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Top Quark Properties from CDF

2. Top Quark Discovery: 1995. . The search for top lasted almost twodecades. Its unexpectedly heavy mass delayed discovery.. CDF Run 1. CDF D0 combined: Mass (top) = 178 ? 4.3 GeV/c2. 3. Why Is Top So Interesting?. Well, top physics is different! Top quark lifetime is short: decays before hadronizingNo spectroscopy like other heavy flavorTop momentum and spin transferred to decay products Probes physics at higher scales than other known fermion30164

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Top Quark Properties from CDF

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    1. Top Quark Properties from CDF Robin D. Erbacher University of California, Davis

    2. 2 Top Quark Discovery: 1995 May play a special role in EWS May play a special role in EWS

    3. 3 Why Is Top So Interesting? Very short lifetime, less than the characteristic timescale of nonperturbative QCD. Free from effects of non-perturbative QCD: don’t have to worry about form factors, decay constants, exclusive decays, and other things associated with heavy flavor physics. This allows eventual precision test of the top sector Very short lifetime, less than the characteristic timescale of nonperturbative QCD. Free from effects of non-perturbative QCD: don’t have to worry about form factors, decay constants, exclusive decays, and other things associated with heavy flavor physics. This allows eventual precision test of the top sector

    4. 4 Elucidating the Top Quark in Run 2

    5. 5 # of Physicists for Particle Discovery

    6. 6 Physics of the Top Quark The Tevatron has the world’s only supply of top quarks. The Tevatron has the world’s only supply of top quarks.

    7. 7 How is Top Produced?

    8. 8 How Else is Top Produced?

    9. 9 How Does Top Decay? The diagram shows the single lepton decay signature of tt pairs: a high Pt charged lepton, four jets (two from b quark hadronization) and an energetic neutrino. In SM, BR(t->W+ + b) ~ 100%. tautop ~ 1/m3top ~ 10-24 s . tauQCD ~ 1/LambdaQCD ~ 10-23 s The diagram shows the single lepton decay signature of tt pairs: a high Pt charged lepton, four jets (two from b quark hadronization) and an energetic neutrino. In SM, BR(t->W+ + b) ~ 100%. tautop ~ 1/m3top ~ 10-24 s . tauQCD ~ 1/LambdaQCD ~ 10-23 s

    10. 10 Identifying Top Quarks Mention digital front end 8 layers of silicon versus 4 layers in Run 1Mention digital front end 8 layers of silicon versus 4 layers in Run 1

    11. 11 Measuring Top Pair Production

    12. 12 Finding Top Is Difficult!

    13. 13 Top Cross Section Measurements (Scorecard)

    14. 14 Collected Dataset for CDF

    15. 15 Multivariate L+J Cross Section: Neural Network Mention here the power of using neural networks to find Higgs: run 1 analysis…Mention here the power of using neural networks to find Higgs: run 1 analysis…

    16. 16 Kinematics to Find Top

    17. 17 Kinematic Cross Section Results

    18. 18 Keys to Improvement

    19. 19 SecVtx B-tagging in Lepton+Jets This is used for the updated SecVtx Cross section, and for the new mass results, etc.This is used for the updated SecVtx Cross section, and for the new mass results, etc.

    20. 20 Optimized L+J Cross Section Analysis Ht cuts 6% signal, 50% of background, mainly in 3 jet bin Mt cuts 3% of signal, 30-40% of non-W backgroundHt cuts 6% signal, 50% of background, mainly in 3 jet bin Mt cuts 3% of signal, 30-40% of non-W background

    21. 21 SecVtx B-tagged Cross Section

    22. 22 SecVtx Cross Section Systematics

    23. 23 SecVtx Double-Tagged Event

    24. 24 CDF Cross Section Results Summary

    25. 25 Run 1: Excess in the b-tagged Lepton + Jets Sample?

