The “Underlying Event”
in Run 2 at CDF
Outline of Talk
 Study the “underlying event” as defined by
Charged Particle Jet
the leading “charged particle jet” and
compare with the Run I analysis.
 Study the “underlying event” as defined
Calorimeter Jet
by the leading “calorimeter jet” and
compare with the “charged particle jet”
analysis.
 Study the relationship between “charged
particle jets” and “calorimeter jets”.
Fermilab MC Workshop
April 30, 2003
Rick Field - Florida/CDF
JetClu R = 0.7
Page 1
The “Underlying Event”
in Run 2 at CDF
Look at charged particle
correlations relative to the
leading “charged particle jet”.
Outline of Talk
 Study the “underlying event” as defined by
the leading “charged particle jet” and
compare with the Run I analysis.
 Study the “underlying event” as defined
by the leading “calorimeter jet” and
compare with the “charged particle jet”
analysis.
Charged Particle Jet
Look at charged particle
correlations relative to the
leading “calorimeter jet”.
Calorimeter Jet
Look at correlations between
the leading “charged particle
jet” and “calorimeter jets”.
 Study the relationship between “charged
particle jets” and “calorimeter jets”.
Fermilab MC Workshop
April 30, 2003
Rick Field - Florida/CDF
JetClu R = 0.7
Page 2
The “Underlying Event”
in Run 2 at CDF
Look at charged particle
correlations relative to the
leading “charged particle jet”.
Outline of Talk
 Study the “underlying event” as defined by
Charged Particle Jet
Look at charged particle
correlations relative to the
leading “calorimeter jet”.
the leading “charged particle jet” and
compare with the Run I analysis.
Compare the data with
PYTHIA
A which
 Study the “underlying
event”Tune
as defined
Calorimeter Jet
was
tuned
to
fit
the
Run
1
Look at correlations between
by the leading “calorimeter jet” and
the
leading “charged particle
“underlying
event”.
compare with the “charged particle jet” jet” and “calorimeter jets”.
analysis.
 Study the relationship between “charged
particle jets” and “calorimeter jets”.
JetClu
Extrapolate to the
LHC!R = 0.7
Fermilab MC Workshop
April 30, 2003
Rick Field - Florida/CDF
Page 3
“Underlying Event”
as defined by “Charged particle Jets”
Look at the charged
particle density in the
“transverse” region!
Charged Particle  Correlations
PT > 0.5 GeV/c |h| < 1
Charged Jet #1
“Transverse” regionDirection
is
very sensitive to the
“underlying event”!
“jet”
(always)
Toward-side
“Toward-Side”
Jet

2p
Charged Jet #1
Direction

Away Region
Transverse
Region
“Toward”
“Toward”

“Transverse”
“Transverse”
“Transverse”
Leading
ChgJet
“Transverse”
Toward Region
“Away”
Transverse
Region
“Away”
“Away-Side” Jet
Away-side “jet”
(sometimes)
Away Region
Perpendicular to the plane of the
2-to-2 hard scattering
0
-1
h
+1
 Look at charged particle correlations in the azimuthal angle  relative to the leading


charged particle jet.
o
o
o
o
Define || < 60 as “Toward”, 60 < || < 120 as “Transverse”, and || > 120 as
“Away”.
o
All three regions have the same size in h- space, hx = 2x120 = 4p/3.
Fermilab MC Workshop
April 30, 2003
Rick Field - Florida/CDF
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
-4
-3
-2
-1
0
1
2
3
4
-4
-3
-2
-1
0
1
2
3
<dNchg
/dh> = 4.2
Shows
CDF “Min-Bias”

4
Pseudo-Rapidity h
Pseudo-Rapidity h

all PT
0.0
0
<dNchg/dhd>
= 0.67 particles per unit pseudo-rapidity
data on the number
of charged
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).
Convert to charged particle density, dNchg/dhd, by dividing by 2p.
hx = 1
There are about 0.67 charged particles per unit h- in “Min-Bias”
 = 1
collisions at 1.8 TeV (|h| < 1, all PT).
0.67
h = 1
Fermilab MC Workshop
April 30, 2003
Rick Field - Florida/CDF
Page 5
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
-4
-3
-2
-1
0
1
2
3
4
-4
-3
-2
-1
0
1
2
3
<dNchg
/dh> = 4.2
Shows
CDF “Min-Bias”


4
Pseudo-Rapidity h
Pseudo-Rapidity h

all PT
0.0
0
<dNchg/dhd>
= 0.67 particles per unit pseudo-rapidity
data on the number
of charged
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).
Convert to charged particle density, dNchg/dhd, by dividing by 2p.
hx = 1
There are about 0.67 charged particles per unit h- in “Min-Bias”
 = 1
collisions at 1.8 TeV (|h| < 1, all PT).
0.67
0.25
There are about 0.25 charged particles per unit h- in “Min-Bias”
h = 1
collisions at 1.8 TeV (|h| < 1, PT > 0.5 GeV/c).
Fermilab MC Workshop
April 30, 2003
Rick Field - Florida/CDF
Page 6
Run 1 Charged Particle Density
“Transverse” PT Distribution
"Transverse" Charged Particle Density: dN/dhd
Charged Particle Jet #1
Direction

