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Catania Lepton Tag

Catania Lepton Tag. Andrea Bocci Vitaliano Ciulli Riccardo Ranieri INFN and Università di Firenze Alessia Tricomi INFN and Università di Catania CMS CPT Week - b Meeting 3 rd November 2004. Soft Lepton Tag. Based on identification of the soft leptons from semileptonic B-meson decays

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Catania Lepton Tag

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  1. Catania Lepton Tag Andrea Bocci Vitaliano Ciulli Riccardo Ranieri INFN and Università di Firenze Alessia Tricomi INFN and Università di Catania CMS CPT Week - b Meeting 3rd November 2004

  2. 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 (20%) • Provide a valuable complement with respect to the impact parameter tagging • Some very very preliminary results with ORCA reconstruction already presented at bτ meeting during July Tracker Week • http://agenda.cern.ch/askArchive.php?base=agenda&categ=a042955&id=a042955s1t7%2Fmoreinfo%2FCataniaLeptonTag.ppt Catania Lepton Tag II

  3. The test samples • QCD jets from Christian’s test samples • 2500 “b”, 4750 “c”, 5000 “udsg” • 80<pT[GeV/c]<120 • no pileup • some problems related to the samples: • Not well defined separation between signal and background • “udsg” means no requests: this sample contains also c or b jets depending on c/b quark production probability • “c”(“b”) means at least one c(b) quark in the final state: this sample is pure QCD enriched in c(b) quark content • Variable number of jets • we have not under control the number and flavour of jets we expect to see • problems in debugging algorithms • if jets are separated in ET bins too few jets per bin ^ Catania Lepton Tag II

  4. 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 and c→μ from b→c→μ • Jets • we used Christian’s BReco/BTagMCTools package • associates to the reconstructed jet the main parton within ΔR(η,φ)<0.3 and assigns jet flavour • some modifications inside JetIdentifier and MCParton/LundCode classes Catania Lepton Tag II

  5. Modified BTagMCTools • JetIdentifier.h • added methods to return not only the HepLorentzVector (Energy-Momentum) of the three partons, but also the partons themselves to access all the MCParton’s methods too MCParton mainParton (){return m_MainParton;} MCParton heaviestParton (){return m_HeaviestParton;} MCParton closestParton (){return m_ClosestParton;} Catania Lepton Tag II

  6. Modified BTagMCTools • JetIdentifier.cc • inside the loop to assign the most suitable MCParton to the jet, partons with PYTHIA status = 3 are excluded • example: Gluon Fusion gg→bb event: - E X C L U D E D Catania Lepton Tag II

  7. Modified BTagMCTools • MCParton • mother and grandmother HEP-PID and top quark decay int getMotherLundCode() const{returnmotherLundCode;} int getGrandMotherLundCode()const{returngrandmotherLundCode;} bool getIsFromT()const{return isFromT;} • Gluon Splitting Finder • loop on PYTHIA lines to find qq pairs from gluon common mother • at least a gluon in PYTHIA event (lines 3 or 4 or 5 or 6 or 7 or 8) • search for parton-antiparton with PYTHIA status≠3 “daughters” of the previous gluon • both q and q are labelled as coming “fromGluonSplitting” • too much PYTHIA-dependent • already passed to Pisa people… waiting for feedback… - - Catania Lepton Tag II

  8. Reconstruction • 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 II

  9. Reconstructed Muons Entries/bin • Association between RecMuon’s and TkSimTrack’s • 93% of the times we are able to say what is the simulated particle reconstructed as a muon Catania Lepton Tag II

  10. Reconstructed Muons Entries/bin • We can study the “life” of the RecMuon associated to a SimTrack • PYHTIA list navigation, decay chains… • for the moment we are not able to reconstruct the story of PYTHIA “stable particles” (GEANT decays) here there are both b→c→μ and c→μ Catania Lepton Tag II

  11. L2 Jets corrected ET Entries/bin • Reconstructed L2 Jets with ET>40 GeV • jet flavour from MC association • more than 80% of b/c jets are selected • jet η and φ recalculated with tracks • improved resolution from 0.05 to 0.03 Catania Lepton Tag II

  12. Gluon Splitting • Fraction of jets coming from Gluon Splitting (GS) • sample: selected L2 jets ET>40 GeV • 50% of b/c jets come from GS Catania Lepton Tag II

  13. Number of L2 Jets • 4 bins in jet ET • light-flavoured jets have lower ET than b/c Low Statistics Catania Lepton Tag II

  14. L3 Muons inside L2 Jets • A L3 Muon is associated to the L3 jet if ΔR(η,φ)<0.5 • 691/924=75% of L3 Muons are inside L2 Jets • Fraction of 40<ET[GeV]<120 jets with muons: • b 12.9%c 6.2% • uds 0.88%g 1.2% Statistical Error: ±0.01 Low Statistics Catania Lepton Tag II

  15. Where are generated b muons? • 494 MC generated b Muons are inside L2 Jets [ET>40 GeV] • Fraction of 40<ET[GeV]<120 jets with generated muons (pT>0.5 GeV/c, |η|<2.5) coming from b mesons/baryons decay: • b 18.6%c <0.1% • uds 0.26%g 0.2% Statistical Error: ±0.01 Low Statistics Catania Lepton Tag II

  16. Conclusions • We have a lot of work to do and problems to solve • A simpler di-jet event sample (DAQ-TDR like) would help to debug our code Catania Lepton Tag II

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