Top Quarks in Year 1
Akira Shibata
New York University
ATLAS Workshop of the Americas @ NYU
5 Aug, 2009

Can Top change our perspective?
• Why is top so heavy (10 water molecules)? Any
special role in EW symmetry breaking?
• Does it play even more fundamental role than
Higgs mechanism + Yukawa coupling?
• If there is new physics signal lighter than top,
does the top quark decay into them?
• Could non-SM physics first manifest itself in non-
standard couplings of the top quark?
• Top quark can be measured at significant
precision at the LHC to answer these questions.
• Top quark has been an extremely productive
ground for speculation and searches at Tevatron.
Workshop of the Americas ’09 2 akira.shibata@nyu.edu

New Physics via Top Decay
• The final state of a t¯system is primarily clas-
t
sified by the decay modes of the two W bosons:
• Various decay modes make top
physics interesting and useful
• The top interfere with a number of
new physics signatures.
• Typical search modes:
• Lepton + jets (e/mu)
• Dileptonic
• All hadronic
• Tau channels
• E.g. If mW<mH+<mt and tanβ>>1, top
can decay into charged higgs,
enhancing the τ lepton rate.
Workshop of the Americas ’09 3 akira.shibata@nyu.edu

New Physics via Top Decay
• The final state of a t¯system is primarily clas-
t
sified by the decay modes of the two W bosons:
• Various decay modes make top
physics interesting and useful
Name
Fully Hadronic
Signature
jets
BR
45.7%
xsec at 10 TeV
191.5 pb • The top interfere with a number of
new physics signatures.
•
Lepton + Jets e + jets 17.2% 71.9 pb
µ + jets 17.2% 71.9 pb Typical search modes:
Dilepton eµ + jets
µµ + jets
3.18%
1.59%
13.3 pb
6.67 pb • Lepton + jets (e/mu)
ee + jets 1.59% 6.67 pb
• Dileptonic
Tau + Jets
Lepton + Tau
τ + jets
τ + e/µ + jets
9.49%
3.54%
39.8 pb
14.8 pb • All hadronic
Tau + Tau τ + τ + jets 0.49% 2.06 pb
• Tau channels
total all 100% 419 pb
• E.g. If mW<mH+<mt and tanβ>>1, top
can decay into charged higgs,
• Diboson (ME: MC@NLO, PS: Herwig + Jimmy) enhancing the τ lepton rate.
The MC samples were generated with 5 TeV against 5 TeV beam energy. CTEQ 6 PDF set
was used and the top mass was set to be 172.5 GeV. Alpgen MLM matching threshold was set to akira.shibata@nyu.edu
Workshop of the Americas ’09 3

80 90 100 110 120 130 140 150 160
MH+ [GeV]
Search for Charged Higgs
FIG. 10: Observed (blue) and expected (red) limit with one standard deviation band (yellow) on Br(t → H + b)
of charged Higgs mass for simultaneous fit of Br(t → H + b) and σtt in the tauonic model.
¯
DØ Run II Preliminary
MH+ [GeV]
+
H # cs H+ # " ! DØ Note 5715-CONF
180 Expected limit 95% CL
Expected limit 95% CL
Excluded 95% CL Excluded 95% CL
160
140 tauonic
leptophobic
120
100
80
1 10
tan $
FIG. 11: Observed (blue) and expected (red) limit with one standard deviation band (yellow) on charged Hi
function of tan β.
Research Council and WestGrid Project (Canada), BMBF (Germany), A.P. Sloan Foundation, Civil
Workshop of the Americas ’09 4
and Development Foundation, Research Corporation, Texas akira.shibata@nyu.edu
Advanced Research Program, and the A

80 90 100 110 120 130 140 150 160
MH+ [GeV]
Search for Charged HiggsFIG. 10: Observed (blue) and expected (red) limit with one standard deviation band (yellow) on Br(t → H + b)
of charged Higgs mass for simultaneous fit of Br(t → H + b) and σtt in the tauonic model.
¯
DØ Run II Preliminary
MH+ [GeV]
+
H # cs H+ # " ! DØ Note 5715-CONF
180 Expected limit 95% CL
Expected limit 95% CL
Excluded 95% CL Excluded 95% CL
160
140 tauonic
leptophobic
120
100
80
1 10
tan $
Good tau/jet calibration and backgroundand expected (red) limit with one standard deviation band (yellow) on charged Hi
FIG. 11: Observed (blue) control is essential for this search.
Not a “Day-1 physics”
function of tan β.
Research Council and WestGrid Project (Canada), BMBF (Germany), A.P. Sloan Foundation, Civil
Workshop of the Americas ’09 4
and Development Foundation, Research Corporation, Texas akira.shibata@nyu.edu
Advanced Research Program, and the A

onance Search New Physics into Top overlapping
ν e
¯
Fraction/25GeV
0.22
ulate pp invariant → t for tt pairs
the → X mass t
(a) SM tt
0.2
pp → X → t t
for a bump!
¯ b W + 0.18
X!tt MX=450GeV
X!tt MX=650GeV
pp → b ¯ → W − t W + t ¯
0.16
b
the dominant background is Standard
0.14 X!tt MX=1000GeV
pp → b ¯ → W − t W + t ¯ 0.12
el tt! b t boosted 0.1
DØ Preliminary
pp → g g → gt g t ¯
challenges for large masses (> 1 TeV)
0.08
0.06
ghly boosted g → gt ¯
pp → topgquarks g t X 0.04
0.02
00 200 400 600 800 1000 1200
verlapping decay products Mtt [GeV]
construct “top quark jets” ¯
t boosted Topcolor Z’ excluded < 800 GeV.
If new physics is leptophobic, Kaluza-Klein gluon excluded < 1TeV
FIG. 1: Shape comparison of expected tt invariant mass distribut
s limits depend on the theoretical model
they may couple strongly to
(histogram) compared to resonant production from narrow-wid
for (a) 3 jet events and (b) ≥ 4 jet events.
ematic errors similar to those for tt W−
s-section Otherwise, dimuon is a
top.
¯
clearer signature.
q b VI. SYSTEMATIC
¯
q
The systematic uncertainties can be classified as those a
of any of the signal or background invariant mass distri
overlapping 8
normalization include the theoretical uncertainty on the S
luminosity (6.1%) [29] and the uncertainty of lepton identifi
Workshop of the Americas ’09 5 akira.shibata@nyu.edu
The systematic uncertainties affecting the shape of the inv

onance Search New Physics into Top overlapping
ν e
¯
Fraction/25GeV
0.22
ulate pp invariant → t for tt pairs
the → X mass t
(a) SM tt
0.2
pp → X → t t
for a bump!
¯ b W + 0.18
X!tt MX=450GeV
X!tt MX=650GeV
pp → b ¯ → W − t W + t ¯
0.16
b
the dominant background is Standard
0.14 X!tt MX=1000GeV
pp → b ¯ → W − t W + t ¯ 0.12
el tt! b t boosted 0.1
DØ Preliminary
pp → g g → gt g t ¯
challenges for large masses (> 1 TeV)
0.08
0.06
ghly boosted g → gt ¯
pp → topgquarks g t X 0.04
0.02
00 200 400 600 800 1000 1200
verlapping decay products Mtt [GeV]
construct “top quark jets” ¯
t boosted Topcolor Z’ excluded < 800 GeV.
If new physics is leptophobic, Kaluza-Klein gluon excluded < 1TeV
FIG. 1: Shape comparison of expected tt invariant mass distribut
s limits depend on the theoretical model
they may couple strongly to
(histogram) compared to resonant production from narrow-wid
for (a) 3 jet events and (b) ≥ 4 jet events.
ematic errors similar to those for tt W−
s-section Otherwise, dimuon is a
top. Good control of SM top and jet
q ¯
b
clearer signature. ¯
q resolution & jet substructure.
VI. SYSTEMATIC
The systematic“Day-1 physics”those a
Not a uncertainties can be classified as
of any of the signal or background invariant mass distri
overlapping 8
normalization include the theoretical uncertainty on the S
luminosity (6.1%) [29] and the uncertainty of lepton identifi
Workshop of the Americas ’09 5 akira.shibata@nyu.edu
The systematic uncertainties affecting the shape of the inv

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Workshop of the Americas ’09 6 akira.shibata@nyu.edu