"Transverse" Charged Density
1.00
CDF Min-Bias
CDF Run 1
CDF JET20
data uncorrected
0.75
“Toward”
0.50
Factor of 2!
“Transverse”
0.25
“Transverse”
1.8 TeV |h|<1.0 PT>0.5 GeV/c
“Away”
0.00
0
5
10
15
20
25
30
35
40
45
50
PT(charged jet#1) (GeV/c)
“Min-Bias”
 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.
Fermilab MC Workshop
April 30, 2003
Rick Field - Florida/CDF
Page 7
Run 1 Charged Particle Density
“Transverse” PT Distribution
"Transverse" Charged Particle Density: dN/dhd
Charged Particle Density
1.0E+00
CDF Min-Bias
CDF Run 1
CDF JET20
data uncorrected
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”
CDF Run 1
"Transverse"
PT(chgjet#1) > 5 GeV/c
0.75
50
Charged Density dN/dhddPT (1/GeV/c)
"Transverse" Charged Density
1.00
data uncorrected
1.0E-01
"Transverse"
PT(chgjet#1) > 30 GeV/c
1.0E-02
1.0E-03
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.
Fermilab MC Workshop
April 30, 2003
Rick Field - Florida/CDF
Page 8
PYTHIA: Multiple Parton
Interaction Parameters
Multiple Parton Interactions
Outgoing Parton
PT(hard)
Proton
AntiProton
Underlying Event
Underlying Event
ParameterOutgoingValue
Parton
MSTP(81)
MSTP(82)
Pythia uses multiple parton
interactions to enhance
the underlying event.
Description
0
Multiple-Parton Scattering off
1
Multiple-Parton Scattering on
1
Multiple interactions assuming the same probability, with
an abrupt cut-off PTmin=PARP(81)
3
Multiple interactions assuming a varying impact
parameter and a hadronic matter overlap consistent with
a single Gaussian matter distribution, with a smooth turnoff PT0=PARP(82)
4
Multiple interactions assuming a varying impact
parameter and a hadronic matter overlap consistent with
a double Gaussian matter distribution (governed by
PARP(83) and PARP(84)), with a smooth turn-off
PT0=PARP(82)
Fermilab MC Workshop
April 30, 2003
Rick Field - Florida/CDF
and now
HERWIG
!
Jimmy: MPI
J. M. Butterworth
J. R. Forshaw
M. H. Seymour
Multiple parton
interaction more
likely in a hard
(central) collision!
Hard Core
Page 9
PYTHIA: Multiple Parton
Interaction Parameters
Multiple Parton Interactions
Outgoing Parton
PT(hard)
Proton
AntiProton
Underlying Event
Underlying Event
ParameterOutgoingValue
Parton
MSTP(81)
0
1
MSTP(82)
1
Pythia uses multiple parton
interactions to enhance
the underlying event.
Note thatDescription
since the same cut-off
parameters govern both the primary
Multiple-Parton Scattering off
hard scattering and the secondary MPI
interaction,
changing
the amount of MPI
Multiple-Parton
Scattering
on
also changes the amount of hard primary
Multiple interactions assuming the same probability, with
in PYTHIA Min-Bias events!
an abruptscattering
cut-off P min=PARP(81)
and now
HERWIG
!
Jimmy: MPI
J. M. Butterworth
J. R. Forshaw
M. H. Seymour
Multiple parton
interaction more
likely in a hard
(central) collision!
T
Same parameter that
cuts-off the hard 2-to-2
parton cross sections!
3
Multiple interactions assuming a varying impact
parameter and a hadronic matter overlap consistent with
a single Gaussian matter distribution, with a smooth turnoff PT0=PARP(82)
4
Multiple interactions assuming a varying impact
parameter and a hadronic matter overlap consistent with
a double Gaussian matter distribution (governed by
PARP(83) and PARP(84)), with a smooth turn-off
PT0=PARP(82)
Fermilab MC Workshop
April 30, 2003
Rick Field - Florida/CDF
Hard Core
Page 10
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)
0.33
0.66
PARP(89)
1 TeV
PARP(90)
0.16
PARP(67)
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. The remaining fraction consists of
quark-antiquark pairs.
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.
Fermilab MC Workshop
April 30, 2003
Rick Field - Florida/CDF
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
Page 11
Tuned PYTHIA 6.206
Double Gaussian
PYTHIA 6.206 CTEQ5L
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
PARP(86)
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)
Fermilab MC Workshop
April 30, 2003
1.00
"Transverse" Charged Density
Parameter
"Transverse" Charged Particle Density: dN/dhd
CDF Preliminary
PYTHIA 6.206 (Set A)
PARP(67)=4
data uncorrected
theory corrected
0.75
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
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
Page 12
Tuned PYTHIA 6.206
“Transverse” PT Distribution
"Transverse" Charged Particle Density: dN/dhd
"Transverse" Charged Density
1.00
CDF Preliminary
PYTHIA 6.206 (Set A)
PARP(67)=4
data uncorrected
theory corrected
0.75
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
5
10
15
20
25
30
35
40
45
50
PT(charged jet#1) (GeV/c)
Can we distinguish between
PARP(67)=1 and PARP(67)=4?
No way! Right!
 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 Monte-Carlo predictions of two tuned versions of PYTHIA 6.206 (PT(hard) > 0,
CTEQ5L, Set B (PARP(67)=1) and Set A (PARP(67)=4)).
Fermilab MC Workshop
April 30, 2003
Rick Field - Florida/CDF
Page 13
Tuned PYTHIA 6.206
“Transverse” PT Distribution
"Transverse" Charged Particle Density
"Transverse" Charged Particle Density: dN/dhd
1.0E+00
CDF Preliminary
PYTHIA 6.206 (Set A)
PARP(67)=4
data uncorrected
theory corrected
0.75
CDF Data
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
5
10
15
20
25
30
35
40
45
PT(charged jet#1) (GeV/c)
PT(charged jet#1) > 30 GeV/c
50
Charged Density dN/dhddPT (1/GeV/c)
"Transverse" Charged Density
1.00
data uncorrected
theory corrected
PT(chgjet#1) > 30 GeV/c
1.0E-01
PYTHIA 6.206 Set A
PARP(67)=4
1.0E-02
1.0E-03
1.0E-04
PT(chgjet#1) > 5 GeV/c
1.0E-05
PYTHIA 6.206 Set B
PARP(67)=1
1.8 TeV |h|<1 PT>0.5 GeV/c
PARP(67)=4.0 (old default) is favored
over PARP(67)=1.0 (new default)!
1.0E-06
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 Monte-Carlo predictions of two tuned versions of PYTHIA 6.206 (PT(hard) > 0,
CTEQ5L, Set B (PARP(67)=1) and Set A (PARP(67)=4)).
Fermilab MC Workshop
April 30, 2003
Rick Field - Florida/CDF
Page 14
Tuned PYTHIA 6.206
Run 1 Tune A
Describes the rise
from “Min-Bias” to
1.0E+00
“underlying event”!
"Transverse" Charged Particle Density: dN/dhd
1.00
PYTHIA 6.206 Set A
data uncorrected
theory corrected
0.75
0.50
0.25
1.8 TeV |h|<1.0 PT>0.5 GeV/c
0.00
0
5
10
15
20
25
30
35
PT(charged jet#1) (GeV/c)
40
45
50
Set A PT(charged jet#1) > 30 GeV/c
“Transverse” <dNchg/dhd> = 0.60
“Min-Bias”
PYTHIA 6.206 Set A
CDF Run 1
Charged Density dN/dhddPT (1/GeV/c)
"Transverse" Charged Density
CDF Run 1
Charged Particle Density
data uncorrected
theory corrected
"Transverse"
PT(chgjet#1) > 5 GeV/c
1.0E-01
"Transverse"
PT(chgjet#1) > 30 GeV/c
1.0E-02
1.0E-03
1.0E-04
CDF Min-Bias
CTEQ5L
1.8 TeV |h|<1 PT>0.5 GeV/c
1.0E-05
Set A Min-Bias
<dNchg/dhd> = 0.24
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” and “Min-Bias” densities with
the QCD Monte-Carlo predictions of a tuned version of PYTHIA 6.206 (PT(hard) > 0,
CTEQ5L, Set A). Describes “Min-Bias” collisions! Describes the “underlying event”!
Fermilab MC Workshop
April 30, 2003
Rick Field - Florida/CDF
Page 15
“Transverse”
Charged Particle Density
“Transverse” region as
defined by the leading
“charged particle jet”
“Toward”
“Transverse”
“Transverse”
“Away”
1.25
"Transverse" Charged Density
Charged Particle Jet #1
Direction

