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Jet Results from CMS
Cosmin DragoiuUniversity of Illinois at Chicago
(for the CMS Collaboration)
XIX International Workshop on Deep-Inelastic Scatteringand Related Subjects, Newport News 2011
Cosmin Dragoiu DIS 2011
! The CMS detector
! Jet reconstruction
! Jet energy calibration
! Jet energy resolution
! Inclusive jet cross section
! Dijet mass cross section
! Dijet azimuthal decorrelations
! Dijet angular distributions
Outline
2
More about jet performance and multijet measurements at CMS
in Joanna!s talk!
Cosmin Dragoiu DIS 20113
CMS Detector
Pixel (|!| < 2.5)3 layers (barrel)2 disks (endcap)
Tracking System (|!| < 2.5)10 layers (barrel): TIB (4L) + TOB (6L)11 disks (endcap): TID (3D) + TEC (9D)
Muon System (|!| < 2.4)4 muon stationsDT + RPC (barrel)CSC + RPC (endcap)
Hadronic CalorimeterHB + HO (|!| < 1.3)HE (1.3 < |!| < 3.0)HF (3.0 < |!| < 5.2)
Electromagnetic CalorimeterEB (|!| < 1.48) + EE (1.48 < |!| < 3.0)Preshower (1.65 < |!| < 2.6)
4T Magnet
Return Yoke CASTOR (5.2 < |!| < 6.6)
ZDC (|!| > 8.3)
Cosmin Dragoiu DIS 20114
CMS 2010 DATA
! Delivered by LHC: 47/pb
! Recorded by CMS: 43/pb
! Data taking efficiency > 90%! with all subdetectors
running > 85%
! Luminosity uncertainty: 4%
Cosmin Dragoiu DIS 20115
Jet Reconstruction
Calorimeter Jets
! from calorimeter towersTrack Jets
! from tracks
Jet plus Track
! from calorimeter towers corrected using tracker information
Particle Flow Jets
! from identified particles using all detector components
! Jet reconstruction algorithms available at CMS:
! kT, Anti-kT
! CMS default: Anti-kT R = 0.5 & 0.7
Cosmin Dragoiu DIS 2011
Jet Energy Calibration
6
Residual Correction(" & pT)
MC Correction(" & pT)
Offset Correction
Reconstructed Jet
Calibrated Jet
! removes pile-up and noise contributions
! flattens the jet response in ! and corrects the jet pT to particle level
! accounts for the differences between data and MC (dijet pT balance, MPF method)
(GeV)!
Tp
20 30 40 50 100 200
Dat
a / M
C
0.96
0.98
1
1.02
1.04
1.06
1.08
1.1
(GeV)!
Tp
20 30 40 50 100 200
Dat
a / M
C
0.96
0.98
1
1.02
1.04
1.06
1.08
1.1
pT balanceMPF
/ NDF = 14.2 / 122"
MC scaled for FSR and QCD bkg
anti-kT 0.5 PF
= 7 TeVs-1CMS preliminary, 2.9 pb
(GeV)T
p20 30 100 200 1000 2000
Abso
lute
sca
le u
ncer
tain
ty [%
]0123456789
10Total uncert.Total MPFPhoton scaleExtrapolationOffset (+1PU)Residuals
particle flow jets 0.5 & 0.7TAnti-k
= 7 TeVs-1CMS preliminary, 2.9 pb
(GeV)T
p20 30 100 200 1000 2000
Abso
lute
sca
le u
ncer
tain
ty [%
]0123456789
10
CMS-PAS-JME-10-010
Cosmin Dragoiu DIS 2011
! Determined using the dijet asymmetry method (dijet pT balancing)
! The asymmetry is:
! The jet pT resolution is related to the width of the asymmetry distribution
Jet Energy Resolution
7
[GeV]T
p50 100 200
reso
lutio
nT
jet p
0
0.1
0.2
0.3total systematic uncertainty
MC truth (c-term added)
MC truth
data
50 100 2000
0.1
0.2
0.3total systematic uncertainty
MC truth (c-term added)
MC truth
data
total systematic uncertainty
MC truth (c-term added)
MC truth
data
total systematic uncertainty
MC truth (c-term added)
MC truth
data
-1=7 TeV, L=35.9 pbs CMS preliminary 2010CaloJets
R=0.5)T
(Anti-k 0.5!| "0 < |
[GeV]T
p50 100 200
reso
lutio
nT
jet p
0
0.1
0.2
0.3total systematic uncertainty
MC truth (c-term added)
MC truth
data
50 100 2000
0.1
0.2
0.3total systematic uncertainty
MC truth (c-term added)
MC truth
data
total systematic uncertainty
MC truth (c-term added)
MC truth
data
total systematic uncertainty
MC truth (c-term added)
MC truth
data
-1=7 TeV, L=35.9 pbs CMS preliminary 2010PFJets
R=0.5)T
(Anti-k 0.5!| "0 < |
A =pjet1
T − pjet2T
pjet1T + pjet2
T
σ(pT )pT
=√
2σA
jet1, jet2 - leading jets in the event (3rd jet pT ! 0)
Calorimeter Jets Particle Flow JetsBetter resolution!
