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b- tagging efficiency in L+jets at 7TeV

b- tagging efficiency in L+jets at 7TeV. Hongbo Liao LPC, Clermont-Ferrand. Tag counting method.

margaret-evans
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b- tagging efficiency in L+jets at 7TeV

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  1. b-tagging efficiency in L+jets at 7TeV Hongbo Liao LPC, Clermont-Ferrand

  2. Tag counting method • The number of events with n btag jets N_i depends on b tagging eb, non-b jet mistag rate enonband Fij, the fraction of number of events having i jets matching b quark and j jets not matching • Fiteband Ntot, enonband Fij fixed Cut SV0 > 8 • eb = 50.2 ± 0.7% • enon b = 1.9 ± 0.1% • Pre-selection : • Exactly 1 isolated lepton Pt>20GeV (e or µ) • At least 4 jets. 3jets Pt>40GeV+ 1 jet Pt>30GeV • Missing Et >20GeV

  3. b tagging weight of SV0, JetProb, TrackCounting and SV1+IP3D Thanks Nabil and Diane

  4. b tagging efficiency One can estimate weight cut to get such as expected 50% tagging efficiency

  5. Light jet rejection

  6. Light jet rejection vsbtag efficiency At same btag efficiency, SV1+IP3D has higher light jet rejection

  7. Fit results (without bkg) Expected : eb = 50.2 ± 0.7% N = 30.1 ± 5.5 Fit : eb = 50.3 ± 7.1% N = 30.4 ± 5.5 Track>2.5 SV0>8 JetPtob<0.001 SV1+IP3D>6 Expected : eb = 48.9 ± 0.7% Fit : eb = 49.1 ± 7.3% Expected : eb = 46.6 ± 0.7% Fit : eb = 47.0 ± 7.0% Expected : eb = 49.4 ± 0.7% Fit : eb = 49.4 ± 7.2% with bkg and more checks

  8. combinational method for Top mass • Full-Hadronic • Semi-leptonic

  9. Semi-leptonic (7TeV) Idea: find the best combination by the minimum (no fit) to define Ttbar events Here: the mean values and sigma come from the reconstructed objets whichmatched the thruth. Additionalchooses: normal method; Pt dependence; fit? Sample: 7TeV Ttbar, W+jets and Single Top samples After reconstruction:Missing Et > 20 GeV; exactly one lepton Pt>20GeV; at least 4 jets, 3jets Pt>40GeV+1jets Pt>30GeV

  10. Pre_selection + chi2<30 + weight of 1 bjet >6 S/B : 1.8 3.1 35

  11. Full-Hadronic (10TeV) Idea: find the best combination by the minimum (no fit) to define Ttbar events • Smaples: full-hadronicttbar 105204; QCD Multijet (108352-108355, 108357-108360, 108362-108371); W+jets (107681-107685,107691-107695,107700-107705) Multi-jet Triggers : 6j35_5j45_4j50_3j60, 4j35_3j45_2j50_j60, 4j45_j60, 5j45_2j60_j100, 5j45_4j60_j100,4j60_2j100_j170

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