Studying the Underlying Event at
CDF and the LHC
Rick Field
University of Florida
Outline of Talk
 Review what we learned about
“min-bias” and the “underlying
event” in Run 1 at CDF.
 Discuss using Drell-Yan lepton-pair
production to study the “underlying
event”.
 Explain the various PYTHIA
PT(hard)
Initial-State Radiation
Proton
AntiProton
Underlying Event
“underlying event” tunes and
extrapolations to the LHC.
University of Toronto Physics
March 18, 2008
Outgoing Parton
Outgoing Parton
Underlying Event
Final-State
Radiation
 “CDF-QCD Data for Theory”: My
latest CDF Run 2 project.
 UE&MB@CMS: Plans to measure
“min-bias” and the “underlying
event” at CMS.
University of Toronto
March 18, 2008
CMS at the LHC
CDF Run 2
Rick Field – Florida/CDF/CMS
Page 1
Proton-AntiProton Collisions
at the Tevatron
Elastic Scattering
The CDF “Min-Bias” trigger
picks up most of the “hard
core” cross-section plus a
Double
Diffraction
small
amount of single &
double diffraction.
M2
M1
Single Diffraction
M
stot = sEL + sIN
SD +sDD +sHC
1.8 TeV: 78mb
= 18mb
+ 9mb
+ (4-7)mb + (47-44)mb
CDF “Min-Bias” trigger
1 charged particle in forward BBC
AND
1 charged particle in backward BBC
Hard Core
The “hard core” component
contains both “hard” and
“soft” collisions.
“Hard” Hard Core (hard scattering)
Outgoing Parton
“Soft” Hard Core (no hard scattering)
Proton
AntiProton
PT(hard)
Beam-Beam Counters
3.2 < |h| < 5.9
Proton
AntiProton
Underlying Event
Underlying Event
Initial-State
Radiation
Final-State
Radiation
Outgoing Parton
University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 2
QCD Monte-Carlo Models:
High Transverse Momentum Jets
Hard Scattering
Initial-State Radiation
Hard Scattering “Jet”
Initial-State Radiation
“Jet”
Outgoing Parton
PT(hard)
Outgoing Parton
PT(hard)
Proton
“Hard Scattering” Component
AntiProton
Final-State Radiation
Outgoing Parton
Underlying Event
Underlying Event
Proton
“Jet”
Final-State Radiation
AntiProton
Underlying Event
Outgoing Parton
Underlying Event
“Underlying Event”
 Start with the perturbative 2-to-2 (or sometimes 2-to-3) parton-parton scattering and add initial and finalstate gluon radiation (in the leading log approximation or modified leading log approximation).
 The “underlying event” consists of the “beam-beam remnants” and from particles arising from soft or
semi-soft multiple parton interactions (MPI).
The “underlying
event” is“jet”
an unavoidable
 Of course the outgoing colored partons fragment
into hadron
and inevitably “underlying event”
background to most collider observables
observables receive contributions from initial
and final-state radiation.
and having good understand of it leads to
more precise collider measurements!
University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 3
Particle Densities
DhD = 4 = 12.6
2

31 charged
charged particles
particle
Charged Particles
pT > 0.5 GeV/c |h| < 1
CDF Run 2 “Min-Bias”
CDF Run 2 “Min-Bias”
Observable
Average
Nchg
Number of Charged Particles
(pT > 0.5 GeV/c, |h| < 1)
3.17 +/- 0.31
0.252 +/- 0.025
PTsum
(GeV/c)
Scalar pT sum of Charged Particles
(pT > 0.5 GeV/c, |h| < 1)
2.97 +/- 0.23
0.236 +/- 0.018
Average Density
per unit h-
dNchg
chg/dhd = 1/4
3/4 = 0.08
0.24
13 GeV/c PTsum
0
-1
h
+1
Divide by 4
dPTsum/dhd = 1/4
3/4 GeV/c = 0.08
0.24 GeV/c
Study the charged particles (pT > 0.5 GeV/c, |h| < 1) and form the charged
particle density, dNchg/dhd, and the charged scalar pT sum density,
dPTsum/dhd.
University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 4
CDF Run 1 “Min-Bias” Data
Charged Particle Density
Charged Particle Density: dN/dhd
Charged Particle Pseudo-Rapidity Distribution: dN/dh
1.0
7
CDF Published
CDF Published
6
0.8
dN/dhd
dN/dh
5
4
3
0.6
0.4
2
0.2
CDF Min-Bias 630 GeV
CDF Min-Bias 1.8 TeV
1
CDF Min-Bias 1.8 TeV
all PT
CDF Min-Bias 630 GeV
all PT
0.0
0
-4
-3
-2
-1
0
1
2
3
4
-4
-3
-1
0
1
2
3
4
Pseudo-Rapidity h
Pseudo-Rapidity h
<dNchg/dh> = 4.2
-2
<dNchg/dhd> = 0.67
 Shows CDF “Min-Bias” data on the number of charged particles per unit pseudo-rapidity
at 630 and 1,800 GeV. There are about 4.2 charged particles per unit h in “Min-Bias”
collisions at 1.8 TeV (|h| < 1, all pT).
DhxD = 1
 Convert to charged particle density, dNchg/dhd, by dividing by 2.
D = 1
There are about 0.67 charged particles per unit h- in “Min-Bias”
0.25
0.67
collisions at 1.8 TeV (|h| < 1, all pT).
 There are about 0.25 charged particles per unit h- in “Min-Bias”
Dh = 1
collisions at 1.96 TeV (|h| < 1, pT > 0.5 GeV/c).
University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 5
CDF Run 2 Min-Bias “Associated”
Charged Particle Density
“Associated” densities do
not include PTmax!
Highest pT
charged particle!
Charged Particle Density: dN/dhd
PTmax Direction
PTmax Direction
0.5
D
Correlations in 
Charged Particle Density
CDF Preliminary
Associated Density
PTmax not included
data uncorrected
0.4
D
Charge Density
0.3
0.2
0.1
Min-Bias
Correlations
in 
Charged Particles
(|h|<1.0, PT>0.5 GeV/c)
PTmax
0.0
0
30
60
90
120
150
180
210
240
270
300
330
360
D (degrees)
 Use the maximum pT charged particle in the event, PTmax, to define a direction and look
It is more probable
to find
a particle
at the the “associated”
density, dN
chg/dhd,
in “min-bias” collisions (pT > 0.5 GeV/c, |h| <
accompanying
PTmax
than
it
is
to
1).
find a particle in the central region!
 Shows the data
on the D dependence of the “associated” charged particle density,
dNchg/dhd, for charged particles (pT > 0.5 GeV/c, |h| < 1, not including PTmax) relative
to PTmax (rotated to 180o) for “min-bias” events. Also shown is the average charged
particle density, dNchg/dhd, for “min-bias” events.
University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 6
CDF Run 2 Min-Bias “Associated”
Charged Particle Density Rapid rise in the particle
density in the “transverse”
region as PTmax increases!
Associated Particle Density: dN/dhd
PTmaxDirection
Direction
PTmax
D
“Toward”
“Transverse”
“Transverse”
Correlations in 
“Away”
Associated Particle Density
Jet #1
D
PTmax > 2.0 GeV/c
1.0
PTmax > 2.0 GeV/c
PTmax > 1.0 GeV/c
0.8
Charged Particles
(|h|<1.0, PT>0.5 GeV/c)
CDF Preliminary
data uncorrected
PTmax > 0.5 GeV/c
Transverse
Region
0.6
Transverse
Region
0.4
0.2
Jet #2
PTmax
PTmax not included
Min-Bias
0.0
0
30
60
90
120
150
180
210
240
270
300
330
360
D (degrees)
Ave Min-Bias
0.25 per unit h-
PTmax > 0.5 GeV/c
 Shows the data on the D dependence of the “associated” charged particle density,
dNchg/dhd, for charged particles (pT > 0.5 GeV/c, |h| < 1, not including PTmax) relative
to PTmax (rotated to 180o) for “min-bias” events with PTmax > 0.5, 1.0, and 2.0 GeV/c.
 Shows “jet structure” in “min-bias” collisions (i.e. the “birth” of the leading two jets!).
University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 7
CDF Run 1: Evolution of Charged Jets
“Underlying Event”
Charged Particle D Correlations
PT > 0.5 GeV/c |h| < 1
Charged Jet #1
Direction
“Transverse” region
very sensitive to the
“underlying event”!
Look at the charged
particle density in the
“transverse” region!
2
“Toward-Side” Jet
D
“Toward”
CDF Run 1 Analysis
Away Region
Charged Jet #1
Direction
D
Transverse
Region
“Toward”
“Transverse”