State of the Art at
Tevatron
Cross-Section Measurement
• Semileptonic channel
• High branching ratio (~36/81)
• Event over-constrained
• Manageable background
• Dileptonic channel
• Low background
• Low branching ratio (~9/81)
• Event under-constrained
• Fully hadronic channel
• Event fully constrained
• Huge QCD and comb. background
• Lepton + Track
• Highly inclusive
• Different systematics for track
performance.
8% precision all combined (summer 2008)
Workshop of the Americas ’09 7 akira.shibata@nyu.edu

Graph
!t t [pb] RULES OF THUMB
1.2
1000 CDF Results ! Running at 10 TeV takes ~twice as 1
much data as 14 TeV for equivalent
Xsec relative to 14 TeV
LHC 14 TeV @ 100pb-1 Expectations (CSC) 0.8
sensitivity W, Z
Theoretical NLO (pp)
0.6 Top
800 Theoretical NLO (pp) ! Running at 8 TeV takes ~twice as Z' (2 TeV)
Theoretical NLO+NNLL much data as 10 TeV for equivalent ee/μμ/eμ 0.4
sensitivity
NLO+NNLL Scale Uncertainty 0.2
600
0
e/μ+jets
Graph
12 ! Below 8 TeV things go “pear 0 2 4 6 8 10 12 14 16
! [pb]
Produced by Akira Shibata and Ulrich Husemann
tt
10 shaped” quickly. CM Energy (TeV)
8
400 6
4
2
Produced by Akira Shibata and Ulrich Husemann
We know a lot about top 4
200 1 1.5 2 2.5 already, from Tevatron and
[hep-ph/0204244]
[arXiv:0907.2527]
theorists, but LHC will show
0
us a LOT more. Priced
0 2 4 14 6 8 10 12 steeply in TeV, much more
s [TeV] so than the background.
NB: Large uncertainty in theory due to PDF not shown.
CSC assumed 5% luminosity
Workshop of the Americas ’09 8 akira.shibata@nyu.edu

Dhiman Chakraborty The Top Quark
First year detector is less than ideal Top Physics Potential
Numerous uncertainties that Triggering
affect measurements with the W tb coupling, |Vtb |
Lepton ID
+
early data: Top mass, width, spin, charge
Top mass constraint
• Trigger efficiency W mass constraint
• Non-uniform detector Initial state rad.
• Lepton identification Luminosity W+
ν
• Missing Et calibration and tails Production
PDF section
cross
e + /¯
q
Missing Et
• Light/b jet energy scale t
• QCD activity (MI, ISR/FSR) Resonant
production ?
Pile-up X
b
• Beam related issues (Pile-up, Underlying event
Production Yukawa coupling ?
Luminosity) kinematics B-tagging
!
• PDF Spin e−/q ¯
t Bjet energy scale
• Background normalization polarization
Kinematic fit B fragmentation
• other unknown unknowns Anomalous couplings ?
?
Jet reconstruction
Real performance need to be estimated from real data. Top is sensitiveRare/non-SM decays ?
Light jet e scale
to a variety of effect but it will also provide means for calibrationBranching fractions ? state rad.
Final
based on constraints in masses and decays.
Workshop of the Americas ’09 9 Oct 2006
9 8
akira.shibata@nyu.edu

• We will look into a very recent
study on single and di-lepton cross
section measurements.
• Much learned about the full approval
process: INT approved, PUB approval
in progress.
• Used the “MC08” Monte Carlo
samples with full Geant 4 simulation
(rel 14.2.20.x) Timeline (Dilepton note)
Apr 28. need for a summer note announced
• Collision energy is 10 TeV. Plots and May 06. editors appointed
tables are normalized to 200 pb-1. May 12. discuss selection
May 22. object and event selection agreed
May 26. discuss systematics
May 29. systematics treatment agreed
June 02. note submitted and comments received
June 05. top group approval
July 13. INT approval
July 28. Sent to collaboration review
cf: https://twiki.cern.ch/twiki/pub/Atlas/OperationModelOverviewDocument/physics_policy.pdf
Workshop of the Americas ’09 10 akira.shibata@nyu.edu

Strategy with the First Data
Do the simplest thing we can do: “cut and count”
N = L σtT BR ϵtrigϵlep A + B
pray for a large number
but expect large uncertainty. part data driven,
May not be available quickly to be estimated part MC driven
well known in SM from data
sensitive to
theoretical
uncertainty
Realistically, e and mu single lepton and dilepton channels
only. Taus, too difficult to calibrate. Fully hadronic too
difficult to trigger.
Workshop of the Americas ’09 11 akira.shibata@nyu.edu

Object Selection
• Trigger Not fully optimized (ongoing study in Top
• EF_e15_medium OR EF_mu15 Reconstruction Group) but emphasis on
• Electrons simplicity and robustness, relying only on
the clearest feature of the events and
• egamma isEM ElectronMedium objects.
• pT > 20GeV
• |η| <1.37 or 1.52<|η| <2.47 • Jets
• etcone20 < 6GeV • Cone4TowerJets, with pT>
• Muons 20GeV, |η| < 2.5.
• STACOmuons: isCombined. • Overlap removal: no selected
• pT > 20GeV electrons within ∆R = 0.2
• |η| < 2.5 • No b-tagging
• etcone20 < 6GeV • MEt
• No overlap with jets within ∆R = 0.3 • MEt_RefFinal
Workshop of the Americas ’09 12 akira.shibata@nyu.edu

