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Catania Lepton Tag. Andrea Bocci Riccardo Ranieri INFN and Università di Firenze Massimiliano Chiorboli Alessia Tricomi INFN and Università di Catania CMS Tracker Week bTau Meeting 20 th July 2004. Soft Lepton Tag.

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Catania lepton tag

Catania Lepton Tag

Andrea Bocci Riccardo Ranieri

INFN and Università di Firenze

Massimiliano Chiorboli Alessia Tricomi

INFN and Università di Catania

CMS Tracker Week bTau Meeting

20th July 2004

Soft lepton tag
Soft Lepton Tag

  • Based on identification of the soft leptons from semileptonic B-meson decays

    • we studied only leptons=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)


  • Now first very very preliminary results with ORCA reconstruction

  • Catania Lepton Tag

    The test samples
    The 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 (6500 evts processed)

      • 120<pT[GeV/c]<170

      • cross section: σ=3.82x10-4 mb

      • Kinematic Selection: ε=5.70x10-2

        • at least 4 jets

        • ΣETjet>300 GeV

        • jets: ET1,2>40 GeV; ET3,4>30 GeV

          • more details from Susannna’s talk on MC requests for ttH channel studies talks/030603/Susanna.pdf





    Catania Lepton Tag


    • Studies done with ORCA_8_2_0

    • Reconstruction of RecMuon objects

      • L3 Muon Reconstructor

        • RecQuery query ("L3MuonReconstructor");

        • no further thresholds applied

    • Reconstruction of JetWithTracks objects

      • L2 Kt jet algorithm

        • RecQuery jetFinder ("PersistentJetFinder");

        • jetFinder.setParameter ("JetAlgorithm", 4); // Kt=4

      • Tracks in cone ∆R<0.3 around jet axis

        • RecQuery query ("BTagJetWithTracksAlgo");

        • query.setComponent ("JetFinder", jetFinder);

        • query.setComponent ("TrackFinder", RecQuery(“CombinatorialTrackFinder”));

        • query.setParameter ("deltaRCut", 0.3);

    Catania Lepton Tag

    Monte carlo truth
    Monte 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 bμ from bcμ

        • 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 JetIdentifier and MCParton/LundCode classes

    Catania Lepton Tag

    L2 jet axis resolution
    L2 Jet Axis Resolution


    from ttH QCD background

    • Jet axis η-φ measurements resolution improved with tracks

      • weighted mean on tracks pT, see DAQ-TDR section

      • before: σ(η)=0.068 σ(φ)=0.060

      • after: σ(η)=0.039σ(φ)=0.036

    Catania Lepton Tag

    Muon p t rel and p t rel excl
    Muon pTrel and pTrel,excl

    • Muon transverse momentum relative to jet axis

      • left: pTrel relative to measured jet momentum direction

        • vector pjet direction

      • right: pTrel,excl relative to jet momentum lepton excluded

        • vector pjet-pμdirection



    Catania Lepton Tag

    Direct vs cascade b decays
    Direct vs Cascade b decays

    pTrel,excl>0.8 GeV/c

    pTrel>0.8 GeV/c

    • Efficiency of bμ chain versus Rejection of bcμ chain

    Catania Lepton Tag

    B c comparison
    b-c comparison

    pTrel>3.2 GeV/c

    pTrel,excl>3.2 GeV/c

    pTrel,excl>0.8 GeV/c

    pTrel>0.8 GeV/c

    • Efficiency of bμ+bcμ versus Rejection of cμ

    Catania Lepton Tag


    • excerpt from ToDo list (bTau Workshop):

    • First step:

      • Start with muons

        • Look for muon inside jet tracks and evaluate pTrel or pTrel,excl and IP for muon candidate

      • pTrel and pTrel,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


    Catania Lepton Tag