"Transverse" Charged Particle Density: dN/dhd
CDF Run 1 Min-Bias
CDF Run 1 Data
CDF Run 1 JET20
data uncorrected
1.00
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)
 Shows the data on the average “transverse” charge particle density (|h|<1, PT>0.5 GeV) as
a function of the transverse momentum of the leading charged particle jet from Run 1.
Fermilab MC Workshop
April 30, 2003
Rick Field - Florida/CDF
Page 16
“Transverse”
Charged Particle Density
“Transverse” region as
defined by the leading
“charged particle jet”
“Toward”
“Transverse”
“Transverse”
“Away”
1.25
1.25
1.25
"Transverse"Charged
ChargedDensity
Density
"Transverse"
"Transverse"
Charged
Density
Charged Particle Jet #1
Direction

"Transverse"
"Transverse" Charged
Charged Particle
Particle
Density:
dN/dhd
Particle Density:
Density: dN/dhd
dN/dhd
CDF Run 1 Min-Bias
CDF Run 1 Min-Bias
CDF
Run
1 JET20
CDF
Run
1 Published
CDF Run 1 JET20
CDF Run 2 Preliminary
CDF Run 2
CDFPreliminary
Run 1 Data
CDF
CDFdata
Preliminary
uncorrected
1.00
1.00
1.00
data
datauncorrected
uncorrected
0.75
0.75
0.75
0.50
0.50
0.25
0.25
1.8
TeV
|h|<1.0
PT>0.5
GeV
|h|<1.0
PT>0.5
|h|<1.0
PT>0.5
GeVGeV/c
0.00
0.00
00
10 5 20
10
30
4015 50
20
60
70 25 80
80
30
40 130
50
90
90 100
10035110
110 120
120
13045140
140 150
150
PT(charged
PT(charged jet#1)
jet#1) (GeV/c)
(GeV/c)
(GeV/c)
Excellent agreement
between Run 1 and 2!
 Shows the data on the average “transverse” charge particle density (|h|<1, PT>0.5 GeV) as
a function of the transverse momentum of the leading charged particle jet from Run 1.
 Compares the Run 2 data (Min-Bias, JET20, JET50, JET70, JET100) with Run 1.
The errors on the (uncorrected) Run 2 data include both statistical and correlated
systematic uncertainties.
Fermilab MC Workshop
April 30, 2003
Rick Field - Florida/CDF
Page 17
“Transverse”
Charged Particle Density
“Transverse” region as
defined by the leading
“charged particle jet”
“Toward”
“Transverse”
“Transverse”
“Away”
1.25
1.25
1.25
"Transverse"Charged
ChargedDensity
Density
Charged
Density
"Transverse"
"Transverse"
Charged Particle Jet #1
Direction

"Transverse"
"Transverse" Charged
Charged Particle
Particle
Density:
dN/dhd
Particle Density:
Density: dN/dhd
dN/dhd
CDF Run 1 Min-Bias
CDFRun
Run11Published
Min-Bias
CDF
CDF
Run
1 JET20
CDF
Run
1 Published
CDFRun
Run21Preliminary
JET20
CDF
CDF Run 2 Preliminary
PYTHIA
Tune
CDF
RunA2
CDFPreliminary
Run 1 Data
CDF
CDF
Preliminary
CDFdata
Preliminary
uncorrected
1.00
1.00
1.00
data
uncorrected
data
uncorrected
data
uncorrected
theory corrected
0.75
0.75
0.75
0.50
0.50
0.25
0.25
1.8
TeV
|h|<1.0
PT>0.5
GeV
|h|<1.0
|h|<1.0
PT>0.5
PT>0.5
GeV/c
GeV/c
|h|<1.0
PT>0.5
GeV
0.00
0.00
00
10 5 20
10
30
30
40
4015 50
50
20
60
60
70
702580
80
30
40 130
50
90
90 100
10035110
110 120
120
13045140
140 150
150
PT(charged
PT(charged jet#1)
jet#1) (GeV/c)
(GeV/c)
(GeV/c)
Excellent agreement
between Run 1 and 2!
 Shows the data on the average “transverse” charge particle density (|h|<1, PT>0.5 GeV) as
a function of the transverse momentum of the leading charged particle jet from Run 1.
 Compares the Run 2 data (Min-Bias, JET20, JET50, JET70, JET100) with Run 1.

The errors on the (uncorrected) Run 2 data include both statistical
and Tune
correlated
PYTHIA
A was tuned to fit
the “underlying event” in Run I!
systematic uncertainties.
Shows the prediction of PYTHIA Tune A at 1.96 TeV after detector simulation (i.e. after
CDFSIM).
Fermilab MC Workshop
April 30, 2003
Rick Field - Florida/CDF
Page 18
“Transverse”
Charged PTsum Density
“Transverse” region as
defined by the leading
“charged particle jet”
“Toward”
“Transverse”
“Transverse”
“Away”
1.25
"Transverse" PTsum Density (GeV)
Charged Particle Jet #1
Direction

"Transverse" Charged PTsum Density: dPTsum/dhd
CDF JET20
CDF Run 1 Data
CDF Min-Bias
data uncorrected
1.00
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)
 Shows the data on the average “transverse” charged PTsum density (|h|<1, PT>0.5 GeV)
as a function of the transverse momentum of the leading charged particle jet from Run 1.
Fermilab MC Workshop
April 30, 2003
Rick Field - Florida/CDF
Page 19
“Transverse”
Charged PTsum Density
“Transverse” region as
defined by the leading
“charged particle jet”
“Toward”
“Transverse”
“Transverse”
“Away”
"Transverse"
PTsum
Density
(GeV)
"Transverse"
"Transverse"PTsum
PTsumDensity
Density(GeV/c)
(GeV)
Charged Particle Jet #1
Direction

sum/dhd
"Transverse" Charged
Charged PTsum
PTsum Density: dPTsum
"Transverse"
1.25
1.25
CDFPreliminary
Preliminary
CDF
CDF
Run
1 Data
CDF JET20
CDF Min-Bias
data
uncorrected
data
datauncorrected
uncorrected
1.00
1.00
0.75
0.75
CDF
Run 2
CDF Run
1 Published
CDF
CDF
RunJET20
2 Preliminary
CDF Min-Bias
0.50
0.50
0.25
0.25
|h|<1.0
PT>0.5
|h|<1.0GeV
PT>0.5GeV
GeV/c
1.8 TeV |h|<1.0 PT>0.5
0.00
0.00
00
10 5 20
20
10
30
30
10
40 15 50
60
20
70 2580
90
140
110 120
120
13045
140 150
150
30 10035110
40 130
50
PT(charged
PT(charged jet#1)
jet#1) (GeV/c)
(GeV/c)
 Shows the
Excellent agreement
between
Run average
1 and 2!
data
on the
“transverse” charged PTsum density (|h|<1, PT>0.5 GeV)
as a function of the transverse momentum of the leading charged particle jet from Run 1.
 Compares the Run 2 data (Min-Bias, JET20, JET50, JET70, JET100) with Run 1. The
errors on the (uncorrected) Run 2 data include both statistical and correlated systematic
uncertainties.
Fermilab MC Workshop
April 30, 2003
Rick Field - Florida/CDF
Page 20
“Transverse”
Charged PTsum Density
“Transverse” region as
defined by the leading
“charged particle jet”
“Toward”
“Transverse”
“Transverse”
“Away”
"Transverse"
PTsum
Density
(GeV)
"Transverse"
"Transverse"PTsum
PTsumDensity
Density(GeV/c)
(GeV)
Charged Particle Jet #1
Direction

