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The Top Quark Yesterday and Today

The Top Quark Yesterday and Today. Hugh Montgomery Jefferson Lab IRFU-CEA Saclay February 4, 2010. Outline. Why do we need the top quark? A virtual life Observation of the Top Quark Properties of the Top Quark Electroweak Coupling of the Top Quark The Top Quark and the Future.

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The Top Quark Yesterday and Today

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  1. The Top Quark Yesterday and Today Hugh Montgomery Jefferson Lab IRFU-CEA Saclay February 4, 2010

  2. Outline Why do we need the top quark? A virtual life Observation of the Top Quark Properties of the Top Quark Electroweak Coupling of the Top Quark The Top Quark and the Future

  3. Elementary Particle Physics

  4. Elementary Particle Physics Fermicentric Dates Major Discoveries • b quark 1977 • t quark 1995 • nt(tau neutrino) 2000 Critical measurements • t and W mass 1998 • proton structure 1984-95 using neutrinos and muons • QCD at highest 1988-now energies

  5. Upsilon Discovery- 1977 bound state of bottom quarks

  6. The Virtual Life of the Top Quark 10

  7. Premature Single Top Production Schwienhorst – Fermilab W&C 4/1/2005

  8. An ephemeral existence UA1 at the SppS 1984: –Using isolated high transverse momentum lepton –2 or 3 hadron jets –Observed 5 events (e+ >=2 jets); 4 events (μ+ >=2 jets) –Expected background: 0.2 events •fake leptons dominate •bb & cc production negligible –Conclude: results consistent with M top = 40 ±10 GeV 1988: –x6 the data – much better understanding of backgrounds – M top > 44 Yagil – Top Turns Ten

  9. For a top mass less than the W mass UA2 (88/89) was competitive with CDF Yagil – Top Turns Ten

  10. Mass Predictions and Limits Quigg, Langacker

  11. Fermilab Antiprotons

  12. 57pb 19pb Tevatron Run I and Top Dec 94 Aug 93 Yagil – Top Turns Ten

  13. CDF - The Experiment

  14. D0 CDF Urgency Glenzinski – Top Turns Ten

  15. DZero

  16. A First Hint for CDF Yagil – Top Turns Ten

  17. A DZero Top Quark?

  18. Profile of the Top Quark Grannis– The Antitop Quark at the Antiproton celebration, LBL

  19. Top Production and decay DIL - both W decay to leptons Low rate, Very clean SVX - one of the b-jets is identified using a displaced vertex tag SVX detector SLT - one of the b-jets is identified using a leptonic decay product lepton I.D. in jets Yagil – Top Turns Ten

  20. Dilepton Observations 1995 Grannis– The Antitop Quark at the Antiproton celebration, LBL

  21. Single Lepton & Jets Grannis– The Antitop Quark at the Antiproton celebration, LBL

  22. Discovery : Observation Grannis– The Antitop Quark at the Antiproton celebration, LBL

  23. List of Institutions on Dzero at time of discovery (Grannis), Hadley – Top Turns Ten

  24. Dzero Author List Abachi to Zylberstejn Thanks to all (Grannis), Hadley – Top Turns Ten

  25. Top Mass

  26. Constraints/Observables • 18 fermion 3-vector components • Use constraints • W mass (twice) (2) • Mass of top = mass of antitop (1) • Assume mass for top • Fit using measurement errors • Measure 1 lepton(3) and 4 jets (12) and Missing Transverse Energy (2) • 20 constraints plus measurements (20-18 2C) • Measure 2 leptons(6) and 2 jets (6) and Missing Transverse Energy (2) • 17 constraints plus measurements (17-18 -1C) • Further constraints • The parton distributions (poor man’s beam energy) • Internal characteristics • Full matrix element

  27. Top Mass: Methodologies • Choose any characteristic of the event which is related to the top mass • Lepton transverse momentum • B quark decay length • Mass reconstructed by constrained fit • To lepton plus jets events (2C) • using just kinematics • Using full matrix element • Reducing combinations with b tagging • To dilepton events (<~0C!!!) • using all the approaches above • To All jets events • Using all the different approaches above • WITH (IN)Efficiencies properly treated!! • Lots of MC studies • WITH BACKGROUNDS properly treated!!