24 all jets 22 435jets
all
Event Selection - Single Lepton
1
24 all jets match 0 20 40 60 80
235 100 120 1
Missing tran
24.1.1 Jet N 0 10i 20GeV
Figure 8: Missing transverse ener
•
Jet Multiplicity (Pt > 20 GeV)
One good lepton jet multiplicity distribution (right)
Jet Multiplicity (Pt > 20 GeV)
Events
entry (11 bins)
entry (11 bins)
140
•
4
based10 background estimations afte
entry (11 bins)
400
MET > 20 GeV (reduces QCD and Z) 1000 ATLAS Preliminary
ATLAS Preliminary
•
120 Simulation 350
Simulation 103
3 Jets with Pt > 40 GeV DRAFT
July 27, 2009 – 22 : 56 (reduces W)
Events
Events
Events
Events
Events
400
July 27, 2009 – 22 : 56 DRAFT 14 15 103
•
104
800 tt dilepton, ee
100 e+jets t t dilepton,tt dilepton, ee
eµ 104 300
4 Jets with Pt > 20 GeV (further reduces W)
120
tt other t t other
single top 102 350
•
single top tt other 250
100 Z+jets 300
ReconstructTable 3: from of events which pass the various muon tt¯ signal criteria for ¯
top Number 3 highest pt jet comb
3
10
3
600 Z+jets80 W+jets single top10
102 10 250
•
W+jets WW/WZ/ZZ
80 Z+jets 200
Table 2: Number of events which pass the various electron selection criteria for the selection and for the the t t signal and for the
mostRequire thereatis one dijet comb−1 (left columns) and 14 TeV normalised to 14 TeV normalised to
relevant backgrounds, 10 TeV normalised to 200 pb with |Mw-Mdijet| columns) and
WW/WZ/ZZ ATLAS Preliminary
102 60 24 all jets Simulation W+jets 10
2 200 22 435jets
all
most relevant backgrounds, at 10 TeV normalised to 200 pb−1 (left 400
ATLAS Preliminary 60
1 150 A
100 pb−1 (right columns). The statistical errors due to limited Monte Carlotop) areMonte Carlo Statistics 40 also shown.
<10 GeV (further(right columns).W and singledue to limited also shown.
100 pb−1 reduces The statistical errors Statistics
Simulation 150 S
WW/WZ/ZZ 0 20 40 60 80 100 120
are 10 40
24 all jets match 235
•
10 10 Missing
100 100
Signal efficiency ~10% analysis
200 ATLAS Preliminary
20 Simulation 50
Electron Muon analysis 20 24.1.1 Jet N 0 10i 20GeV
50
ejets μjets
1 1
120 140 160 180 200Figure 8: 0
−1140 160 −1 200 14TeV00 −1 ) 3 0 1020 Missing transverse en
10TeV (200 ) 20 pb−1 40 10TeV (200 pb (100 pb 180
100 120 )
60 80 14TeV ) 1
20 (100 60 280 100 4
0 1 pb
0 40 60 80 100 120 1 Jet Multiplicity (Pt > 20 GeV)
0 0 40 5 6 7 8 9 1 2 3 4 5
0 2 Missing transverse energyNumber of Jets 10
4 6 8 0 Missing tran
+mt cut default cut W +mt cut tdefault +MW cut 140 t0cut Jet Multiplicity (Pt jet20 GeV) 8 multiplicity distribution (righ
Jet Multiplicity (Pt > 20 GeV)
Missing transverse energy [GeV] 0 [GeV]
Sample default Sample cut
+MW default +MW +M cut +m cut +m
entry (11 bins)
0 2
entry (11 bins)
2 4 6 > 10
1400
ATLAS based background estimations a
entry (11 bins)
400 Jet M
ttbar 2600 ± 15 ttbar ± 11 3144 ± 7
1286 581 17 1584 ± 12 1262 ± 8 561
2555 712 3274 1606 755 Jet Multiplicity (Pt >Preliminary 20 GeV)
ATLAS Preliminary Missing transverse energ
Figure 9:
W+jets 1305 ± 33 W+jets± 20 8: Missing transverse energy distribution (left)1200Multiplicity two opposite distribution (left) afterFig. 181: Jet 350
448 Figure 1766 ± 9
108 44 628 ± 27 148 ± 13 Figure 10:after 319 transverse energy signed leptons be found in Multiplicity oppo
761 241 60 199: Jet Missing 120 (Pt > 20 GeV)Simulation and requiring two (Pt
1052 requiring 98 Simulation
multiplicity distribution (right)eaft
Fig. (can
210 ± 9 single top multiplicity± 9
jet 227 distribution ± 6 after ± 4cuts 23 3
183 (right) 33 all jet(except the Ndistribution 25 jets/Jet Ntt0dilepton, eµbased background estimations afte
multiplicity jets > 1 cut) for jets ee dilepton signal stack.eps) found
Multiplicity match/Jet N 20 10iGeV)
(Pt 0 20GeV(can andbeMC jets ../../../eps/default/emu/all
../../../eps/default/ejets/all(right) after all cuts (except the N in > 1 cut) for µ je
Fig. 199: Jet
Events
Events
Events
>
Events
Events
single top 81 ± 6 27 ± 3 98 67 227
10 99 ../../../eps/default/ee/all 10i 20GeV stack.eps) 400
148 ± 4 Z→ ll +jets background estimations2after all cuts. The 8 84 120 normalized to 200pb tsingle topThe samples 350 normalized to 200p
based samples are 23 100 3 −1 . 300
13 ± 1 based background estimations after all tcuts. are
104 tt dilepton, ee 1000 mu+jets 104
tt dilepton, ee
Z→ ll +jets 43 ± 2 11 ±± 4
144 1 115 ±
49 35
tt other other
¯ single top tt other
hadronic t t 10 t ¯3
16 ± 3 hadronic±t2 2 ±± 2
11 1 11 ± 1
5 4
2±1 0.0 35 100 17
800 7 Z+jets 300 250
The scale factors are defined as !
3
¯ 10 Z+jets 80 W+jets single top10
¯
Events
W+jets 1 µµ 3 64 Expected number of selected events for the ee channel selection for 20
Table2 1: 200
Events
W bb 21 ± 1 W bb 7 ± 1 4 2 ±± 2
32 0 44 ± 1
10 15 ±
3 10 19 4 WW/WZ/ZZ 250
10 tt dilepton,
WW/WZ/ZZ only 26
80
180 measured in data from200
Z+jets
tt dilepton, µµ
1 shown for the9last 60 columnsATLAS Preliminary but2 they are fully taken into ac Z events, an
W cc ¯ W cc¯ 19 tt 6
600 two 3 for readability, 10 200
7 ± 1 ATLAS2Preliminary the S/B calculation. The column labeledt ”true” represents the effect of geome
t other convolution of kinematic,
a
2 other Simulation W+jets
10 160
60
WW 11 ± 2 WW 6 ± 1 3 2 ±± 2
14 1 7 4 ± 1 and 7 140
single top
0.4 3 0.7 150 applyi
10 Simulation
Z+jets 400 WW/WZ/ZZ Dilepton branching ratios inclu
150
WZ 3 ± 1 WZ 1 ± 1 ±0
05 ± 1 4 ± 1 0.2W+jets The 107 120labeled ”fake”0.8
2 1
± 0.2 0.4 column 40 3 40 shows the number oftop 10 which failed the truth-ma
single
events 100
ATLAS Preliminarydecay. From MC@NLO
top pair
10 100
Z+jets
ZZ 0.4 ± 0.1 ZZ0.2 ± 0.1 2 0.1 ±± 0.1
0.5 0.1 0.2 ± 0.1 0.1WW/WZ/ZZ 0.1
0.5 0.2 0.0
± 0.7 100 0.3
200 0.1
10
ATLAS Preliminary
20
lepton sel. inv. mass cut ET 1 0.05)% and BR(t t → eµ )
20 Simulation
W+jets (1.64 miss cut jet cut trigger
± 50 ¯
Signal 2600 Signal 1286 581
3144 2555 1262712 561 1
1584 Simulation 3274 80
1606 755 50
322 7 A(ee) = (16.5 ± 220 A(µ µ ) = (
0.4)%, 214±6 120
1
0 20 40 60 80 100 120 140 160 180 200 ¯ dilepton
0 t t 600 400 1 60 280 351 4 4 140 160 180 200 9261
20 0
0
3100 120 5 6 6 WW/WZ/ZZ 0 10 00 40 1 60 2 80 3100 4
8 1020
Background 1715 Background598 154 1144 799transverse energy [GeV]
374201 96 2 143 8
0 15 Jet Multiplicity Preliminary10 on MC 9
13 (Pt > Based10 simulation for si
10 2199 1497 40 495 0 Missing
Missing
¯
t t other3.2 Missing transverse energyNumber of Jets
0 ATLAS 6
[GeV]
20 GeV) 8±1 2
0
S/B 1.5 S/B 2.1 3.8
1.4 2.2 2.0 3.4 3.5 5.82.2 20 5.3 2 4 8
for an integrated luminosity of 200
single top 27 Jet Multiplicity (Ptmiss2018
akira.shibata@nyu.edu 9
25 9±2 Je
Simulation
Workshop of the Americas ’09 13 > GeV)
8 T 9 and jet multiplicity distributi
1
0 20 40 60 80 100 120 140 160 180 200
0
0 1 2 3 4 5 6 7 EFigure10 Missing transverse en
9: +2

ment, in percent, for electrons and muons. The entries in bold indicate the errors which are finally quoted
and constitute the total estimates. The final summed totals do not include the luminosity error which is
quoted separately.
Source
Cut and Count method
e-analysis µ -analysis
• Lepton efficiency to be estimated using
Fit method
tag and probe
e-analysis µ -analysis
•
default +MW cut default +MW cut +MW cut +MW cut
(%) (%) (%) (%) (%) Applicable after correction in η, pT
(%)
Stat. ± 2.5 ± 3.4 ±2.3 ±3.1 ± 14.1 and isolation.
± 15.2
•
Lepton ID eff. ±1.0 ±1.0 ±1.0 ±1.0 ± 1.0 ± 1.0
Lepton trig. eff. ±1.0 ±1.0 ±1.0 ±1.0 ± 1.0 W+Jets is the dominant background
± 1.0
50% W+jets
20% W+jets
JES (10%,-10%)
±25.1
±10.0
±17.4
±7.0
±28.1
±11.2
±19.8
±7.9
+24.8-23.4 +15.9-19.1 +20.5-22.3 +11.9-17.9
± 3.3
± 1.5
-14.4
• Studied data-driven estimation based
± 5.6
± 2.6
on Z/W ratio. Estimates 20% unc.
-15.4
JES (5%,-5%)
PDFs
ISR/FSR
+12.3-11.9 +8.6-9.3
±1.6
+9.1-9.1
± 1.9
+7.6-8.2
+10.4-10.9
±1.2
+8.2-8.2
+6.1-8.4
± 1.4
+5.2-8.3
•
-3.7
± 1.9
-12.9
-3.9
The analysis rather sensitive to JES
± 1.4
variation.
-12.9
Signal MC
Back. Uncertainty
Fitting Model
±3.3
±0.6
-
±4.4
±0.4
-
±0.3
±0.5
-
±2.8
±0.4
-
± 4.5
-
± 3.3
• ± 1.4
Constant scaling of jet energy applied
-
(MEt varied correspondingly).
± 4.7
•
10% Lumi. ±11.6 ±11.2 ±11.4 ±11.1 ±10 ±10
20% Lumi. ±23.2 ±22.3 ±22.8 ±22.2 ±20 ISR/FSR effects evaluated using Pythia
± 20
Tot. without Lumi. +18.8-18.5 +14.4-15.2 +17.5-17.7 +11.9-14.7
• Variation of ΛQCD and cutoff leads to
+6.4 -14.9 +6.0 - 14.7
large variation.
Bold is used in final combination
538 6.7 Cross-section Evaluation with the Baseline analysis
With the first 200 pb−1 ¯
of data, we demonstrate that we can observe a t t
• By far the dominant effect is the
signal anduncertainty on Luminosity.
determine its
540 production cross-section. In the default scenario with 5% JES uncertainty and 20% uncertainty on the
¯
W+jets background this simple method yields the following uncertainty on the t t cross-section using the
542 default lepton analysis plus the MW cut in the Cut and Count method:
Workshop of the Americas ’09 14 akira.shibata@nyu.edu

