Catania Lepton TagCatania Lepton Tag

Andrea Bocci Riccardo Ranieri

INFN INFN andand Università di Firenze Università di Firenze Massimiliano Chiorboli Alessia

Tricomi

INFN INFN andand Università di Catania Università di Catania

CMS Tracker Week bTau MeetingCMS Tracker Week bTau Meeting2020thth July 2004 July 2004

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Soft Lepton TagSoft Lepton Tag– Based on identification of the soft leptons from

semileptonic B-meson decays we studied only leptons=muonsleptons=muons case

– Efficiency of soft lepton tagging limited by the fraction of B-meson decays containing leptons (17%)

– Provide a valuable complement with respect to the impact parameter tagging

– Preliminary studies at parton level presented at bTau Workshop in Bari (28th May-1st June)

» http://agenda.cern.ch/askArchive.php?http://agenda.cern.ch/askArchive.php?base=agenda&categ=a041643&id=a041643s5t13%2Fmorebase=agenda&categ=a041643&id=a041643s5t13%2Fmoreinfo%2Fsoftleptontagging.pptinfo%2Fsoftleptontagging.ppt

– Now first very very preliminary very very preliminary results with ORCA reconstruction

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The test samplesThe test samples– di-jets from Christian’s test samples

2500 b, 4750 c, [5000 udsg] 80<pT[GeV/c]<120

no pileup

– QCD jets for ttH background (65006500 evts processed) 120<pT[GeV/c]<170

cross section: σσ=3.82x10=3.82x10-4-4 mb mb Kinematic Selection: εε=5.70x10=5.70x10-2-2

– at least 4 jets

– ΣETjet>300 GeV

– jets: ET1,2>40 GeV; ET

3,4>30 GeV» more details from Susannna’s talk on MC requests for ttH

channel studies http://cmsdoc.cern.ch/cms/Physics/btau/management/http://cmsdoc.cern.ch/cms/Physics/btau/management/2003/ talks/030603/Susanna.pdf2003/ talks/030603/Susanna.pdf

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ReconstructionReconstruction– Studies done with ORCA_8_2_0– Reconstruction of RecMuonRecMuon objects

L3 Muon Reconstructor– RecQuery query ("L3MuonReconstructor""L3MuonReconstructor");– no further thresholds applied

– Reconstruction of JetWithTracksJetWithTracks objects L2 KtKt jet algorithm

– RecQuery jetFinderjetFinder ("PersistentJetFinder");– jetFinder.setParameter ("JetAlgorithm", 4); // Kt=4

Tracks in cone ∆R<0.3∆R<0.3 around jet axis– RecQuery query ("BTagJetWithTracksAlgo""BTagJetWithTracksAlgo");– query.setComponent ("JetFinder", jetFinder);– query.setComponent ("TrackFinder",

RecQuery(“CombinatorialTrackFinder”“CombinatorialTrackFinder”));– query.setParameter ("deltaRCut""deltaRCut", 0.30.3);

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Monte Carlo TruthMonte Carlo Truth• Muons

– information on the origin of the muon (i.e. “mother” particle of the generated

muon)– information on the origin of the decay chain

(i.e. the particle which originates the decay chain) to separate bμ from bcμ some problems with u,d,s,g, results need better

understanding

• Jets– we used Christian’s BReco/BTagMCTools package– associates main parton to the reconstructed jet

and assigns jet flavour some modifications inside JetIdentifierJetIdentifier and

MCPartonMCParton/LundCodeLundCode classes

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L2 Jet Axis ResolutionL2 Jet Axis Resolution

Jet axis η-φ measurements resolution improved with tracks

– weighted mean on tracks pT, see DAQ-TDR section 15.6.3.1DAQ-TDR section 15.6.3.1

– before: σσ((ηη)=0.068)=0.068 σσ((φφ)=0.060)=0.060– after: σσ((ηη)=0.039)=0.039 σσ((φφ)=0.036)=0.036

from ttH QCD backgroundfrom ttH QCD background--

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Muon pMuon pTTrelrel and p and pTT

rel,exclrel,excl

– Muon transverse momentum relativerelative to jet axis left: pT

rel relative to measured jet momentum direction– vector ppjetjet direction

right: pTrel,excl relative to jet momentum lepton excluded

– vector ppjetjet-p-pμμ direction

Entr

ies/

bin

Entr

ies/

bin

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Direct vs Cascade b decaysDirect vs Cascade b decays

Efficiency of bbμμ chain versus Rejection of bbccμμ chain

ppTTrel,exclrel,excl>0.8 GeV/c>0.8 GeV/c

ppTTrelrel>0.8 >0.8 GeV/cGeV/c

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b-c comparisonb-c comparison

Efficiency of bbμμ+bbccμμ versus Rejection of ccμμ

ppTTrel,exclrel,excl>0.8 GeV/c>0.8 GeV/c

ppTTrelrel>3.2 >3.2 GeV/cGeV/c

ppTTrelrel>0.8 >0.8 GeV/cGeV/c

ppTTrel,exclrel,excl>3.2 GeV/c>3.2 GeV/c

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ConclusionConclusion

• excerpt from ToDo list (bTau Workshop):• First step:

– Start with muons• Look for muon inside jet tracks and evaluate pT

rel or pTrel,excl

and IP for muon candidate

– pTrel and pT

rel,excl done but… problems with samples too few events MC info on u,d,s,g to be better understood

– The bulk of the code is there, we miss only the last point: Impact Parameter coming soon

– WE NEED MORE EVENTS !!!WE NEED MORE EVENTS !!!