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Measurement of W Helicity in Lepton+Jets Channel Using JLIP

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thom
18 diapositives · 324 Views · Oct 03, 2014

This presentation by Vincent Siccardi at the Institute of Subatomic Research details the measurement of W helicity in lepton+jets channels utilizing Jet Lifetime Probability (JLIP) as a b-tagging method. The study outlines the event preselection criteria based on topological cross-section analysis and various kinematic requirements. It discusses the implementation of advanced b-tagging algorithms, continuous working points for JLIP, and the upcoming analysis of invariant mass correlations to derive the decay angle of the W boson. The analysis aims to enhance signal-to-background discrimination and streamline tagging processes for effective measurement.

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  1. Measurement of the W helicity in lepton+jets channel using JLIP Vincent Siccardi Institut de Recherches Subatomiques - Strasbourg Top Properties Meeting 08/11/2005

  2. Event preselection Preselection based on topological cross section analysis >= 3 tracks attached to PV |zPV|<60cm >= 4 jets pT>15 GeV |eta|<2.5 Missing ET>20 GeV Triangular cuts l+jets trigger requirement Kinematic fit convergence not yet used. Implementation ongoing muon medium nseg = 3 |eta| < 2 ; pT > 20 GeV |Deltaz(e,PV)| < 1 cm ; |dca|/sigdca < 3 mu track Chi2 < 4 DeltaR(mu,jet) > 0.5 matched to central track cosmic veto Halo(0.1,0.4)/pT < 0.08 & TrkCone(0.5)/pT < 0.06 (tight) No 2nd tight mu pT > 15 GeV Z veto No e pT > 15 GeV electron fEM > 0.9 ; fiso < 0.15 ; hmx7 Chi2 < 50 |eta| < 1.1 |Deltaz(e,PV)| < 1 cm matched to central track likelihood > 0.85 (tight) only 1 tight e pT > 15 GeV no tight mu pT > 15 GeV

  3. Preselection Data samples : Ipanema full PASS2 top_analyzed EMQCD & MUQCD Number of events after loose or tight preselection, without b-tagging

  4. JLIP : Jet LIfetime Probability B-tagging algorithm developped by Strasbourg For each calorimeter jet, a probability is computed using the impact parameter information of tracks seen in the SMT layers. PJLIP = probability that all the tracks of a jet come from the primary vertex Currently : ‘tagging’ in MC by use of TRFs We have made studies to tag the MC, but did not succed until now. If we finally succed, MC will be directly tagged instead of using the TRFs

  5. b-tagging Continuous set of working points. PJLIP < 0.1% UltraTight PJLIP < 0.3% Tight PJLIP < 0.5% Medium PJLIP < 1.0% Loose PJLIP < 2.0% SuperLoose PJLIP < 4.0% ExtraLoose loose tight • Several tagging schemes : • Single Tag ST : == 1 btagged jet • Double Tag DT : >=2 btagged jets • Will be studied : • Asymmetric Double Tag : >= 1 ‘Tight’ && >= 1 ‘Loose’ btagged jets • should increase the signal acceptance in the DT sample and reduce the total TRFs systematcis

  6. Preselected tagged events JLIP working points : Tight PJLIP<0.3% - Loose PJLIP<1%

  7. Signal to background discrimination Matrix method implemented Already implemented variables for the likelihood discriminant for the W+jets background discrimination: Aplanarity, Centrality, Sphericity, HT, HT3, HT20, HT2P, KpTmin, minimal dijet invariant mass HifFit Chi2 will be implemented soon

  8. Measurement Plan first to use the invariant mass M2lb between the b quark and the lepton to calculate the decay angle Need to find a method to select the combination lepton-jet Maybe will study the possibiliy of a likelihood between several variables (lepton pt, ...)

  9. Summary • - W helicity analysis using JLIP as b-tagger • Timescale : middle of 2007 : p17, CAF • Preselection and tagging ready, kinematic fit implementation ongoing • Matrix method available • input variables for likeihood discriminant implemented • plan first to make the analysis using the invariant mass lepton-quark b

  10. Backup Slides

  11. e+jets – Tight ST

  12. e+jets – Tight DT

  13. e+jets – Loose ST

  14. e+jets – Loose DT

  15. mu+jets – Tight ST

  16. mu+jets – Tight DT

  17. mu+jets – Loose ST

  18. mu+jets – Loose DT