Events
Events
Event Selection - Di-lepton
104 tt dilepton, ee tt dilepton, ee
120
tt other
single top tt other
100
3
10 Z+jets single top
W+jets
•
80 Z+jets
Two good leptons,10opposite charge (reduces most fake background) 2
60 W+jets
WW/WZ/ZZ
•
ATLAS Preliminary
MET > 35 GeV for10ee/mumu, > 20 GeV for emu (reduces QCD and Z)WW/WZ/ZZ
Simulation
40
• Z veto (for ee and mumu, |Mz-Mdilep|>10 GeV) (furthers reduce Z) ATLAS Preliminary
20
•
24 all jets Simulation
22 435jets
all 396
24 all jets 435
2 or more jets with10 Pt20>4020 GeV (reduces180 200 diboson) 00 1 2 3 4 5 6 7 8 9 10
•
60 80 100 120 140 160
Signal efficiency ~20% Missing transverse energy [GeV] Number of Jets
ee (S/B 3.9) Figure 8: Missing transverse energy distribution (left) after requiring two opposite signed leptons and
eμ (S/B 5.6) μμ (S/B 3.8)
Jet Multiplicity (Pt > 20 GeV)
Jet Multiplicity (Pt > 20 GeV)
Jet Multiplicity (Pt > 20 GeV)
jet multiplicity distribution (right) after all cuts (except the N jets > 1 cut) for ee dilepton signal and MC
entry (11 bins)
entry (11 bins)
entry (11 bins)
140
based background estimations after all cuts. The samples are normalized to 200pb −1 . ATLAS Preliminary
ATLAS Preliminary
400
ATLAS Preliminary 200
Simulation Simulation 180 Simulation
120 350
Events
Events
Events
Events
Events
400 200 160
103 t t dilepton,tt dilepton, ee
eµ 300 tt dilepton, dilepton, e µ
µµ
120 100 104 tt 180 tt dilepton, µµ
t t other 350 140
single top tt other
tt other single topt other 160
Z+jets 250 t tt other
100 300
80 W+jets single top10
3
Z+jets single top 140 120 single top
2
10 WW/WZ/ZZ 250 W+jets 120
80 Z+jets 200 Z+jets 100 Z+jets
ATLAS Preliminary WW/WZ/ZZ 100
60 Simulation W+jets 10
2 200
60
150 ATLAS Preliminary
W+jets 80 80 W+jets
150 Simulation
10 WW/WZ/ZZ 60
40 40 10
WW/WZ/ZZ 60 WW/WZ/ZZ
100 100
ATLAS Preliminary ATLAS Preliminary 40 40 ATLAS Preliminary
20 Simulation 50 Simulation 20
20 Simulation
1 50 20
1 0 0
0 0 1020 40 60 80 100 120 140 160 180 200
0 0 1 2 3 4 5 6 7 8 9 10
0 20 0 40 1 60 280 3
100 4120 140 160 180 200 9
5 6 7 8 0 1 2 3 4 5 6 7 8 9 10
V] 0 Missing transverse energyNumber of Jets
[GeV] 0 Missing transverse energyNumber of Jets
[GeV]
0 Number of Jets
0 2 4 6 8 10 0 2 4 6 8 10 0 2 4 6 8 10
Jet Multiplicity (Pt > 20 GeV) Jet Multiplicity (Pt > 20 GeV) Jet Multiplicity (Pt > 20 GeV)
n (left) after requiring two opposite distribution (left) after requiring two energy distribution (left) after requiring two opposite signed leptons and jet
gure 10: Missing transverse energy signed leptons 9: Missing transverse opposite signed leptons and
Figure and
t(except the NFig. 199:> 1 cut)of the after0 all20GeV stack.eps) beMC distribution (right)e(Pt jets/Jetall0 10i 20GeV stack.eps) beMC jets in ../../../eps/default/mumu/alldilepton signal and MC
multiplicity distribution (right) dilepton cuts’09and the NFig. in > 1 cut) for after> 15 cuts (except the found > 1 cut) for µ µ jets/Jet N 0 10i 20GeV stack.eps)
Workshop for ee Americas multiplicity jets Jet Multiplicity µ dilepton GeV) (can
jets ../../../eps/default/ee/all jets/Jet N 10i signal
(except found 181: ../../../eps/default/emu/all signal and N akira.shibata@nyu.eduin
Jet Multiplicity (Pt > 20 GeV) (can 20 Fig. 199: Jet Multiplicity (Pt > 20 GeV) (can be found
N
−1

•
6: The individual contributions to the relative uncertainty on the cross-section expected for each of
hannels individually and in combination for 200 pb−1 . The uncertainties are asymmetric and define Effect of lepton
dilepton.
efficiency is larger in
% confidence interval.
!" /" (%)
Stat only
ee channel
-7.5 / 7.8
! ! channel
-6.0 / 6.2
e! channel
-4.0 / 4.1
combined
-3.1 / 3.1
• Z+Jets is the main background in ee
and μμ
Luminosity -17.3 / 26.3 -17.4 / 26.2 -17.4 / 26.2 -17.4 / 26.2
Electron Efficiency
Muon Efficiency
-4.5 / 5.0
0.0 / 0.0
0.0 / 0.0
-4.6 / 5.2
-2.2 / 2.4
-2.1 / 2.2
-1.9 / 1.9
-2.2 / 2.3 •Studied data-driven estimation based
on low MEt control region.
Lepton Energy Scale -0.3 / 1.6 -2.4 / 2.0 -0.5 / 0.5 -0.8 / 0.8
Jet Energy Scale
PDF
ISR FSR
-3.4 / 3.2
-2.1 / 2.3
-4.0 / 4.2
-3.0 / 4.5
-1.4 / 1.6
-3.6 / 3.7
-2.5 / 2.5
-1.6 / 1.8
-3.5 / 3.5
-2.8 / 3.0
-1.7 / 1.8
-3.6 / 3.7
• Measurement robust against JES
variation
Signal Generator
Cross-Sections
Drell Yan
-4.7 / 5.4
-0.3 / 0.3
-1.4 / 1.3
-4.6 / 5.4
-0.3 / 0.3
-2.2 / 2.2
-4.7 / 5.3
-0.3 / 0.3
-0.5 / 0.5
-4.7 / 5.3
-0.3 / 0.3
-0.8 / 0.9
• Signal acceptance is a remaining
concern
•
Fake Rate -9.7 / 9.5 -1.1 / 1.1 -6.2 / 6.2 -4.0 / 4.0
All syst but Luminosity -12.7 / 13.9 -8.9 / 10.2 -9.4 / 10.2 -8.7 / 9.6 Compared MC@NLO and Alpgen
All systematics
Stat + Syst
-21.0 / 30.3
-22.3 / 31.3
-19.3 / 28.3
-20.2 / 29.0
-19.5 / 28.5
-19.9 / 28.8
-19.3 / 28.1
-19.5 / 28.3 • Studied data-driven estimation of fake
background
•
r and the jet energy scale is lower than their nominal values, then the expected number of events Matrix method. Systematics estimated
not be very different than the nominal prediction. The correlated effect on the measurement is by comparing two control regions
marized by a correlation matrix in the fitted parameters of the model (see Table 7).
(low MEt and low ΔΦ)
•
he log-likelihood curves obtained from fitting each channel individually and combined are shown
. 11. Note the asymmetric nature of the profile likelihood curve introduced by the systematics. Again, luminosity is the dominant unc.
Workshop of the Americas ’09
Conclusion 16 akira.shibata@nyu.edu

stat only
Single vs Di-lepton Assuming
systematics
as constant
stat + syst
stat + syst + 10% lumi
stat + syst + 20% lumi
Dilepton Combined Single Lepton Combined
30 30
25 25
20 20
15 15
10 10
5 5
0 0
0 25 50 75 100 125 150 175 200 pb-1 0 25 50 75 100 125 150 175 200 pb-1
Smaller statistics in dilepton but S/B significantly higher than single lepton. Systematics
is dominant very quickly in both channels. Final sensitivity is much higher in dilepton. If
20% uncertainty on luminosity, it will totally dominate the measurement.
Workshop of the Americas ’09 17 akira.shibata@nyu.edu