CMS-PAS-JME-10-014
Cosmin Dragoiu DIS 2011
Inclusive Jet Production I
8
! Represents an important test of the Standard Model
! Extends up to pT of 1.1 TeV and as low as pT of 18 GeV when using particle flow jets
! NLO pQCD using NLOJET++! Non-perturbative corrections (< 30%)
from PYTHIA6 and HERWIG++
! The data is corrected to particle level using an ansatz method
(GeV)T
p20 30 100 200 1000
dy (p
b/G
eV)
T/d
p!2 d
-1101
10210310410510
610710810
91010101110 3125)"|y|<0.5 (
625)"|y|<1 (#0.5125)"|y|<1.5 (#125)"|y|<2 (#1.55)"|y|<2.5 (#2
|y|<3#2.5
NP theory$NLOExp. uncertainty
R=0.5TAnti-k
Data for: = 7 TeVs-1CMS, 34 pb
(GeV)T
p20 30 100 200 1000
dy (p
b/G
eV)
T/d
p!2 d
-1101
10210310410510
610710810
91010101110
"r = "f = pTPDF4LHC
CMS-PAS-QCD-10-011
Cosmin Dragoiu DIS 2011
Inclusive Jet Production II
9
(GeV)T
p20 30 100 200 1000
Cor
rect
ion
0.50.550.6
0.650.7
0.750.8
0.850.9
0.951
|y| < 0.5 |y| < 1!0.5
|y| < 1.5!1 |y| < 2!1.5
|y| < 2.5!2 |y| < 3!2.5
R=0.5TAnti-k
= 7 TeVs-1CMS, 34 pb
! Main experimental uncertainties:
! Jet energy scale (3% to 5%)! Jet energy resolution (10% to 30%)
! Main theoretical uncertainties:! Scale ("r,"f) (5% to 10%)! PDF using PDF4LHC recipe (10%)
The data is compatible with NLO predictions!
(GeV)T
p20 30 100 200 1000
NP (P
DF4L
HC)
!Da
ta /
NLO
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
|y| < 0.5
PFCalo
NP theory!Data / NLOTheory uncertaintyExp. uncertainty
(GeV)T
p20 30 100 200 1000
NP (P
DF4L
HC)
!Da
ta /
NLO
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
= 7 TeVs-1CMS, 34 pb
Corrections to particle level
Cosmin Dragoiu DIS 2011
! Another important test of the Standard Model
! The dijet invariant mass probes the proton momentum fractions of the scattering partons:
! The data is corrected to particle level! Unfolding factors (0.95 to 0.98)
! NLO pQCD using NLOJET++
! Non-perturbative corrections (5% to 30%) from PYTHIA6 and HERWIG++
Dijet Mass Production I
10
(TeV)JJM0.2 0.3 1 2 3 4
(pb/
TeV)
max
d|y|
JJ/d
M!2 d
-310
210
710
1210
1710 < 0.5max|y|)1 10" < 1.0 (max0.5 < |y|)2 10" < 1.5 (max1.0 < |y|)3 10" < 2.0 (max1.5 < |y|)4 10" < 2.5 (max2.0 < |y|
Non Pert. Corr.#pQCD at NLO
PDF4LHCaveT
= pRµ =
Fµ
-1 = 36 pbintL
= 7 TeVs R = 0.7Tanti-k
CMS
M2JJ = x1 · x2 · s
8 · 10−4 ≤ x1 · x2 ≤ 0.25
Using particle flow jets!