"Transverse" Charged
Charged PTsum
PTsum Density: dPTsum
sum/dhd
"Transverse"
1.25
1.25
1.25
CDFPreliminary
Preliminary
CDF
CDF
Run
1 Data
CDF JET20
CDF Min-Bias
data
uncorrected
data
datauncorrected
uncorrected
1.00
1.00
1.00
theory corrected
0.75
0.75
0.75
CDF Run
1Run
Published
CDF
2
CDF Run
1 Published
CDF Run 2 Preliminary
CDF
CDF
RunJET20
2 Preliminary
PYTHIA Tune A
CDF Min-Bias
0.50
0.50
0.50
0.25
0.25
0.25
|h|<1.0
PT>0.5
|h|<1.0GeV
PT>0.5GeV
GeV/c
1.8 TeV |h|<1.0 PT>0.5
0.00
0.00
0.00
000
10 5 20
20
10
30
30
10
40
4015 50
50
60
60
20
70
70 2580
80
90
140
90
10035110
110 120
120
130 45
140 150
150
30 100
40 130
50
PT(charged
PT(charged jet#1)
jet#1) (GeV/c)
(GeV/c)
 Shows the
Excellent agreement
between
Run average
1 and 2!
data
on the
“transverse” charged PTsum density (|h|<1, PT>0.5 GeV)
as a function of the transverse momentum of the leading charged particle jet from Run 1.
 Compares the Run 2 data (Min-Bias, JET20, JET50, JET70, JET100) with Run 1. The
errors on the (uncorrected) Run 2 data include both statistical and
correlated
systematic
PYTHIA
Tune A was
tuned to fit
the “underlying event” in Run I!
uncertainties.
 Shows the prediction of PYTHIA Tune A at 1.96 TeV after detector simulation (i.e. after
CDFSIM).
Fermilab MC Workshop
April 30, 2003
Rick Field - Florida/CDF
Page 21
Charged Particle Density
“Transverse” PT Distribution
"Transverse" Charged Particle Density: dN/dhd
Charged Particle Density
1.0E+00
CDF Run 1 Min-Bias
CDF Preliminary
1.00
CDF Run 1
CDF Run 1 JET20
data uncorrected
data uncorrected
1.0E-01
0.75
0.50
0.25
|h|<1.0 PT>0.5 GeV
0.00
0
10
20
30
40
50
60
70
80
90
100 110 120 130 140 150
PT(charged jet#1) (GeV/c)
 Compares the average “transverse”
charge particle density (|h|<1, PT>0.5
GeV) versus PT(charged jet#1) with the
PT distribution of the “transverse”
density, dNchg/dhddPT. Shows how the
“transverse” charge particle density is
distributed in PT.
Fermilab MC Workshop
April 30, 2003
Charged Density dN/dhddPT (1/GeV/c)
"Transverse" Charged Density
1.25
"Transverse"
PT(chgjet#1) > 30 GeV/c
1.0E-02
1.0E-03
1.0E-04
1.0E-05
Min-Bias
1.0E-06
Charged Particles |h| < 1.0
1.0E-07
0
Rick Field - Florida/CDF
2
4
6
8
10
12
14
16
18
20
PT(charged) (GeV/c)
Page 22
Charged Particle Density
“Transverse” PT Distribution
"Transverse" Charged Particle Density: dN/dhd
Charged Particle Density
CDF Run 1 Min-Bias
CDF
Run
11
Published
CDF
Run
JET20
CDF Run 2 Preliminary
CDF Run 2
CDF Preliminary
Preliminary
CDF
datauncorrected
uncorrected
data
1.00
0.75
0.50
0.25
|h|<1.0
PT>0.5
|h|<1.0
PT>0.5
GeV GeV/c
0.00
0
10
20
30
40
1.0E+00
1.0E+00
50
60
70
80
90 100 110 120 130 140 150
PT(charged jet#1) (GeV/c)
 Compares the average “transverse”
charge particle density (|h|<1, PT>0.5
GeV) versus PT(charged
jet#1)agreement
with the
Excellent
PT distribution of the between
“transverse”
Run 1 and 2!
density, dNchg/dhddPT. Shows how the
“transverse” charge particle density is
distributed in PT.
Fermilab MC Workshop
April 30, 2003
"Transverse"
PT(chgjet#1) > 30 GeV/c
1.0E-01
1.0E-01
Charged Density
(1/GeV/c)
Density dN/dhddPT
dN/dhddPT (1/GeV/c)
Charged
"Transverse"
"Transverse" Charged
Charged Density
Density
1.25
Run 1
Preliminary
CDF CDF
uncorrected
datadata
uncorrected
uncorrected
data
"Transverse"
Run 2 Min-Bias Preliminary
PT(chgjet#1) > 30 GeV/c
Run 1 Min-Bias Preliminary
1.0E-02
1.0E-02
Run 2 Preliminary
Run 1 Published
1.0E-03
1.0E-03
1.0E-04
1.0E-04
1.0E-05
1.0E-05
Min-Bias
1.0E-06
1.0E-06
Charged
Charged Particles
Particles |h|
|h| << 1.0
1.0
1.0E-07
1.0E-07
00
22
44
66
88
10
10
12
12
14
14
16
16
18
18
20
20
PT(charged) (GeV/c)
 Compares the Run 2 data (Min-Bias,
JET20, JET50, JET70, JET100) with
Run 1.
Rick Field - Florida/CDF
Page 23
Charged Particle Density
“Transverse” PT Distribution
"Transverse" Charged Particle Density: dN/dhd
"Transverse" Charged Particle Density
1.0E+00
CDF Preliminary
CDF
Run
Published
CDF
Run
11
Published
CDF
Run
Preliminary
CDF
Run
22
Preliminary
PYTHIA Tune A
data uncorrected
uncorrected
data
theory corrected
1.00
0.75
0.50
0.25
|h|<1.0
PT>0.5
GeV/c
|h|<1.0
PT>0.5
GeV/c
0.00
0
10
20
30
40
50
60
70
80
90 100 110 120 130 140 150
PT(charged jet#1) (GeV/c)
CDF Preliminary
Charged Density dN/dhddPT (1/GeV/c)
"Transverse" Charged
Charged Density
Density
"Transverse"
1.25
data uncorrected
theory corrected
1.96 TeV |h|<1.0
1.0E-01
PYTHIA Tune A 1.96 TeV
70 < PT(chgjet#1) < 95 GeV/c
1.0E-02
1.0E-03
1.0E-04
70 < PT(charged jet#1) > 95 GeV/c
“Transverse” <dNchg/dhd> = 0.62
30 < PT(chgjet#1) < 70 GeV/c
1.0E-05
30 < PT(charged jet#1) < 50 GeV/c
“Transverse” <dNchg/dhd> = 0.59
0
2
4
6
8
10
12
14
16
18
20
PT(charged) (GeV/c)
 Compares the average “transverse” charge particle density (|h|<1, PT>0.5 GeV) versus
PT(charged jet#1) with the PT distribution of the “transverse” density, dNchg/dhddPT.
 Shows the prediction of PYTHIA Tune A at 1.96 TeV after detector simulation (i.e. after
CDFSIM).
Fermilab MC Workshop
April 30, 2003
Rick Field - Florida/CDF
Page 24
Relationship Between
“Calorimeter” and “Charged Particle” Jets
PT(chgjet#1)/ET(matched jet) vs PT(chgjet#1)
ET(matched jet) vs PT(charged jet#1)
1.2
160
CDF Preliminary
140
data uncorrected
theory corrected
120
PYTHIA Tune A
100
CDF Run 2 Preliminary
80
60
JetClu (R = 0.7, |h(jet#1)| < 2)
40
PT(chgjet#1)/ET(matched jet)
Matched Jet ET (GeV)
180
1.0
0.8
PYTHIA Tune A
CDF Run 2 Preliminary
0.6
data uncorrected
theory corrected
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
20
JetClu (R = 0.7, |h(jet#1)| < 2)
CDF Preliminary
0.4
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
0.2
0
0
10
20
30
40
50
60
70
80
90
100 110 120 130 140 150
0
10
20
30
40
50
60
70
80
90
100 110 120 130 140 150
PT(charged jet#1) (GeV/c)
PT(charged jet#1) (GeV/c)
 Shows the “matched” JetClu jet ET
versus the transverse momentum of the
leading “charged particle jet” (closest
jet within R = 0.7 of the leading chgjet).
 Shows the ratio of PT(chgjet#1) to the
“matched” JetClu jet ET versus
PT(chgjet#1).
 Shows the EM fraction of the “matched”
JetClu jet and the EM fraction of a
typical JetClu jet.
Fermilab MC Workshop
April 30, 2003
Rick Field - Florida/CDF
Page 25
Relationship Between
“Calorimeter” and “Charged Particle” Jets
PT(chgjet#1)/ET(matched jet) vs PT(chgjet#1)
ET(matched jet) vs PT(charged jet#1)
1.2
160
CDF Preliminary
140
data uncorrected
theory corrected
120
PYTHIA Tune A
100
CDF Run 2 Preliminary
80
60
JetClu (R = 0.7, |h(jet#1)| < 2)
40
PT(chgjet#1)/ET(matched jet)
Matched Jet ET (GeV)
180
1.0
0.8
PYTHIA Tune A
CDF Run 2 Preliminary
0.6
data uncorrected
theory corrected
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
20
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
0.2
0
0
10
20
30
40
50
60
70
80
90
0
100 110 120 130 140 150
10
20
30
40
60
70
80
90
100 110 120 130 140 150
versus the transverse momentum of the
leading “charged particle jet” (closest
jet within R = 0.7 of the leading chgjet).
The leading
chgjet
from a
Shows the EM
fraction
of comes
the “matched”
JetClu jet that is, on the average,
JetClu jet and the
EM
fraction
about
90%
charged!of a
"Calorimeter Jet" EM Fraction
 Shows the
ratio of PT(chgjet#1) to the
0.8
Electromagnetic Fraction
 Shows the “matched” JetClu jet ET
typical JetClu jet.
50
PT(charged jet#1) (GeV/c)
PT(charged jet#1) (GeV/c)

