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Физика t- кварка.

Физика t- кварка. (задачи). The top group CSC Notes. TopGroupNoteT1Leptons ? (Pralavorio) TopGroupNoteT2LightJets ? (Schwindling) TopGroupNoteT3BJets (Hawkings) TopGroupNoteT5Trigger (Wengler) TopGroupNoteT6CrossSection (Bentvelsen, Cobal)

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Физика t- кварка.

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  1. Физика t-кварка. (задачи)

  2. The top group CSC Notes • TopGroupNoteT1Leptons? (Pralavorio) • TopGroupNoteT2LightJets? (Schwindling) • TopGroupNoteT3BJets (Hawkings) • TopGroupNoteT5Trigger (Wengler) • TopGroupNoteT6CrossSection (Bentvelsen, Cobal) • TopGroupNoteT7TopProperties? (Onofre, Tokar) • TopGroupNoteT8SingleTop (A. Lucotte, S. Rolli, A. Shibata) • TopGroupNoteT9TopMass (Pallin, Etienvre)

  3. T1Leptons • lepton performance in all top samples (MCatNLO? +HERWIG and AcerMC +Pythia): reconstruction efficiency, purity and isolation as well as momemtum and angular resolutions. The interplay between the lepton selection and the trigger will also be discussed. Emphasis will be put on what can be expected at the LHC start-up, namely measurements with standalone detectors (Tracker, EM calorimeter, Muon spectrometer). Degradations induced by the "as-built" geometry will be adressed. • tt-decays as lepton source. σtt = 833 pb → 8M events/year (low L=1033cm-2s-1) tt→l+jets (l=e,µ) 30% 2.5M/year tt→l+l 5% tt→jets 44% l+jets : S/B≈80 → clear sample

  4. T8SingleTop • σt=1/3σtt →2M/year • These measurements will constitute the first direct measurement of Vtb at the few percent level of precision, and constitute a powerful probe for new physics, via the search for evidence of anomalous couplings to the top quark or the measurements of additional bosonic contributions to the single top production. • Vtb=0.999100+0.000034−0.000004 (PDG2006)

  5. Single top channels

  6. List of contributors • M. Barisonzi (NIKHEF) • F. Chevallier, A. Lleres, A. Lucotte (LPSC/IN2P3) • M. Cobal (INFN) • C. Cojocaru, M. Khakzad (U. Carleton) • A. Shibata (Queen Mary, U. of London) • B.G. Pope, P. Ryan, R. Shwienhorst (Michigan State U.) • S. Rolli (Tufts) • N. Triplett (Iowa State U.)

  7. Synopsis (proposal) Introduction ... [Simona,Arnaud] I. Single-top Phenomenology [Arnaud,Reinhard] : • Single top cross-section • SM backgrounds

  8. Synopsis (proposal) II Single top pre-selection • L1 Triggering ..... [Bernard,Reinhard,Patrick, Alessandro, others ?] • Inclusive lepton triggers • Jet triggers • Trigger efficiency & redundance • Preselection ..... [All] • Lepton selection (in link with lepton perf. note) • Selection efficiency • Definition & reconstruction efficiency • Light jet selection [Mohsen,Claudiu, Akira, Marcello, others?] • Definition % recon efficiency : cone size studies (in link with jet perf. note) • Threshold optimization (non-top, top pair bckgds) • b-tagged jet selection ..... [Simona,Monica,Mohsen,Claudiu,Akira] • Definition % recon efficiency : cone size studies (in link with jet perf. note) • Threshold optimization (non-top, top pair bckgds) . • Missing ET • W-transverse mass and /or angular discriminating power [Reinhard, others?] • Definition • Performance • Leptonic top mass reconstruction ..... [Claudiu, Mohsen, Akira] • optimization of the neutrino solution • optimization in the M(lvb) reconstruction • Influence of jet cone algorithm & size

  9. Synopsis (proposal) III Single top cross-section measurements • Wg channel analysis • standard cut-based selection [Claudiu, Mohsen,Akira, Marcello] • NeuralNet? selection [Nathan] • systematics : [All the above] • b-tagging • Jet Energy scale • Gluon radiation Modeling • Forward jet reconstruction & b-tagging • Wt channel analysis ..... [Marina, Annick, others ?] • Selection & performance • systematics : • b-tagging • Jet Energy scale • Gluon radiation Modeling • W* channel analysis ..... [Arnaud, others?] • selection & performance • systematics : • b-tagging • Jet Energy scale • Gluon radiation Modeling

  10. Synopsis (proposal) IV. Interpretation : top width measurements ..... [Ketevi,others ?] • Selected samples • Performance and systematics V. Single top evidence with the early data ..... [Bernard, Reinhard,Patrick,Akira,Alessandro] • Triggering [Bernard, Reinhard, Patrick] • Selection • Influence of b-tagging performance • Background studies [Akira, Reinhard] • Combined Wg and other single top channels ? [Bernard, Reinhard, Patrick,Alessandro, ?]