CMS-PAS-QCD-10-025
Cosmin Dragoiu DIS 2011
! Main experimental uncertainties:
! Jet energy scale (15% to 60%)! Jet energy resolution (1%)
! Main theoretical uncertainties:! PDF using PDF4LHC recipe
(5% to 30%)! Non-perturbative correction
(2% to 15%)! Scale ("r,"f) (2% to 32%)
Dijet Mass Production II
11
< 0.5max0.0 < |y|
(TeV)JJM0.2 0.3 0.4 1 2
Dat
a/Th
eory
0.5
1
1.5 < 1.0max0.5 < |y|
(TeV)JJM0.2 0.3 0.4 1 2 3
Dat
a/Th
eory
0.5
1
1.5
< 1.5max1.0 < |y|
(TeV)JJM0.4 0.5 1 2 3
Dat
a/Th
eory
0.5
1
1.5 < 2.0max1.5 < |y|
(TeV)JJM0.6 1 2 3
Dat
a/Th
eory
0.5
1
1.5
< 2.5max
2.0 < |y|
(TeV)JJM0.7 1 2 3
Dat
a/Th
eory
0.5
1
1.5 CMS-1 = 36 pbintL
= 7 TeVs R = 0.7Tanti-k
Data/TheoryExp. Uncertainty
UncertaintyS! "PDF Scale UncertaintyNon. Pert. Uncertainty
Good agreement between data and NLO predictions!
Cosmin Dragoiu DIS 2011
!" Decorrelations I
12
∆ϕdijet = |ϕjet1 − ϕjet2|
! Measurement sensitive to higher order radiation without the need to reconstruct the radiated jets
! Systematic uncertainty (3% to 11%):! Jet energy scale (1% to 5%)! Jet energy resolution (1% to 5%)! Unfolding (1.5% to 8%)! Smearing (2.5%)
!Reasonable agreement between PYTHIA6, HERWIG++ and data
! MADGRAPH (PYTHIA8) predicts less (more) decorrelations than data
[ rad ] dijet
ϕ∆
]-1
[ ra
d
dije
tϕ
∆d
dije
tσ
d
dije
tσ
1
-210
-110
1
10
210
310
410
510 )410× > 300 GeV (
T
max p
)3
10× < 300 GeV (T
max 200 < p
)210× < 200 GeV (T
max 140 < p
10)× < 140 GeV (T
max 110 < p
< 110 GeVT
max 80 < p
PYTHIA6 D6T
PYTHIA6 Z2
PYTHIA8
HERWIG++
MADGRAPH
-1L = 2.9 pb
= 7 TeVs
|y| < 1.1
CMS
/2π /3π2 /6π5 π
Using particle flow jets!
PRL 106, 122003 (2011)
Cosmin Dragoiu DIS 2011
0.5
1
1.5
2
0.5
1
1.5
2 CMSCMSCMSCMSCMS > 300 GeVT
max p
0.5
1
1.5
2
0.5
1
1.5
2 < 300 GeVT
max 200 < p
0.5
1
1.5
2
0.5
1
1.5
2 < 200 GeVT
max 140 < p
0.5
1
1.5
2
0.5
1
1.5
2 < 140 GeVT
max 110 < p
0.5
1
1.5
2
0.5
1
1.5
2 < 110 GeVT
max 80 < p
PYTHIA6 D6T
PYTHIA6 Z2
PYTHIA8
HERWIG++
MADGRAPH
Systematic Uncert.
