TeV4LHC Workshop
Talk #2
Rick Field
University of Florida
Drell-Yan Production
Lepton
Multiple Parton Interactions
Outgoing Parton
PT(hard)
Proton
AntiProton
Underlying Event
Proton
Underlying Event
AntiProton
Underlying Event
Underlying Event
Initial-State
Radiation
Anti-Lepton
TeV4LHC - Fermilab
October 21, 2005
CDF Run 2
Rick Field - Florida/CDF
Outgoing Parton
Page 1
Recent CDF Run 2
“Underlying Event” Results
Jet #1 Direction

The “underlying event” consists of
hard initial & final-state radiation
plus the “beam-beam remnants” and
possible multiple parton interactions.
Outgoing Parton
“Toward”
PT(hard)
Initial-State Radiation
“Trans 1”
“Trans 2”
Proton
AntiProton
Underlying Event
“Transverse” region is
very sensitive to the
“underlying event”!
Underlying Event
“Away”
Outgoing Parton
Final-State
Radiation
New CDF Run 2 results (L = 385 pb-1) :
 Two Classes of Events: “Leading Jet” and “Back-to-Back”.
 Two “Transverse” regions: “transMAX”, “transMIN”, “transDIF”.
 Data Corrected to the Particle Level: unlike our previous CDF Run 2 “underlying event”
analysis which used JetClu to define “jets” and compared uncorrected data with the QCD
Monte-Carlo models after detector simulation, this analysis uses the MidPoint jet algorithm and
corrects the observables to the particle level. The corrected observables are then compared
with the QCD Monde-Carlo models at the particle level.
 For the 1st time we study the energy density in the “transverse” region.
TeV4LHC - Fermilab
October 21, 2005
Rick Field - Florida/CDF
Page 2
The “Transverse” Regions
Look at the density of
charged particles and
calorimeter towers in the
“transverse” region.
as defined by 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

2p
Away Region
Jet #1 Direction
Transverse
Region 1

“Toward”
“Toward”
“Transverse”
“Transverse”
“Away”
“Trans 1”

Leading
Jet
“Trans 2”
Toward Region
Transverse
Region 2
“Away”
“Away-Side” Jet
Away Region
0
-1
h
+1
 Look at charged particle and calorimeter tower correlations in the azimuthal angle 

relative to the leading calorimeter jet (MidPoint, R = 0.7, fmerge = 0.75, |h| < 2).
o
o
o
o
o
Define || < 60 as “Toward”, 60 < - < 120 and 60 <  < 120 as “Transverse 1” and
o
“Transverse 2”, and || > 120 as “Away”. Each of the two “transverse” regions have
o
area h = 2x60 = 4p/6. The overall “transverse” region is the sum of the two
o
transverse regions (h = 2x120 = 4p/3).
TeV4LHC - Fermilab
October 21, 2005
Rick Field - Florida/CDF
Page 3
Refer to this as a
“Leading Jet” event
Charged Particle Density
 Dependence
Jet #1 Direction

Charged Particle Density: dN/dhd
“Toward”
“Transverse”
CDF Preliminary
“Transverse”
“Away”
Refer to this as a
“Back-to-Back” event
Jet #1 Direction

“Toward”
“Transverse”
Charged Particle Density
Subset
10.0
30 < ET(jet#1) < 70 GeV
Back-to-Back
Leading Jet
Min-Bias
data uncorrected
"Transverse"
Region
1.0
Jet#1
Charged Particles
(|h|<1.0, PT>0.5 GeV/c)
“Transverse”
0.1
“Away”
0
30
60
90
120
150
180
210
240
270
300
330
360
 (degrees)
Jet #2 Direction
 Look at the “transverse” region as defined by the leading jet (|h| < 2) or by the leading