JetClu (R = 0.7, |h(jet#1)| < 2)
CDF Preliminary
0.4
0.7
0.6
PYTHIA Tune A 1.96 TeV
CDF Preliminary
“matched”
JetClu jet ET versus
PT(chgjet#1).
Leading Jet
|h(jet)| < 0.7
data uncorrected
theory corrected
0.5
0.4
Jet matching
ChgJet#1
0.3
JetClu R = 0.7
0.2
0
25
50
75
100
125
150
175
200
225
250
PT(chgjet#1) or ET(jet#1) (GeV)
Fermilab MC Workshop
April 30, 2003
Rick Field - Florida/CDF
Page 26
“Underlying Event”
as defined by “Calorimeter Jets”
JetClu Jet #1
Charged Particle  Correlations
Direction
PT > 0.5 GeV/c |h| < 1
“Transverse” region is
2p
very sensitive to the
JetClu Jet #1
“Toward-Side” Jet
“underlying event”!
Direction

“Toward”
Look at the charged
particle density in the
“transverse” region!
Away Region

Transverse
Region
“Toward”

“Transverse”
“Transverse”
“Transverse”
Leading
Jet
“Transverse”
Toward Region
“Away”
Transverse
Region
“Away”
“Away-Side” Jet
Away-side “jet”
(sometimes)
Away Region
Perpendicular to the plane of the
2-to-2 hard scattering
0
-1
h
+1
 Look at charged particle correlations in the azimuthal angle  relative to the leading


JetClu jet.
o
o
o
o
Define || < 60 as “Toward”, 60 < || < 120 as “Transverse”, and || > 120 as
“Away”.
o
All three regions have the same size in h- space, hx = 2x120 = 4p/3.
Fermilab MC Workshop
April 30, 2003
Rick Field - Florida/CDF
Page 27
“Transverse”
Charged Particle Density
“Toward”
“Toward”
“Transverse”
“Transverse”
“Transverse”
“Transverse”
“Away”
“Away”
"Transverse" Charged Particle Density: dN/dhd
1.00
"Transverse" Charged Density
JetClu Jet #1
JetClu
Jet #1
or
ChgJet#1
Direction
Direction