= 7 TeV |y| < 1.1s -1L = 2.9 pb
/2π /3π2 /6π5 π
[ rad ] dijet
ϕ∆
dije
tϕ
∆d
dije
tσ
d
dije
tσ
1
M
CD
AT
A
!" Decorrelations I
13
∆ϕdijet = |ϕjet1 − ϕjet2|
! Measurement sensitive to higher order radiation without the need to reconstruct the radiated jets
! Systematic uncertainty (3% to 11%):! Jet energy scale (1% to 5%)! Jet energy resolution (1% to 5%)! Unfolding (1.5% to 8%)! Smearing (2.5%)
!Reasonable agreement between PYTHIA6, HERWIG++ and data
! MADGRAPH (PYTHIA8) predicts less (more) decorrelations than data
Using particle flow jets!
PRL 106, 122003 (2011)
Cosmin Dragoiu DIS 201114
1
2
3
1
2
3CMS
NLO QCD Predictions CTEQ 6.6max
T = p
fµ =
rµ
> 300 GeVT
max p
1
2
3
1
2
3 < 300 GeV
T
max 200 < p
1
2
3
1
2
3 < 200 GeV
T
max 140 < p
1
2
3
1
2
3 < 140 GeV
T
max 110 < p
1
2
3
1
2
3 < 110 GeV
T
max 80 < p
Scale Dependencef
µ, r
µ
PDF Uncertainty
Non-Pert. Uncertainty
= 7 TeV |y| < 1.1s -1L = 2.9 pb
/2π /3π2 /6π5 π
[ rad ] dijet
ϕ∆
dije
tϕ
∆d
dije
tσ
d
dije
tσ
1
T
HE
OR
YD
AT
A
! NLO pQCD predictions using NLOJET++
! Non-perturbative corrections derived from PYTHIA6 and HERWIG++ (4% to 13%)
! Theoretical uncertainty:
! Scale ("r,"f) (< 50%)! PDF using CTEQ6.6 (2% to 9%)! Non-perturbative corrections (2% to 6%)
! NLO pQCD predictions mostly agree with data but undershoot the data for "# < 2$/3 (effectively 2 ! 4 LO)
!" Decorrelations II
Cosmin Dragoiu DIS 201115
1
2
3
1
2
3CMSCMSCMSCMSCMS > 300 GeV
T
max p
1
2
3
1
2
3 < 300 GeV
T
max 200 < p
1
2
3
1
2
3 < 200 GeV
T
max 140 < p
1
2
3
1
2
3 < 140 GeV
T
max 110 < p
1
2
3
1
2
3 < 110 GeV
T
max 80 < p
=1.0ISR
k=2.0
ISRk
=2.5ISR
k
=3.0ISR
k=4.0
ISRk
Systematic Uncert.
= 7 TeV |y| < 1.1s -1L = 2.9 pb
/2π /3π2 /6π5 π
[ rad ] dijet
ϕ∆
dije
tϕ
∆d
dije
tσ
d
dije
tσ
1
P
YT
HIA
6D
AT
A
! Variation of ISR parameter PARP(67) in PYTHIA6! D6T value 2.5 (tuned to D0 data)! Change by ± 0.5 and ± 1.5
!Sensitive to initial state radiation and mostly insensitive to final state radiation
! Changing PARP(67) by ± 0.5 ! ± 30% change in !"
!Could be used to further tune ISR
!" Decorrelations III
Cosmin Dragoiu DIS 2011
Dijet Angular Distributions I
16
! Probes the parton-parton scattering angle
! QCD predicts a relatively flat % distribution while new physics (quark compositeness) is expected to produce an excess at low values of %
! The data is corrected to particle level (< 3%)
! NLO pQCD predictions using NLOJET++! Non-perturbative corrections from PYTHIA6
and HERWIG++
! Good agreement with pQCD predictions! dijet!