two jets (|h| < 2). “Back-to-Back” events are selected to have at least two jets with Jet#1
and Jet#2 nearly “back-to-back” (12 > 150o) with almost equal transverse momenta
(PT(jet#2)/PT(jet#1) > 0.8) and PT(jet#3) < 15 GeV/c.
Shows the  dependence of the charged particle density, dNchg/dhd, for charged
particles in the range pT > 0.5 GeV/c and |h| < 1 relative to jet#1 (rotated to 270o) for 30
< ET(jet#1) < 70 GeV for “Leading Jet” and “Back-to-Back” events.
TeV4LHC - Fermilab
October 21, 2005
Rick Field - Florida/CDF
Page 4
“Transverse” Observables
Particle and Detector Level
“Leading Jet”
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)
PTmax = 0 for no charged
particle
Maximum pT “good” charged tracks
(pT > 0.5 GeV/c, |h| < 1)
PTmax = 0 for no “good” charged track
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)
Jet #1 Direction

“Toward”
“Transverse”
“Transverse”
“Away”
Jet #1 Direction

“Toward”
“Transverse”
“Transverse”
“Away”
Jet #2 Direction
“Back-to-Back”
TeV4LHC - Fermilab
October 21, 2005
Rick Field - Florida/CDF
Page 5
“TransDIF” PTsum Density
PYTHIA Tune A vs HERWIG
“Leading Jet”
Jet #1 Direction

"TransDIF" Charged PTsum Density: dPT/dhd
“Toward”
Jet #1 Direction
“TransMIN”
“Away”

“Toward”
“TransMAX”
“TransMIN”
“Away”
“Back-to-Back”
Jet #2 Direction
"Transverse" PTsum Density (GeV/c)
“TransMAX”
2.5
CDF Run 2 Preliminary
data corrected to particle level
2.0
"Leading Jet"
1.96 TeV
1.5
PY Tune A
1.0
"Back-to-Back"
0.5
MidPoint R = 0.7 |h(jet#1) < 2
HW
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
0.0
“transDIF” is very sensitive to
the “hard scattering” component
of the “underlying event”!
0
50
100
150
200
250
300
350
400
450
PT(jet#1) (GeV/c)
 Use the leading jet to define the MAX and MIN “transverse” regions on an event-byevent basis with MAX (MIN) having the largest (smallest) charged PTsum density.
 Shows the “transDIF” = MAX-MIN charge PTsum density, dPTsum/dhd, for pT > 0.5
GeV/c, |h| < 1 versus PT(jet#1) for “Leading Jet” and “Back-to-Back” events.
TeV4LHC - Fermilab
October 21, 2005
Rick Field - Florida/CDF
Page 6
“TransMAX/MIN” Nchg Density
PYTHIA Tune A vs HERWIG
“Leading Jet”
“Back-to-Back”
Jet #1 Direction
Jet #1 Direction

“TransMAX”
“TransMIN”
“Away”
CDF Run 2 Preliminary
"Transverse" Charged Density

“Toward”
"TransMAX" Charged Particle Density: dN/dhd
1.4
“Toward”
“TransMAX”
“TransMIN”
“Away”
"Leading Jet"
data corrected to particle level
1.2
1.0
"Back-to-Back"
0.8
0.6
HW
PY Tune A
MidPoint R = 0.7 |h(jet#1) < 2
0.4
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
1.96 TeV
Jet #2 Direction
0.2
 Shows the charged particle density,
50
100
150
200
250
300
350
400
450
PT(jet#1) (GeV/c)
"TransMIN" Charged Particle Density: dN/dhd
0.6
CDF Run 2 Preliminary
"Transverse" Charged Density