Leading
Jet
“Transverse”
Toward Region
“Transverse”
“Transverse”
Transverse
Region
“Away”
“Away”
Away Region
“Away-Side” Jet
0
-1
h
+1
 Look at charged particle correlations in the azimuthal angle D relative to the leading charged
particle jet.
 Define |D| < 60o as “Toward”, 60o < |D| < 120o as “Transverse”, and |D| > 120o as “Away”.
 All three regions have the same size in h- space, DhxD = 2x120o = 4/3.
University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 8
Run 1 Charged Particle Density
“Transverse” pT Distribution
"Transverse" Charged Particle Density: dN/dhd
Charged Particle Density
Charged Particle Jet #1
Direction
"Transverse"
PT(chgjet#1) > 5 GeV/cD
1.0E+00
CDF Min-Bias
CDF Run 1
CDF JET20
data uncorrected
0.75
0.50
Factor of 2!
0.25
1.8 TeV |h|<1.0 PT>0.5 GeV/c
0.00
0
5
10
15
20
25
30
35
40
45
PT(charged jet#1) (GeV/c)
PT(charged jet#1) > 30 GeV/c
“Transverse” <dNchg/dhd> = 0.56
“Min-Bias”
50
Charged Density dN/dhddPT (1/GeV/c)
"Transverse" Charged Density
1.00
CDF Run 1
data uncorrected
1.0E-01
“Toward”
"Transverse"
PT(chgjet#1) > 30 GeV/c
1.0E-02
“Transverse”
“Transverse”
1.0E-03
“Away”
1.0E-04
Min-Bias
1.0E-05
1.8 TeV |h|<1 PT>0.5 GeV/c
1.0E-06
CDF Run 1 Min-Bias data
<dNchg/dhd> = 0.25
0
2
4
6
8
10
12
14
PT(charged) (GeV/c)
 Compares the average “transverse” charge particle density with the average “Min-Bias”
charge particle density (|h|<1, pT>0.5 GeV). Shows how the “transverse” charge particle
density and the Min-Bias charge particle density is distributed in pT.
University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 9
ISAJET 7.32
“Transverse” Density
ISAJET uses a naïve leading-log
parton shower-model which does
not agree with the data!
Charged Jet #1
Direction
1.00
D
“Transverse”
“Transverse”
“Away”
CDF Run 1Data
"Transverse" Charged Density
“Toward”
ISAJET
"Transverse" Charged Particle Density: dN/dhd
Isajet
data uncorrected
theory corrected
0.75
"Hard"
0.50
0.25
“Hard”
Component
"Remnants"
1.8 TeV |h|<1.0 PT>0.5 GeV
Beam-Beam
Remnants
0.00
0
5
10
15
20
25
30
35
40
45
50
PT(charged jet#1) (GeV/c)
 Plot shows average “transverse” charge particle density (|h|<1, pT>0.5 GeV) versus PT(charged jet#1)
compared to the QCD hard scattering predictions of ISAJET 7.32 (default parameters with
PT(hard)>3 GeV/c) .
 The predictions of ISAJET are divided into two categories: charged particles that arise from the
break-up of the beam and target (beam-beam remnants); and charged particles that arise from the
outgoing jet plus initial and final-state radiation (hard scattering component).
University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 10
HERWIG 6.4
“Transverse” Density
D
“Toward”
“Transverse”
“Transverse”
“Away”
1.00
CDF Run 1Data
"Transverse" Charged Density
Charged Jet #1
Direction
HERWIG uses a modified leadinglog parton shower-model which
does agrees better with the data!
"Transverse" Charged Particle Density: dN/dhd
Total
"Hard"
data uncorrected
theory corrected
0.75
0.50
0.25
"Remnants"
Beam-Beam
Remnants
HERWIG
Herwig 6.4 CTEQ5L
PT(hard) > 3 GeV/c
1.8 TeV |h|<1.0 PT>0.5 GeV
0.00
0
5
10
15
20
25
30
PT(charged jet#1) (GeV/c)
35
40
45
50
“Hard”
Component
 Plot shows average “transverse” charge particle density (|h|<1, pT>0.5 GeV) versus PT(charged
jet#1) compared to the QCD hard scattering predictions of HERWIG 5.9 (default parameters with
PT(hard)>3 GeV/c).
 The predictions of HERWIG are divided into two categories: charged particles that arise from the
break-up of the beam and target (beam-beam remnants); and charged particles that arise from the
outgoing jet plus initial and final-state radiation (hard scattering component).
University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 11
HERWIG 6.4
“Transverse” PT Distribution
HERWIG has the too steep of a pT
dependence of the “beam-beam remnant”
"Transverse" Chargedcomponent
Particle Density:
dN/dhd
of the
“underlying event”!
"Transverse" Charged Particle Density
Charged Jet #1
Direction
CDF Data
"Hard"
Total
data uncorrected
theory corrected
0.75
1.0E+00
Herwig 6.4 CTEQ5L
PT(hard) > 3 GeV/c
D
0.50
0.25
"Remnants"
1.8 TeV |h|<1.0 PT>0.5 GeV
0.00
0
5
10
CDF Data
PT(chgjet#1) > 5 GeV/c
15
20
25
30
35
40
45
PT(charged jet#1) (GeV/c)
Herwig PT(chgjet#1) > 30 GeV/c
“Transverse” <dNchg/dhd> = 0.51
50
Charged Density dN/dhddPT (1/GeV/c)
"Transverse" Charged Density
1.00
data uncorrected
theory corrected
1.0E-01
“Toward”
1.8 TeV |h|<1 PT>0.5 GeV/c
1.0E-02
“Transverse”
1.0E-03
“Transverse”
“Away”
1.0E-04
1.0E-05
PT(chgjet#1) > 30 GeV/c
Herwig 6.4 CTEQ5L
1.0E-06
Herwig PT(chgjet#1) > 5 GeV/c
<dNchg/dhd> = 0.40
0
2
4
6
8
10
12
14
PT(charged) (GeV/c)
 Compares the average “transverse” charge particle density (|h|<1, pT>0.5 GeV) versus
PT(charged jet#1) and the pT distribution of the “transverse” density, dNchg/dhddPT with the
QCD hard scattering predictions of HERWIG 6.4 (default parameters with PT(hard)>3 GeV/c.
Shows how the “transverse” charge particle density is distributed in pT.
University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 12
MPI: Multiple Parton
Interactions
“Hard”
Collision
Multiple
Parton
Interaction
outgoing parton
“Hard” Component
“Semi-Hard” MPI
“Soft” Component
AntiProton
Proton
initial-state radiation
initial-state radiation
outgoing parton
final-state radiation
or
+
outgoing jet
final-state radiation
 PYTHIA models the “soft” component of the underlying event
with color string fragmentation, but in addition includes a
contribution arising from multiple parton interactions (MPI) in
which one interaction is hard and the other is “semi-hard”.
Beam-Beam Remnants
color string
color string
 The probability that a hard scattering events also contains a semi-hard multiple parton
interaction can be varied but adjusting the cut-off for the MPI.
 One can also adjust whether the probability of a MPI depends on the PT of the hard
scattering, PT(hard) (constant cross section or varying with impact parameter).
 One can adjust the color connections and flavor of the MPI (singlet or nearest neighbor,
q-qbar or glue-glue).
 Also, one can adjust how the probability of a MPI depends on PT(hard) (single or double
Gaussian matter distribution).
University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 13
Tuning PYTHIA:
Multiple Parton Interaction Parameters
Parameter
Default
Description
PARP(83)
0.5
Double-Gaussian: Fraction of total hadronic
matter within PARP(84)
PARP(84)
0.2
Double-Gaussian: Fraction of the overall hadron
radius containing the fraction PARP(83) of the
total hadronic matter.
Multiple Parton Interaction
Color String
Color String
PARP(86)
PARP(89)
PARP(90)
PARP(67)
0.33
0.66
1 TeV
0.16
1.0
Probability that the MPI produces two gluons
with color connections to the “nearest neighbors.
Multiple PartonDetermine
Interactionby comparing
with 630 GeV data!
Probability that the MPI produces two gluons
either as described by PARP(85) or as a closed
gluon
loop.
remaining
fraction consists of
Affects
the The
amount
of
quark-antiquark
pairs.
initial-state radiation!
Color String
Hard-Scattering Cut-Off PT0
5
Determines the reference energy E0.
Determines the energy dependence of the cut-off
PT0 as follows PT0(Ecm) = PT0(Ecm/E0)e with
e = PARP(90)
A scale factor that determines the maximum
parton virtuality for space-like showers. The
larger the value of PARP(67) the more initialstate radiation.
PYTHIA 6.206
e = 0.25 (Set A))
4
PT0 (GeV/c)
PARP(85)
Take E0 = 1.8 TeV
3
2
e = 0.16 (default)
1
100
1,000
10,000
100,000
CM Energy W (GeV)
Reference point
at 1.8 TeV
University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 14
PYTHIA 6.206 Defaults
MPI constant
probability
scattering
PYTHIA default parameters
6.115
6.125
6.158
6.206
MSTP(81)
1
1
1
1
MSTP(82)
1
1
1
1
PARP(81)
1.4
1.9
1.9
1.9
PARP(82)
1.55
2.1
2.1
1.9
PARP(89)
1,000
1,000
1,000
PARP(90)
0.16
0.16
0.16
4.0
1.0
1.0
PARP(67)
4.0
1.00
"Transverse" Charged Density
Parameter
"Transverse" Charged Particle Density: dN/dhd
CDF Data
Pythia 6.206 (default)
MSTP(82)=1
PARP(81) = 1.9 GeV/c
data uncorrected
theory corrected
0.75
0.50
0.25
1.8 TeV |h|<1.0 PT>0.5 GeV
0.00
0
5
10
15
20
25
30
35
40
45
50
PT(charged jet#1) (GeV/c)
CTEQ3L
CTEQ4L
CTEQ5L
CDF Min-Bias
CDF JET20
 Plot shows the “Transverse” charged particle density versus PT(chgjet#1) compared to the
QCD hard scattering predictions of PYTHIA 6.206 (PT(hard) > 0) using the default
parameters for multiple parton interactions and CTEQ3L, CTEQ4L, and CTEQ5L.
Note Change
PARP(67) = 4.0 (< 6.138)
PARP(67) = 1.0 (> 6.138)
University of Toronto
March 18, 2008
Default parameters give
very poor description of
the “underlying event”!
Rick Field – Florida/CDF/CMS
Page 15
Run 1 PYTHIA Tune A
CDF Default!
PYTHIA 6.206 CTEQ5L
"Transverse" Charged Particle Density: dN/dhd
Parameter
Tune B
Tune A
MSTP(81)
1
1
MSTP(82)
4
4
PARP(82)
1.9 GeV
2.0 GeV
PARP(83)
0.5
0.5
PARP(84)
0.4
0.4
PARP(85)
1.0
0.9
"Transverse" Charged Density
1.00
CDF Preliminary
0.75
1.0
0.95
PARP(89)
1.8 TeV
1.8 TeV
PARP(90)
0.25
0.25
PARP(67)
1.0
4.0
New PYTHIA default
(less initial-state radiation)
University of Toronto
March 18, 2008
Run 1 Analysis
0.50
0.25
CTEQ5L
PYTHIA 6.206 (Set B)
PARP(67)=1
1.8 TeV |h|<1.0 PT>0.5 GeV
0.00
0
PARP(86)
PYTHIA 6.206 (Set A)
PARP(67)=4
data uncorrected
theory corrected
5
10
15
20
25
30
35
40
45
50
PT(charged jet#1) (GeV/c)
 Plot shows the “transverse” charged particle density
versus PT(chgjet#1) compared to the QCD hard
scattering predictions of two tuned versions of PYTHIA
6.206 (CTEQ5L, Set B (PARP(67)=1) and Set A
(PARP(67)=4)).
Old PYTHIA default
(more initial-state radiation)
Rick Field – Florida/CDF/CMS
Page 16
PYTHIA Tune A Min-Bias
“Soft” + ”Hard”
Tuned to fit the CDF Run 1
“underlying event”!
PYTHIA Tune A
CDF Run 2 Charged
DefaultParticle Density
Charged Particle Density: dN/dhd
1.0
CDF Published
1.0E+00
0.8
CDF Min-Bias Data
1.0E-01
0.6
0.4
0.2
Pythia 6.206 Set A
1.8 TeV all PT
CDF Min-Bias 1.8 TeV
0.0
-4
-3
-2
-1
0
1
2
3
4
Pseudo-Rapidity h
 PYTHIA regulates the perturbative 2-to-2
parton-parton cross sections with cut-off
parameters
which allows one to run with
Lots of “hard” scattering in
PT“Min-Bias”
(hard) > 0.
One
can simulate both “hard”
at the
Tevatron!
and “soft” collisions in one program.
Charged Density dN/dhddPT (1/GeV/c)
dN/dhd
Pythia 6.206 Set A
1.8 TeV |h|<1
1.0E-02
12% of “Min-Bias” events
have PT(hard) > 5 GeV/c!
PT(hard) > 0 GeV/c
1.0E-03
1% of “Min-Bias” events
have PT(hard) > 10 GeV/c!
1.0E-04
1.0E-05
CDF Preliminary
1.0E-06
0
2
4
6
8
10
12
14
PT(charged) (GeV/c)
 The relative amount of “hard” versus “soft” depends on the cut-off and can be tuned.
 This PYTHIA fit predicts that 12% of all “Min-Bias” events are a result of a hard 2-to-2
parton-parton scattering with PT(hard) > 5 GeV/c (1% with PT(hard) > 10 GeV/c)!
University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 17
PYTHIA Tune A
LHC Min-Bias Predictions
Hard-Scattering in Min-Bias Events
Charged Particle Density
50%
12% of “Min-Bias”
events
have|h|<1
PT(hard) > 10 GeV/c!
1.0E+00
Pythia 6.206 Set A
Pythia 6.206 Set A
40%
% of Events
Charged Density dN/dhddPT (1/GeV/c)
1.0E-01
1.0E-02
PT(hard) > 5 GeV/c
PT(hard) > 10 GeV/c
30%
20%
1.8 TeV
1.0E-03
10%
14 TeV
1.0E-04
0%
100
1,000
10,000
100,000
CM Energy W (GeV)
630 GeV
LHC?
1.0E-05
 Shows the center-of-mass energy dependence
CDF Data
1.0E-06
0
2
4
6
8
PT(charged) (GeV/c)
1% of “Min-Bias” events
have PT(hard) > 10 GeV/c!
10
12
14
of the charged particle density,
dNchg/dhddPT, for “Min-Bias” collisions
compared with PYTHIA Tune A with
PT(hard) > 0.
 PYTHIA Tune A predicts that 1% of all “Min-Bias” events at 1.8 TeV are a result of a hard
2-to-2 parton-parton scattering with PT(hard) > 10 GeV/c which increases to 12% at 14 TeV!
University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 18
QCD Monte-Carlo Models:
Lepton-Pair Production
Lepton-Pair Production
Anti-Lepton
Initial-State Radiation
Lepton-Pair Production
Initial-State Radiation
“Jet”
Proton
Anti-Lepton
“Hard Scattering” Component
AntiProton
Lepton
Underlying Event
Underlying Event
Proton
Lepton
AntiProton
Underlying Event
Underlying Event
“Underlying Event”
 Start with the perturbative Drell-Yan muon pair production and add initial-state gluon radiation (in the
leading log approximation or modified leading log approximation).
 The “underlying event” consists of the “beam-beam remnants” and from particles arising from soft or
semi-soft multiple parton interactions (MPI).
 Of course the outgoing colored partons fragment into hadron “jet” and inevitably “underlying event”
observables receive contributions from initial and final-state radiation.
University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 19
The “Central” Region
in Drell-Yan Production
Drell-Yan Production
Look at the charged
particle density and the
PTsum density in the
“central” region!
Charged Particles (pT > 0.5 GeV/c, |h| < 1)
Lepton
2
Proton
AntiProton
Underlying Event
Underlying Event
Initial-State
Radiation