2 4 6 8 10 12 14 16di
jet
!/d
dije
t"
ddi
jet
"1/
0.1
0.2
0.3
0.4
0.5
0.6
0.7
dijet!
2 4 6 8 10 12 14 16di
jet
!/d
dije
t"
ddi
jet
"1/
0.1
0.2
0.3
0.4
0.5
0.6
0.7
> 2.2 TeVjjM (+0.5)
dijet!
2 4 6 8 10 12 14 16di
jet
!/d
dije
t"
ddi
jet
"1/
0.1
0.2
0.3
0.4
0.5
0.6
0.7
< 2.2 TeVjjM1.8 < (+0.4)
dijet!
2 4 6 8 10 12 14 16di
jet
!/d
dije
t"
ddi
jet
"1/
0.1
0.2
0.3
0.4
0.5
0.6
0.7
< 1.8 TeVjjM1.4 < (+0.3)
dijet!
2 4 6 8 10 12 14 16di
jet
!/d
dije
t"
ddi
jet
"1/
0.1
0.2
0.3
0.4
0.5
0.6
0.7
< 1.4 TeVjjM1.1 < (+0.25)
dijet!
2 4 6 8 10 12 14 16di
jet
!/d
dije
t"
ddi
jet
"1/
0.1
0.2
0.3
0.4
0.5
0.6
0.7
< 1.1 TeVjjM0.85 < (+0.2)
dijet!
2 4 6 8 10 12 14 16di
jet
!/d
dije
t"
ddi
jet
"1/
0.1
0.2
0.3
0.4
0.5
0.6
0.7
< 0.85 TeVjjM0.65 < (+0.15)
dijet!
2 4 6 8 10 12 14 16di
jet
!/d
dije
t"
ddi
jet
"1/
0.1
0.2
0.3
0.4
0.5
0.6
0.7
< 0.65 TeVjjM0.5 < (+0.1)
dijet!
2 4 6 8 10 12 14 16di
jet
!/d
dije
t"
ddi
jet
"1/
0.1
0.2
0.3
0.4
0.5
0.6
0.7
< 0.5 TeVjjM0.35 < (+0.05)
dijet!
2 4 6 8 10 12 14 16di
jet
!/d
dije
t"
ddi
jet
"1/
0.1
0.2
0.3
0.4
0.5
0.6
0.7
< 0.35 TeVjjM0.25 <
CMS = 7 TeVs
-1L = 36 pb
DataQCD prediction
= 5 TeV+# = 5 TeV-#
#r = #f = pTave
χdijet = e|y1−y2| ∼ 1 + |cos θ∗|1− |cos θ∗|
CMS-PAS-QCD-10-016
Cosmin Dragoiu DIS 2011
Dijet Angular Distributions II
17
! Experimental uncertainties (< 3%):
! Jet energy scale (< 2.5%)! Jet energy resolution (< 1%)! Unfolding (< 1%)
! Theoretical uncertainties (< 9%):
! Scale ("r,"f) (< 9%)! PDF using CTEQ6.6 (< 0.5%)! Non-perturbative correction (< 4%)
! Limits obtained using a modified CLs approach:! Exclude $+ < 5.6 TeV at 95% CL
(expected $+ < 5.0 TeV )! Exclude $- < 6.7 TeV at 95% CL
(expected $- < 5.8 TeV )
Contact Interaction
!q q
[TeV]+!
1 2 3 4 5 6
SC
L
0.04
0.06
0.08
0.1CMS = 7 TeVs
-1L = 36 pb
observed expected
" 1±expected " 2±expected
Cosmin Dragoiu DIS 2011
Summary
18
! LHC and CMS performed extremely well in 2010
! CMS has a rich jet physics program including precise QCD measurements and searches of new phenomena
! Many results are already submitted for publication or published
! Analyses are already beginning to exceed the Tevatron reach
! High probability of reaching 1/fb in the coming months (25/pb already collected)
! Many new and interesting physics results are on the way
! All CMS public results can be accessed at:
https://twiki.cern.ch/twiki/bin/view/CMSPublic/PhysicsResults
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