0 40
0 20 40 60 80 100 10
120 140 160 180 200 0 1 2 3 4 5
Single vs Di-lepton (visually)
¯
Missing transverse energy [GeV]
Introduction It is possible to isolate a pure biased sample of fully-leptonic t t events by selecting low529
7 4366 20GV cum
jets 609
6 trigger cum 1
24 all jets
20 22 435jets
all 396
24 all jets
ET (to reject SUSY signal) opposite sign dilepton events where one and only one pair of [GeV] Missing transverse energy invariant mass
0
367 / 0 20 40 60 80 100 120 140 160 180 200 0 1 2 3 4
combinations m(l j) between the two leptons and two hardest jets (b-jets if tagging(left) after requiring two opposite
Figure 8: Missing transverseMlb energy distribution available) gives values
7.1.35 HadronicTop Mass 6.1.44 Dilepton
Jet Multiplicity (Pt > 20 GeV)
Jet Multiplicity (Pt > 20 GeV)
368
jet multiplicity distribution (right) after transverse energy distributionjets >aftercut) for ee dile
Figure 8: maxMissing all cuts (except the N (left) 1 requiring two opp
2 2 (neglecting
below the expected endpoint from t → W b → l ν b decays:jet multiplicity = mtop − mafter all cuts (exceptmb ). > 1 cut) for ee
m(l j)
entry (11 bins)
entry (11 bins)
Jet Multiplicity (Pt > 20 GeV)
entry (11 bins)
Jet Multiplicity (Pt > 20 GeV)
140
Hadronic Top Mass [GeV]
369
distribution (right) W
Mass of 1st/2nd jet plus 1st/2nd lepton (all comb) [GeV]
based 140 background estimations after all cuts. The samples are normalized to 200pb −
400 the
200N jets
entry (11 bins)
entry (11 bins)
entry (11 bins)
400 possible use of such a sample is to estimate the background of fully-leptonic t tATLAS Preliminary SUSY200
A ATLAS Preliminary
ATLAS based
ATLAS Preliminary
¯ events to
250 background estimations after all cuts. The samples are normalized to 200
entry (30 bins)
entry (30 bins)
400
370 Preliminary
Simulation ATLAS Preliminary 180
371
120 One can reconstructSimulation 120
searches. the kinematics of the decaying particles
ATLAS Preliminary 350 Simulation 350 (W ’s or top quarks), remove180 Simulation
350 Simulation Simulation
Events
Events
Events
Events
Events
Events
Events
200
Events
Events
Et
Events
Events
10 10 372 their inferred decay products eµ t dilepton,tt from the100
mu+jets 104 reconstructed event 10 (including fromdilepton, e µt dilepton,tT ), redecay
the event 180dilepton, e µ 180
3 10
400 200 3 400
300 / 160 the160
200
120
4
300 100
tt dilepton,tee
120
dilepton, ee 300
t t dilepton,tt dilepton, ee
t t other
eµ
350 tt dilepton, µµ
tt
t µµ 4
140
reconstructed W ’s or top quarks using an event generator (e.g. PYTHIA) tt other and then merge the simulated
tt other t t other 350 tt other
373 single top
single top 100
single top
Z+jets
tt other
300 250 single topt other
160
t 140
160
3 tt other 80 single top10 single topt other
t Z+jets single top 140 120 3
Z+jets
250 150
re-decay productsW+jets W+jets the80 top103 (‘seed’) event. By redecayingZ+jets singleearlier in Z+jets decay chain100
back into single parent particles top W+jets the
10 W+jets
100 250 Z+jets 10 300 2
374 80 WW/WZ/ZZ
Z+jets
250
200 140 120
120
ATLAS Preliminary
200 the top rather Preliminary W ) the kinematic bias obtained from the event selection Preliminary minimised. 80
80 (i.e. ATLAS than the 150 Z+jets ATLAS can
120 be
WW/WZ/ZZ
102 10 2
WW/WZ/ZZ
WW/WZ/ZZ 60 60250 Simulation W+jets 10 200 W+jets
100 2
375 Z+jets 200 W+jets 100
80
ATLAS Preliminary 150 Simulation
This technique has Simulation W+jets 102 40200 over conventional 100
a number of advantages 100
Monte 100 W+jets
Carlo techniques. In particular 60
Simulation WW/WZ/ZZ WW/WZ/ZZ 100
376 150 60 10 40 10
WW/WZ/ZZ 60
y
10 60
150 Preliminary ATLAS Preliminary ATLAS Preliminary 40
80 80
the event generator is used purely for 20150 modelling relatively 1well-understood decay Simulation and hadronisation 40
ATLAS
377 20 Simulation Simulation
50 20
10 100 WW/WZ/ZZ 50 WW/WZ/ZZ 60
40 120 140 160 180 200 1 60 1 2 3 4
20 processes – initially poorly understood aspects of process200 9 generation, such0 Missing transverse energy [GeV]
2 as parton distributions 10 and the 0
1 40
0 10 280 3 50 0 20 40 60 80 100 120 140 160 180 200 0
0
20
378 6100 0
0 40 60 80 100 0 20 0 40 1 60 100 4 140 160 180 8
100 120 5 7 10 0 1 3 4 5 6 7 8 9
50 Missing transverse energy [GeV]ATLAS Preliminary 0 Missing transverse energyNumber of Jets [GeV] ATLAS Preliminary 40Number of Jets 40
20 underlying event model, Simulation
379 are effectively obtainedMultiplicity6(Pt > 8 GeV) principle this technique > 8 applicable 0 Jet
0
50
2 from the data.10
4 In 0
Simulation
2 4
20 is
6 10 2
20 Jet 50 020 Jet Multiplicity (Pt 20 GeV)
8: Missing 0 otherenergy 200 250 300 350 400 0 1020 0 Zenergy signed3100 (left) afterbe transverse8 oppositereplacing identified 4
Figure380 00 40 1 60 250 100 150distributionprocesses 9 transverseopposite distribution04could50160 180two energy distribution (left) after requiring two oppos
also transverse background (left) after requiring as 40→ 60 2, 80 leptons 9: Missing modelled by signed leptons and 3
0 to
Figure 10: 200 such two
Missing 450 500 1 ττ which 120 5 requiring 200 150 10 0
1 20
1 0 Figure and 140 100 0 200
1 250
2 5
00 0 20 80 3 100 4 120 140 160 180 8
5 6 7 6 1st/2nd leptonall cuts (except the N
7 (right) after (all comb) [GeV]
9
electrons0 Missing transverse (except − control1 sample after all0with andbackground estimations after all cuts. The samples are normalizedfor 200
Z jetenergy [GeV] jets Jetscut)
the Mass
multiplicity
Mass ofMissing MC distribution [GeV]
multiplicity plusenergy
eV] jet multiplicity distribution (right) after allHadronic lNumber of> [GeV]for eeevents cuts (except the N jets > 1 cut) for eµ of Jets signal and MC jets
or muons in cuts→ l + Top Ndistribution (right) dilepton signal redecayed taus. Number dilepton 1st/2nd jet
transverse
0 > 1 cut) µµ found Fig. 199: Jet
181: Jet
found Fig. in Multiplicity (Pt 20 GeV) (can be in Multiplicity (P
381
Fig. 199: Jet Multiplicity (Pt > 20 GeV) (can be >
../../../eps/default/mumu/
based to
../../../eps/default/ee/all jets/Jet N 0 10i 20GeV stack.eps) ../../../eps/default/emu/all jets/Jet N 0 10i 20GeV stack.eps)
based background estimations after all cuts. The samples are normalized to 200pb −1cuts. The samples are normalized to 200pb −1 .10
0 2 4based background estimations after all .
6 8 10 0 2 4 6 8 0 2 4
Jet Multiplicity (Pt > 20 GeV) Jet Multiplicity (Pt > 20 GeV) Jet Mult
Visible mass peak is an advantage9: Missing transverseanalysis (left). Currently studying two opposite s
Figure and single lepton energy distribution (left) after requiring
of Fig. 476: Mass of 1st/2nd jet plus 1st/2nd lepton (all comb) [GeV] (can be found in
Fig. 575: Hadronic Top Mass [GeV] (can be found in ../../../eps/default tmp/mujets/4 jets 20GV cum/HadronicTop
The scale factors are defined as !data /!MC , where !data are identification
(ID
../../../eps/default tmp/emu/trigger cum/Dilepton Mlb stack.eps) i
on (left) aftervariables two visibly confirmleptons after requiringdilepton, µµ
igure 10 Missing transverseopposite distribution (left)
10: requiring to energyµµ signed top quark in dilepton channel. M(lb) has an iend point
two opposite from Z events, and ! and efficiencies measured in inclusive
signed leptons are
i i
Events
Table 1: Expected number of selected events for the ee channel selection for 200pb
Events
200 −1 . The errors are
18 tt measured in data
et(except the Ndistribution (right) after all cutsMw=80.4 GeV). 1 cut) convolution of kinematic, geometricthe reconstruction efficiency contributio
only shown for the last MC distribution (right) they areall cuts (except MC in N jets > 1 cut) for µ µ dile
multiplicity N for readability, buteafter fully taken into account the summation
4 tt dilepton, 180
two columns
multiplicity~152.6 cut) for singledilepton signal and the jets > tt other for µ dilepton signal andand
jets > 1 GeV (Mtop=172.5, (except MC found Fig. 199: Jet
181: Jet
found Fig. in Multiplicity (Pt 20 GeV) (can be in Multiplicity (Pt >
ee top
tt other Fig. 199: Jet
160
Multiplicity (Pt
a
> 20 GeV) (can be >
../../../eps/default/mumu/all jets/J
−1 the S/B calculation. The column labeled ”true”Dilepton branching ratios includetruth-matching cuts. leptonic200pb
and 140based background estimations after all cuts. of applying
represents−1 effect The samples are normalized to
the
../../../eps/default/ee/all jets/Jet N 0 10i 20GeV stack.eps) ../../../eps/default/emu/all jets/Jet N 0 10i 20GeV stack.eps)
−
ased background estimations200pb The column labeled ”fake” are normalized top 200pb failed the truth-matching cuts.
e samples are normalized to after all cuts. The samples shows the number ofto which .
. 29 electrons, muons and tau decay
3
10 Z+jets
events
single
W+jets 120
¯ top ¯
pair decay. From MC@NLO t t MC we estimate BR(t t → ee) = (1.67 ±
Z+jets
WW/WZ/ZZ
Workshop of the Americas ’09 ¯
100
18 (1.64 miss cut jet cut trigger akira.shibata@nyu.edu estimate top di
lepton sel. inv. mass cut ET 0.05)% and BR(t t → eµ ) =true ±fake
(3.40 0.10)%. We also
2
10 ±
ATLAS Preliminary 80 W+jets