Central Region
Anti-Lepton
Multiple Parton Interactions
Proton
Lepton
AntiProton
Underlying Event
0
-1
Underlying Event
Anti-Lepton
h
+1
After removing the leptonpair everything else is the
“underlying event”!
 Look at the “central” region after removing the lepton-pair.
 Study the charged particles (pT > 0.5 GeV/c, |h| < 1) and form the charged particle
density, dNchg/dhd, and the charged scalar pT sum density, dPTsum/dhd, by dividing
by the area in h- space.
University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 20
CDF Run 1 PT(Z)
PYTHIA 6.2 CTEQ5L
Tune A
Tune A25
Tune A50
MSTP(81)
1
1
1
MSTP(82)
4
4
4
PARP(82)
2.0 GeV
2.0 GeV
2.0 GeV
PARP(83)
0.5
0.5
0.5
PARP(84)
0.4
0.4
0.4
PARP(85)
0.9
0.9
0.9
PARP(86)
0.95
0.95
0.95
PARP(89)
1.8 TeV
1.8 TeV
1.8 TeV
ISR Parameter PARP(90)
0.25
0.25
0.25
PARP(67)
4.0
4.0
4.0
MSTP(91)
1
1
1
PARP(91)
1.0
2.5
5.0
PARP(93)
5.0
15.0
25.0
s = 1.0
Z-Boson Transverse Momentum
0.12
PT Distribution 1/N dN/dPT
UE Parameters Parameter
CDF Run 1 Data
PYTHIA Tune A
PYTHIA Tune A25
PYTHIA Tune A50
s = 2.5
0.08
CDF Run 1
published
1.8 TeV
s = 5.0
Normalized to 1
0.04
0.00
0
2
4
6
8
10
12
14
16
18
Z-Boson PT (GeV/c)
 Shows the Run 1 Z-boson pT distribution
(<pT(Z)> ≈ 11.5 GeV/c) compared with PYTHIA
Tune A (<pT(Z)> = 9.7 GeV/c), Tune A25
(<pT(Z)> = 10.1 GeV/c), and
Tune A50
(<pT(Z)> = 11.2 GeV/c).
Vary the intrensic KT!
Intrensic KT
University of Toronto
March 18, 2008
20
Rick Field – Florida/CDF/CMS
Page 21
CDF Run 1 PT(Z)
UE Parameters
ISR Parameters
Parameter
Tune A
Tune AW
MSTP(81)
1
1
MSTP(82)
4
4
PARP(82)
2.0 GeV
2.0 GeV
PARP(83)
0.5
0.5
PARP(84)
0.4
0.4
PARP(85)
0.9
0.9
PARP(86)
0.95
0.95
PARP(89)
1.8 TeV
1.8 TeV
PARP(90)
0.25
0.25
PARP(62)
1.0
1.25
PARP(64)
1.0
0.2
PARP(67)
4.0
4.0
MSTP(91)
1
1
PARP(91)
1.0
2.1
PARP(93)
5.0
15.0
Tune used by the
CDF-EWK group!
Z-Boson Transverse Momentum
0.12
PT Distribution 1/N dN/dPT
PYTHIA 6.2 CTEQ5L
CDF Run 1 Data
PYTHIA Tune A
PYTHIA Tune AW
CDF Run 1
published
0.08
1.8 TeV
Normalized to 1
0.04
0.00
0
2
4
6
8
10
12
14
16
18
20
Z-Boson PT (GeV/c)
 Shows the Run 1 Z-boson pT distribution (<pT(Z)>
≈ 11.5 GeV/c) compared with PYTHIA Tune A
(<pT(Z)> = 9.7 GeV/c), and PYTHIA Tune AW
(<pT(Z)> = 11.7 GeV/c).
Effective Q cut-off, below which space-like showers are not evolved.
Intrensic KT
The Q2 = kT2 in as for space-like showers is scaled by PARP(64)!
University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 22
Jet-Jet Correlations (DØ)
Jet#1-Jet#2 D Distribution
D Jet#1-Jet#2
 MidPoint Cone Algorithm (R = 0.7, fmerge = 0.5)
 L = 150 pb-1 (Phys. Rev. Lett. 94 221801 (2005))
 Data/NLO agreement good. Data/HERWIG agreement
good.
 Data/PYTHIA agreement good provided PARP(67) =
1.0→4.0 (i.e. like Tune A, best fit 2.5).
University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 23
CDF Run 1 PT(Z)
PYTHIA 6.2 CTEQ5L
ISR Parameters
Tune DW
Tune AW
MSTP(81)
1
1
MSTP(82)
4
4
PARP(82)
1.9 GeV
2.0 GeV
PARP(83)
0.5
0.5
PARP(84)
0.4
0.4
PARP(85)
1.0
0.9
PARP(86)
1.0
0.95
PARP(89)
1.8 TeV
1.8 TeV
PARP(90)
0.25
0.25
PARP(62)
1.25
1.25
PARP(64)
0.2
0.2
PARP(67)
2.5
4.0
MSTP(91)
1
1
PARP(91)
2.1
2.1
PARP(93)
15.0
15.0
Z-Boson Transverse Momentum
0.12
PT Distribution 1/N dN/dPT
UE Parameters
Parameter
CDF Run 1 Data
PYTHIA Tune DW
HERWIG
CDF Run 1
published
0.08
1.8 TeV
Normalized to 1
0.04
0.00
0
2
4
6
8
10
12
14
16
18
20
Z-Boson PT (GeV/c)
Intrensic KT
 Shows the Run 1 Z-boson pT distribution (<pT(Z)>
≈ 11.5 GeV/c) compared with PYTHIA Tune DW,
and HERWIG.
Tune DW uses D0’s perfered value of PARP(67)!
Tune DW has a lower value of PARP(67) and slightly more MPI!
University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 24
Use LO as
with L = 192 MeV!
UE Parameters
ISR Parameter
PYTHIA 6.2 Tunes
Parameter
Tune DW
Tune DWT
ATLAS
Tune D6
Tune D6T
PDF
CTEQ5L
CTEQ5L
CTEQ5L
CTEQ6L
CTEQ6L
MSTP(2)
1
1
1
1
1
MSTP(33)
0
0
0
0
1
PARP(31)
1.0
1.0
1.0
1.0
1.0
MSTP(81)
1
1
1
1
1
MSTP(82)
4
4
4
4
4
PARP(82)
1.9 GeV
1.9409 GeV
1.8 GeV
1.8 GeV
1.8387 GeV
PARP(83)
0.5
0.5
0.5
PARP(84)
0.4
0.4
0.4
PARP(85)
1.0
1.0
0.33
1.0
1.0
PARP(86)
1.0
1.0
0.66
1.0
1.0
PARP(89)
1.8 TeV
1.96 TeV
1.0 TeV
1.8 TeV
1.96 TeV
PARP(90)
0.25
0.16
0.16
0.25
0.16
PARP(62)
1.25
1.25
1.0
1.25
1.25
PARP(64)
0.2
0.2
1.0
0.2
0.2
PARP(67)
2.5
2.5
1.0
2.5
2.5
MSTP(91)
1
1
1
1
1
PARP(91)
2.1
2.1
1.0
2.1
2.1
PARP(93)
15.0
15.0
5.0
15.0
15.0
CMS0.5uses Tune0.5DWT
and
0.4 Tune D6T!
0.5
CTEQ6L Tune
Intrinsic KT
University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 25
PYTHIA 6.2 Tunes
s(MPI) at 1.96 TeV
s(MPI) at 14 TeV
Tune A
309.7 mb
484.0 mb
Tune DW
351.7 mb
549.2 mb
Tune DWT
Charged
Average PT 351.7 mb
829.1 mb
PYTHIA 6.2 CTEQ5L
Parameter
Tune A
Tune DW
Tune DWT
ATLAS
MSTP(81)
1
1
1
1
MSTP(82)
4
PARP(82)
2.0 GeV
4
1.7GeV
1.9
PARP(83)
0.5
0.9
1.0
1.3
1.0
PARP(86)
0.95
PARP(89)
1.8 TeV
PARP(90)
0.25
PARP(62)
1.0
PARP(64)
1.0
0.2
PARP(67)
4.0
MSTP(91)
1
0.72.5
0
1
1.8
1.1 TeV
0.25
0.33
1.0
0.66
1.96 TeV
1.0 TeV
0.16
0.16
1.25
1.0
1.96 TeV
0.2
2.5
50
1
100
HERWIG
1.0
1.0
150
1
PARP(91)
1.0
2.1
2.1
1.0
PARP(93)
5.0
15.0
15.0
5.0
Identical to DW at 1.96 TeV but uses
ATLAS extrapolation to the LHC!
768.0 mb
"Transverse"
Charged
Particle
Average
pT
"Transverse"
Charged
Particle
Density:
dN/dhd
"Transverse"
PTsum
Density:
dPT/dhd
1.0
1.25
0.9
324.5
mbRun 2 Data!
CDF
"Leading Jet"
0.5 data corrected
0.5 to particle level
0.5
1.5
0.4
0.5
PY Tune0.4
A, DW
PARP(85)
University of Toronto
March 18, 2008
ATLAS
1.8 GeV
"Transverse"
Charged
PTDensity
(GeV/c)
"Transverse"
Charged
"Transverse"
PTsum
Density
(GeV/c)
0.4
1.9409 GeV
CDF Run 2 Preliminary
"Transverse" <PT> (GeV/c)
PARP(84)
4"Transverse"
4
1.6
1.0
1.5
RDF
RDFPreliminary
Preliminary
RDF
Preliminary
generator
generatorlevel
level
generator
level
0.8
1.2
1.3
PY Tune DW
PY Tune DW
0.6
PY Tune DW
PY Tune A
PY Tune A
PY-ATLAS
PY-ATLAS
0.8
1.1
PY-ATLAS
0.4
PY Tune A
MidPoint R = 0.7 |h(jet#1) <PY-ATLAS
2
1.96TeV
TeV
1.96
1.96 TeV
HERWIG
0.4
0.9
HERWIGPT>0.5 GeV/c)
Charged
Particles (|h|<1.0,
0.2
Leading
JetJet
(|h|<2.0)
Leading
(|h|<2.0)
Leading
Jet (|h|<2.0)
Charged
Particles
(|h|<1.0,
PT>0.5
GeV/c)
Charged
Particles
(|h|<1.0,
PT>0.5
GeV/c)
Charged
Particles
(|h|<1.0,
PT>0.5
GeV/c)
HERWIG
0.0
0.0
200 0.7 250
00
0
50
50
50
300
100
100
100
PT(jet#1) (GeV/c)
350
150
150
150
400
200
200
200
250
250
250
450
300
300
300
350
350
350
400
400
400
450
450
450
500
500
500
PT(particle
jet#1)
PT(particle jet#1)
jet#1) (GeV/c)
(GeV/c)
PT(particle
(GeV/c)
 Shows
Shows the
the “transverse”
“transverse” charged
charged PTsum
particledensity,
density,

