away from jet trigger • Jet triggers are now heavily prescaled • HLT_Jet15U prescale is now 200 ( 4.1 v3 at 3.5x1030 ) • Alternatively, can derive fake rates from lepton triggered samples ( Mu9, Ele10_LW_L1R ) • Then apply threshold to offline jet away from lepton • Lepton & Jet triggers should give the same result • Lepton triggers offer more statistics

  8. Electron Fake Rates in DataComparison of Jet & Lepton Triggers Luminosity ~ 840 / nb V1 Fake Rate V2 Fake Rate V3 Fake Rate HLT_Jet15U HLT_Ele10_LW_L1RAND 15 GeV Offline Jet Jet & Lepton Triggered Fake Rates are Comparable - Lepton Triggered samples offer higher statistics

  9. Muon Fake Rates in DataComparison of Jet & Lepton Triggers Luminosity ~ 840 / nb HLT_Jet15U HLT_Mu9 AND 15 GeV Offline Jet All Runs Runs before 137000 Jet & Lepton Triggered Fake Rates Agree Before Run 137000 -Difference after run 137000 not yet understood -Lepton triggered samples offer higher statistics

  10. Jet Threshold Dependence of Lepton Fake Rates • Systematic errors are estimated by measuring the dependence of the fake rate on the jet threshold • Comparison of lepton triggered fake rates with different offline jet pt thresholds are shown on the following slides

  11. Muon Fake Rates in DataDependence on Jet Threshold Luminosity ~ 840 / nb HLT_Mu9 5 GeV 15 GeV 30 GeV 50 GeV Systematics ~ 50% Isolation relaxed ( 0.15 to 0.40 ) in the muon fake rate denominator

  12. Electron Fake Rates in DataDependence on Jet Threshold HLT_Ele10_LW_L1R 5 GeV 15 GeV 30 GeV 50 GeV Luminosity ~ 840 / nb V1 Fake Rate V2 Fake Rate V3 Fake Rate Systematics ~ 50% V2 fake rate ( which does not relax isolation) shows least dependence on jet threshold

  13. Summary • Leptons from W decay pollute QCD fake rates • Results in tolerable bias for electrons • Muon fake rate is dominated by W above ~ 35 GeV in spite of requiring low MET and Mt. • Solution: Extend fake rate from lower Pt or require b tagged jets • Fake rates derived from lepton triggers offer more statistics than those from jet triggers • Jet Threshold • Systematics ~ 50%

  14. Samples • /InclusiveMu15/Spring10-START3X_V26_S09-v1/GEN-SIM-RECO • /QCD_Pt30/Spring10-START3X_V26_S09-v1/GEN-SIM-RECO • /Wenu/Spring10-START3X_V26_S09-v1/GEN-SIM-RECO • /Wmunu/Spring10-START3X_V26_S09-v1/GEN-SIM-RECO • /MinimumBias/Commissioning10-SD_EG-Jun14thSkim_v1/RECO • /EG/Run2010A-Jun14thReReco_v1/RECO • /EG/Run2010A-Jul16thReReco-v2/RECO • /EG/Run2010A-PromptReco-v4/RECO • /MinimumBias/Commissioning10-SD_Mu-Jun14thSkim_v1/RECO • /Mu/Run2010A-Jun14thReReco_v1/RECO • /Mu/Run2010A-Jul16thReReco-v1/RECO • /Mu/Run2010A-PromptReco-v4/RECO • /MinimumBias/Commissioning10-SD_JetMETTau-Jun14thSkim_v1/RECO • /JetMETTau/Run2010A-Jun14thReReco_v2/RECO • /JetMETTau/Run2010A-Jul16thReReco-v1/RECO • /JetMETTau/Run2010A-PromptReco-v4/RECO

  15. Backup Slides

  16. Run Dependence of Muon Fake Rate HLT_15u HLT_Mu9 AND 15 GeV Offline Jet All Runs Runs > 136500 Runs < 137000 Runs > 137000 Runs < 139000 Runs > 139000 Runs < 141000 Runs > 141000 Runs < 143000 Discrepancy between Jet & Lepton triggered FR for runs>137000 not understood