“Transverse” region as
defined by the leading
“calorimeter jet”
CDF
CDF Preliminary
PYTHIA Tune A
CDF Run 2 Preliminary
data
data uncorrected
uncorrected
theory corrected
0.75
0.50
JetClu (R = 0.7, |h(jet#1)| < 2)
0.25
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
0.00
0
25
50
75
100
125
150
175
200
225
250
ET(jet#1) (GeV)
 Shows the data on the average “transverse” charge particle density (|h|<1, PT>0.5 GeV)
as a function of the transverse energy of the leading JetClu jet (R = 0.7, |h(jet)| < 2)
from Run 2., compared with PYTHIA Tune A after CDFSIM.
Fermilab MC Workshop
April 30, 2003
Rick Field - Florida/CDF
Page 28
“Transverse”
Charged Particle Density
“Toward”
“Toward”
“Transverse”
“Transverse”
“Transverse”
“Transverse”
“Away”
“Away”
"Transverse"
Charged Particle
Particle Density: dN/dhd
"Transverse" Charged
1.00
1.00
1.00
Density
"Transverse"
"Transverse" Charged
Charged Density
Density
JetClu Jet #1
JetClu
Jet #1
or
ChgJet#1
Direction
Direction


“Transverse” region as
defined by the leading
“calorimeter jet”
CDF
CDF
Preliminary
CDFPreliminary
CDF
data Preliminary
uncorrected
data
data uncorrected
uncorrected
data uncorrected
theory
theorycorrected
corrected
0.75
0.75
0.75
PYTHIA Tune A
JetCluJetClu
Jet#1 (R
= 0.7,
Jet#1
(R |h(jet)|<2)
= 0.7,|h(jet)|<2)
CDF Run 2 Preliminary
0.50
0.50
ChgJet#1 R = 0.7
PYTHIA
Tune A 1.96
JetClu (R
= 0.7, |h(jet#1)|
< 2)TeV
ChgJet#1 R = 0.7
0.25
0.25
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)
0.00
0.00
00
25
25
50
50
75
75
100
100
125
125
150
150
175
175
200
225
250
ET(jet#1)
(GeV) (GeV)
PT(chgjet#1)
or ET(jet#1)
 Shows the data on the average “transverse” charge particle density (|h|<1, PT>0.5 GeV)
as a function of the transverse energy of the leading JetClu jet (R = 0.7, |h(jet)| < 2)
from Run 2., compared with PYTHIA Tune A after CDFSIM.
 Compares the “transverse” region of the leading “charged particle jet”, chgjet#1, with
the “transverse” region of the leading “calorimeter jet” (JetClu R = 0.7), jet#1.
Fermilab MC Workshop
April 30, 2003
Rick Field - Florida/CDF
Page 29
“Transverse”
Charged PTsum Density
“Transverse” region as
defined by the leading
“calorimeter jet”
"Transverse" Charged PTsum Density: dPTsum/dhd
JetClu Jet #1
JetClu
Jet #1
or ChgJet#1
Direction

“Toward”
“Transverse”
“Transverse”
“Transverse”
“Away”
"Transverse"
"Transverse" PTsum
PTsum Density
Density (GeV/c)
(GeV/c)
1.5
CDF Preliminary
data uncorrected
theory corrected
1.0
0.5
PYTHIA Tune A
CDF Run 2 Preliminary
JetClu (R = 0.7, |h(jet#1)| < 2)
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
0.0
0
25
50
75
100
125
150
175
200
225
250
ET(jet#1) (GeV)
 Shows the data on the average “transverse” charged PTsum density (|h|<1, PT>0.5
GeV) as a function of the transverse energy of the leading JetClu jet (R = 0.7, |h(jet)| <
2) from Run 2., compared with PYTHIA Tune A after CDFSIM.
Fermilab MC Workshop
April 30, 2003
Rick Field - Florida/CDF
Page 30
“Transverse”
Charged PTsum Density
“Transverse” region as
defined by the leading
“calorimeter jet”
"Transverse" Charged PTsum Density: dPTsum/dhd
JetClu Jet #1
JetClu
Jet #1
or ChgJet#1
Direction