*
,-./#-012-03..4
Statistical Formalism we can now derive the ex
2 Extracting Measurements from the Profile Likelihood Ratio )&(
)&'
)&+
rmed with the final likelihood function in Eq. 18 and the Asimov dataset, )&*
obs − exp
ected uncertainty on the desired cross section measurement. The likelihood function can be maximize
N ∑k∈{bkg} Nk
)
Based on the principle: σ estimate of all the parameters !sig , Lˆ , $ j . One can then conside
determine the maximum likelihoodsig =
ˆ
%&(
, ˆ ˆ
L ∏ j ε j sig %&'
%&+
e likelihood ratio !"#!$%&'()*+*,-'.
Construct the likelihood function as product ˆofˆ PDFs of uncertainties:
%&* !"#$%&'"()
L(!sig , L , $ j )
r(!sig ) =
%
%&'
(19
%&( ) )&* )&+ )&' )&(
! #$#!!"
ˆ ˆ ˆ
L( exp ) Gaus(L)|L , σ )
obs !sig , L , $ j ˜
L(σ , L , α ) =
sig j ∏ ∏
Pois(N |N
i i,tot Gaus(0|α , 1) ∏
L (a) Likelihood Curvesj for the ee channel
j∈syst
nd the profile likelihoodl∈{ee,µ µ,eµ}
ratio: i∈bins
ˆ ,$ )
Calculate profile likelihood: & (! ) = L(!sig , L ˆ j
ˆ ˆ *
,-./#-012-03..4
sig
)&(
(20
ˆ ˆ ˆ
L(!sig , L , $ j ) )&'
)&+
Use Wilks’ theorem conditional maximum likelihood estimates of L and $j holding !sig fixed
ˆ and $ represent the to extract confidence interval )&*
ˆ
here L ˆj
ˆ )
%&(
Wilks’ theorem states that under certain conditions, which are satisfied in this case, the distributio
%&'
−2 log & (!sig ) is asymptotically11) distributed as a ' 2 distribution with one degree of freedom. W
true
Uniform approach for including systematics and %&+
!"#!$%&'()*+*,-'.
!"#$%&'"()
%&*
o not combining the results ,from multiple measurements. by −2 log & (!sig ) < 1 will cover th
true
know the value of !sig but the interval of points defined %
%&' %&( ) )&* )&+ )&' )&(
ue value 68% of the time. Similarly, the intervals defined by −2 log & (!sig ) < 2.71 (3.84) will cove
! #$#!!"
Workshop of the Americas ’09 19 akira.shibata@nyu.edu
(c) Likelihood Curves for the e! channel

Understanding correlation
SigXsecOverSM_emu
SigXsecOverSM_mumu
SigXsecOverSM_emu
2.4 2.4
2.4
2.2 2.2 2.2
2 2 2
1.8 1.8 1.8
SigXsecOverSM_emu
SigXsecOverSM_mumu
SigXsecOverSM_emu
2.4 1.6 2.4 1.6 2.4 1.6
2.2 1.4 Stat only 2.2 1.4 Stat only 2.2 1.4 Stat only
1.2 2 1.2 2 1.2
2
1 1 1
1.8 1.8 1.8
0.8 0.8 0.8
1.6 1.6 1.6
0.6 0.6 0.6
1.4 0.6 0.8 1 1.2 1.4 1.6 1.8 1.42 2.2 2.4 0.6 0.8 1 1.2 1.4 1.6 1.8 1.4 2 2.2 2.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2
SigXsecOverSM_ee SigXsecOverSM_ee SigXsecOve
1.2 1.2 1.2
1 1 1
0.8 0.8 0.8
0.6 0.6 0.6
0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.4
SigXsecOverSM_ee SigXsecOverSM_ee SigXsecOverSM_mumu
Extract three dilepton cross sections in a simultaneous fit. This allows
us to understand the correlation between the measurements. As
expected, smaller correlation is seen between ee/μμ than ee/eμ or
μμ/emu. Shown here excluding luminosity uncertainty. Correlated
systematics will cancel out when we measure the ratio.
Workshop of the Americas ’09 20 akira.shibata@nyu.edu

