single top search ~ new kinematics fitter ~ k nakamura
TRANSCRIPT
Single Top Search
~ New Kinematics Fitter ~
K Nakamura
S-channel single top event @ CM Frame
W*
t
b
b
l
ambiguity
Selection of bjet from top quark
t-channel : tagged jet -> 95%
s-channel : tagged jet -> 53%
CDFNOTE
top mass resolution +15 GeV
Selection of neutrino Pz solution30% … no solution
Mlb : for 4 cases
This Top Mass constraint gave some bias to Mlnb distribution??
Neutrino solution
Likelihood Function for neutrino Pz
To define a Likelihood as the function of Neutrino Pz
Move three parameters: METx METy PZ
2 solution case
0 or 1 solution case
PZ @GenLev
---- W*+
---- W*-
To have pronounced tendency to separate W*+ and W*-
P PW*-
t
b
b
l-
W*+
t
b
b
l+
+Z
correct wrong
PZ *Qlep
@Sim
---- correct---- wrong
W*
t
b
b
l
MW*2
> Mt2+Mb
2~ Mt2
MW* =q2=sW* has the mass as small as possible to keep larger than Mt…??
W* mass
MW*
@SimUsing L5 jet
No b jet correction
Likelihood … correlation check
MW*
PZ *Qlep
MET
Gaussian
DoubleGaussian
We use this one !
Result of the Likelihood fitting
bbbar ambiguity
Likelihood Function for bbbar ambiguity
is the angle of b-jet @ Wstar Rest Frame
B-jet Pt distribution
W*
t
b
b
l
Using L5 jet
No b jet correction
Gen Lev Sim Lev
-- top-- other
-- top-- other
Use these distribution as the Probability Density Function
Mlb distribution
W*
t
b
b
l
Using L5 jet
No b jet correction
Gen Lev Sim Lev
-- top-- other
-- top-- other
Use these distribution as the Probability Density Function
cosb x Qlep
P P
W*-t
b
b
l-
W*+t
b
b
l+
+Z
tb production process has the V-A coupling, so it is easy for the b-jet to be produced in the direction of quark in proton, and bbar-jet to be produced in the direction of anti-quark in anti-proton @ the Wstar rest frame.
@ Wstar Rest Frame
cos angle shown in upper figure times lepton charge is the powerful variable to select b-jet which is directory producedform Wstar.
cosb distribution
Gen Lev
Sim Lev
top other
top other
---- W*+
---- W*-
cosb x Qlep distribution
Gen Lev
-- top-- other
Sim Lev-- top-- other
Use these distribution as the Probability Density Function
Parameter correlation
These figure shows some correlations between the Likelihood parameters……But Likelihood is only used as the choosing bbbar ambiguity, so we use this likelihood !
Top Specific Correction for b-jet
Correlation Factor as the function of Pt Eta
After Correction check
Top Mass DistributionLinear Scale Log Scale
Wbb background Shape
---- Wbb---- Signal
Normalization is not correct…
Use MC Wbb+0j bkg
---- Wbb---- Signal
Mlnb distribution normalized by # of events of CDFnote
Wbb 198.5 events s-channel 15.00 events
At least 1 b-tag
64.3%
29.5%
52.4%
19.7%
B-tag
45.9%37.6%
Signal W(mu)bb
---- Wbb---- Signal
At least 1 b-tag S+S S+J double tag
Double tag…
---- Wbb---- Signal
Enhancement !?
ConclusionWe developed new likelihood fitter without using top mass constraintMake Likelihood fitter like blow :
For the 75.2% events of the 2 solution events we can choose the correct solution.After decided neutrino Pz, we can choose the correct b-jet from the top quark for the 81% of the total events.But Mlnub distribution is not so improved…We will try to check correlation between the likelihood variables and top mass
2 solution case
0 or 1 solution case
Backup
W*
t
b
b
l
wrong
correct
PW*Z
@GenLev
---- W*+
---- W*-
Bug is Fixed !
PZ *Qlep
@GenLev
---- correct---- wrong
W*
t
b
b
l
wrong
correct
MW*
@GenLev
Probability Density Function
Neutrino Solution Check
@GenLev @SimChoose CorrectSolution
Result of the Likelihood fitting What??
PZ=0 ??
-2Log L distribution as the function of PZ First 6 events…
Likelihood distribution for the case of PZ=0
Most likely PZ is really 0 ?? Is this correct??
---- correct---- wrong
corr
wrong
72.7%75.2%
Likelihood for Solution
corr
wrong