average
p
T,
dN/dhd,
versus
PPTT(jet#1)
“leading
dPT/dhd,
versusfor
(jet#1)for
for
“leading
jet”
versus
PT(jet#1)
“leading
jet”
eventsjet”
at 1.96
events
atTune
1.96A,
TeV
forATLAS,
Tune A,
A,and
DW,HERWIG
ATLAS, and
and
events
1.96
TeV
for
Tune
DW,
ATLAS,
TeV
forat
DW,
HERWIGMPI).
(without MPI).
MPI).
HERWIG
(without
(without
Rick Field – Florida/CDF/CMS
Page 26
The “Underlying Event” in
High PT Jet Production (LHC)
High PT Jet Production
Outgoing Parton
PT(hard)
Initial-State
Radiation
The “Underlying Event” Proton
Underlying Event
Underlying Event
“Underlying event” much
more active at the LHC!
Final-State
Radiation
Outgoing Parton
"Transverse" Charged Particle Density: dN/dhd
"Transverse" Charged Particle Density: dN/dhd
1.0
2.0
RDF Preliminary
LHC
RDF Preliminary
generator level
0.8
0.6
PY Tune AW
HERWIG
0.4
1.96 TeV
0.2
"Leading Jet"
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
0.0
"Transverse" Charged Density
"Transverse" Charged Density
Charged particle density
versus PT(jet#1)
AntiProton
generator level
1.5
PY Tune AW
HERWIG
1.0
CDF
0.5
"Leading Jet"
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
0.0
0
50
100
150
200
250
300
350
400
450
500
0
250
500
PT(particle jet#1) (GeV/c)
750
1000
1250
1500
1750
2000
2250
2500
PT(particle jet#1) (GeV/c)
 Charged particle density in the “Transverse”  Charged particle density in the “Transverse”
region versus PT(jet#1) at 1.96 TeV for PY
region versus PT(jet#1) at 14 TeV for PY Tune
Tune AW and HERWIG (without MPI).
AW and HERWIG (without MPI).
University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 27
PYTHIA 6.2 Tunes
s(MPI) at 1.96 TeV
s(MPI) at 14 TeV
Tune A
309.7 mb
484.0 mb
PYTHIA 6.2 CTEQ5L
Tune A
Tune DW
Tune DWT
ATLAS
MSTP(81)
1
1
1
1
Tune DW
351.7 mb
549.2 mb
MSTP(82)
4
4
4
4
Tune DWT
351.7 mb
829.1 mb
PARP(82)
2.0 GeV
1.9 GeV
1.9409 GeV
1.8 GeV
ATLAS
324.5 mb
768.0 mb
PARP(83)
0.5
0.5
0.5
0.5
PARP(84)
0.4
0.4
0.4
0.5
PARP(85)
0.9
1.0
1.0
0.33
PARP(86)
0.95
1.0
1.0
0.66
PARP(89)
1.8 TeV
1.8 TeV
1.96 TeV
1.0 TeV
PARP(90)
0.25
0.25
0.16
0.16
PARP(62)
1.0
1.25
1.25
1.0
PARP(64)
1.0
0.2
0.2
1.0
PARP(67)
4.0
2.5
2.5
1.0
MSTP(91)
1
1
1
1
PARP(91)
1.0
2.1
2.1
1.0
PARP(93)
5.0
15.0
15.0
5.0
Identical to DW at 1.96 TeV but uses
ATLAS extrapolation to the LHC!
University of Toronto
March 18, 2008
"Transverse"
Charged
Density
"Transverse"
Density
(GeV/c)
"Transverse"PTsum
Charged
PT (GeV/c)
Parameter
"Transverse"Charged
PTsum Density:
dPT/dhdpT
"Transverse"
Particle Average
"Transverse" Charged Particle Density: dN/dhd
8.0
2.5
2.5
PY Tune DWT
PY Tune DWT PY Tune DWT
RDF Preliminary
RDFgenerator
Preliminary
level
generator
level
RDF
Preliminary
6.0
generator level
PY Tune DW
PY Tune DW
2.0
2.0
1.5
4.0
PY-ATLAS
HERWIG
PY Tune DW
1.0
1.5
2.0
0.5
1.0
0.0
0.0
PY-ATLAS
HERWIG HERWIG
00
0
250
250
500
500
PY-ATLAS
750
750
14 TeV
14 TeV
14 TeV
Leading
LeadingJet
Jet(|h|<2.0)
(|h|<2.0)
Leading
Jet
(|h|<2.0)
Charged
(|h|<1.0,
PT>0.5
ChargedParticles
Particles
(|h|<1.0,
PT>0.5GeV/c)
GeV/c)
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
1000
1000
1250
1250
1500
1500
1750
1750
2000
2000
PT(particle jet#1)
jet#1) (GeV/c)
PT(particle
(GeV/c)
PT(particle jet#1) (GeV/c)
 Shows the “transverse” charged PTsum
particle density,
 Shows the “transverse” charged averagedensity,
pT,
dN/dhd,
versus
P
(jet#1)
for
“leading
jet”
dPT/dhd,
versusfor
PT T(jet#1)
forjet”
“leading
versus PT(jet#1)
“leading
eventsjet”
at 14
events
at
14
TeV
for
Tune
A,
DW,
ATLAS,
and
TeV for Tune A, DW, ATLAS, and HERWIG
HERWIG
(without MPI).
(without MPI).
Rick Field – Florida/CDF/CMS
Page 28
Summary
Outgoing Parton
“Minumum Bias” Collisions
Tevatron
LHC
PT(hard)
Initial-State Radiation
Proton
AntiProton
Proton
AntiProton
Underlying Event
Outgoing Parton
Underlying Event
Final-State
Radiation
 PYTHIA Tune DW is very similar to Tune A except that it fits the CDF PT(Z) distribution
and it uses the DØ prefered value of PARP(67) = 2.5 (determined from the dijet D
distribution).
 PYTHIA Tune DWT is identical to Tune DW at 1.96 TeV but uses the ATLAS energy
extrapolation to the LHC (i.e. PARP(90) = 0.16).
 PYTHIA Tune D6 and D6T are similar to Tune DW and DWT, respectively, but use
CTEQ6L (i.e. LHAPDF = 10042).
University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 29
Drell-Yan Production (Run 2 vs LHC)
Drell-Yan Production
Proton
<pT(m+m-)> is much
larger at the LHC!
Lepton-Pair Transverse
Momentum
Lepton
AntiProton
Underlying Event
Underlying Event
Shapes of the pT(m+m-)
distribution at the Z-boson mass.
Initial-State
Radiation
Anti-Lepton
Lepton-Pair Transverse Momentum
Drell-Yan PT(m+m-) Distribution
80
0.10
Drell-Yan
Drell-Yan
LHC
60
1/N dN/dPT (1/GeV)
Average Pair PT
generator level
40
Tevatron Run 2
20
0
0.08
PY Tune DW (solid)
HERWIG (dashed)
0.06
70 < M(m-pair) < 110 GeV
|h(m-pair)| < 6
0.04
0.02
PY Tune DW (solid)
HERWIG (dashed)
Z
generator level
Tevatron Run2
LHC
Normalized to 1
0.00
0
100
200
300
400
500
600
700
800
900
1000
0
5
Lepton-Pair Invariant Mass (GeV)
10
15
20
25
30
35
40
PT(m+m-) (GeV/c)
 Average Lepton-Pair transverse momentum  Shape of the Lepton-Pair pT distribution at the
Z-boson mass at the Tevatron and the LHC for
at the Tevatron and the LHC for PYTHIA
PYTHIA Tune DW and HERWIG (without MPI).
Tune DW and HERWIG (without MPI).
University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 30
The “Underlying Event” in
Drell-Yan Production
Drell-Yan Production
The “Underlying Event”
Lepton
Proton
HERWIG (without MPI)
is much less active than
PY Tune AW (with MPI)!
Underlying Event
Charged particle density
versus M(pair)
AntiProton
Underlying Event
“Underlying event” much
more active at the LHC!
Initial-State
Radiation
Anti-Lepton
Charged Particle Density: dN/dhd
Charged Particle Density: dN/dhd
1.5
1.0
RDF Preliminary
generator level
PY Tune AW
0.8
0.6
0.4
HERWIG
0.2
Drell-Yan
1.96 TeV
Z
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
(excluding lepton-pair )
Charged Particle Density
Charged Particle Density
RDF Preliminary
generator level
Z
LHC
1.0
PY Tune AW
CDF
0.5
Drell-Yan
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
(excluding lepton-pair )
HERWIG
0.0
0.0
0
50
100
150
200
250
0
50
100
150
200
250
Lepton-Pair Invariant Mass (GeV)
Lepton-Pair Invariant Mass (GeV)
 Charged particle density versus the lepton-  Charged particle density versus the lepton-pair
invariant mass at 14 TeV for PYTHIA Tune AW
pair invariant mass at 1.96 TeV for PYTHIA
and HERWIG (without MPI).
Tune AW and HERWIG (without MPI).
University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 31
Extrapolations to the LHC:
Drell-Yan Production
Drell-Yan Production
Charged particle density
versus M(pair)
Lepton
The “Underlying Event”
Proton
AntiProton
Underlying Event
Tune DW and DWT are
identical at 1.96 TeV, but
have different MPI energy
dependence!
Underlying Event
Initial-State
Radiation
Anti-Lepton
Charged Particle Density: dN/dhd
Charged Particle Density: dN/dhd
1.0
2.5
PY Tune BW
generator level
RDF Preliminary
PY Tune DW
0.8
0.6
0.4
PY Tune A
PY Tune AW
1.96 TeV
0.2
HERWIG
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
(excluding lepton-pair )
Z
0.0
0
50
Charged Particle Density
Charged Particle Density
RDF Preliminary
generator level
PY-ATLAS
PY Tune DWT
2.0
1.5
PY Tune DW
1.0
14 TeV
0.5
Z
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
(excluding lepton-pair )
HERWIG
0.0
100
150
200
250
300
350
400
450
500
0
100
Lepton-Pair Invariant Mass (GeV)
200
300
400
500
600
700
800
900
1000
Lepton-Pair Invariant Mass (GeV)
 Average charged particle density versus the  Average charged particle density versus the
lepton-pair invariant mass at 1.96 TeV for
lepton-pair invariant mass at 14 TeV for
PYTHIA Tune A, Tune AW, Tune BW, Tune
PYTHIA Tune DW, Tune DWT, ATLAS and
DW and HERWIG (without MPI).
HERWIG (without MPI).
University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 32
Extrapolations to the LHC:
Drell-Yan Production
Drell-Yan Production
The “Underlying Event”
The ATLAS tune has a much “softer”
distribution of chargedAntiProton
particles than
Underlying Event
the CDF Run 2 Tunes!
Initial-State
Proton
Charged Particles
(|h|<1.0, pT > 0.5 GeV/c)
Charged particle density
versus M(pair)
Lepton
Underlying Event
Radiation
Charged Particles
(|h|<1.0, pT > 0.9 GeV/c)
Anti-Lepton
Charged Particle Density: dN/dhd
Charged Particle Density: dN/dhd
Drell-Yan
PY Tune DWT
Generator Level
14 TeV
Charged Particle
4.0 Density: dN/dhd
PY-ATLAS
generator level
2.0
1.5
1.0
0.5
Z
HERWIG
100
200
0.0
0
Charged Particle Density
Charged Particle Density
RDF Preliminary
300
1.2
PY-ATLAS
PY Tune DWT
3.0
PY Tune DW
PY Tune DW
2.0
14 TeV
1.0
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
(excluding lepton-pair )
Charged Particle Density
2.5
0.8
Charged Particles (pT > min, |h|<1.0)
(excluding lepton-pair
PY Tune DW )
0.4
PY-ATLAS
70 < M(m+m-) < 110 GeV
Z
Generator Level
14 TeV
HERWIG
Charged Particles (|h|<1.0, PT>0.9 GeV/c)
(excluding lepton-pair )
0.0
400
500
600
HERWIG
700
800
900
1000
0
100
200
300
400
500
600
700
800
900
1000
Lepton-Pair Invariant Mass (GeV)
Lepton-Pair Invariant Mass (GeV)
0.0
particle
0.0
0.2
0.4(pT >0.60.5 0.8  Average
1.0
1.2charged
1.4
1.6
1.8density (pT > 0.9 GeV/c)
 Average charged particle
density
the lepton-pair invariant mass at 14 TeV
GeV/c) versus the lepton-pair invariantMinimum
mass pversus
T (GeV/c)
at 14 TeV for PYTHIA Tune DW, Tune DWT, for PYTHIA Tune DW, Tune DWT, ATLAS and
HERWIG (without MPI).
ATLAS and HERWIG (without MPI).
University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 33
Most Recent CDF
“Underlying Event” Studies
Fermilab 2008
CDF-QCD Data for Theory
The goal is to produce data (corrected to the
particle level) that can be used by the theorists to
tune and improve the QCD Monte-Carlo models
that are used to simulate hadron-hadron
collisions.
Outline of the Project
 The “Towards”, “Away”, and
“Transverse” regions of h- space.
Four Jet Topologies.

