Single Top Search

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Single Top Search
New Kinematics Fitter for event selection
and Wcc background
K Nakamura
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61.21
9.5
1.9
0.49
3.3
7.02
----
0.6

20.67
S/B7.02/96.60.07 S/sq(B)0.71
S/B15.3/534.50.03 S/sq(B)0.66
improvement
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Mlb distribution
Mlnb distribution normalized by of events of
CDFnote
At least 1 b-tag
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Double tag
At least 1 b-tag
SS SJ double tag
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W boson direction at the W rest frame
Dominant channel of Wbb background is t-channel
like upper right feynman diagram. -gt W boson
direction is close to p or pbar direction
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Signal
W
W
f
b
f
b
t
t
d
u
d
P
P
u
W-
W
Z
_at_ 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
_at_ Wbb Rest Frame
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cosfw distribution
generator level w/o acceptance cut
simulated
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cosfw distribution
generator level w/ acceptance cut
simulated
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cosfwxQlep distribution
We can use this variable for event selection !
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lepton direction at the Top rest frame
_at_ Top Rest Frame
n
n
l-
l
f
u
d
u
d
f
t
t
P
P
b
Z
b
Top quark is polarizing the d-type-quark
direction at the top rest frame. -gt lepton is
boosted d-type-quark direction
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bb system behavior for the event selection
-gt bb invariant mass in the Wbb background looks
much smaller than signal -gt gluon
splitting to bbbar is very soft like ISR. -gt
distance between bb and W of the Wbb bkg is
larger than signal
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Ptbb
Mbb
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Collation of Ptbb and Mbb distribution
Signal gen
Signal simulated
Mbb
Wbb simulated
Wbb gen
Ptbb
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distance between bb and W
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distance between bb and W
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gen
-2logL
simulated
Use only signal PDF
gen
simulated
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-2logL vs Mlnb
signal
ttbar
wbb
wcc
Shape of distribution is made from pretag sample
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Significance
S/sqB 0.80
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Backup
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S-channel single top event _at_ CM Frame
ambiguity
CDFNOTE
Selection of bjet from top quark
t-channel tagged jet -gt 95
s-channel tagged jet -gt 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??
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Neutrino solution
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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
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bbbar ambiguity
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Likelihood Function for bbbar ambiguity
f is the angle of b-jet _at_ Wstar Rest Frame
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Top Specific Correction for b-jet
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Top Specific Correlation Factor
gen P Rec P
Rec P
p02.12 p123.3 p20.057
p01.83 p124.8 p20.032
p01.31 p125.0 p20.081
From takeuchi-san
From takeuchi-san
From takeuchi-san
distribution
Xaxis value of each bin is weighted mean
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Mlnb distribution
Sim Lev
-- top -- other
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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
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-2Log L distribution as the function of PnZ
First 6 events
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Likelihood distribution for the case of PnZ0
Most likely PnZ is really 0 ?? Is this
correct??