  28. The Mass of the Top Quark CDF 1994 CDF measured: 1994 Mtop = 174 +- 10 +- 13 GeV 1995 Mtop = 176 +- 8 +- 10 GeV Yagil – Top Turns Ten

  29. Top Mass Grannis– The Antitop Quark at the Antiproton celebration, LBL

  30. D0 Run I – Full Matrix Element For each event estimate probability for a top mass value using all measured quantities compared to distribution of t-tbar production matrix element. (Need to integrate over measurement resolutions)

  31. Contemporary Top Mass Tevatron (Winter 09): mt=173.1 ± 0.6 (stat) ± 1.1 (syst) GeV mt=173.1 ± 1.3 (stat+syst) GeV CDF (4.3 fb-1): mt(l+j)=172.6±0.9(stat)±0.7(JES) ±1.1(syst)GeV Single Experiment Uncertainty ~1 GeV!!!! FlorenciaCanelli, LP2009

  32. Implications of the Top Quark Mass The total width of the top quark is 1- 1.5 GeV ( proportional to m3 ) The top quark decays in 0.5 * 10-24 seconds Before it can form a hadron No top mesons No toponium No hadronisation Hadronisation does not modify the spin orientation The observed mass is that of the quark The top quark is our only bare quark!

  33. Luminosity Helps FlorenciaCanelli, LP2009

  34. Top Quark Pair Production Cross Section Quadt– Top Quark Physics at Hadron Colliders- Habilitationschrift

  35. Top Quark Pair Production Cross Section 6% precision! ~ 6% Precision FlorenciaCanelli, LP2009

  36. ttbar production spectra Grannis– The Antitop Quark at the Antiproton celebration, LBL

  37. ttbar Production

  38. Single Top Production Schwienhorst – Fermilab W&C 4/1/2005

  39. Single Top Production Tevatron (3.2 fb-1): st=2.76 +0.58 -0.47 (stat+syst) pb Tevatron (3.2 fb-1), PRD66 054024, 2002: |Vtb|=0.91 ± 0.08 (stat+syst) FlorenciaCanelli, LP2009

  40. Top Quark Properties

  41. Top Quark Properties FlorenciaCanelli, LP2009

  42. Top Quark Decays R = B(tWb)/B(tWq) Related to Vtb Determined from the relative numbers of 0, 1 and, 2 b quark tags D0 Result (CDF similar) R = 1.03+/-0.19/0.17 Vtb >~ 0.8 Quadt– Top Quark Physics at Hadron Colliders- Habilitationschrift Buescher- D0 Report to PAC, December 2005

  43. Top Quark Decays t  H+b? Different possible decays of the H+ Quadt– Top Quark Physics at Hadron Colliders- Habilitationschrift

  44. W-Helicity in top Decay Correlations between the lepton and b jet direction in the W rest frame. lepton pT spectrum depends on W helicity Effective mass of lepton and b jet Fit to full matrix element κ = N(↑↑) + N(↓↓) − N(↑↓) − N(↑↓) N(↑↑) + N(↓↓) + N(↑↓) + N(↑↓) Grannis– The Antitop Quark at the Antiproton celebration, LBL Quadt– Top Quark Physics at Hadron Colliders- Habilitationschrift

  45. Top-antitop spin correlations κ = N(↑↑) + N(↓↓) − N(↑↓) − N(↑↓)SM predicts κ = 0.78 N(↑↑) + N(↓↓) + N(↑↓) + N(↑↓) D0 (4 fb-1): κ =-0.17 +0.64 -0.53 CDF (2.8 fb-1): κ =0.32 +0.55-0.78 FlorenciaCanelli, LP2009

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