 The “transMAX”, “transMIN”, and
Rick Field
Craig Group
Deepak Kar
“transDIF” regions.
 Also, study the “underlying event”
in Drell-Yan production.
 Over 128 plots to get “blessed” and
then to published. So far we have only
looked at average quantities. We plan
to also produce distributions and flow
Proton
plots.
Proton
 We plan to construct a “CDF-QCD
Jet #1 Direction
Lepton Parton
Outgoing
D
PT(hard)
Initial-State Radiation
AntiProton
AntiProton
UnderlyingEvent
Event
Underlying
Data for Theory” WEBsite with the
“blessed” plots together with tables of
the data points and errors so that
people can have access to the results.
University of Toronto
March 18, 2008
Drell-Yan Production
Anti-Lepton
Outgoing
Parton
UnderlyingEvent
Event
Underlying
Final-State
Radiation
Rick Field – Florida/CDF/CMS
“Toward”
“Transverse”
“Transverse”
“Away”
Page 34
“Towards”, “Away”, “Transverse”
Look at the charged
particle density, the
charged PTsum density
and the ETsum density in
all 3 regions!
D Correlations relative to the leading jet
Jet #1 Direction
“Transverse” region is
very sensitive to the
“underlying event”!
Charged particles pT > 0.5 GeV/c |h| < 1
Calorimeter towers ET > 0.1 GeV |h| < 1
“Toward-Side” Jet
2
Away Region
Z-Boson
Direction
Jet #1 Direction
D
D
Transverse
Region
“Toward”
“Toward”
“Transverse”
“Transverse”
“Away”
“Transverse”
“Transverse”

Leading
Jet
Toward Region
“Away”
Transverse
Region
“Away-Side” Jet
Away Region
0
-1
h
+1
 Look at correlations in the azimuthal angle D relative to the leading charged particle jet (|h| <
1) or the leading calorimeter jet (|h| < 2).
 Define |D| < 60o as “Toward”, 60o < |D| < 120o as “Transverse ”, and |D| > 120o as “Away”.
o
Each of the three regions have area DhD = 2×120 = 4/3.
University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 35
Event Topologies
 “Leading Jet” events correspond to the leading
calorimeter jet (MidPoint R = 0.7) in the region |h| < 2
with no other conditions.
 “Inclusive 2-Jet Back-to-Back” events are selected to
have at least two jets with Jet#1 and Jet#2 nearly “backto-back” (D12 > 150o) with almost equal transverse
energies (PT(jet#2)/PT(jet#1) > 0.8) with no other
conditions .
 “Exclusive 2-Jet Back-to-Back” events are selected to
have at least two jets with Jet#1 and Jet#2 nearly “backto-back” (D12 > 150o) with almost equal transverse
energies (PT(jet#2)/PT(jet#1) > 0.8) and PT(jet#3) < 15
GeV/c.
 “Leading ChgJet” events correspond to the leading
charged particle jet (R = 0.7) in the region |h| < 1 with
no other conditions.
 “Z-Boson” events are Drell-Yan events
with 70 < M(lepton-pair) < 110 GeV
with no other conditions.
University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Jet #1 Direction
D
“Leading Jet”
“Toward”
“Transverse”
“Transverse”
subset
“Away”
Jet #1 Direction
D
“Inc2J Back-to-Back”
“Toward”
subset
“Transverse”
“Transverse”
“Away”
“Exc2J Back-to-Back”
Jet #2 Direction
ChgJet #1 Direction
D
“Charged Jet”
“Toward”
“Transverse”
“Transverse”
“Away”
Z-Boson Direction
D
“Toward”
Z-Boson
“Transverse”
“Transverse”
“Away”
Page 36
“Leading Jet” Observables at the
Particle and Detector Level
“Leading Jet”
Jet #1 Direction
Observable
Particle Level
Detector Level
dNchg/dhd
Number of charged particles
per unit h-
(pT > 0.5 GeV/c, |h| < 1)
Number of “good” charged tracks
per unit h-
(pT > 0.5 GeV/c, |h| < 1)
dPTsum/dhd
Scalar pT sum of charged particles
per unit h-
(pT > 0.5 GeV/c, |h| < 1)
Scalar pT sum of “good” charged tracks per
unit h-
(pT > 0.5 GeV/c, |h| < 1)
<pT>
Average pT of charged particles
(pT > 0.5 GeV/c, |h| < 1)
Average pT of “good” charged tracks
(pT > 0.5 GeV/c, |h| < 1)
PTmax
Maximum pT charged particle
(pT > 0.5 GeV/c, |h| < 1)
Require Nchg ≥ 1
Maximum pT “good” charged tracks
(pT > 0.5 GeV/c, |h| < 1)
Require Nchg ≥ 1
dETsum/dhd
Scalar ET sum of all particles
per unit h-
(all pT, |h| < 1)
Scalar ET sum of all calorimeter towers
per unit h-
(ET > 0.1 GeV, |h| < 1)
PTsum/ETsum
Scalar pT sum of charged particles
(pT > 0.5 GeV/c, |h| < 1)
divided by the scalar ET sum of
all particles (all pT, |h| < 1)
Scalar pT sum of “good” charged tracks
(pT > 0.5 GeV/c, |h| < 1)
divided by the scalar ET sum of
calorimeter towers (ET > 0.1 GeV, |h| < 1)
D
“Toward”
“Transverse”
“Transverse”
“Away”
Jet #1 Direction
D
“Toward”
“Transverse”
“Transverse”
“Away”
Jet #2 Direction
“Back-to-Back”
University of Toronto
March 18, 2008
Also include the leading jet mass (new)!
Rick Field – Florida/CDF/CMS
Page 37
Overall Totals (|h| < 1)
ETsum = 775 GeV!
“Leading Jet”
Overall Totals versus PT(jet#1)
ETsum = 330 GeV
1000
CDF Run 2 Preliminary
ETsum (GeV)
data corrected
pyA generator level
Jet #1 Direction
D
PTsum (GeV/c)
Average
100
“Overall”
Nchg
"Leading Jet"
MidPoint R=0.7 |h(jet#1)|<2
10
PTsum = 190 GeV/c
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
Stable Particles (|h|<1.0, all PT)
1
0
50
Nchg = 30
100
150
200
250
300
350
400
PT(jet#1) (GeV/c)
 Data at 1.96 TeV on the overall number of charged particles (pT > 0.5 GeV/c, |h| < 1) and the overall
scalar pT sum of charged particles (pT > 0.5 GeV/c, |h| < 1) and the overall scalar ET sum of all
particles (|h| < 1) for “leading jet” events as a function of the leading jet pT. The data are corrected to
the particle level (with errors that include both the statistical error and the systematic uncertainty) and
are compared with PYTHIA Tune A at the particle level (i.e. generator level)..
University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 38
Overall Totals (|h| < 1)
“Leading Jet”
Overall
Number
ofversus
Charged
Particles
Overall
Charged
PTsum
Overall
ETsum
PT(jet#1)
Jet #1 Direction
D
Average
PTsum
Average
ETsum
(GeV)
Average
Number
of(GeV/c)
Charged
Particles
400
80040
CDF
Run
CDF
Run
2Preliminary
Preliminary
CDF
Run
22 Preliminary
300
60030
PY Tune A
data
corrected
data
corrected
data
corrected
generator
level
theory
generator
level
theory
generator
level
theory
HW
PY Tune A
PY Tune A
200
40020
“Overall”
20010
100
"Leading Jet"
"Leading Jet"
MidPoint R=0.7 |h(jet#1)|<2
MidPoint R=0.7 |h(jet#1)|<2
HW
HW
00 0
00 0
50
50
50
100
100
150
150
ChargedStable
Particles
(|h|<1.0,
PT>0.5
GeV/c)
Particles
(|h|<1.0,
all
PT)
Charged
Particles
(|h|<1.0,
PT>0.5
GeV/c)
200
200
250
250
300
300
350
350
400
400
PT(jet#1)
PT(jet#1) (GeV/c)
(GeV/c)
Data
at
1.96
TeV
on
the
overall
number
ofsum
charged
(p(|h|
0.5
|h| < 1)
“leading
events
 Data
ofofcharged
particles
>
GeV/c,
|h|for
<events
1)
for as
“leading
jet”
T ><(p
Data at
at 1.96
1.96 TeV
TeV on
on the
the overall
overall scalar
scalar pET
allparticles
particles
1)T GeV/c,
for0.5
“leading
jet”
ajet”
function
T sum
as
function
ofjetthe
jet are
pT. The
are
corrected
tolevel
the particle
levelthat
(with
errors
that
include
both
events
as a function
thedata
leading
jet pdata
data
are
corrected
to theerrors
particle
level
(withboth
errors
that
include
of athe
leading
pTleading
.of
The
corrected
the
particle
(with
include
the
statistical
T. Theto
both
the
error
and
the systematic
uncertainty)
and
are
compared
with
PYTHIA
AHERWIG
and MPI)
the
statistical
and the
systematic
uncertainty)
and are
compared
with
PYTHIA
TuneTune
A and
error
andstatistical
the error
systematic
uncertainty)
and
are
compared
with
PYTHIA
Tune
A and
HERWIG
(without
HERWIG
(without
at the
particle
level (i.e. level).
generator level).
(without
MPI)
at theMPI)
particle
level
(i.e. generator
at the particle
level
(i.e.
generator
level).
University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 39
CDF DiJet Event: M(jj) ≈ 1.4 TeV
ETjet1 = 666 GeV ETjet2 = 633 GeV
Esum = 1,299 GeV M(jj) = 1,364 GeV
M(jj)/Ecm ≈ 70%!!
University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 40
“Towards”, “Away”, “Transverse”
“Leading Jet”
Jet #1 Direction
D
“Toward”
“Transverse”
“Transverse”
“Away”
ETsum
Density
(GeV)
Charged
PTsum
Density
(GeV/c)
Average
Charged
Density
Charged
Particle
Density:
dN/dhd
Charged
PTsum
Density:
dPT/dhd
ETsum
Density:
dET/dhd
5
100.0
100.0
CDFCDF
RunRun
2 Preliminary
2 Preliminary
4
data corrected
data"Toward"
corrected
pyA generator level
pyA generator level
10.0
3
"Toward"
"Away"
"Away"
Factor of ~13
"Toward"
"Transverse"
Factor of ~16
"Away"
"Transverse" "Leading Jet"
Factor of MidPoint
~4.5 R=0.7 |h(jet#1)|<2
2
1.0
1.0
1
0 0.1
0.1
0 0
0
"Transverse"
CDF Run 2 Preliminary
data corrected
pyA generator level
50 50
50
100100
100
150
150
150
"Leading Jet"
"Leading Jet"
MidPoint R=0.7 |h(jet#1)|<2
MidPoint R=0.7 |h(jet#1)|<2
ChargedStable
Particles
(|h|<1.0,
PT>0.5
GeV/c)
Charged
Particles
(|h|<1.0,
PT>0.5
GeV/c)
Particles
(|h|<1.0,
all
PT)
200
200
200
250
250
250
300
300
300
350
350
350
400
400
400
PT(jet#1)
PT(jet#1)(GeV/c)
(GeV/c)
PT(jet#1)
(GeV/c)
 Data
Data at
at 1.96
1.96 TeV
TeV on
on the
the charged
density ofparticle
charged
particles,
dN/dhd,
p > 0.5 GeV/c
and |h| < 1 for