Ratio Measuremens
1 results 200 40 0
1 results 200 40 0
2 combined 200 40 0 1 AllsystbutLuminosity ee
ee/eμ
results 200 40 0 1 ee over emu.table μμ/eμ
results 200 40 0 1 mumu over emu.table ee/μμ
results 200 40 0 1 ee over mumu.table
Statonly -8.4 / 8.9 Statonly -7.1 / 7.5 Statonly -9.4 / 10.2 2
-log likelihood
Luminosity -0.3 / nan Luminosity -0.4 / nan Luminosity -0.3 / nan
1.8
JetEnergyScale -1.4 / nan JetEnergyScale -0.7 / 1.9 JetEnergyScale -1.2 / nan
ElectronEfficiency
MuonEfficiency
-2.3 / 2.6
-2.1 / 2.2
ElectronEfficiency
MuonEfficiency
-2.3 / 2.3
-2.7 / 2.8
ElectronEfficiency
MuonEfficiency
-4.4 / 5.1
-4.6 / 5.3
1.6
1.4
ee/mumu
FakeRate -4.0 / 2.7 FakeRate -4.6 / 5.7 FakeRate -8.6 / 8.5
1.2
Cross-Sections nan / 0.3 Cross-Sections -0.2 / nan Cross-Sections nan / 0.8
1
PDF nan / 1.0 PDF nan / 0.6 PDF -0.6 / 0.8
ISRFSR -0.6 / 0.6 ISRFSR nan / 0.5 ISRFSR -1.0 / nan 0.8
SignalGenerator -0.6 / nan SignalGenerator -0.7 / nan SignalGenerator -0.3 / nan 0.6
DrellYan -1.3 / nan DrellYan -2.2 / 2.1 DrellYan -2.1 / 2.6
0.4
LeptonEnergyScale nan / 0.8 LeptonEnergyScale -2.1 / 1.7 LeptonEnergyScale -1.9 / 3.1
AllsystbutLuminosity -11.0 / 12.2 0.2
AllsystbutLuminosity -5.3 / 4.8 AllsystbutLuminosity -6.5 / 7.6
Allsystematics -5.2 / 4.7 Allsystematics -6.5 / 7.7 Allsystematics -10.9 / 12.3 0
0 0.5 1 1.5 2 2.5 3
Stat + Syst -9.9 / 10.1 Stat + Syst -9.6 / 10.7 Stat + Syst -14.4 / 16.0 ! / !SM
Fig. 4: profile likelihood ratio (can be found
Simple variable substitution enables ratio measurements in likelihood clude/combined 200 40 0 1 AllsystbutLuminosity ee over m
formalism. Ratio measurements are not sensitive to luminosity at all,
10
6
making it an ideal early measurement. Many correlated systematics cancel
out such as JES. On the other hand uncertainties that affect channels
differently can affect ratio measurement severely (such as MuonEff and
FakeRate). Larger statistical unc. is now the leading effect.
Workshop of the Americas ’09 21 akira.shibata@nyu.edu

Result of Multibin Fit
1 results 200 40 0
ee 200 40μμ
results 0 1.table eμ comb ee 200 40 μμ
results 0 5.table eμ comb
Statonly -7.5 / 7.8 -6.0 / 6.2 -4.0 / 4.1 -3.1 / 3.1 Statonly -7.4 / 7.7 -6.0 / 6.2 -4.0 / 4.1 -3.1 / 3.1
Luminosity -17.3 / 26.3 -17.4 / 26.1 -17.4 / 26.2 -17.4 / 26.2 Luminosity -16.9 / 25.8 -17.5 / 25.7 -17.5 / 25.3 -16.9 / 25.2
JetEnergyScale -3.4 / 3.2 -3.0 / 4.5 -2.5 / 2.5 -2.8 / 3.0 JetEnergyScale -2.0 / 3.3 -2.5 / 3.9 -1.7 / 1.7 -1.6 / 1.8
ElectronEfficiency -4.5 / 5.0 0.0 / 0.0 -2.2 / 2.4 -1.9 / 1.9 ElectronEfficiency -4.4 / 5.0 0.0 / 0.0 -2.2 / 2.4 -1.8 / 1.9
MuonEfficiency 0.0 / 0.0 -4.6 / 5.2 -2.1 / 2.2 -2.2 / 2.3 MuonEfficiency 0.0 / 0.0 -4.6 / 5.2 -2.1 / 2.2 -2.2 / 2.3
FakeRate -9.7 / 9.5 -1.1 / 1.1 -6.2 / 6.2 -4.0 / 4.0 FakeRate -8.8 / 8.8 -1.1 / 1.1 -6.2 / 6.2 -3.8 / 3.9
Cross-Sections -0.3 / 0.3 -0.3 / 0.3 -0.3 / 0.3 -0.3 / 0.3 Cross-Sections -0.4 / 0.3 -0.3 / 0.3 -0.3 / 0.3 -0.3 / 0.3
PDF -2.1 / 2.3 -1.4 / 1.6 -1.6 / 1.8 -1.7 / 1.8 PDF -2.0 / 2.3 -1.4 / 1.6 -1.6 / 1.8 -1.7 / 1.8
ISRFSR -4.0 / 4.2 -3.6 / 3.7 -3.5 / 3.5 -3.6 / 3.7 ISRFSR -1.7 / 1.6 -1.8 / 1.8 -1.5 / 0.8 -0.9 / 0.8
SignalGenerator -4.7 / 5.4 -4.6 / 5.4 -4.7 / 5.3 -4.7 / 5.3 SignalGenerator -4.5 / 5.4 -4.6 / 5.4 -4.7 / 5.3 -4.7 / 5.3
DrellYan -1.4 / 1.3 -2.2 / 2.2 -0.5 / 0.5 -0.8 / 0.9 DrellYan -1.4 / 1.3 -2.2 / 2.2 -0.5 / 0.5 -0.8 / 0.8
LeptonEnergyScale -0.3 / 1.6 -2.4 / 2.0 -0.5 / 0.5 -0.8 / 0.8 LeptonEnergyScale -0.5 / 1.3 -2.5 / 2.0 -0.4 / 0.5 -0.8 / 0.8
AllsystbutLuminosity -12.7 / 13.9 -8.9 / 10.2 -9.4 / 10.2 -8.7 / 9.6 AllsystbutLuminosity -11.3 / 12.7 -8.0 / 9.3 -8.6 / 9.4 -7.4 / 8.5
Allsystematics -21.0 / 30.3 -19.3 / 28.3 -19.5 / 28.5 -19.3 / 28.1 Allsystematics -20.1 / 29.4 -18.9 / 28.1 -19.1 / 28.0 -18.6 / 27.4
Stat + Syst -22.3 / 31.3 -20.2 / 29.0 -19.9 / 28.8 -19.5 / 28.3 Stat + Syst -21.4 / 30.4 -19.8 / 28.8 -19.5 / 28.3 -18.9 / 27.6
Left, 2 or more jets in one bin. Right, 2/3/4/5/6(inclusive) bins, i.e. same statistics
but measurements over multiple bins combined. Large reduction of systematics
4
that are treated separately in bins of jets such as jet energy scale, ISRFSR
(Other systematics are treated as overall scaling.) Gain ~1% in precision!
Workshop of the Americas ’09 22 akira.shibata@nyu.edu

1 results 200 40 0
Using multiple bins in 5-channels
ejets μjets200 40 0ee
results 5.table μμ eμ comb
Statonly -3.3 / 3.3 -3.0 / 3.0 -7.4 / 7.7 -6.0 / 6.2 -4.0 / 4.1 -1.8 / 1.8
Luminosity -18.3 / 26.7 -18.0 / 26.4 -16.9 / 25.8 -17.5 / 25.7 -17.5 / 25.3 -16.5 / 24.1
JetEnergyScale -4.9 / 8.0 -4.0 / 7.6 -2.0 / 3.3 -2.5 / 3.9 -1.7 / 1.7 -1.8 / 2.7
ElectronEfficiency -2.1 / 2.3 0.0 / 0.0 -4.4 / 5.0 0.0 / 0.0 -2.2 / 2.4 -1.1 / 1.1
MuonEfficiency 0.0 / 0.0 -2.1 / 2.2 0.0 / 0.0 -4.6 / 5.2 -2.1 / 2.2 -1.3 / 1.3
FakeRate 0.0 / 0.0 0.0 / 0.0 -8.8 / 8.8 -1.1 / 1.1 -6.2 / 6.2 -0.9 / 0.9
Cross-Sections -0.3 / 0.3 -0.3 / 0.3 -0.4 / 0.3 -0.3 / 0.3 -0.3 / 0.3 -0.3 / 0.3
PDF -1.8 / 2.0 -1.4 / 1.4 -2.0 / 2.3 -1.4 / 1.6 -1.6 / 1.8 -1.6 / 1.7
ISRFSR -3.4 / 3.5 -3.9 / 4.8 -1.7 / 1.6 -1.8 / 1.8 -1.5 / 0.8 -1.4 / 1.5
SignalGenerator -4.0 / 4.4 -3.9 / 4.1 -4.5 / 5.4 -4.6 / 5.4 -4.7 / 5.3 -4.1 / 4.5
DrellYan 0.0 / 0.0 0.0 / 0.0 -1.4 / 1.3 -2.2 / 2.2 -0.5 / 0.5 -0.3 / 0.3
LeptonEnergyScale nan / 0.1 -0.6 / 0.5 -0.5 / 1.3 -2.5 / 2.0 -0.4 / 0.5 -0.5 / 0.5
Westimate -5.4 / 5.4 -6.2 / 6.2 0.0 / 0.0 0.0 / 0.0 0.0 / 0.0 -1.8 / 1.8
AllsystbutLuminosity -10.5 / 13.9 -10.8 / 14.9 -11.3 / 12.7 -8.0 / 9.3 -8.6 / 9.4 -6.4 / 8.0
Allsystematics -20.9 / 32.0 -20.7 / 32.2 -20.1 / 29.4 -18.9 / 28.1 -19.1 / 28.0 -18.6 / 27.3
Stat + Syst -21.2 / 32.2 -20.9 / 32.3 -21.4 / 30.4 -19.8 / 28.8 -19.5 / 28.3 -18.7 / 27.3
Combining measurements from multiple jet bins for all 5 channels using the
multiple bin measurement. As the effect of the systematics is rather different for
5
single lepton and dilepton analyses, the combination needs to be done carefully.
Workshop of the Americas ’09 23 akira.shibata@nyu.edu