  17. Difference between Jet15U and Muon triggers at high PT? • This was also seen earlier in the summer • The most likely explanation was that of a run dependence • Jet15U samples the very earliest runs • Muon triggers are uniform • We need to verify this again by making the same plots as the previous page but broken up in run periods • Slide from this summer are in backup (as a reminder of what we had then)

  18. Slide circulated in an emai message by Claudio on 10 July 2010

  19. Slide circulated in an emai message by Claudio on 10 July 2010

  20. Slide circulated in an emai message by Claudio on 10 July 2010

  21. Electron Fake Rates in Monte Carlo Numerator & Denominator Pt distributions QCD_Pt30 Only Weν Only QCD_Pt30 + Weν Num V1 Den V2 Den V3 Den Fake Rates QCD_Pt30 Only QCD_Pt30 + Weν V1 Fake Rate V2 Fake Rate V3 Fake Rate Presence of W does not dominate Fake Rate at high Pt

  22. Muon Fake Rates in Monte Carlo Fake Rate Numerator Denominator InclusiveMu15 + Wmunu InclusiveMu15 Wmunu W dominates Fake Rate above ~ 25 GeV

  23. Muon Fake Rates – Comparison of Data and Monte Carlo Fake Rate Numerator Denominator Luminosity ~ 840 / nb Data ( HLT_Mu9 AND 15 GeV Offline Jet ) InclusiveMu15 + Wmunu InclusiveMu15 Wmunu • W Supression: • tcmet< 20 • Mt < 25 W evident in Data also - Good agreement between data and Monte Carlo - W starts to dominate above ~ 35 GeV

  24. Muon Fake Rates in DataDependence on Muon Trigger Luminosity ~ 840 / nb • W Supression: • tcmet< 20 • Mt < 25 Fake Rate stable for different Muon triggers

  25. Electron Fake Rates in DataComparison of 10 & 15 GeV Lepton Triggers Luminosity ~ 840 / nb V1 Fake Rate V2 Fake Rate V3 Fake Rate HLT_Ele10_LW_L1R HLT_Ele15_LW_L1R W Supression: tcmet< 20, Mt < 25 Electron 10 & 15 triggers are comparable

  26. Electron Fake Rates in DataComparison of 10 GeV Lepton Triggers Luminosity ~ 840 / nb V1 Fake Rate V2 Fake Rate V3 Fake Rate HLT_Ele10_LW_L1R HLT_Ele10_SW_L1R HLT_Ele10_LW_EleId_L1R HLT_Ele10_SW_EleId_L1R W Supression: tcmet< 20, Mt < 25 Trigger ID cancels out in V3. V1 & V2 have no offline ID. Trigger ID decreases the denominator, increasing the Fake Rate Trigger ID increases V1 & V2 Fake Rates

  27. Electron Fake Rates in DataComparison of 15 GeV Lepton Triggers Luminosity ~ 840 / nb V1 Fake Rate V2 Fake Rate V3 Fake Rate HLT_Ele15_LW_L1R HLT_Ele15_SW_L1R HLT_Ele15_SW_EleId_L1R HLT_Ele15_LW_CaloEleId_L1R W Supression: tcmet< 20, Mt < 25 Trigger ID increases V1 & V2 Fake Rates

  28. Electron Selections • ttbar: Tight Electron Selections • Pt > 10 • SC Et > 10 • |η| < 2.5 • ECAL Seeded • Spike Removal • VBTF 90 ID • Data corrected for Endcap alignment • dEta cut removed • d0 < 400 • Iso< 0.15 • No muon with dR of 0.10 • Conversion Rejection • Hit Pattern • Dist < 002 • Dcottheta< 002 • Loose Electron Selections • d0 removed for V1, V2, V3 • V1: V2 AND V3 • V2: Electron ID removed • V3: Isolation relaxed to 0.40

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