pT sum
density, with
dPT/dhd,
and“leading
|h|
T > 0.5 GeV/c

Data at
1.96 TeV
on the
particle scalar
ETscalar
sum density,
dET/dhd,
forT|h| < with
1 for p“leading
jet” events
as<a1
jet” events as a function of the leading jet p for the “toward”, “away”, and “transverse” regions. The
for “leading
jet”
eventsjet
as pa function
of the Tleading
jet pand
the “toward”,
“away”,The
anddata
“transverse”
T for“transverse”
function
of the
leading
“toward”,
“away”,
regions.
are corrected
T for the
data
are
corrected
to
the
particle
level
(with
errors
that
include
both
the
statistical
error
and
the systematic
regions.
The
data
are
corrected
to
the
particle
level
(with
errors
that
include
both
the
statistical
errorand
andare
to the particle level (with errors that include both the statistical error and the systematic uncertainty)
uncertainty)
and
are
compared
with
PYTHIA
Tune
A
at
the
particle
level
(i.e.
generator
level).
the systematic
and A
are
with
PYTHIA
Tune Alevel).
at the particle level (i.e. generator
compared
withuncertainty)
PYTHIA Tune
at compared
the particle
level
(i.e. generator
level).
University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 41
The “Toward” Region
“Leading Jet”
"Toward"
Charged
Particle
Density:
dN/dhd
"Toward"
ETsum
Density:
dET/dhd
"Toward"
Charged
PTsum
Density:
dPT/dhd
Jet #1 Direction
D
“Toward”
“Transverse”
“Transverse”
“Away”
"Toward"
ETsum
Density
(GeV)
"Toward"
PTsum
Density
(GeV/c)
"Toward"
Charged
Density
4
100
50
CDFRun
Run22 2Preliminary
Preliminary
CDF
Run
Preliminary
80
40
3
HW
data
corrected
data
corrected
data
corrected
generator
level
theory
generator
level
theory
generator
level
theory
30
60
2
PY Tune A
PY Tune A
PY Tune A
20
40
1
10
20
00
0
00
0
HW
HW
50
50
50
100
100
100
150
150
150
"Leading Jet"
MidPoint R=0.7 |h(jet#1)|<2
"Leading Jet"
"Leading
Jet"
MidPoint
R=0.7 |h(jet#1)|<2
MidPoint
R=0.7 |h(jet#1)|<2
Charged Particles
(|h|<1.0,
PT>0.5 GeV/c)
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
Stable Particles (|h|<1.0, all PT)
200
200
200
250
250
250
300
300
300
350
350
350
400
400
400
PT(jet#1)
(GeV/c)
PT(jet#1)
PT(jet#1) (GeV/c)
(GeV/c)

at 1.96
TeV on
the density
of charged
particles,
dN/dhd,
withwith
pT >p0.5
and |h| <|h|1 <
for “leading
jet”
Data
pT sum
density,
dPT/dhd,
> GeV/c
0.5 GeV/c
“leading
 Data
Data at
at 1.96
1.96 TeV
TeV on
on the
the charged
scalar ETscalar
sum density,
dET/dhd,
with |h| <
1 forT“leading
jet” and
events as 1a for
function
of
events
as a as
function
of the
jet pjet
“toward”
region.
The The
datadata
are corrected
to the
level
jet”
events
ofleading
the leading
pTthe
fordata
the “toward”
region.
are
corrected
toparticle
thethat
particle
T for
the leading
jetapfunction
are corrected
to the particle
level
(with errors
include
T for the “toward” region. The
(with
errorserrors
that include
both the
statistical
error error
and the
systematic
uncertainty)
and are
with with
level
(with
include
both
the statistical
and
the
systematic
uncertainty)
andcompared
are compared
both the
statisticalthat
error
and the
systematic
uncertainty)
and
are
compared
with PYTHIA
Tune
A and HERWIG
PYTHIA
Tune A
A and
and HERWIG
HERWIG (without
MPI)
the
particle level
PYTHIA
Tune
(without
MPI) at
at level).
the particle
level (i.e.
(i.e. generator
generator level).
level).
(without MPI)
at the particle
level
(i.e. generator
University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 42
The “Away” Region
“Leading Jet”
"Away"
Charged
Particle
Density:
dN/dhd
"Away"
Charged
PTsum
Density:
dPT/dhd
dET/dhd
Density:
ETsum
"Away"
Jet #1 Direction
D
“Toward”
“Transverse”
“Transverse”
“Away”
"Away"
ETsum
Density
(GeV)
"Away"
PTsum
Density
(GeV/c)
"Away"
Charged
Density
5
50
100
CDFRun
Run22Preliminary
Preliminary
CDF
CDF Run 2 PreliminaryPY Tune A
480
40
datacorrected
corrected
data
corrected
data level
generatorlevel
theory
generator
theory
generator level theory
HW
PY Tune A
PY Tune A
360
30
240
20
1
10
20
00
0
00
0
HW
"Leading Jet"
"Leading Jet"
MidPoint
R=0.7 |h(jet#1)|<2
Jet"
"Leading
MidPoint R=0.7 |h(jet#1)|<2
MidPoint R=0.7 |h(jet#1)|<2
HW
50
50
50
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
Stable Particles (|h|<1.0, all PT)
100
100
100
150
150
150
200
200
200
250
250
250
300
300
300
350
350
400
400
PT(jet#1)
(GeV/c)
PT(jet#1)
(GeV/c)
PT(jet#1) (GeV/c)

charged
particles,
dN/dhd,
p1Tfor
>p0.5
andand
|h| <|h|1 as
for
jet”
 Data
Data
at
1.96
TeV
on
the
charged
scalar
pT sum
density,
dPT/dhd,
with
> GeV/c
0.5 GeV/c
<
1a“leading
for
“leading
Data at
at 1.96
1.96 TeV
TeV on
on the
the density
scalar Eof
dET/dhd,
withwith
|h| <
jet”
events
function
of
T“leading
T sum density,
events
as a as
function
of the
jet pjet
“away”
region.
The
data
are corrected
to the
level
T for
jet”
events
ofleading
the leading
pTthe
for
theare
“away”
region.
The
data
are
corrected
toparticle
thethat
particle
the leading
jetapfunction
data
corrected
to the
particle
level
(with
errors
include
T for the “away” region. The
(with
errors
that include
boththe
the
statistical
error error
and the
systematic
uncertainty)
and are
with
level
(with
errors
that
include
both
the statistical
and
the
systematic
uncertainty)
andcompared
are compared
with
both the
statistical
error
and
systematic
uncertainty)
and
are
compared
with PYTHIA
Tune
A and
HERWIG
PYTHIA
Tune
HERWIG
(without
MPI)
the
PYTHIA
Tune A
A
and
HERWIG
(without
MPI) at
at level).
the particle
particle level
level (i.e.
(i.e. generator
generator level).
level).
(without MPI)
at and
the particle
level
(i.e. generator
University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 43
The “Transverse” Region
“Leading Jet”
Particle
Density:
dN/dhd
"Transverse"
Charged
PTsum
Density:
dPT/dhd
"Transverse"
Average
PTmax
dET/dhd
Density:
ETsum
"Transverse"
"Transverse"
Average
PT
Jet #1 Direction
D
“Toward”
“Transverse”
“Transverse”
“Away”
"Transverse" Charged Density
"Transverse"
Average
"Transverse"
ETsum
Density
(GeV)
"Transverse"
PTsum
Density
(GeV/c)
"Transverse"
Average
PTPTmax
(GeV/c)
(GeV/c)
1.2
2.04.0
5.0
CDF
Run
22Preliminary
Preliminary
Run
CDF
CDF
Run
2 Preliminary
CDF
Run
2 Preliminary
data corrected
4.0
0.9
1.53.0
1.5
3.0
0.6
1.02.0
2.0
1.0
0.3
0.51.0
1.0
0.0
0.0
0.50.0
0.0
000 0
data
corrected
corrected
data
data
corrected
data corrected
generator
level
theory
generator
level
theory
generator
level
theory
theory
level
generator
generator level theory
HW
HW
HW
HWHW
50
5050
50
100
100
100
100
PY Tune A
PY Tune A
PY Tune A PY Tune A
"Leading Jet"
PY Tune A MidPoint R=0.7 |h(jet#1)|<2
"Leading
Jet"
"LeadingJet"
Jet"
"Leading
MidPoint
R=0.7
|h(jet#1)|<2
Charged Particles
(|h|<1.0,
PT>0.5 GeV/c)
Jet"
"Leading
MidPointR=0.7
R=0.7|h(jet#1)|<2
|h(jet#1)|<2
MidPoint
MidPoint R=0.7 |h(jet#1)|<2
Charged
Particles
(|h|<1.0,
PT>0.5
GeV/c)
Excludes events
with no
"Transverse"
Charged
Particles
Charged
Particles
(|h|<1.0,
PT>0.5
GeV/c)
Charged
Particles
(|h|<1.0,
PT>0.5
GeV/c)
all PT)
(|h|<1.0,
Particles
Stable
150
150
150
150
200
200
200
200
250
250
250
250
300
300
300
300
350
350
350
400
400
400
PT(jet#1)
PT(jet#1)
(GeV/c)
PT(jet#1)(GeV/c)
(GeV/c)
(GeV/c)
PT(jet#1)

Data
at 1.96
TeV on
the density
of charged
particles,
dN/dhd,
withwith
pT >p0.5
andand
|h| <|h|1 <
for “leading

Data
pTaverage
sum
density,
dPT/dhd,
> GeV/c
0.5
GeV/c
for
“leading

Data
at
1.96
TeV
on
the
scalar
ETscalar
sum density,
dET/dhd,
with
|h|
<GeV/c
1GeV/c
forTand
“leading
jet”
events
as1ajet”
function
ofas
Data at
at 1.96
1.96 TeV
TeV on
on the
the charged
charged
particle
pTp
, with
p
>
0.5
|h|
<
1
for
“leading
events
 jet”
Data
at
1.96
TeV
on
the
charged
particle
maximum
,
with
p
>
0.5
and
|h|
<
1
for
“leading
jet”
events
T
T
T
events as a function of the leading jet p for the “transverse”
region. The data are corrected to the
jet”
events of
as
apfunction
jet pTT for
thedata
“transverse”
region.
The
data are
corrected
tolevel
thethat
the
leading
jetthe
forleading
theof
“transverse”
region.
The
are corrected
to are
the
particle
(with
errors
a function
leading
jetthe
pTleading
for
thethe
“transverse”
region.
The
data
are
corrected
tolevel
the
particle
(with
T
as
a
function
of
the
jet
p
for
“transverse”
region.
The
data
corrected
to
the
particle
level
(with
T
particle
level
(with
errors
that
include
both
the
statistical
error
and
the
systematic
uncertainty)
and
are
particle
level
(with
errors
that
include
both
the
statistical
error
and
the
systematic
uncertainty)
and
are
compared
include
both
the
statistical
error
and
the
systematic
uncertainty)
and
are
compared
with
PYTHIA
Tune
A
and
errors
that
include
both
the
statistical
error
and
the
systematic
uncertainty)
and
are
compared
with
PYTHIA
errors thatwith
include
both the
statistical
error and the
systematic
uncertainty)
andlevel
are compared
with level).
PYTHIA
compared
PYTHIA
Tune
A and HERWIG
(without
at the
particle
(i.e. level).
generator
with
PYTHIA
Tune
A and
HERWIG
(without
MPI)
at
theMPI)
particle
level
(i.e.
generator
HERWIG
(without
MPI)
at
the
particle
level
(i.e.
generator
level).
Tune
A
and
HERWIG
(without
MPI)
at
the
particle
level
(i.e.
generator
level).
Tune A and HERWIG (without MPI) at the particle level (i.e. generator level).
University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 44
The “Transverse” Region
“Leading Jet”
Jet #1 Direction
D
“Toward”
“Transverse”
“Transverse”
“Away”
"Transverse"
Data Charged
- TheoryDensity
0.4
1.2
"Transverse"
Density:
dN/dhd
0.1 density
corresponds
to
"Transverse" Charged
Charged Particle
Particle
Density:
dN/dhd
0.42 charged particles in the
“transverse”
CDF Run 2 Preliminary
CDF region!
Run 2 Preliminary
"Leading Jet"
0.9
0.2
data corrected
MidPoint R=0.7 |h(jet#1)|<2
generator level theory
data corrected
generator level theory
HW
0.6
PY Tune A
0.0
"Leading Jet"
MidPoint R=0.7 |h(jet#1)|<2
HW
PY Tune A
0.3
Charged
Particles
(|h|<1.0,
PT>0.5
GeV/c)
Charged
Particles
(|h|<1.0,
PT>0.5
GeV/c)
-0.2
0.0
00
50
50
100
100
150
150
200
200
250
250
300
300
350
350
400
400
PT(jet#1) (GeV/c)
(GeV/c)
PT(jet#1)