“Toward”
“Transverse”
“Transverse”
“Transverse”
“Away”
"Transverse"
"Transverse" PTsum
PTsum Density
Density (GeV/c)
(GeV/c)
1.5
CDF Preliminary
CDF
Preliminary
data uncorrected
data
uncorrected
theory
corrected
1.0
JetClu Jet#1 (R = 0.7,|h(jet)|<2)
JetClu Jet#1 (R = 0.7,|h(jet)|<2)
0.5
PYTHIA Tune A
ChgJet#1 RR= =0.7
0.7
CDF ChgJet#1
Run 2 Preliminary
PYTHIA Tune A 1.96 TeV
JetClu (R = 0.7, |h(jet#1)| < 2)
Charged Particles
Particles (|h|<1.0,
(|h|<1.0, PT>0.5
PT>0.5 GeV/c)
GeV/c)
Charged
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
0.0
0
25
50
75
100
125
150
175
200
225
250
PT(chgjet#1)
or ET(jet#1)
ET(jet#1)
(GeV) (GeV)
 Shows the data on the average “transverse” charged PTsum density (|h|<1, PT>0.5
GeV) as a function of the transverse energy of the leading JetClu jet (R = 0.7, |h(jet)| <
2) from Run 2., compared with PYTHIA Tune A after CDFSIM.
 Compares the “transverse” region of the leading “charged particle jet”, chgjet#1, with
the “transverse” region of the leading “calorimeter jet” (JetClu R = 0.7), jet#1.
Fermilab MC Workshop
April 30, 2003
Rick Field - Florida/CDF
Page 31
Charged Particle Density
“Transverse” PT Distribution
"Transverse" Charged Particle Density: dN/dhd
"Transverse" Charged Particle Density
CDF Preliminary
CDF Preliminary
CDF Run 2 Preliminary
data uncorrected
theory corrected
0.75
1.0E+00
PYTHIA Tune A
0.50
JetClu (R = 0.7, |h(jet#1)| < 2)
0.25
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
0.00
0
25
50
data uncorrected
theory corrected
JetClu R = 0.7 |h(jet)| < 2
75
100
125
150
175
200
225
250
ET(jet#1) (GeV)
Charged Density dN/dhddPT (1/GeV/c)
"Transverse" Charged Density
1.00
1.0E-01
PYTHIA Tune A 1.96 TeV
1.0E-02
95 < ET(jet#1) < 130 GeV
1.0E-03
1.0E-04
1.0E-05
30 < ET(jet#1) < 70 GeV
95 < ET(jet#1) > 130 GeV
“Transverse” <dNchg/dhd> = 0.65
Charged Particles |h| < 1.0
1.0E-06
0
30 < ET(jet#1) < 70 GeV/c
“Transverse” <dNchg/dhd> = 0.61
5
10
15
20
25
PT(charged) (GeV/c)
 Compares the average “transverse” charge particle density (|h|<1, PT>0.5 GeV) versus
ET(jet#1) with the PT distribution of the “transverse” density, dNchg/dhddPT.
 Shows the prediction of PYTHIA Tune A at 1.96 TeV after detector simulation (i.e. after
CDFSIM).
Fermilab MC Workshop
April 30, 2003
Rick Field - Florida/CDF
Page 32
Charged Particle Density
“Transverse” PT Distribution
"Transverse" Charged Particle Density: dN/dhd
"Transverse" Charged Particle Density
CDF Preliminary
CDF
Preliminary
data uncorrected
1.0E+00
Jet#1
(R|h(jet)|<2)
= 0.7,|h(jet)|<2)
JetClu JetClu
Jet#1 (R
= 0.7,
CDF Preliminary
data uncorrected
theory
corrected
0.75
0.50
PYTHIA Tune A 1.96 TeV
ChgJet#1 R = 0.7
ChgJet#1 R = 0.7
0.25
Charged Particles
Particles (|h|<1.0,
(|h|<1.0, PT>0.5
PT>0.5 GeV/c)
GeV/c)
Charged
0.00
0
25
50
75
100
125
150
175
200
PT(chgjet#1) or ET(jet#1) (GeV)
30 < PT(charged jet#1) < 50 GeV/c
“Transverse” <dNchg/dhd> = 0.59
30 < ET(jet#1) < 70 GeV/c
“Transverse” <dNchg/dhd> = 0.61
225
250
"Transverse" Density dN/dhddPT (1/GeV/c)
"Transverse" Charged Density
1.00
data uncorrected
theory corrected
1.0E-01
1.96 TeV
PYTHIA Tune A 1.96 TeV
1.0E-02
30 < PT(chgjet#1) < 70 GeV/c
1.0E-03
1.0E-04
30 < ET(jet#1) < 70 GeV
1.0E-05
Charged Particles |h| < 1.0
1.0E-06
0
5
10
15
20
25
PT(charged) (GeV/c)
 Compares the average “transverse” as defined by “calorimeter jets” (JetClu R = 0.7) with the
“transverse” region defined by “charged particle jets”.
 Shows the prediction of PYTHIA Tune A at 1.96 TeV after detector simulation (i.e. after
CDFSIM).
Fermilab MC Workshop
April 30, 2003
Rick Field - Florida/CDF
Page 33
Tuned PYTHIA (Set A)
LHC Predictions
"Transverse" Charged PTsum Density: dPTsum/dhd
"Transverse" Charged Particle Density: dN/dhd
2.5
3.0
"Transverse" PTsum Density (GeV)
"Transverse" Charged Density
HERWIG 6.4
14 TeV
2.5
2.0
1.5
1.8 TeV
1.0
PYTHIA 6.206 Set A
0.5
CTEQ5L
|h|<1.0 PT>0 GeV
PYTHIA 6.206 Set A
2.0
14 TeV
Factor of 2!
HERWIG 6.4
1.5
1.0
1.8 TeV
0.5
CTEQ5L
|h|<1.0 PT>0 GeV
0.0
0.0
0
5
10
15
20
25
30
35
40
45
50
0
5
10
15
20
25
30
35
40
45
50
PT(charged jet#1) (GeV/c)
PT(charged jet#1) (GeV/c)
 Shows the average “transverse” charge particle and PTsum density (|h|<1, PT>0) versus
PT(charged jet#1) predicted by HERWIG 6.4 (PT(hard) > 3 GeV/c, CTEQ5L). and a tuned
versions of PYTHIA 6.206 (PT(hard) > 0, CTEQ5L, Set A) at 1.8 TeV and 14 TeV.
 At 14 TeV tuned PYTHIA (Set A) predicts roughly 2.3 charged particles per unit h- (PT > 0)

in the “transverse” region (14 charged particles per unit h) which is larger than the HERWIG
prediction.
At 14 TeV tuned PYTHIA (Set A) predicts roughly 2 GeV/c charged PTsum per unit h- (PT
> 0) in the “transverse” region at PT(chgjet#1) = 40 GeV/c which is a factor of 2 larger than
at 1.8 TeV and much larger than the HERWIG prediction.
Fermilab MC Workshop
April 30, 2003
Rick Field - Florida/CDF
Page 34
Tuned PYTHIA (Set A)
LHC Predictions
"Transverse" Charged Particle Density: dN/dhd
"Transverse" Charged PTsum Density: dPTsum/dhd
2.5
"Transverse" PTsum Density (GeV)
"Transverse" Charged Density
3.0
PYTHIA 6.206 Set A
2.5
2.0
1.5
HERWIG 6.4
1.0
0.5
CTEQ5L
14 TeV |h|<1.0 PT>0 GeV
0.0
PYTHIA 6.206 Set A
2.0
Big difference!
1.5
1.0
HERWIG 6.4
0.5
CTEQ5L
14 TeV |h|<1.0 PT>0 GeV
0.0
0
10
20
30
40
50
60
70
80
90
100
0
10
PT(charged jet#1) (GeV/c)
20
30
40
50
60
70
80
90
100
PT(charged jet#1) (GeV/c)
 Shows the average “transverse” charge particle and PTsum density (|h|<1, PT>0) versus