dNchg/dhd, in the “transMAX” and
“transMIN” region (pT > 0.5 GeV/c,
|h| < 1) versus PT(jet#1) for
“Leading Jet” and “Back-to-Back”
events.
Compares the (corrected) data with
PYTHIA Tune A (with MPI) and
HERWIG (without MPI) at the
particle level.
0
MidPoint R = 0.7 |h(jet#1) < 2
data corrected to particle level
0.5
1.96 TeV
HW
0.4
"Leading Jet"
0.3
0.2
"Back-to-Back"
0.1
PY Tune A
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
0.0
0
50
100
150
200
250
300
350
400
450
PT(jet#1) (GeV/c)
TeV4LHC - Fermilab
October 21, 2005
Rick Field - Florida/CDF
Page 7
“TransMAX/MIN” PTsum Density
PYTHIA Tune A vs HERWIG
“Leading Jet”
“Back-to-Back”
Jet #1 Direction
Jet #1 Direction
“TransMAX”
“TransMIN”
“Away”
"Transverse" PTsum Density (GeV/c)


“Toward”
"TransMAX" Charged PTsum Density: dPT/dhd
3.0
“Toward”
“TransMAX”
“TransMIN”
“Away”
Jet #2 Direction
CDF Run 2 Preliminary
"Leading Jet"
1.96 TeV
2.0
PY Tune A
1.5
"Back-to-Back"
1.0
MidPoint R = 0.7 |h(jet#1) < 2
0.5
HW
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
0.0
 Shows the charged PTsum density,
dPTsum/dhd, in the “transMAX”
and “transMIN” region (pT > 0.5
GeV/c, |h| < 1) versus PT(jet#1) for
“Leading Jet” and “Back-to-Back”
events.
Compares the (corrected) data with
PYTHIA Tune A (with MPI) and
HERWIG (without MPI) at the
particle level.
0
50
100
150
200
250
300
350
400
450
PT(jet#1) (GeV/c)
"TransMIN" Charged PTsum Density: dPT/dhd
0.6
"Transverse" PTsum Density (GeV/c)

data corrected to particle level
2.5
CDF Run 2 Preliminary
MidPoint R = 0.7 |h(jet#1) < 2
data corrected to particle level
0.5
1.96 TeV
"Leading Jet"
0.4
0.3
"Back-to-Back"
0.2
0.1
PY Tune A
HW
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
0.0
0
50
100
150
200
250
300
350
400
450
PT(jet#1) (GeV/c)
TeV4LHC - Fermilab
October 21, 2005
Rick Field - Florida/CDF
Page 8
“Transverse” <PT> and <PTmax>
PYTHIA Tune A vs HERWIG
“Back-to-Back”
Jet #1 Direction
Jet #1 Direction


“Toward”
“Transverse”
“Transverse”
“Away”
"Transverse" Charged Particle Mean PT
2.0
"Transverse" Charged <PT> (GeV/c)
“Leading Jet”
“Toward”
“Transverse”
“Transverse”
“Away”
Jet #2 Direction
CDF Run 2 Preliminary
1.5
1.0
"Back-to-Back"
HW
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
0.5
0
50
100
150
200
250
300
350
400
450
PT(jet#1) (GeV/c)
"Transverse" Charged PTmax
3.0
CDF Run 2 Preliminary
"Transverse" <PTmax> (GeV/c)
momentum, <PT>, and <PTmax> for
charged particles in the
“transverse” region (pT > 0.5 GeV/c,
|h| < 1) versus PT(jet#1) for
“Leading Jet” and “Back-to-Back”
events.
Compares the (corrected) data with
PYTHIA Tune A (with MPI) and
HERWIG (without MPI) at the
particle level.
TeV4LHC - Fermilab
October 21, 2005
"Leading Jet"
PY Tune A
1.96 TeV
 Shows the average transverse

MidPoint R = 0.7 |h(jet#1) < 2
data corrected to particle level
data corrected to particle level
2.5
"Leading Jet"
1.96 TeV
2.0
PY Tune A
1.5
"Back-to-Back"
1.0
0.5
MidPoint R = 0.7 |h(jet#1) < 2
HW
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
0.0
0
50
Rick Field - Florida/CDF
100
150
200
250
300
350
400
450
PT(jet#1) (GeV/c)
Page 9
“TransMAX/MIN” ETsum Density
PYTHIA Tune A vs HERWIG
“Leading Jet”
“Back-to-Back”
Jet #1 Direction
Jet #1 Direction
“TransMAX”
“TransMIN”
“Away”
"Transverse" ETsum Density (GeV)