  11. T9TopMass • Motivations: observables in the Standard Model (SM)and theMinimal Supersymetric StandardModel (MSSM) depend on the value of the top mass • The most important top mass dependence contribution to the Electroweak observables arises via the one-loop radiative correction term ΔR ~ mt2/mZ2 , ~log mH/mZ

  12. Mt PDG : • Mt = 172.5 ± 2.7 GeV(using data from Tevatron Run-I and Run-II ) Theoretical uncertainties (hep-ex/0403021) : • renormalisation scale < 10 MeV • αS < 75 MeV • fragmentation effects ~O(ΛQCD) ~250 MeV LHC (10 fb-1, 1 year at L=1033cm-2s-1) : • statistical error ≈ 100 MeV • systematic ≈ 1 GeV

  13. Cross section Process σ(pb)ε(%) tt signal 2503.5 bb → lν + jets 2.2 × 1063 × 10−8 W + jets → lν + jets 7.8 × 1032 × 10−4 Z + jets → l+l− + jets 1.2 × 1036 × 10−5 WW → lν + jets 17.1 7 × 10−3 WZ → lν + jets 3.4 1 × 10−2 ZZ → l+l− + jets 9.2 3 × 10−3

  14. Event selection and background rejection • Oneisolated lepton with pT > 20 GeV, • ETmiss > 20 GeV • at least 4 jetsreconstructed with a cone size of R = 0.4 with pT > 40 GeV and |η| < 2.5 • at least oneis tagged as b-jets → S/B ≈ 78

  15. Top mass measurement • lepton plus jets channel • using the hadronic top decay • using a kinematic fit • using a continuous jet algorithm (ATL-PHYS-2001-006, V. Kostioukhine IHEP,Protvino) • using large pT events (large cone R=0.8-1.8) • dilepton channel • six jets channel • leptonic final states with J/Ψ

  16. top mass in the l+jets channel with 2 b-tagged jets

  17. Summary of the systematics errors Source of errorLepton+jetsLepton+jetsDileptonAll jets in GeVinclusivelarge clustershigh pTsamplesamplesample Energy scale Light jet energy scale0.2 - - 0.8 b-jet energy scale 0.7 - 0.6 0.7 Mass scale calibration - 0.9 - - UE estimate -1.3 - - Physics Background0.10.1 0.2 0.4 b-quark fragmentation0.1 0.3 0.7 0.3 Initial state radiation0.1 0.1 0.1 0.4 Final state radiation0.5 0.1 0.6 2.8 PDF - - 1.2 -

  18. Jets scale calibrations • mis-measurement of 1% of the Ej→ΔMt≈ 1.6 GeV. • mis-measurement of 1% of the cosθjj→ΔMt≈ 1.2 GeV. • fast MC: differences of the physics effects between light quarkjets and b-jets →systematic error ≈130 MeV • full simulation?

  19. Contributors • Clermont FD (E Cogneras,PO Defay,D Pallin) Saclay (AI Etienvre, A.Marzin, JP Meyer, J Schwindling) • Nikhef (S bentvelsen, I Van Vulpen, W Verkerke) • Prague (R Leitner, V Simak, J chudoba) • Lpnhe (F Derue, D Lacour, I Nikolic-Audit,M Ridel, S Trincaz-Duvoid, P Cavalleri ) • MPI Munich (N Ghobdane, R Nisius, T Goettfert, R Haertel) • Athens ( N Giokaris, A Kalogeropoulos, C Vellidis,A Manousakis,G Arabitze, V Giakoumopoulou) • Victoria ( K Edmonds, M Lefebvre, R McPherson?, R Seuster) • TUFTS (K Sliwa, S Rolli) • Dortmund(Joerg Walbersloh,Ingo Reisinger,Daniel Dobos,Reiner Klingenberg)

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