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Mass of Top quark and related Physics

This article discusses the measurement of the mass of the top quark and its implications in various decay channels such as single lepton, double lepton, and multijet final states. It also explores the physics related to the top quark, including spin correlations, Higgs mass, and potential new phenomena. The research was conducted at LHC-Praha in 2003.

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Mass of Top quark and related Physics

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  1. 1 TeV t t t b b b  c 1 GeV c c s s s  d d d  1 MeV u u u  e 1 keV e 1 eV Mass of Top quark and related Physics • Measurement of Top mass 1. single lepton final states - hadronic and leptonic decay - reconstruction of mass 2. Double lepton final states 3. Multijet final states • Physics around * spin correlations ** Higgs mass and CP *** new phenomena,… LHC-Praha - 10.07.2003

  2. Mt = 174.3 5.1 GeVc2 D0+CDF NLO cross section at LHC =833 pb LHC-Praha - 10.07.2003

  3. Top quark mass measurement with the ATLAS detector at LHC I. Borjanovic, I. Efthymiopoulos, F. Fassi, P. Grenier, P. Homola, V. Kostioukhine, R. Leitner, I. Mendes, D. Pallin, D. Popovic, P. Roy, V. Simak, L. Simic, G. Skoro, J. Valenta ATL-COM-2003-025 Purity 55% for 1 b-tagged, eff=2.5 % 66% for 2 b-tagged, eff=1.2% For mass t +-35 GeV 2.5 millions tt pairs per year running at low luminosity LHC-Praha - 10.07.2003

  4. Top mass in lepton plus jets channel Energy jet correction K=1.029+3.20/Eraw Mass of jjb (b-jets calibtrated usin Z+b events, Mw +-20 GeV) Statistical error 100 MeV for 10 fb-1 (one year of low luminosity running) systematic errors ~ 1.3 GeV (FSR,..) LHC-Praha - 10.07.2003

  5. Top mass in lepton plus jets channel Leptonic part - reconstructed mass Using transverse energy missing (neutrino) The entire tt final state can be reconstructed with twofold ambiguity Due to neutrino reconstruction The kinematics constraints Mjj = Mln = Mw, Mjjb = Mlnb = Mt Probability to have two b-tagged jets Well reconstructed as function chi2 LHC-Praha - 10.07.2003

  6. Top mass in lepton plus jets channel Mt = M +- 0.1(stat) +- (0.3-0.6) internal sys. +- 0.7x external sys. x = b-quark jet miscalibration in % LHC-Praha - 10.07.2003

  7. Top mass in lepton plus jets channel Cone study Reconstructed Mt before and after the rescaling from W reconstruction for three values of e/h Underlying event energy study Fast (447.5 MeV) and full (42.5MeV) simulation mass measurement using large calorimeter cluster LHC-Praha - 10.07.2003

  8. Top mass in lepton plus jets channel LHC-Praha - 10.07.2003

  9. Top mass in two leptons plus jets channel Assume mass t and solve equations and calculate probability of each solution LHC-Praha - 10.07.2003

  10. Top mass in two leptons plus jets channel Atlfast ISR, FSR on Atlfast ISR=FSR=0 LHC-Praha - 10.07.2003

  11. Top mass in two leptons plus jets channel D0 experiment 2 lepton final state, Run I Phys. Rev. D60 1999, 052001 LHC-Praha - 10.07.2003

  12. Top mass in multijets channel S/B =1/19 • Kinematic fit (two steps) • W’s selection and reconstruction with W mass constraints • (look at each pair of light jets) • Both W candidates are combined with the b-jets. • Combination chosen using top mass constraint: m(t1) = m(t2) • Top mass window (130-200 GeV)  S/B = 6/1 • High PT subsample • Selection • pT (t) > 200 GeV • 3300 evts/10 fb-1 S/B = 18/1 • dmstat(t) = 0.2 GeV/c2 • dmsys(t) = 3 GeV/c2 LHC-Praha - 10.07.2003

  13. Top mass in J/ymm channel • Correlation between • m(t) and m(lJ/y) • Require a non-iso m • inside b-jet • BR=BR(ppttXb+lnb)xBR(bJ/ymm)xBR(bm)= • 3. 2x10-5 • Channel can be used only with high L (2700evts/year) • Selection: 1 iso lepton, pT > 30 GeV, |h| < 2.4 • 3 non-iso muons, pT > 3 GeV, |h| < 2.4, m(mm) = m(lJ/y) • e ~16%  430 evts/ year at high L • Background: W/Z +jets, WW,WZ. Wbb, e ~12%  S/B=55 J/ymm dmstat(t) ~ 0.8-0.9 Gev Uncertainties:no sensitive to jet E scale, ISR,PDF,b-quark fragmentation dmsys(lJ/y) ~0.5 GeV -> dm(t)sys < 0.9 LHC-Praha - 10.07.2003

  14. New [preliminary] Result The relative error in this result is 3%, compare to 2.9% from the previous CDF and DØ combined average for all channels. D0 LHC-Praha - 10.07.2003

  15. Summary of mass measurement All hadronic channel Dilepton channel Single lepton channel BR~44% BR~5% BR~30%  ~3.5x106 evts  ~0.4x106 evts  ~2.5x106 evts Both tops reconstructed No top rec. One top rec. Huge backgnd from QCD Clean sample Clean sample Seems possible to measure m(t) in ATLAS with a precision of less than 1 GeV in one year of running at low L. LHC-Praha - 10.07.2003

  16. t t t b b b  c c c s s s  d d d  u u u  e e Standard Model and Top • Mass: 175 GeV • Short life-time: 10-24 s Run2, 2fb-1 • Dynamics of production • strong cupling • virtual exchange of • Higgs, CP+, CP- • SUSY • Spin, charge, …. • In the p-p interaction at 14 TeV: • gluon-gluon fusion (87 %) • quark-antiquark fusion (13 %) LHC-Praha - 10.07.2003

  17. Standard Model and Top LHC-Praha - 10.07.2003

  18. Standard Model and Top K. Smolek LHC-Praha - 10.07.2003

  19. Standard Model and Top LHC-Praha - 10.07.2003

  20. Top beyond Standard Model • Neutral Higgs boson φ with unspecified CP parity a, ã – reduced scalar and pseudoscalar couplings (SM Higgs boson: a=1, ã=0) • Coupling of φ to the weak vector boson gVV=0 • Influence of heavy Higgs boson on spin correlations • was studied on the parton level in: • W. Bernreuther, M. Flesch, P. Haberl – Phys. Rev. D58 (1998) LHC-Praha - 10.07.2003

  21. Virtual graviton and top production [hep-ph/9811501, hep-ph/0010010] Errors on SM LHC For 0.3 0.5 1.0 pb Variation of cross section with variation of Ms scale at Tevatron and LHC For LHC the dashed lines correspond to errors on the SM cross section of 0.3, 0,5 pb At LHC it is expected that the Ms value 2.5-5 TeV can be probed in this channel Two models LHC-Praha - 10.07.2003

  22. For pp collider Very preliminary Sensitivity large in forward/backward regions e.g. LHC-Praha - 10.07.2003

  23. CONCLUSIONS - OUTLOOK Top beyond Standard Model Standard Model and Top SUSY particles CP properties of strong dynamics Extra dimensions ……….. Spin correlations Yukawa coupling Single top production Rare decays …………… LHC = top factory with potential of discovery new physics LHC-Praha - 10.07.2003

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