“Toward”
"TransMAX" ETsum Density: dET/dhd
7.0
“Toward”
“TransMAX”
“TransMIN”
“Away”
Jet #2 Direction
CDF Run 2 Preliminary
6.0
"Leading Jet"
1.96 TeV
5.0
4.0
3.0
HW
"Back-to-Back"
2.0
1.0
PY Tune A
MidPoint R = 0.7 |h(jet#1) < 2
Particles (|h|<1.0, all PT)
0.0
 Shows the ETsum density,
0
50
100
150
200
250
300
350
400
450
PT(jet#1) (GeV/c)
dETsum/dhd, in the “transMAX”
and “transMIN” region (all particles
|h| < 1) versus PT(jet#1) for
“Leading Jet” and “Back-to-Back”
events.
Compares the (corrected) data with
PYTHIA Tune A (with MPI) and
HERWIG (without MPI) at the
particle level.
"TransMIN" ETsum Density: dET/dhd
3.0
"Transverse" ETsum Density (GeV)

data corrected to particle level
CDF Run 2 Preliminary
MidPoint R = 0.7 |h(jet#1) < 2
data corrected to particle level
2.5
Particles (|h|<1.0, all PT)
1.96 TeV
2.0
HW
"Leading Jet"
1.5
1.0
0.5
"Back-to-Back"
PY Tune A
0.0
0
50
100
150
200
250
300
350
400
450
PT(jet#1) (GeV/c)
TeV4LHC - Fermilab
October 21, 2005
Rick Field - Florida/CDF
Page 10
“Transverse” Charged Fraction
PYTHIA Tune A vs HERWIG
“Back-to-Back”
Jet #1 Direction
Jet #1 Direction


“Toward”
“Transverse”
“Transverse”
“Away”
"Transverse" Charged Fraction: PTsum/ETsum
0.6
CDF Run 2 Preliminary
"Transverse" PTsum/ETsum
“Leading Jet”
“Toward”
“Transverse”
“Transverse”
“Away”
Jet #2 Direction
data corrected to particle level
0.4
0.2
1.96 TeV
PTsum(|charged, h|<1.0, PT>0.5 GeV/c)
0.0
0
50
100
150
200
250
300
350
400
450
PT(jet#1) (GeV/c)
"Transverse" Charged Fraction: PTsum/ETsum
0.6
CDF Run 2 Preliminary
"Transverse" PTsum/ETsum
“transverse” region versus PT(jet#1) for
“Leading Jet” and “Back-to-Back”
events, where PTsum is the scalar PT
sum of charged particles (pT > 0.5
GeV/c, |h| < 1) and ETsum is the scalar
ET sum of all particles (|h| < 1).
Compares the (corrected) data with
PYTHIA Tune A (with MPI) and
HERWIG (without MPI) at the particle
level.
TeV4LHC - Fermilab
October 21, 2005
MidPoint R = 0.7 |h(jet#1) < 2
"Leading Jet"
ETsum (|h|<1.0, all PT)
 Shows the PTsum/ETsum in the

PY Tune A
HW
"Back-to-Back"
data corrected to particle level
PY Tune A
1.96 TeV
HW
0.4
0.2
ETsum (|h|<1.0, all PT)
MidPoint R = 0.7 |h(jet#1) < 2
PTsum(|charged, h|<1.0, PT>0.5 GeV/c)
0.0
0
50
Rick Field - Florida/CDF
100
150
200
250
300
350
400
450
PT(jet#1) (GeV/c)
Page 11
“TransDIF” ETsum Density
PYTHIA Tune A vs HERWIG
“Leading Jet”
Jet #1 Direction

"TransDIF" ETsum Density: dET/dhd
“Toward”
Jet #1 Direction
“TransMIN”
“Away”