1.96
TeV- on
the density
charged
particles,particles,
dN/dhd,dN/dhd,
with pT >with
0.5 GeV/c
|h| <and
1 for
 Data
Showsatthe
Data
Theory
for theofdensity
of charged
pT > 0.5and
GeV/c
|h|“leading
< 1 for
jet”
events
as events
a function
the leading
pT forjet
thep“transverse”
region. The data are corrected to the
“leading
jet”
as a of
function
of thejet
leading
T for the “transverse” region for PYTHIA Tune A and
particle
level
(with errors
HERWIG
(without
MPI).that include both the statistical error and the systematic uncertainty) and are
compared with PYTHIA Tune A and HERWIG (without MPI) at the particle level (i.e. generator level).
University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 45
The “Transverse” Region
Jet #1 Direction
D
“Toward”
“Transverse”
“Transverse”
“Away”
Data - Theory
(GeV/c)(GeV/c)
"Transverse"
PTsum Density
“Leading Jet”
2.0
0.6
0.1 density
corresponds
to
"Transverse"
"Transverse" Charged
Charged PTsum
PTsum
Density:
Density:
dPT/dhd
dPT/dhd
420 MeV/c in the
“transverse”
region!
CDF Run 2 Preliminary
CDF Run 2 Preliminary
"Leading Jet"
data corrected
MidPoint R=0.7 |h(jet#1)|<2
generator level theory
data corrected
generator level theory
1.5
0.4
HW
1.0
0.2
PY Tune A
"Leading Jet"
MidPoint R=0.7 |h(jet#1)|<2
0.5
0.0
HW
PY Tune A
Charged
ChargedParticles
Particles(|h|<1.0,
(|h|<1.0,PT>0.5
PT>0.5GeV/c)
GeV/c)
-0.2
0.0
00
50
50
100
150
200
250
300
350
350
400
400
PT(jet#1) (GeV/c)

1.96
TeV- on
the charged
scalar pTscalar
sum density,
with pT >with
0.5 GeV/c
|h| <and
1 for
 Data
Showsatthe
Data
Theory
for the charged
pT sum dPT/dhd,
density, dPT/dhd,
pT > 0.5and
GeV/c
|h| < 1 for
“leading
The
data areTune
corrected
“leading jet”
jet” events
events as
as aa function
function of
of the
the leading
leading jet
jet p
pTT for
for the
the “transverse”
“transverse” region.
region for
PYTHIA
A andto
the
particle(without
level (with
errors that include both the statistical error and the systematic uncertainty) and are
HERWIG
MPI).
compared with PYTHIA Tune A and HERWIG (without MPI) at the particle level (i.e. generator level).
University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 46
The “Transverse” Region
“Leading Jet”
Jet #1 Direction
D
“Toward”
“Transverse”
“Transverse”
“Away”
Data - Theory
(GeV) (GeV)
"Transverse"
ETsum Density
5.0
1.6
0.4Density:
density corresponds
"Transverse" ETsum
dET/dhdto
1.67 GeV in the
CDF CDF
Run Run
2 Preliminary
2 Preliminary “transverse”
"Leading
Jet"
region!
data corrected
data corrected
generator
level theory
generator
level theory
4.0
1.2
MidPoint R=0.7 |h(jet#1)|<2
Stable Particles (|h|<1.0, all PT)
HW
3.0
0.8
PY Tune A
2.0
0.4
PY Tune A
1.0
0.0
"Leading Jet"
MidPoint R=0.7 |h(jet#1)|<2
HW
Stable Particles (|h|<1.0, all PT)
0.0
-0.4
00
50
50
100
100
150
150
200
250
300
350
400
PT(jet#1) (GeV/c)

1.96
TeV- on
the scalar
ETscalar
sum density,
with |h| <with
1 for
jet” events
a function
 Data
Showsatthe
Data
Theory
for the
ET sum dET/dhd,
density, dET/dhd,
|h|“leading
< 1 for “leading
jet”asevents
as a
of
the leading
pT forjet
thep“transverse”
region. The data are corrected to the particle level (with errors that
function
of thejet
leading
T for the “transverse” region for PYTHIA Tune A and HERWIG (without MPI).
include both the statistical error and the systematic uncertainty) and are compared with PYTHIA Tune A and
HERWIG (without MPI) at the particle level (i.e. generator level).
University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 47
“transMAX” & “transMIN”
Jet #1 Direction
Jet #1 Direction
D
Area = 4/6
“transMIN” very sensitive to
the “beam-beam remnants”!
“Toward-Side” Jet
D
“Toward”
“TransMAX”
“Toward”
“TransMIN”
“TransMAX”
“Away”
“TransMIN”
Jet #3
“Away”
“Away-Side” Jet
 Define the MAX and MIN “transverse” regions (“transMAX” and “transMIN”) on an
event-by-event basis with MAX (MIN) having the largest (smallest) density. Each of the
two “transverse” regions have an area in h- space of 4/6.
 The “transMIN” region is very sensitive to the “beam-beam remnant” and multiple
parton interaction components of the “underlying event”.
 The difference, “transDIF” (“transMAX” minus “transMIN”), is very sensitive to the
“hard scattering” component of the “underlying event” (i.e. hard initial and final-state
radiation).
 The overall “transverse” density is the average of the “transMAX” and “transMIN”
densities.
University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 48
The “TransMAX/MIN” Regions
“Leading Jet”
"TransMAX"
Charged
Particle
Density:
dN/dhd
"TransMIN"
Particle
Density:
dN/dhd
"TransMAX/MIN"
Charged
Particle
Density:
dN/dhd
"TransDIF" Charged
Particle
Density:
dN/dhd
Jet #1 Direction
D
“Toward”
“TransMAX”
“TransMIN”
“Away”
"Transverse"
Charged
Density
TransMAX
- TransMIN
Density
"TransMIN"
Charged
"TransMAX"
ChargedDensity
Density
2.0
0.8
2.0
1.2
CDF Run
2 Preliminary
CDF
Run
Preliminary
CDF
222Preliminary
CDFRun
Run
Preliminary
data corrected
"Leading Jet"
MidPoint R=0.7 |h(jet#1)|<2
datacorrected
corrected
data
data corrected
generator
level
generatorlevel
level theory
theory
generator
generator leveltheory
theory
1.5
0.6
1.5
0.9
"transMAX"
HW
1.0
0.4
0.6
1.0
PY Tune A
PY Tune A
PY Tune A
HW
HW
HW
0.5
0.2
0.3
0.5
PY Tune A
0.0
0.0
0.0
0.0
0
0
00
50
50
50
50
100
100
100
100
150
150
150
150
"Leading Jet"
"Leading
Jet"
MidPoint
R=0.7
|h(jet#1)|<2
"Leading
Jet"
"transMIN"
MidPoint
R=0.7
|h(jet#1)|<2
MidPoint R=0.7 |h(jet#1)|<2
Charged Particles
Particles (|h|<1.0,
(|h|<1.0, PT>0.5
Charged
PT>0.5 GeV/c)
GeV/c)
Charged Particles (|h|<1.0, PT>0.5
GeV/c)
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
200
200
200
200
250
250
250
250
300
300
300
300
350
350
350
350
400
400
400
400
PT(jet#1) (GeV/c)
(GeV/c)
PT(jet#1)
PT(jet#1) (GeV/c)
(GeV/c)
PT(jet#1)

Data
at
1.96
TeV
on
the
density
of
charged
particles,
dN/dhd,
with
0.5
GeV/c
and
|h|
for
“leading
 Data
Data at
at 1.96
1.96 TeV
TeV on
on the
the density
density of
of charged
charged particles,
particles, dN/dhd,
dN/dhd, with
with pp
pTTT>>
> 0.5
0.5 GeV/c
GeV/c and
and |h|
|h| <<
< 111 for
for “leading
“leadingjet”
jet”

jet”
events
as
a function
ofleading
the leading
pTthe
for“transMIN”
the “transMAX”
region.
The are
datacorrected
are corrected
the
events
as aa function
function
of the
the
jet ppTjet
for
region.
The data
toare
theto
particle
events
as
of
leading jet
“transDIF”
= “transMAX”-”transMIN.
The data
corrected
to
T for
particle
level
(with
errors
thatboth
include
both
the statistical
error
and the systematic
uncertainty)
and are with
level
(with
errors
that
include
the
statistical
error
and
the
systematic
uncertainty)
and
are
compared
the particle level (with errors that include both the statistical error and the systematic uncertainty) and are
compared
with PYTHIA
Tune A and HERWIG
(without
MPI) at the
particle
level (i.e. generator level).
PYTHIA Tune
and HERWIG
MPI) at
the particle
generator
compared
with A
PYTHIA
Tune A (without
and HERWIG
(without
MPI)level
at the(i.e.
particle
levellevel).
(i.e. generator level).
University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 49
The “TransMAX/MIN” Regions
“Leading Jet”
"TransMAX"
ChargedCharged
PTsumDensity:
Density:Density
dPT/dhd
"TransMIN"
Charged
PTsum
dPT/dhd
"TransDIF"
Charged
PTsum
Density:
dPT/dhd
"TransMAX/MIN"
PTsum
Jet #1 Direction
D
“Toward”
“TransMAX”
“TransMIN”
“Away”
"Transverse"
Density
(GeV/c)
"TransMIN"
PTsum
Density
(GeV/c)
TransMAXPTsum
- TransMIN
Density
"TransMAX"
PTsum
Density
(GeV/c)
(GeV/c)
3.03.0
0.8
3.0
CDF
Run
Preliminary
CDF
Run
2 Preliminary
CDF
Run
Preliminary
CDF
Run
222Preliminary
0.6
2.02.0
2.0
data
corrected
data
corrected
data
corrected
data
corrected
generator
level
theory
generator
theory
generator
level
theory
generator levellevel
theory
"transMAX"
HW
PY Tune A
PY Tune A
PY Tune A
0.4
1.0
1.0 1.0
0.2
0.0
0.0
0.0 0.0
00
0 0
HWHW
PY Tune A
HW
50
50
50 50
100
100
100
100
"Leading Jet"
"Leading Jet"
Jet"
MidPoint"Leading
R=0.7 |h(jet#1)|<2
MidPoint
R=0.7
|h(jet#1)|<2
MidPoint
R=0.7
"Leading
Jet"|h(jet#1)|<2
MidPoint R=0.7 |h(jet#1)|<2
"transMIN"
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
150
150
150
150
200
200
200
200
250
250
250
250
300
300
300
300
350
350
350
350
400
400
400
400
PT(jet#1)
(GeV/c)
PT(jet#1)
PT(jet#1)(GeV/c)
(GeV/c)
PT(jet#1)
(GeV/c)

Data at
1.96 TeV
on the
charged scalar
p sum density,
dPT/dhd, with
p > 0.5
GeV/c and
|h| <
1 for “leading