PT(charged jet#1) predicted by HERWIG 6.4 (PT(hard) > 3 GeV/c, CTEQ5L). and a tuned
versions of PYTHIA 6.206 (PT(hard) > 0, CTEQ5L, Set A) at 1.8 TeV and 14 TeV. Also
shown is the 14 TeV prediction of PYTHIA 6.206 with the default value e = 0.16.
Tuned PYTHIA (Set A) predicts roughly 2.5 GeV/c per unit h-
(PT > 0) from charged particles in the “transverse” region for
3.8 GeV/c (charged)
PT(chgjet#1) = 100 GeV/c. Note, however, that the “transverse”
in cone of
radius R=0.7
charged PTsum density increases as PT(chgjet#1) increases.
at 14 TeV
Fermilab MC Workshop
April 30, 2003
Rick Field - Florida/CDF
Page 36
Tuned PYTHIA (Set A)
LHC Predictions
Charged Particle Density: dN/dhd
Charged Particle Density: dN/dhd
1.4
1.4
Pythia 6.206 Set A
CDF Data
14 TeV
Charged density dN/dhd
1.0
dN/dhd
Pythia 6.206 Set A
CDF Data
UA5 Data
Fit 2
Fit 1
1.2
1.2
1.8 TeV
0.8
0.6
0.4
0.2
0.8
0.6
0.4
0.2
all PT
630 GeV
1.0
h=0
0.0
-6
-4
-2
0
Pseudo-Rapidity h
2
4
6
LHC?
0.0
10
100
1,000
10,000
100,000
CM Energy W (GeV)
 Shows the center-of-mass energy dependence of the charged particle density, dNchg/dhd,
for “Min-Bias” collisions compared with the a tuned version of PYTHIA 6.206 (Set A) with
PT(hard) > 0.
 PYTHIA was tuned to fit the “underlying event” in hard-scattering processes at 1.8 TeV
and 630 GeV.
 PYTHIA (Set A) predicts a 42% rise in dNchg/dhd at h = 0 in going from the Tevatron (1.8
TeV) to the LHC (14 TeV).
Fermilab MC Workshop
April 30, 2003
Rick Field - Florida/CDF
Page 37
Tuned PYTHIA (Set A)
LHC Predictions
Charged Particle Density
12% of “Min-Bias” events
50%
have PT(hard) > 10 GeV/c!
1.0E+00
|h|<1
Pythia 6.206 Set A
Hard-Scattering in Min-Bias Events
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
630 GeV
100,000
LHC?
 Shows the center-of-mass energy
CDF Data
1.0E-06
2
10,000
CM Energy W (GeV)
1.0E-05
0
1,000
4
6
8
PT(charged) (GeV/c)
1% of “Min-Bias” events
have PT(hard) > 10 GeV/c!
10
12
14
dependence of the charged particle density,
dNchg/dhddPT, for “Min-Bias” collisions
compared with the a tuned version of
PYTHIA 6.206 (Set A) with PT(hard) > 0.
 This PYTHIA fit 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!
Fermilab MC Workshop
April 30, 2003
Rick Field - Florida/CDF
Page 38
The “Underlying Event”
Summary & Conclusions
Outgoing Parton
PT(hard)
Initial-State Radiation
Proton
AntiProton
Underlying Event
Outgoing Parton
Underlying Event
The “Underlying Event”
Final-State
Radiation
 There is excellent agreement between the Run 1 and the Run 2. The
“underlying event” is the same in Run 2 as in Run 1 but now we can study the
evolution out to much higher energies!
 PYTHIA Tune A does a good job of describing the “underlying event” in the
Run 2 data as defined by “charged particle jets” and as defined by
“calorimeter jets”. HERWIG Run 2 comparisons will be coming soon!
 Lots more CDF Run 2 data to come including MAX/MIN “transverse” and
MAX/MIN “cones”.
Fermilab MC Workshop
April 30, 2003
Rick Field - Florida/CDF
Page 39
LHC Predictions
Summary & Conclusions
Outgoing Parton
PT(hard)
Initial-State Radiation
Proton
AntiProton
Underlying Event
Outgoing Parton
Tevatron
LHC
Underlying Event
Final-State
Radiation
 Both HERWIG and the tuned PYTHIA (Set A) predict a 40-45% rise in dNchg/dhd at h



= 0 in going from the Tevatron (1.8 TeV) to the LHC (14 TeV). 4 charged particles per
unit h at the Tevatron becomes 6 per unit h at the LHC.
The tuned PYTHIA (Set A) predicts that 1% of all “Min-Bias” events at the Tevatron
(1.8 TeV) are the result of a hard 2-to-2 parton-parton scattering with PT(hard) > 10
GeV/c which increases to 12% at LHC (14 TeV)!
For the “underlying event” in hard scattering processes the predictions of HERWIG and
the tuned PYTHIA (Set A) differ greatly (factor of 2!). HERWIG predicts a smaller
increase in the activity of the “underlying event” in going from the Tevatron to the LHC.
The tuned PYTHIA (Set A) predicts about a factor of two increase at the LHC in the
charged PTsum density of the “underlying event” at the same PT(jet#1) (the “transverse”
charged PTsum density increases rapidly as PT(jet#1) increases).
Fermilab MC Workshop
April 30, 2003
Rick Field - Florida/CDF
Page 40
LHC Predictions
Summary & Conclusions
Outgoing Parton
PT(hard)
Initial-State Radiation
Proton
AntiProton
Underlying Event




Tevatron
LHC
Underlying Event
12 times more likely
to find a 10 GeV
Both HERWIG and the tuned PYTHIA (Set A) predict a 40-45% rise
inindN
“jet”
“Min-Bias”
chg/dhd at
at theparticles
LHC!
= 0 in going from the Tevatron (1.8 TeV) to the LHC (14 TeV). 4 charged
per
Outgoing Parton
Final-State
Radiation
h
unit h at the Tevatron becomes 6 per unit h at the LHC.
Twice as much
The tuned PYTHIA (Set A) predicts that 1% of all “Min-Bias” events at the Tevatron
activity in the
(1.8 TeV) are the result of a hard 2-to-2 parton-parton scattering with PT(hard)
> 10
“underlying event”
GeV/c which increases to 12% at LHC (14 TeV)!
at the LHC!
For the “underlying event” in hard scattering processes the predictions of HERWIG and
the tuned PYTHIA (Set A) differ greatly (factor of 2!). HERWIG predicts a smaller
increase in the activity of the “underlying event” in going from the Tevatron to the LHC.
The tuned PYTHIA (Set A) predicts about a factor of two increase at the LHC in the
charged PTsum density of the “underlying event” at the same PT(jet#1) (the “transverse”
charged PTsum density increases rapidly as PT(jet#1) increases).
Fermilab MC Workshop
April 30, 2003
Rick Field - Florida/CDF
Page 41
LHC Predictions
Summary & Conclusions
Outgoing Parton
PT(hard)
Initial-State Radiation
Proton
AntiProton
Underlying Event


Tevatron
LHC
Underlying Event
12 times more likely
Final-State
Radiation
“Min-Bias” at the LHC contains
to find a 10 GeV
much PYTHIA
more hard (Set
collisions
than at athe
Both HERWIG and the tuned
A) predict
40-45% rise
inindN
“jet”
“Min-Bias”
chg/dhd at h
Tevatron!
At the
Tevatron
at theparticles
LHC!
= 0 in going from the Tevatron
(1.8 TeV)
to the
LHC the
(14 TeV). 4 charged
per
“underlying
event”
is athe
factor
of 2
unit h at the Tevatron becomes
6 per unit
h at
LHC.
more active than “Tevaron Min-Bias”.
Twice as much
The tuned PYTHIA (SetAt
A)the
predicts
that
1% of allevent”
“Min-Bias”
events at the Tevatron
LHC the
“underlying
will
activity in the
(1.8 TeV) are the result of a hard
> 10
be at2-to-2
least a parton-parton
factor of 2 more scattering with PT(hard)
“underlying event”
GeV/c which increases to 12%
at LHC
(14 TeV)!
active
than “LHC
Min-Bias”!
at the LHC!
Outgoing Parton
 For the “underlying event” in hard scattering processes the predictions of HERWIG and

the tuned PYTHIA (Set A) differ greatly (factor of 2!). HERWIG predicts a smaller
increase in the activity of the “underlying event” in going from the Tevatron to the LHC.
The tuned PYTHIA (Set A) predicts about a factor of two increase at the LHC in the
charged PTsum density of the “underlying event” at the same PT(jet#1) (the “transverse”
charged PTsum density increases rapidly as PT(jet#1) increases).
Fermilab MC Workshop
April 30, 2003
Rick Field - Florida/CDF
Page 42