“Toward”
“TransMAX”
“TransMIN”
“Away”
Jet #2 Direction
“Back-to-Back”
"Transverse" ETsum Density (GeV)
“TransMAX”
5.0
CDF Run 2 Preliminary
data corrected to particle level
4.0
"Leading Jet"
1.96 TeV
3.0
PY Tune A
2.0
HW
"Back-to-Back"
1.0
MidPoint R = 0.7 |h(jet#1) < 2
Particles (|h|<1.0, all PT)
0.0
“transDIF” is very sensitive to
the “hard scattering” component
of the “underlying event”!
0
50
100
150
200
250
300
350
400
450
PT(jet#1) (GeV/c)
 Use the leading jet to define the MAX and MIN “transverse” regions on an event-byevent basis with MAX (MIN) having the largest (smallest) charged PTsum density.
 Shows the “transDIF” = MAX-MIN ETsum density, dETsum/dhd, for all particles (|h| <
1) versus PT(jet#1) for “Leading Jet” and “Back-to-Back” events.
TeV4LHC - Fermilab
October 21, 2005
Rick Field - Florida/CDF
Page 12
“TransMAX/MIN” ETsum Density
PYTHIA Tune A vs JIMMY
“Leading Jet”
“Back-to-Back”
Jet #1 Direction
Jet #1 Direction
“TransMIN”
“Away”
"Transverse" ETsum Density (GeV)
“TransMAX”
7.0


“Toward”
"TransMAX" ETsum Density: dET/dhd
“Toward”
“TransMAX”
“TransMIN”
“Away”
Jet #2 Direction
data corrected to particle level
"Leading Jet"
1.96 TeV
5.0
4.0
JIM
3.0
"Back-to-Back"
2.0
1.0
PY Tune A
MidPoint R = 0.7 |h(jet#1) < 2
0
Particles (|h|<1.0, all PT)
50
100
150
200
250
300
350
400
450
PT(jet#1) (GeV/c)
JIMMY: MPI
J. M. Butterworth
J. R. Forshaw
MidPoint R = 0.7 |h(jet#1) < 2
M. H. Seymour
"TransMIN" ETsum Density: dET/dhd
3.0
"Transverse" ETsum Density (GeV)
dETsum/dhd, in the “transMAX”
and “transMIN” region (all particles
|h| < 1) versus PT(jet#1) for
“Leading Jet” and “Back-to-Back”
events.
Compares the (corrected) data with
PYTHIA Tune A (with MPI) and a
tuned version of JIMMY (with MPI,
PTJIM = 3.25 GeV/c, default = 2.5
GeV/c) at the particle level.
TeV4LHC - Fermilab
October 21, 2005
CDF Run 2 Preliminary
6.0
0.0
 Shows the ETsum density,

JIMMY was tuned to fit
the energy density in the
“transverse” region for
“leading jet” events!
CDF Run 2 Preliminary
data corrected to particle level
2.5
Particles (|h|<1.0, all PT)
1.96 TeV
JIM
2.0
"Leading Jet"
1.5
1.0
0.5
"Back-to-Back"
PY Tune A
0.0
0
50
100
Rick Field - Florida/CDF
150
200
250
300
350
400
450
PT(jet#1) (GeV/c)
Page 13
JIMMY at CDF
The Energy in the “Underlying
Event” in High PT Jet Production
Jet #1 Direction
JIMMY: MPI
J. M. Butterworth
J. R. Forshaw
M. H. Seymour

