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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. - PowerPoint PPT Presentation

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Lepton Fakes in ~ 840 /nb26 August 2010Intro & SelectionsReference current ttbar selectionsNew: Mt < 25Electrons: endcap alignment correction for data, no Data & Monte Carlo samples listed at the end 2 W contribution to QCD Fake RatesWe want to measure the rate of fake leptons from QCD in dataLeptonic W decays will contribute to some extentWe have so far required low MET ( tcmet < 20 GeV ) to reduce the contribution from WWe now require low transverse mass also ( Mt < 25 )What effect does the presence of W have on the fake rate?

3Electron Fake Rates in Monte CarloQCD_Pt30 OnlyQCD_Pt30 + We

V1 Fake RateV3 Fake RateV2 Fake RatePresence 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 CarloW 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

InclusiveMu15 + Wmunu - tcmet< 20 AND Mt < 25

InclusiveMu15

InclusiveMu15- tcmet< 20 AND Mt < 25

5Fake Rate Dominated by W

Muon Fake Rates Comparison of Data and Monte CarloW 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 jetsData ( HLT_Mu9 AND 15 GeV Offline Jet )MC InclusiveMu15 + WmunuMC InclusiveMu15Luminosity ~ 840 / nb6 Fake Rates - Jet vs. Lepton TriggeredLepton fake rates have so far been determined from jet triggered ( HLT_Jet15U ) samplesThen require offline lepton away from jet triggerJet triggers are now heavily prescaledHLT_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 leptonLepton & Jet triggers should give the same result Lepton triggers offer more statistics

7Electron Fake Rates in DataComparison of Jet & Lepton Triggers

Luminosity ~ 840 / nbHLT_Jet15UHLT_Ele10_LW_L1RAND 15 GeV Offline JetJet & Lepton Triggered Fake Rates are Comparable - Lepton Triggered samples offer higher statisticsV1 Fake RateV3 Fake RateV2 Fake Rate8

Muon Fake Rates in DataComparison of Jet & Lepton TriggersLuminosity ~ 840 / nbHLT_Jet15U

HLT_Mu9 AND15 GeV Offline JetJet & Lepton Triggered Fake Rates Agree Before Run 137000 - Difference after run 137000 not yet understood - Lepton triggered samples offer higher statistics 9

Runs before 137000All Runs Jet Threshold Dependence of Lepton Fake RatesSystematic 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

10Muon Fake Rates in DataDependence on Jet ThresholdLuminosity ~ 840 / nbSystematics ~ 50%Isolation relaxed ( 0.15 to 0.40 ) in the muon fake rate denominator 11

HLT_Mu9

5 GeV 15 GeV 30 GeV 50 GeVElectron Fake Rates in DataDependence on Jet ThresholdLuminosity ~ 840 / nb12

HLT_Ele10_LW_L1R 5 GeV 15 GeV 30 GeV 50 GeVSystematics ~ 50%V2 fake rate ( which does not relax isolation) shows least dependence on jet threshold

V1 Fake RateV3 Fake RateV2 Fake Rate SummaryLeptons from W decay pollute QCD fake ratesResults in tolerable bias for electronsMuon 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 jetsFake rates derived from lepton triggers offer more statistics than those from jet triggers Jet ThresholdSystematics ~ 50%

13Samples/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

14Backup Slides15

Runs < 137000Runs > 137000 Runs < 139000Runs > 139000 Runs < 141000Runs > 141000 Runs < 14300016

Run Dependence of Muon Fake Rate All Runs

Runs > 136500HLT_15u

HLT_Mu9 AND 15 GeV Offline JetDiscrepancy between Jet & Lepton triggered FR for runs>137000 not understoodDifference between Jet15U and Muon triggers at high PT?This was also seen earlier in the summerThe most likely explanation was that of a run dependenceJet15U samples the very earliest runsMuon triggers are uniformWe need to verify this again by making the same plots as the previous page but broken up in run periodsSlide 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 201018

Slide circulated in an emai message by Claudio on 10 July 201019Slide circulated in an emai message by Claudio on 10 July 2010

20Electron Fake Rates in Monte Carlo

QCD_Pt30 OnlyWe OnlyQCD_Pt30 + We

Numerator & Denominator Pt distributionsNumV2 DenV1 DenV3 DenFake RatesQCD_Pt30 OnlyQCD_Pt30 + We

V1 Fake RateV3 Fake RateV2 Fake RatePresence of W does not dominate Fake Rate at high Pt21

Muon Fake Rates in Monte CarloW dominates Fake Rate above ~ 25 GeVInclusiveMu15 + WmunuInclusiveMu15WmunuFake RateDenominatorNumerator22

Muon Fake Rates Comparison of Data and Monte CarloW evident in Data also- Good agreement between data and Monte Carlo - W starts to dominate above ~ 35 GeVData ( HLT_Mu9 AND 15 GeV Offline Jet )InclusiveMu15 + WmunuInclusiveMu15Wmunu

Luminosity ~ 840 / nbFake RateDenominatorNumeratorW Supression:tcmet< 20 Mt < 2523Muon Fake Rates in DataDependence on Muon TriggerLuminosity ~ 840 / nbFake Rate stable for different Muon triggers W Supression:tcmet< 20 Mt < 25

24Electron Fake Rates in DataComparison of 10 & 15 GeV Lepton TriggersLuminosity ~ 840 / nb

HLT_Ele10_LW_L1RHLT_Ele15_LW_L1R

W Supression: tcmet< 20, Mt < 25 V1 Fake RateV3 Fake RateV2 Fake Rate25Electron 10 & 15 triggers are comparableElectron Fake Rates in DataComparison of 10 GeV Lepton TriggersLuminosity ~ 840 / nbHLT_Ele10_LW_L1RHLT_Ele10_SW_L1RHLT_Ele10_LW_EleId_L1RHLT_Ele10_SW_EleId_L1RW Supression: tcmet< 20, Mt < 25

V1 Fake RateV3 Fake RateV2 Fake Rate26Trigger ID increases V1 & V2 Fake Rates Trigger ID cancels out in V3.

V1 & V2 have no offline ID. Trigger IDdecreases the denominator, increasing the Fake Rate

Electron Fake Rates in DataComparison of 15 GeV Lepton TriggersLuminosity ~ 840 / nbHLT_Ele15_LW_L1RHLT_Ele15_SW_L1RHLT_Ele15_SW_EleId_L1RHLT_Ele15_LW_CaloEleId_L1RW Supression: tcmet< 20, Mt < 25

V1 Fake RateV3 Fake RateV2 Fake Rate27Trigger ID increases V1 & V2 Fake Rates Electron Selectionsttbar: Tight Electron SelectionsPt > 10SC Et > 10|| < 2.5ECAL SeededSpike RemovalVBTF 90 IDData corrected for Endcap alignmentdEta cut removedd0 < 400 Iso< 0.15No muon with dR of 0.10Conversion RejectionHit PatternDist < 002Dcottheta< 002Loose Electron Selectionsd0 removed for V1, V2, V3V1: V2 AND V3V2: Electron ID removedV3: Isolation relaxed to 0.4028