Graph
!t t [pb]
1000 CDF Results
LHC 10 TeV @ 200pb-1 Expectations
LHC 10 TeV @ 200pb-1 Expectations (no Lumi)
LHC 14 TeV @ 100pb-1 Expectations (CSC)
800 Theoretical NLO (pp)
Theoretical NLO (pp)
Theoretical NLO+NNLL
NLO+NNLL Scale Uncertainty
600 Graph
12
! [pb]
Produced by Akira Shibata and Ulrich Husemann
tt
10
400 8
6
Produced by Akira Shibata and Ulrich Husemann
4
2
1 1.5 2 2.5 ATLAS 2010?
200
[hep-ph/0204244]
[arXiv:0907.2527]
0
0 2 4 6 8 10 12 14
s [TeV]
Workshop of the Americas ’09 24 akira.shibata@nyu.edu

Summary & Outlook
• Simple and robust analysis has been established for the re-discovery of the top
quark with the LHC collisions in year one.
• Learning much about the strength and the weakness of the analyses fully
including the systematic uncertainties.
• Studying methods to extract more information from the limited data. Profile
likelihood method allow us to measure cross section in different channels and
combine them.
• Established good communication and methods to collaborate with many
groups. Had a useful experience with publication process.
• Once tT observation is established, implication is tremendous
• Indicates good understanding of the combined performance of the detector
• Powerful tool to understand JES, b-tagging, trigger efficiency and processes
with more complicated event topology, new physics!
Workshop of the Americas ’09 25 akira.shibata@nyu.edu

Back up
Workshop of the Americas ’09 26 akira.shibata@nyu.edu

Single lepton channels selection
ejets:
process all trigger one_elec met 3_jets_40GV 4_jets_20GV mW mtop
---------------------------------------------------------------------------------------------------------------------------------------
tbart onelepton 30164.70703 8187.08203 6535.53467 5883.80615 3019.78711 2448.61890 1266.27783 594.25214
tbart other 13254.96484 2640.54346 1055.60046 995.50897 247.87746 157.25546 53.91260 16.11322
Ztautau 295499.84375 15484.37500 8822.18066 2845.60278 65.04361 40.93086 13.04008 4.18833
Zll 588124.25000 190923.15625 98764.57812 3779.99609 181.01596 107.35683 32.28349 7.56154
W 9686345.00000 1509114.50000 1206295.00000 1084657.75000 2523.32275 1306.57996 453.86389 116.41811
Wbb 3572.16333 611.40002 475.88712 407.85770 40.74120 27.14357 8.81521 2.67438
Diboson 7431.87793 2281.33594 1604.79541 1294.66089 31.50813 14.76664 7.65403 2.21097
SingleTop 11488.52734 2515.74512 1931.61731 1723.91162 316.31812 208.08707 76.92590 25.88531
mujets:
process all trigger one_muon met 3_jets_40GV 4_jets_20GV mW mtop
---------------------------------------------------------------------------------------------------------------------------------------
tbart onelepton 30164.70703 10220.02344 7827.36523 7104.29834 3658.92944 2978.71240 1562.58765 735.75818
tbart other 13254.96484 3258.23901 1199.52881 1130.10925 265.68686 161.85925 55.48757 14.78055
Ztautau 295499.84375 19437.99219 11480.51465 3712.91309 81.10379 48.38579 16.00406 3.29914
Zll 588124.25000 211228.51562 90148.96094 49378.42578 172.53560 97.04016 33.73303 8.68211
W 9686345.00000 1668069.75000 1447907.75000 1141870.50000 3450.38599 1806.83667 632.86090 162.10670
Wbb 3572.16260 788.74146 624.22107 541.64465 60.04836 38.86301 12.19687 3.93595
Diboson 7431.87793 2681.06226 1948.86670 1655.71423 39.05885 19.40950 9.52840 2.13509
SingleTop 11488.52734 3060.96240 2326.75708 2091.45801 357.05862 221.21556 89.15331 27.45181
Workshop of the Americas ’09 27 akira.shibata@nyu.edu

Dilepton channels selection
ee:
process all ee opposite mass met two_jets trigger
tbart dilepton 5353.67871 352.43198 349.28201 320.20541 259.38693 218.55858 213.10672
tbart other 38078.43750 24.35155 15.14400 13.20557 9.69216 8.84410 8.23834
Ztautau 295499.84375 160.86870 156.66675 154.78156 10.04045 7.17354 7.01191
Zll 588124.25000 68790.92969 68287.06250 16279.47852 23.59300 13.95325 13.38151
W 9686345.00000 266.38525 171.44244 158.57240 80.94560 8.88327 8.35310
Wbb 3572.16138 0.87689 0.47965 0.47965 0.00000 0.00000 0.00000
Diboson 7431.87891 151.74471 145.05826 73.23516 32.85203 2.97346 2.97346
SingleTop 11488.52734 29.65409 27.31582 24.91289 18.81128 9.19955 9.19955
mumu:
process all mumu opposite mass met two_jets trigger
tbart dilepton 5353.67871 533.31244 531.85870 491.27258 401.49869 344.55710 334.13797
tbart other 38078.43750 17.68820 9.08640 7.99603 6.17875 5.93645 5.57299
Ztautau 295499.84375 262.88242 262.80087 261.73590 18.71443 10.69080 10.28443
Zll 588124.25000 109379.18750 109376.47656 24725.50586 112.87164 49.45387 47.55950
W 9686345.00000 20.15652 16.88178 16.45122 2.36805 0.21528 0.21528
Wbb 3572.16187 1.90057 1.10806 0.79266 0.55384 0.47453 0.39377
Diboson 7431.87793 215.32411 211.21104 100.62133 45.16145 5.34200 5.34200
SingleTop 11488.52734 40.19653 36.81574 34.71317 26.80936 11.80857 11.46106
emu:
process all emu opposite met two_jets trigger
tbart dilepton 5353.67871 913.48877 907.67346 845.52222 716.01025 696.38367
tbart other 38078.43359 44.22046 24.35155 22.17082 21.32275 20.11124
Ztautau 295499.84375 425.54050 421.09479 97.20030 28.25817 26.95681
Zll 588124.25000 30.74260 14.51010 2.64526 0.66244 0.66244
W 9686345.00000 295.31229 222.72047 187.26189 18.39359 15.87207
Wbb 3572.16333 2.62599 1.42752 1.03316 0.39599 0.39599
Diboson 7431.87793 143.22598 134.61403 110.98006 10.42713 10.00050
SingleTop 11488.52734 65.17408 59.94395 56.24528 26.57366 25.67256
Workshop of the Americas ’09 28 akira.shibata@nyu.edu

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Workshop of the Americas ’09 29 akira.shibata@nyu.edu

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Workshop of the Americas ’09 30 akira.shibata@nyu.edu

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Workshop of the Americas ’09 31 akira.shibata@nyu.edu