    26. 26 Understanding Wbb+Jets

    27. 27 W+bb/W+jj Ratio Results

    28. 28 Top Mass: Current World’s Best

    29. 29 New Top Mass: Updated Dynamic Likelihood Result

    30. 30 New DLM Top Mass Result Expected background fraction is 21%. To get mapping, backgrounds are fluctuated (separately or together) w/ poisson b/w 0 and 50%.Expected background fraction is 21%. To get mapping, backgrounds are fluctuated (separately or together) w/ poisson b/w 0 and 50%.

    31. 31 DLM Top Mass Systematics

    32. 32 New Top Mass Comparisons

    33. 33 CDF Top Mass Summary

    34. 34 Future for Top Mass

    35. 35 Top Decay Properties

    36. 36 Measuring BR(t?Wb)/BR(t?Wq)

    37. 37 Measuring BR(t?Wb)/BR(t?Wq)

    38. 38 ”R” Consistent with Standard Model

    39. 39 Measurement of BR(t?H±b) For a given higgs mass, compute the efficiency for each decay channel for that cross section. Charge higgs bosons appear in 2HDM such as MSSMFor a given higgs mass, compute the efficiency for each decay channel for that cross section. Charge higgs bosons appear in 2HDM such as MSSM

    40. 40 Expected Events v. tan(?) Per Sample

    41. 41 Limits: MH+ v. tan?, Min Stop Scenario Benchmark #5 : ?This is the typical benchmark scenario developed for the search of h0 at LEP(hep-ph/9912223). The value of At is computed as a function of tan(b), allowing for the minimum mass of the h0 for each value of tan(b). Benchmark #5 : ?This is the typical benchmark scenario developed for the search of h0 at LEP(hep-ph/9912223). The value of At is computed as a function of tan(b), allowing for the minimum mass of the h0 for each value of tan(b).

    42. 42 What Can We Take from This?

    43. 43 W Helicity from t?Wb Decays

    44. 44 Run 2 W Helicity in Top Events

    45. 45 Run 2 W Helicity Using cos?*

    46. 46 What About Production?

    47. 47 Search for High ET Top-Like Events

    48. 48 HT Plot with t' Signal, M(t') =225 GeV

    49. 49 Result: Limits (pb) Versus M(t')

    50. 50 Projected Limits: Higher Luminosity

    51. 51 Run 1 Searches for ttbar Resonances Use Bayesian statistics to derive posterior probability distns by fitting mttbar from data weighted to sum of 3 sources. Write Nx=A*L*Sx*B, can define Sx*B at 95% CL. No statistically significant excess is found. Use Bayesian statistics to derive posterior probability distns by fitting mttbar from data weighted to sum of 3 sources. Write Nx=A*L*Sx*B, can define Sx*B at 95% CL. No statistically significant excess is found.

    52. 52 What Else is in the Top Sample?

    53. 53 Run 1: Anomalies in the Top Di-lepton Sample?

    54. 54 Run 2: Di-lepton Kinematics

    55. 55 Analysis of SM Agreement Probability Using Kinematics Larg T consistent with ttbar dilepton topology-- consistency of met with expectedLarg T consistent with ttbar dilepton topology-- consistency of met with expected

    56. 56 Kinematic Discriminants Look Standard

    57. 57 CDF Top Physics Publications

    58. 58 Near Term Plans

    59. 59 Summary

    60. 60 Conclusions

    61. 61 Searches for Single Top

    62. 62 Standard Model Higgs? 96 GeV preferred is the 68% CL using delta chisquare = 1 (for black line, not including theory errors). Upper limit of 219 is from a one-sided 95% CL using delta chisquare = 2.7 for the blue band…96 GeV preferred is the 68% CL using delta chisquare = 1 (for black line, not including theory errors). Upper limit of 219 is from a one-sided 95% CL using delta chisquare = 2.7 for the blue band…

    63. 63 Can a t' Exist?

    64. 64 Neural Network Details

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