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Update on top dilepton analysis with b- tagging (36 pb -1 )

Update on top dilepton analysis with b- tagging (36 pb -1 ).

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Update on top dilepton analysis with b- tagging (36 pb -1 )

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  1. Updateon top dileptonanalysiswith b-tagging (36 pb-1) A.Calderón, SH.Chuang, J.Cuevas, J.Duarte, J.Fernández, S.Folgueras, M.Felcini, R.González, I.González, C.Jordá, L.Lloret, P.Lobelle,C.Martínez, J.Piedra, L.Scodellaro, T.Rodrigo, A.Rodríguez, I.Vila, R.Vilar IFCA-Universidad de Oviedo group

  2. Introduction • Selection • Referenceselectionpass v6 • https://twiki.cern.ch/twiki/bin/viewauth/CMS/TopDileptonRefAnalysis2010Pass6 • JPT and tcMET Appendix A: Selection using PF Appendix B: Selection without MET

  3. Samples With PU

  4. Eventyields : mm channel 36 pb-1

  5. Eventyields : eechannel 36 pb-1

  6. Eventyields : emchannel 36 pb-1

  7. Backgroundestimation: DrellYan 76<mll<106 AN-2009/023

  8. Lepton fakes background (tight – to – loose method) CMSAN-2010/261 Takethe final FR as theweighted mean valuebetween jet samples and wetakethe error as themax. differencebetweenthen. We estimate the systematic error as the maximum difference between observed and predicted values estimated from the different jet samples  We assign a 30% final systematic error to the fake rate estimation. Final prediction for mumu channel

  9. Electron fake rate We define loose electrons as those which pass electron ID and conversion rejection cuts which correspond to WP90. In addition, we requiere a relative isolation to be smaller than 1. Final prediction for ee channel Final prediction for emu channel

  10. Tag and Probe ~ 36 pb-1

  11. Muon reco, ID, isoefficiencies

  12. Muon triggerefficiencies

  13. b-tagsystematics Efficiency and mistagratesassociatedtothe WP used (1.7) are shiftedbytheirrelativeuncertaintiestoobtain new discriminatorcuts. Thevariation in efficiencyisappliedtotheselected jets that are comingfrom b , and thevariation in mistagratetotheother jets. TCHE loosepoint ( 1.7) 79% b-efficiency 12% mistagrate • Apply SF data/MC  movethediscriminatorcuttothepointwitheMC*SF efficiency, whichistaken as the nominal value. • This new efficiencyisshifted up and downbyitsuncertainty and 2 new b-tagdiscriminatorcuts are obtained. • - Analysisrepeatedaplyingthese new set of b-tagcuts 2 values: positive and negativevariationwrtthe nominal number of events

  14. Example for Ttbar mumu signal SFb= 0.9 +/- 15% SFc = 0.9 +/- 30% SFl= 1 +/- 25%

  15. SFb= 0.9 +/- 15% SFc = 0.9 +/- 30% SFl = 1 +/- 25% https://twiki.cern.ch/twiki/bin/view/CMS/TopLeptonPlusJets2010Systematics

  16. Cross sectiondetermination Estimation of MET systematics and PDFs to be completed in order to provide the final systematic uncertainty on the cross section At least 1 btag in mumu/ee, no btag in emu: At least 1 btag in mumu/ee/emu: No btag requirement:

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