 Data
Data at
at 1.96
1.96 TeV
TeV on
on the
the charged
charged scalar
scalar ppTTT sum
sum density,
density, dPT/dhd,
dPT/dhd, with
with ppTTT >
> 0.5
0.5 GeV/c
GeV/c and
and |h|
|h| <
< 11 for
for “leading
“leading jet” events as a function of the leading jet p for the “transMAX” region. The data are corrected to
T
jet”
“transMIN”
region. The data are corrected
to the
jet” events
events as
as aa function
function of
of the
the leading
leading jet
jet ppTT for
for the
“transDIF”
= “transMAX”-”transMIN.
The data
are particle
the
particle
level
(with
errors
that
include
both
the
statistical
error
and
the
systematic
uncertainty)
and
arewith
level
(with to
errors
that include
statistical
error and
are compared
corrected
the particle
levelboth
(withthe
errors
that include
boththe
thesystematic
statisticaluncertainty)
error and theand
systematic
uncertainty)
compared
withAPYTHIA
Tune A and HERWIG
(without
MPI)level
at the
particle
levellevel).
(i.e. generator level).
PYTHIA
Tune
and
HERWIG
MPI)HERWIG
at
the particle
(i.e.
generator
and are compared
with
PYTHIA(without
Tune A and
(without
MPI)
at
the particle
level (i.e. generator
level).
University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 50
The “TransMAX/MIN” Regions
“Leading Jet”
Jet #1 Direction
D
“Toward”
“TransMAX”
“TransMIN”
“Away”
"TransMAX"
Density
(GeV)
"Transverse"
Density
(GeV)
TransMAX ETsum
-ETsum
TransMIN
(GeV)
"TransveMIN"
ETsum
Density
(GeV)
"TransMAX"
"TransMIN"
ETsum
Density:
dET/dhd
"TransMAX/MIN"
ETsum
Density:
dET/dhd
"TransDIF" ETsum
Density:
dET/dhd
6.0
3.0
6.0
5.0
CDF
"Leading Jet"
CDF Run
Run 22 Preliminary
Preliminary
CDF
Run
4.0
4.0
2.0
4.0
3.0
PY Tune A
2.0
2.0
1.0
2.0
HW
data corrected
generator level theory
HW
PY
PYTune
TuneAA
"Leading Jet"
MidPoint R=0.7 |h(jet#1)|<2
"Leading Jet"
"transMIN"
Jet"
MidPoint "Leading
R=0.7 |h(jet#1)|<2
MidPoint
R=0.7 |h(jet#1)|<2
PY Tune
A
Stable Particles (|h|<1.0, all PT)
Stable
Particles
(|h|<1.0,
all PT)
Stable
Particles
(|h|<1.0,
all PT)
HW
1.0
HW
0.0
0.0
0.0
0.0
CDF Run 2 Preliminary
data
MidPoint R=0.7 |h(jet#1)|<2
datacorrected
corrected
data
corrected
"transMAX"
generator
theory
generatorlevel
level
theory
generator
level
theory
Stable
Particles (|h|<1.0, all PT)
000
50
50
50
100
100
100
150
150
150
200
200
200
250
250
250
250
300
300
300
300
350
350
350
350
400
400
400
400
PT(jet#1)
PT(jet#1) (GeV/c)
(GeV/c)
PT(jet#1)
(GeV/c)

 Data
Data at
at 1.96
1.96 TeV
TeV on
on the
the scalar
scalar E
ETTT sum
sum density,
density, dET/dhd,
dET/dhd, with
with |h|
|h| <
< 11 for
for “leading
“leading jet”
jet” events
events as
as aa function
function of
of
of
leading
“transMAX”
region.
corrected
to the
particle
(with
errors
the
leading
jet
ppT pfor
thethe
“transMIN”
region.
TheThe
datadata
are are
corrected
to the
particle
levellevel
(with
errors
thatthat
T for
thethe
leading
jetjet
T for “transDIF” = “transMAX”-”transMIN. The data are corrected to the particle level (with
include
both
the statistical
and the
systematic
and are compared
PYTHIA
A and
errors that
include
both theerror
statistical
error
and the uncertainty)
systematic uncertainty)
and are with
compared
withTune
PYTHIA
HERWIG
MPI)
at the MPI)
particle
levelparticle
(i.e. generator
Tune A and(without
HERWIG
(without
at the
level (i.e.level).
generator level).
University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 51
“TransMIN” Nchg Density
"TransMIN" Charged Particle Density: dN/dhd
0.6
CDF Run 2 Preliminary
D
“Toward”
“TransMAX”
“TransMIN”
“Away”
"TransMIN" Charged Density
Jet #1 Direction
"Leading Jet"
MidPoint R=0.7 |h(jet#1)|<2
data corrected
generator level theory
HW
0.4
0.2
PY Tune A
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
0.0
0
50
100
These are the key plots!
Tune A does not produce
enough activity in the
“transMIN” region!
150
200
250
300
350
400
PT(jet#1) (GeV/c)
 Data at 1.96 TeV on the density of charged particles, dN/dhd, with pT > 0.5 GeV/c and |h| < 1 for “leading jet”
events as a function of the leading jet pT for the “transMIN” region. The data are corrected to the particle
level (with errors that include both the statistical error and the systematic uncertainty) and are compared with
PYTHIA Tune A and HERWIG (without MPI) at the particle level (i.e. generator level).
University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 52
“TransMIN” PTsum Density
"TransMIN" Charged PTsum Density: dPT/dhd
Jet #1 Direction
D
“Toward”
“TransMAX”
“TransMIN”
“Away”
"TransMIN" PTsum Density (GeV/c)
0.6
CDF Run 2 Preliminary
"Leading Jet"
MidPoint R=0.7 |h(jet#1)|<2
data corrected
generator level theory
0.4
0.2
PY Tune A
HW
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
0.0
0
50
100
These are the key plots!
Tune A does not produce
enough activity in the
“transMIN” region!
150
200
250
300
350
400
PT(jet#1) (GeV/c)
 Data at 1.96 TeV on the charged scalar PTsum density, dPT/dhd, with pT > 0.5 GeV/c and |h| < 1 for “leading
jet” events as a function of the leading jet pT for the “transMIN” region. The data are corrected to the particle
level (with errors that include both the statistical error and the systematic uncertainty) and are compared with
PYTHIA Tune A and HERWIG (without MPI) at the particle level (i.e. generator level).
University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 53
“TransMIN” ETsum Density
"TransMIN" ETsum Density: dET/dhd
D
“Toward”
“TransMAX”
“TransMIN”
“Away”
"TransveMIN" ETsum Density (GeV)
3.0
Jet #1 Direction
"Leading Jet"
MidPoint R=0.7 |h(jet#1)|<2
CDF Run 2 Preliminary
data corrected
generator level theory
Stable Particles (|h|<1.0, all PT)
2.0
HW
1.0
PY Tune A
0.0
0
50
100
These are the key plots!
Tune A does not produce
enough activity in the
“transMIN” region!
150
200
250
300
350
400
PT(jet#1) (GeV/c)
 Data at 1.96 TeV on the scalar ETsum density, dET/dhd, with |h| < 1 for “leading jet” events as a function of
the leading jet pT for the “transMIN” region. The data are corrected to the particle level (with errors that
include both the statistical error and the systematic uncertainty) and are compared with PYTHIA Tune A and
HERWIG (without MPI) at the particle level (i.e. generator level).
University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 54
The Leading Jet Mass
“Leading Jet”
Leading Jet Invariant
Off by ~2Mass
GeV
12.0
70
“Toward”
“Transverse”
“Transverse”
“Away”
Data
Theory
(GeV)
Jet-Mass
(GeV)
Jet #1 Direction
D
CDF
CDFRun
Run22Preliminary
Preliminary
60
"Leading Jet"
MidPoint R=0.7 |h(jet#1)|<2
data
datacorrected
corrected
generator
generatorlevel
leveltheory
theory
8.0
50
HW
PY Tune A
40
4.0
30
PY Tune A
20
0.0
10
-4.0
0
00
"Leading Jet"
MidPoint R=0.7 |h(jet#1)|<2
HW
5050
100
100
150
150
200
200
250
250
300
300
350
400
PT(jet#1
uncorrected)
PT(jet#1)
(GeV/c)(GeV/c)

atthe
1.96
TeV- on
the leading
invariant
mass for mass
“leading
jet” events
asevents
a function
of the leading
pT
 Data
Shows
Data
Theory
for thejet
leading
jet invariant
for “leading
jet”
as a function
of thejet
leading
for
“transverse” region. The data are corrected to the particle level (with errors that include both the
jet pthe
T for the “transverse” region for PYTHIA Tune A and HERWIG (without MPI).
statistical error and the systematic uncertainty) and are compared with PYTHIA Tune A and HERWIG
(without MPI) at the particle level (i.e. generator level).
University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 55
Min-Bias at the LHC
 We have learned a lot about “Min-Bias” at the
Tevatron, but we do not know what to expect at
the LHC. This will depend on the Min-Bias Trigger!
 We are making good progress in understanding
and modeling the “underlying event”. However,
we do not yet have a perfect fit to all the features
of the CDF “underlying event” data!
“Minumum Bias” Collisions
Proton
AntiProton
Charged Particle Density: dN/dh
10
Charged Particle Density
 “Min-Bias” is not well defined. What you
see depends on what you trigger on! Every
trigger produces some biases.
pyA
pyDW
pyDWT
ATLAS
Generator Level
14 TeV
8
6
4
2
Charged Particles (all pT)
0
-10
-8
-6
-4
-2
0
2
4
6
8
10
PseudoRapidity h
Outgoing Parton
PT(hard)
 Need to measure “Min-Bias” and the “underlying
event” at the LHC as soon as possible and tune the
Monte-Carlo modles and compare with CDF!
Initial-State Radiation
Proton
AntiProton
Underlying Event
Outgoing Parton
University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Underlying Event
Final-State
Radiation
Page 56
UE&MB@CMS
UE&MB@CMS
“Minimum-Bias” Collisions
Proton
Proton
High PT Jet Production
Outgoing Parton
PT(hard)
Initial-State
Radiation
Proton
Proton
Underlying Event
Outgoing Parton
 Min-Bias Studies: Charged particle distributions and
correlations. Construct “charged particle jets” and look
at “mini-jet” structure and the onset of the “underlying
event”. (requires only charged tracks)
Underlying Event
Final-State
Radiation
Drell-Yan Production
Lepton
Proton
Proton
Underlying Event
Underlying Event
Study charged
particles
 “Underlying
Event”
Studies: The “transverse region” in
and“leading
muons using
the
CMS
detector charged particle jet
Jet” and “back-to-back”
atproduction
the LHC (as
soon
possible)!
and
theas“central
region” in Drell-Yan
production. (requires charged tracks and muons for DrellYan)
Initial-State
Radiation
Anti-Lepton
Drell-Yan Production
Lepton-Pair
PT(pair)
Proton
Proton
Underlying Event
Underlying Event
Initial-State
Radiation
Final-State
Radiation
 Drell-Yan Studies: Transverse momentum distribution of
the lepton-pair versus the mass of the lepton-pair,
<pT(pair)>, <pT2(pair)>, ds/dpT(pair) (only requires
muons). Event structure for large lepton-pair pT (i.e. mm
+jets, requires muons).
Outgoing Parton
University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 57
Summary
 It is important to produce a lot of plots (corrected to the particle level) so that the theorists
can tune and improve the QCD Monte-Carlo models. If they improve the “transverse”
region they might miss-up the “toward” region etc.. We need to show the whole story!
 We are making good progress in understanding and
modeling the “underlying event”. However, we do not
analysis approval
in December 2007!
Proton
yet have a perfect fit to allCMS
the features
of the CDF
“underlying event” data!
Outgoing Parton
PT(hard)
Initial-State Radiation
AntiProton
Underlying Event
 There are over 128 plots to get “blessed” and then
published. So far we have only looked at average
quantities. We plan to also produce distributions and
flow plots
 I will construct a “CDF-QCD Data for Theory”
WEBsite with the “blessed” plots together with
tables of the data points and errors so that people
can have access to the results .
Final-State
Radiation
CDF-QCD Data for Theory
 Need to measure “Min-Bias” and the “underlying
event” at the LHC as soon as possible and tune the
Monte-Carlo modles and compare with CDF!
University of Toronto
March 18, 2008
Outgoing Parton
Underlying Event
Rick Field – Florida/CDF/CMS
UE&MB@CMS
Page 58