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QCD Estimation Update: Signal Fraction Analysis Using Chi-Squared Minimization

This presentation by William Edson from SUNY Albany details the application of chi-squared minimization in estimating QCD contributions in high-energy physics events. It covers the total number of events and distributions of signal and background types, emphasizing uncertainties and fractions derived from Monte Carlo simulations. The analysis involves event selection criteria, efficiency calculations, and various error addition methods to refine the signal fraction estimations. Key metrics include derived signal fractions, uncertainties, and acceptance evaluations based on stringent selection criteria.

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QCD Estimation Update: Signal Fraction Analysis Using Chi-Squared Minimization

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  1. ttbarτ + jets:Update on QCD Estimation William Edson SUNY at Albany

  2. Chi-squared minimization • Equation: • N(x): total number of events of type x for distribution • n(x)i: number of events in bin of type x • frac(Sig): fraction of N(Remain) expected to be Signal • binfrac(x)i: fraction of events in bin of type x expected from MC or template • σi: uncertainty in bin i

  3. Chi-squared minimization cont. • σi determined using factors for: • bin error: • data • signal, MC • QCD template • other backgrounds, MC • statistical error: • data: signal region • other backgrounds, MC • signal, MC • QCD template (uncertainty of background region data and all MC background region carried through via default SumW2

  4. Fractional Error Addition Signal Fraction: 0.91632 ± 0.167012 Minimum: 3.76511 Gaus Mean: 0.933425 Sigma: 0.0439541

  5. By Operation Error Addition For details see backup, slide 11 Signal Fraction: 0.897266 ± 0.141041 Minimum: 8.56055 Gaus Mean: 0.970150 Sigma: 0.0389473

  6. First Derivative Error Addition For details see backup, slide 12 Signal Fraction: 0.505793 ± 0.135081 Minimum: 29.0232 Gaus Mean: 0.721834 Sigma: 0.0662957

  7. Event Selection Verification

  8. MET > 60 GeV and SumET < 500 GeV

  9. MT < 70 GeV

  10. Back-up

  11. σi by Operation Details

  12. σi by First Derivative

  13. Function Fits of QCD Templates Mean: 171.283 ± 5.986

  14. Proceeding Acceptance and Efficiency Work • Efficiency: Limiting to events in 105200 sample satisfying: • contain truth matched taus • single prong • muonVeto and eleBDTMedium == 0 • calo-seeded taus • Acceptance: Using all MC types • Nrec: MC events passing entire cutflow • Ngen: 105200 events using mc and trueTau branch information matched to single prong, BDTJetScore > 0.7 taus

  15. Cutflow • C0: GRL • C1: Trigger • C2: Primary vertex with ntracks > 4 • C3: Electron/muon overlap, larVeto • C4: Jet cleaning • C5: Lepton Veto • C6: njets >= 4 with eta < 2.5 and |jvf| > 0.75 • C7: MET > 60GeV • C8: MT < 70GeV • C9: Sum ET < 500GeV • C10: >= 1 bjet • C11: Tau n ≥ 1, BDTScore > 0.7 • C12: Trigger matched tau n ≥ 1 and pT >= 40GeV • C13: MC tau object match

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