1 / 31

Top Quark Properties and Physics at LHC

Top Quark Properties and Physics at LHC. Weak Interactions and Neutrinos (WIN'05) 6-11 June 2005 , Delphi, Greece. V Šimák CTU-FJFI, ASCR-FZU Prague (on behalf of ATLAS collaboration). Electroweak gauge bosons Top quark mass Physics with top quark. Atlas.

mostyn
Download Presentation

Top Quark Properties and Physics at LHC

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Top Quark Properties and Physics at LHC Weak Interactions and Neutrinos (WIN'05) 6-11 June 2005, Delphi, Greece V Šimák CTU-FJFI, ASCR-FZU Prague (on behalf of ATLAS collaboration) • Electroweak gauge bosons • Top quark mass • Physics with top quark

  2. Atlas p-p collisions at √s = 14 TeV bunch crossing every 25 ns (40MHz) • low-luminosity: L ≈ 2 x 1033cm-2s-1 (L ≈ 20 fb-1/year) • high-luminosity: L ≈ 1034cm-2s-1 (L ≈ 100 fb-1/year) WIN05 Delphi 6-11 June 2005 V. Šimák, CTU Prague

  3. Magnetic Field 2T solenoid plus air core toroid Inner Detector s/pT ~ 0.05% pT(GeV) (+) 0.1% Tracking in range |h| < 2.5 EM Calorimetry s/E ~ 10% / √E(GeV) (+) 1% Fine granularity up to |h| < 2.5 Hadronic Calorimetry s/E ~ 50% / √E(GeV) (+) 3% Muon Spectrometer s/pT ~ 2-7 % Covers |h| < 2.7 WIN05 Delphi 6-11 June 2005 V. Šimák, CTU Prague

  4. W - mass pp → W+X with W→ ln and l = e, m • isolated charged lepton with • pT > 25 GeV inside |h| < 2.4 • missing transverse energy • ETmiss > 25 GeV • rejection of large pT W’s and plot the transverse mass, mT, given by where Df is the azimuthal angle between the l and the recoil X sensitivity is reduced by detector smearing LHC cross section is 30nb: after selection acceptance, reconstruction and identification expect 60M Ws per low luminosity year => precision on mW is systematics limited… WIN05 Delphi 6-11 June 2005 V. Šimák, CTU Prague

  5. Combining channels this reduces to 20MeV (15MeV combined with CMS) WIN05 Delphi 6-11 June 2005 V. Šimák, CTU Prague

  6. WIN05 Delphi 6-11 June 2005 V. Šimák, CTU Prague

  7. stt(th)=825±150 pb NNLO-NNNLL: Kidonakis, Vogt, PRD 68 (03) 114014 8 millions tt pairs/year (1 pair/second) at low luminosity! Top decays classification: di-lepton, lepton+jets, all jets qq->tt: 13% gg->tt: 87% WIN05 Delphi 6-11 June 2005 V. Šimák, CTU Prague

  8. Cross sections 1.96 TeV 14 TeV hep-ph/9806332] WIN05 Delphi 6-11 June 2005 V. Šimák, CTU Prague

  9. gg->tt: 87% Top decays classification: di-lepton, lepton+jets, all jets charge, mass, spin, decay, dynamics of production Top quark properteis: WIN05 Delphi 6-11 June 2005 V. Šimák, CTU Prague

  10. Qt = +2/3 Qt = -4/3 Atlas • t coupling to photon • can be probed via t tbar  events • can also be used to confirm Q=2/3 • SM: • Br(t Wb)  99.9% • Br(t  Ws)  0.1%, • Br(t  Wd)  0.01% • Many Beyond SM models involve anomalous top couplings • Several possible rare decay modes (eg. FCNC) have clear experiment signatures and, if observed at the LHC, would be evidence for new physics pT() [GeV] WIN05 Delphi 6-11 June 2005 V. Šimák, CTU Prague

  11. Atlas Semileptonic channel: • 0.2% efficiency • Total background 5% • Mass extracted from jjb system • (-> large error from jet scale uncertainty) • Stat. error: ±0.25 GeV • Error from Pt(t) spectrum: ±0.4 GeV • Jet scale: DEj/Ej~1% -> DM~±0.3 GeV • Require: • Isolated lepton with pT(l)> 20 GeV • Exactly 4 jets (R=0.4), each with pT(j) > 40 GeV • No b-tagging used • Plot m(jjj) of combo with max pT mt  1-2 GeV WIN05 Delphi 6-11 June 2005 V. Šimák, CTU Prague

