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 2

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? 3

Electron Fake Rates in Monte Carlo QCD_Pt30 Only QCD_Pt30 + Weν V1 Fake RateV3 Fake RateV2 Fake Rate Presence of W does not dominate Fake Rate - W contribution introduces some bias - QCD prevails 4 ( No cuts on MET or Mt )

Muon Fake Rates in Monte Carlo 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 InclusiveMu15 + Wmunu - tcmet< 20 AND Mt < 25 InclusiveMu15 - tcmet< 20 AND Mt < 25 5 Fake Rate Dominated by W

Muon Fake Rates – Comparison of Data and Monte Carlo 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 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 Data ( HLT_Mu9 AND 15 GeV Offline Jet ) MC InclusiveMu15 + Wmunu MC InclusiveMu15 Luminosity ~ 840 / nb 6

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 3.5x10 30 ) 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 7

Electron Fake Rates in Data Comparison of Jet & Lepton Triggers Luminosity ~ 840 / nb HLT_Jet15U HLT_Ele10_LW_L1RAND 15 GeV Offline Jet Jet & Lepton Triggered Fake Rates are Comparable - Lepton Triggered samples offer higher statistics V1 Fake RateV3 Fake RateV2 Fake Rate 8

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

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 10

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

Electron Fake Rates in Data Dependence on Jet Threshold Luminosity ~ 840 / nb 12 HLT_Ele10_LW_L1R 5 GeV 15 GeV 30 GeV 50 GeV Systematics ~ 50% V2 fake rate ( which does not relax isolation) shows least dependence on jet threshold V1 Fake RateV3 Fake RateV2 Fake Rate

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% 13

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 14

Backup Slides 15

Runs < Runs > Runs < Runs > Runs < Runs > Runs < Run Dependence of Muon Fake Rate All RunsRuns > HLT_15u HLT_Mu9 AND 15 GeV Offline Jet Discrepancy between Jet & Lepton triggered FR for runs> not understood

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) 17

Slide circulated in an emai message by Claudio on 10 July

Slide circulated in an emai message by Claudio on 10 July

Slide circulated in an emai message by Claudio on 10 July

Electron Fake Rates in Monte Carlo QCD_Pt30 Only Weν Only QCD_Pt30 + Weν Numerator & Denominator Pt distributions NumV2 DenV1 DenV3 Den Fake Rates QCD_Pt30 Only QCD_Pt30 + Weν V1 Fake RateV3 Fake RateV2 Fake Rate Presence of W does not dominate Fake Rate at high Pt 21

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

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

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

Electron Fake Rates in Data Comparison of 10 & 15 GeV Lepton Triggers Luminosity ~ 840 / nb HLT_Ele10_LW_L1R HLT_Ele15_LW_L1R W Supression: tcmet< 20, Mt < 25 V1 Fake RateV3 Fake RateV2 Fake Rate 25 Electron 10 & 15 triggers are comparable

Electron Fake Rates in Data Comparison of 10 GeV Lepton Triggers Luminosity ~ 840 / nb HLT_Ele10_LW_L1R HLT_Ele10_SW_L1R HLT_Ele10_LW_EleId_L1R HLT_Ele10_SW_EleId_L1R W Supression: tcmet< 20, Mt < 25 V1 Fake RateV3 Fake RateV2 Fake Rate 26 Trigger ID increases V1 & V2 Fake Rates Trigger ID cancels out in V3. V1 & V2 have no offline ID. Trigger ID decreases the denominator, increasing the Fake Rate

Electron Fake Rates in Data Comparison of 15 GeV Lepton Triggers Luminosity ~ 840 / nb HLT_Ele15_LW_L1R HLT_Ele15_SW_L1R HLT_Ele15_SW_EleId_L1R HLT_Ele15_LW_CaloEleId_L1R W Supression: tcmet< 20, Mt < 25 V1 Fake RateV3 Fake RateV2 Fake Rate 27 Trigger ID increases V1 & V2 Fake Rates

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