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

A.Calderón, SH.Chuang, J.Cuevas, J.Duarte, J.Fernández, S.Folgueras, M.Felcini, A.Calderón, SH.Chuang, J.Cuevas, J.Duarte, J.Fernández, S.Folgueras, M.Felcini, R.González, I.González, C.Jordá, L.Lloret, R.González, I.González, C.Jordá, L.Lloret, P.LobelleP.Lobelle,, C.Martínez, J.Piedra, C.Martínez, J.Piedra, L.Scodellaro, T.Rodrigo, A.Rodríguez, I.Vila, R.VilarL.Scodellaro, T.Rodrigo, A.Rodríguez, I.Vila, R.Vilar

IFCA-Universidad de Oviedo groupIFCA-Universidad de Oviedo group

IntroductionIntroduction• SelectionSelection— Reference selection pass v6https://twiki.cern.ch/twiki/bin/viewauth/CMS/TopDileptonRefAnalysis2010Pass6—JPT and tcMETJPT and tcMET

Appendix A:Selection using PF

Appendix B:Selection without MET

With PU

SamplesSamples

Event yields : Event yields : channel channel 36 pb36 pb-1-1

Event yields : ee channelEvent yields : ee channel 36 pb36 pb-1-1

Event yields : eEvent yields : e channel channel 36 pb36 pb-1-1

Background estimation: Drell YanBackground estimation: Drell Yan

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76<mll<10676<mll<106

AN-2009/023AN-2009/023

Lepton fakes background(tight – to – loose method)

CMS AN-2010/261

Take the final FR as the weighted mean value between jet samples and we take the error as the max. difference between then.

Final prediction for mumu channel

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 ee channel

Final prediction for emu channel

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.

Tag and Probe ~ 36 Tag and Probe ~ 36 pbpb-1-1

Muon reco, ID, iso efficienciesMuon reco, ID, iso efficiencies

Muon trigger efficienciesMuon trigger efficiencies

b-tag systematics b-tag systematics

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- Apply SF data/MC move the discriminator cut to the point with MC*SF efficiency, which is taken as the nominal value.- This new efficiency is shifted up and down by its uncertainty and 2 new b-tag discriminator cuts are obtained.- Analysis repeated aplying these new set of b-tag cuts 2 values: positive and negative 2 values: positive and negative variation wrt the nominal number of eventsvariation wrt the nominal number of events

Efficiency and mistag rates associated to the Efficiency and mistag rates associated to the WP used (1.7) are shifted by their relative WP used (1.7) are shifted by their relative uncertainties to obtain new discriminator uncertainties to obtain new discriminator cuts.cuts.The variation in efficiency is applied to the The variation in efficiency is applied to the selected jets that are coming from b , and the selected jets that are coming from b , and the variation in mistag rate to the other jets.variation in mistag rate to the other jets.

TCHE loose point ( 1.7) TCHE loose point ( 1.7) 79% b-efficiency 79% b-efficiency 12% mistag rate 12% mistag rate

Example for Ttbar mumu signal

SFSFbb= 0.9 +/- 15%= 0.9 +/- 15%SFSFcc = 0.9 +/- 30% = 0.9 +/- 30%

SFSFll = 1 +/- 25% = 1 +/- 25%

SFSFbb= 0.9 +/- 15%= 0.9 +/- 15%SFSFcc = 0.9 +/- 30% = 0.9 +/- 30%SFSFll = 1 +/- 25% = 1 +/- 25%

https://twiki.cern.ch/twiki/bin/view/CMS/TopLeptonPlusJets2010Systematics

Cross section determinationCross section determination

At least 1 btag in mumu/ee, no btag in emu:

At least 1 btag in mumu/ee/emu:

No btag requirement:

Estimation of MET systematicsand PDFs to be completed in order to provide the final systematic uncertainty on the cross section