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Single Top Search

Single Top Search. ~ New Kinematics Fitter for event selection and Wcc background ~. K Nakamura. 61.21. 9.5. 1.9. 0.49. 3.3. 7.02. ----. 0.6. }. 20.67. S/B=7.02/96.6=0.07 S/sq(B)=0.71. S/B=15.3/534.5=0.03 S/sq(B)=0.66. improvement. Mlb distribution.

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Single Top Search

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  1. Single Top Search ~ New Kinematics Fitter for event selection and Wcc background ~ K Nakamura

  2. 61.21 9.5 1.9 0.49 3.3 7.02 ---- 0.6 } 20.67 S/B=7.02/96.6=0.07 S/sq(B)=0.71 S/B=15.3/534.5=0.03 S/sq(B)=0.66 improvement

  3. Mlb distribution Mlnb distribution normalized by # of events of CDFnote At least 1 b-tag

  4. Double tag… At least 1 b-tag S+S S+J double tag

  5. W boson direction at the W* rest frame Dominant channel of Wbb background is t-channel like upper right feynman diagram. -> W boson direction is close to p or pbar direction

  6. Signal W W f b f b t t d u d P P u W*- W*+ +Z @ Wstar Rest Frame b b Wbb b b b b u d u d f d u d u P P f + - + - +Z W W @ Wbb Rest Frame

  7. cosfw distribution generator level … w/o acceptance cut simulated

  8. cosfw distribution generator level … w/ acceptance cut simulated

  9. cosfwxQlep distribution We can use this variable for event selection !

  10. lepton direction at the Top rest frame @ Top Rest Frame n n l- l+ f d u f u d t t P P b +Z b Top quark is polarizing the d-type-quark direction at the top rest frame. -> lepton is boosted d-type-quark direction

  11. bb system behavior for the event selection -> bb invariant mass in the Wbb background looks much smaller than signal… -> gluon splitting to bbbar is very soft like ISR. -> distance between bb and W of the Wbb bkg is larger than signal

  12. Ptbb Mbb

  13. Collation of Ptbb and Mbb distribution Signal gen Signal simulated Mbb Wbb gen Wbb simulated Ptbb

  14. distance between bb and W

  15. distance between bb and W

  16. gen -2logL simulated Use only signal PDF gen simulated

  17. -2logL vs Mlnb signal ttbar wbb wcc **Shape of distribution is made from pretag sample

  18. Significance S/sqB = 0.80

  19. Backup

  20. S-channel single top event @ CM Frame n l t W* b b ambiguity CDFNOTE Selection of bjet from top quark t-channel : tagged jet -> 95% s-channel : tagged jet -> 53% top mass resolution +15 GeV Selection of neutrino Pz solution 30% … no solution Mlnb : for 4 cases This Top Mass constraint gave some bias to Mlnb distribution??

  21. Neutrino solution

  22. Likelihood Function for neutrino Pz To define a Likelihood as the function of Neutrino Pz 2 solution case 0 or 1 solution case Move three parameters: METx METy PnZ

  23. bbbar ambiguity

  24. Likelihood Function for bbbar ambiguity f is the angle of b-jet @ Wstar Rest Frame

  25. Top Specific Correction for b-jet

  26. Top Specific Correlation Factor gen P – Rec P Rec P p0=2.12 p1=23.3 p2=0.057 p0=1.83 p1=24.8 p2=0.032 p0=1.31 p1=25.0 p2=0.081 From takeuchi-san From takeuchi-san From takeuchi-san Xaxis value of each bin is weighted mean distribution

  27. Mlnb distribution Sim Lev -- top -- other

  28. B-tag Signal W(mu)bb ttbar 64.3% 52.4% 57.2% 45.9% 37.6% 36.5% 29.5% 19.7% 20.9%

  29. -2Log L distribution as the function of PnZ First 6 events…

  30. Likelihood distribution for the case of PnZ=0 Most likely PnZ is really 0 ?? Is this correct??

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