PT(JIM)= 2.5 GeV/c.
“Toward”
“Transverse”
“Transverse”
“Away”
2.0
PY Tune A
JM325
"Leading Jet"
1.0
CDF Run 2 Preliminary
MidPoint R = 0.7 |h(jet)| < 2
generator level theory
All Particles (|h|<1.0)
0
100
200
300
400
500
PT(particle jet#1) (GeV/c)
"Transverse" PTsum Density: dPT/dhd
Outgoing Parton
AntiProton
Underlying Event
Initial-State
Radiation
Final-State
Radiation
Outgoing Parton
“Transverse” <Densities> vs PT(jet#1)
"Transverse" PTsum Density (GeV/c)
1.6
PT(hard)
TeV4LHC - Fermilab
October 21, 2005
HW
3.0
0.0
“Hard” Scattering
Underlying Event
JIMMY Default
1.96 TeV
PT(JIM)= 3.25 GeV/c.
Proton
JIMMY was tuned to fit
the energy density in the
“transverse” region for
“leading jet” events!
"Transverse" ETsum Density: dET/dhd
4.0
"Transverse" ETsum Density (GeV)
JIMMY
Runs with HERWIG and adds
multiple parton interactions!
JIMMY Default
1.96 TeV
1.2
JM325
PY Tune A
0.8
"Leading Jet"
HW
0.4
MidPoint R = 0.7 |h(jet)| < 2
CDF Run 2 Preliminary
generator level theory
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
0.0
0
50
Rick Field - Florida/CDF
100
150
200
250
300
350
400
450
500
PT(particle jet#1) (GeV/c)
Page 14
“TransMAX/MIN” PTsum Density
PYTHIA Tune A vs JIMMY
“Leading Jet”
“Back-to-Back”
Jet #1 Direction
Jet #1 Direction
“TransMAX”
“TransMIN”
“Away”
"Transverse" PTsum Density (GeV/c)


“Toward”
"TransMAX" Charged PTsum Density: dPT/dhd
3.0
“Toward”
“TransMAX”
“TransMIN”
“Away”
Jet #2 Direction
TeV4LHC - Fermilab
October 21, 2005
"Leading Jet"
1.96 TeV
2.0
PY Tune A
1.5
"Back-to-Back"
1.0
MidPoint R = 0.7 |h(jet#1) < 2
0.5
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
0
50
100
150
200
250
300
350
400
450
PT(jet#1) (GeV/c)
"TransMIN" Charged PTsum Density: dPT/dhd
0.6
"Transverse" PTsum Density (GeV/c)

JIM
data corrected to particle level
0.0
 Shows the charged PTsum density,
dETsum/dhd, in the “transMAX”
and “transMIN” region (pT > 0.5
GeV/c, |h| < 1) versus PT(jet#1) for
“Leading Jet” and “Back-to-Back”
events.
Compares the (corrected) data with
PYTHIA Tune A (with MPI) and a
tuned version of JIMMY (with MPI,
PTJIM = 3.25 GeV/c) at the particle
level.
CDF Run 2 Preliminary
2.5
CDF Run 2 Preliminary
MidPoint R = 0.7 |h(jet#1) < 2
data corrected to particle level
0.5
1.96 TeV
JIM
"Leading Jet"
0.4
0.3
"Back-to-Back"
0.2
0.1
PY Tune A
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
0.0
0
50
Rick Field - Florida/CDF
100
150
200
250
300
350
400
450
PT(jet#1) (GeV/c)
Page 15
“TransMAX/MIN” Nchg Density
PYTHIA Tune A vs JIMMY
“Leading Jet”
“Back-to-Back”
Jet #1 Direction
Jet #1 Direction

“TransMAX”
“TransMIN”
“Away”
CDF Run 2 Preliminary
"Transverse" Charged Density

“Toward”
"TransMAX" Charged Particle Density: dN/dhd
1.4
“Toward”
“TransMAX”
“TransMIN”
“Away”
"Leading Jet"
data corrected to particle level
1.2
JIM
1.0
"Back-to-Back"
0.8
0.6
PY Tune A
MidPoint R = 0.7 |h(jet#1) < 2
0.4
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
1.96 TeV
Jet #2 Direction
0.2
 Shows the charged particle density,
TeV4LHC - Fermilab
October 21, 2005
50
100
150
200
250
300
350
400
450
PT(jet#1) (GeV/c)
"TransMIN" Charged Particle Density: dN/dhd
0.6
CDF Run 2 Preliminary
"Transverse" Charged Density

