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

2. WIN05 Delphi 6-11 June 2005 V. Šimák, CTU Prague 2 p-p collisions at √s = 14 TeV bunch crossing every 25 ns (40MHz)  low-luminosity: L ≈ 2 x 10 33 cm -2 s -1 ( L ≈ 20 fb -1 /year )  high-luminosity: L ≈ 10 34 cm -2 s -1 ( L ≈ 100 fb -1 /year) Atlas

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

4. WIN05 Delphi 6-11 June 2005 V. Šimák, CTU Prague 4 pp → W+X with W→ l and l = e,  isolated charged lepton with p T > 25 GeV inside |  | < 2.4 missing transverse energy E T miss > 25 GeV rejection of large p T W’s and plot the transverse mass, m T, given by LHC cross section is 30nb: after selection acceptance, reconstruction and identification expect 60M Ws per low luminosity year => precision on m W is systematics limited… where  is the azimuthal angle between the l and the recoil X sensitivity is reduced by detector smearing W - mass

5. WIN05 Delphi 6-11 June 2005 V. Šimák, CTU Prague 5 Process Rate [Hz] Events /Year Events (total) Z→e + e - 1.5~10 7 ~10 7 LEP W→ev15~10 8 ~10 4 LEP t anti-t800~10 7 10 4 Tevatron At low luminosity Combining channels this reduces to 20MeV (15MeV combined with CMS) Source  M W (Me) Statistics  2 2 E-p scale15 Energy resolution5 Recoil model5 Lepton identification5 pTWpTW 5 Parton distribution functions  10 W width7 Radiative decays10 Background5 Total  25

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

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

8. WIN05 Delphi 6-11 June 2005 V. Šimák, CTU Prague 8 ttbar pairs6.70 +0.71 -0.88 pb825±150 pb Single top (s-channel) 0.75±0.12 pb10±1 pb Single top (t-channel) 1.47±0.22 pb245±17 pb Single top (Wt channel) 0.15±0.04 pb60±10 pb Wjj~1200 pb~7500 pb bb+other jets~2.4x10 5 pb~5x10 5 pb 1.96 TeV14 TeV hep-ph/9806332]9806332 Cross sections

9. WIN05 Delphi 6-11 June 2005 V. Šimák, CTU Prague 9 % e qq e 1.22.5 14.8  1.22.514.8  1.214.8 qq44.4 Top decays classification: di-lepton, lepton+jets, all jets gg->tt: 87% charge, mass, spin, decay, dynamics of production Top quark properteis:

10. WIN05 Delphi 6-11 June 2005 V. Šimák, CTU Prague 10 Atlas Q t = +2/3 Q t = -4/3 t coupling to photon can be probed via t tbar  events can also be used to confirm Q=2/3 pT(  ) [GeV] 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

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

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

13. 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 m t   1 GeV

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

15. WIN05 Delphi 6-11 June 2005 V. Šimák, CTU Prague 15 t t W Polarization in Top Decays b t f0f0

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

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

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

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

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

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

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

23. 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 p T (lep) > 20 GeV Njet  6 with p T (jet) > 15 GeV Nbjet = 4

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

25. WIN05 Delphi 6-11 June 2005 V. Šimák, CTU Prague 25 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 Atlas

26. 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

27. Helicity angle correlations in model with graviton (M D = 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 M D is lower than ~1.5-2 TeV Phys.Rev. D70, p15015, 2004 e-Print Archive: hep-ph/0409273

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

29. WIN05 Delphi 6-11 June 2005 V. Šimák, CTU Prague 29 Test some models beyond SM : New type of interactions (resonant Higgs, extra-dimensions, …) Modifications of SM couplings : anomalous gtt couplings anomalous Wtb coupling 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… u d s c b t

30. 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)

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