  12. Dilepton channel WIN05 Delphi 6-11 June 2005 V. Šimák, CTU Prague

  13. Unfeasible at low luminosity • Independent from jet scale • Promising at high luminosity • Among main systematics: • b fragmentation mt  1 GeV WIN05 Delphi 6-11 June 2005 V. Šimák, CTU Prague

  14. WIN05 Delphi 6-11 June 2005 V. Šimák, CTU Prague

  15. f0 t t t b W Polarization in Top Decays WIN05 Delphi 6-11 June 2005 V. Šimák, CTU Prague

  16. V-A weak interaction determines the top quark decay in SM WIN05 Delphi 6-11 June 2005 V. Šimák, CTU Prague

  17. Polarization of Top WIN05 Delphi 6-11 June 2005 V. Šimák, CTU Prague

  18. « Spin studies in tt pairs » WIN05 Delphi 6-11 June 2005 V. Šimák, CTU Prague

  19. κ= 0 κ= -0.34 SM LO WIN05 Delphi 6-11 June 2005 V. Šimák, CTU Prague

  20. WIN05 Delphi 6-11 June 2005 V. Šimák, CTU Prague

  21. Atlas κ= 0 κ= -0.34 SM LO WIN05 Delphi 6-11 June 2005 V. Šimák, CTU Prague

  22. Neutral Higgs boson φ with unspecified CP parity W. Bernreuther, M. Flesch, P. Haberl – Phys. Rev. D58 (1998) a, ã – reduced scalar and pseudoscalar couplings (SM Higgs boson: a=1, ã=0) WIN05 Delphi 6-11 June 2005 V. Šimák, CTU Prague

  23. top quark Yukawa coupling can be measured from t tbar H production for m(H) < 130 GeV, Hbb is dominant decay • ttH final state is WWbbbb) • look for events with one W l, • the other W jj • pT(lep) > 20 GeV • Njet  6 with pT(jet) > 15 GeV • Nbjet = 4 WIN05 Delphi 6-11 June 2005 V. Šimák, CTU Prague

  24. Single Top Production 3,000,000 events/yr WIN05 Delphi 6-11 June 2005 V. Šimák, CTU Prague

  25. Atlas • there are large bkgnds (eg. tt [830 pb], Wbb [>300 pb]) with similar final states • ability to extract signal depends critically on detector performance, including • look at lepton, jet, bjet multiplicities, as well as kinematic distributions, to separate single top processes from ttbar, Wjj, Wbb, as well as from each other Jet eta WIN05 Delphi 6-11 June 2005 V. Šimák, CTU Prague

  26. Each process is sensitive to possible new physics in different ways • Some examples: • heavy W’  enhancement in s-channel W* • FCNC gu  t  enhancement in “Wg fusion” • It is important to measure each process separately • Also want to measure W, top helicities • Eg. sensitivity to V+A, anomalous couplings WIN05 Delphi 6-11 June 2005 V. Šimák, CTU Prague

  27. Phys.Rev. D70, p15015, 2004e-Print Archive: hep-ph/0409273 Helicity angle correlations in model with graviton (MD = 0.5 TeV, λ = 1) A = +0.97 The influence of extra-dimensions on the spin correlations of top-antitop quarks could be visible at the LHC in the case the effective scale MD is lower than ~1.5-2 TeV

  28. W helicity Top Mass l+ Top Width Anomalous Couplings Production cross-section Top Spin W+ CP violation Top Charge Resonance production n Y t b Production kinematics Top Spin Polarization _ t Rare/non SM Decays X Branching Ratios |Vtb| WIN05 Delphi 6-11 June 2005 V. Šimák, CTU Prague

  29. One of the most urgent problems in HEP to identify the mechanism of EWSB and mass generation, in which the top quark may play a special role. The LHC has a large potential for discovery of New Physics effects: e.g. heavy tt resonances, FCNC decays, etc… • Test some models beyond SM : • New type of interactions (resonant Higgs, extra-dimensions, …) • Modifications of SM couplings : • anomalous gtt couplings • anomalous Wtb coupling u d s c b t WIN05 Delphi 6-11 June 2005 V. Šimák, CTU Prague

  30. I would like to thank to my collegues from ATLAS and CMS for most of pictures in this talk Directly from Apollo: “If you switch on LHC you will see what you have never seen” Pythia (Delphi. June 7, 2005) WIN05 Delphi 6-11 June 2005 V. Šimák, CTU Prague

  31. WIN05 Delphi 6-11 June 2005 V. Šimák, CTU Prague

More Related