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Single Top Search. ~ New Kinematics Fitter for event selection ~. 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 ~ New Kinematics Fitter for event selection ~ 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 Mlnb distribution normalized by # of events of CDFnote At least 1 b-tag
Double tag… At least 1 b-tag S+S S+J double tag
Likelihood for Event Selection 2D Likelihood
distribution MbbGeV MbbGeV PtbbGeV PtbbGeV
-2logL old new simulated simulated simulated
Mlnb distribution Double tag shape
Mlnb distribution pre tag shape normalized by # of double tag events
Definition of most significant mass region Width of mass region [GeV] Center of mass region [GeV]
Conclusion No threshold S/sqB=0.75 threshold=1 S/sqB=0.81 TO DO Estimate the significance to fit bkg and signal distribution… Study Event selection to reject ttbar background… Estimate data based background event yield for double tag…
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
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
cosfw distribution generator level … w/o acceptance cut simulated
cosfw distribution generator level … w/ acceptance cut simulated
cosfwxQlep distribution We can use this variable for event selection !
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
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
Ptbb Mbb
Collation of Ptbb and Mbb distribution Signal gen Signal simulated Mbb Wbb gen Wbb simulated Ptbb
-2logL vs Mlnb signal ttbar wbb wcc **Shape of distribution is made from pretag sample
Significance S/sqB = 0.80
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??
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
Likelihood Function for bbbar ambiguity f is the angle of b-jet @ Wstar Rest Frame
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
Mlnb distribution Sim Lev -- top -- other
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%
-2Log L distribution as the function of PnZ First 6 events…
Likelihood distribution for the case of PnZ=0 Most likely PnZ is really 0 ?? Is this correct??
Likelihood for Event Selection 2D Likelihood