dNchg/dhd, in the “transMAX” and
“transMIN” region (pT > 0.5 GeV/c,
|h| < 1) versus PT(jet#1) for
“Leading Jet” and “Back-to-Back”
events.
Compares the (corrected) data with
PYTHIA Tune A (with MPI) and a
tuned version of JIMMY (with MPI,
PTJIM = 3.25 GeV/c) at the particle
level.
0
JIM
data corrected to particle level
0.5
MidPoint R = 0.7 |h(jet#1) < 2
1.96 TeV
0.4
"Leading Jet"
0.3
0.2
"Back-to-Back"
0.1
PY Tune A
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
0.0
0
50
Rick Field - Florida/CDF
100
150
200
250
300
350
400
450
PT(jet#1) (GeV/c)
Page 16
“Transverse” <PT>
PYTHIA Tune A vs JIMMY
“Leading Jet”
“Back-to-Back”
Jet #1 Direction
Jet #1 Direction
“TransMIN”
“Away”
"Transverse" Charged <PT> (GeV/c)
“TransMAX”
2.0


“Toward”
"Transverse" Charged Particle Mean PT
“Toward”
“TransMAX”
“TransMIN”
“Away”
Jet #2 Direction
"Leading Jet"
PY Tune A
1.96 TeV
1.5
1.0
"Back-to-Back"
HW
0
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
50
100
150
200
250
300
350
400
450
PT(jet#1) (GeV/c)
"Transverse" Charged Particle Mean PT
2.0
"Transverse" Charged <PT> (GeV/c)

MidPoint R = 0.7 |h(jet#1) < 2
data corrected to particle level
0.5
 Shows the charged particle <PT> in
the “transverse” region (pT > 0.5
GeV/c, |h| < 1) versus PT(jet#1) for
“Leading Jet” and “Back-to-Back”
events.
Compares the (corrected) data with
PYTHIA Tune A (with MPI) and
HERWIG and a tuned version of
JIMMY (with MPI, PTJIM = 3.25
GeV/c) at the particle level.
CDF Run 2 Preliminary
CDF Run 2 Preliminary
MidPoint R = 0.7 |h(jet#1) < 2
data corrected to particle level
"Leading Jet"
PY Tune A
1.96 TeV
1.5
1.0
"Back-to-Back"
JIM
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
0.5
0
50
100
150
200
250
300
350
400
450
PT(jet#1) (GeV/c)
TeV4LHC - Fermilab
October 21, 2005
Rick Field - Florida/CDF
Page 17
“Transverse” PTsum Density
PYTHIA Tune A vs JIMMY
Jet #1 Direction

“Toward”
“Transverse”
“Transverse”
“Away”
“Back-to-Back”
"Transverse" Charged PTsum Density: dPT/dhd
Jet #1 Direction

2.0
"Transverse" PTsum Density (GeV/c)
“Leading Jet”
“Toward”
“Transverse”
“Transverse”
“Away”
Jet #2 Direction
1.96 TeV
"Leading Jet"
PY Tune A
1.2
0.8
"Back-to-Back"
0.4
MidPoint R = 0.7 |h(jet#1) < 2
HW
0
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
50
100
150
200
250
300
350
400
450
PT(jet#1) (GeV/c)
"Transverse" Charged PTsum Density: dPT/dhd
2.0
"Transverse" PTsum Density (GeV/c)

data corrected to particle level
1.6
0.0
 Shows the charged PTsum density in
the “transverse” region (pT > 0.5
GeV/c, |h| < 1) versus PT(jet#1) for
“Leading Jet” and “Back-to-Back”
events.
Compares the (corrected) data with
PYTHIA Tune A (with MPI) and
HERWIG and a tuned version of
JIMMY (with MPI, PTJIM = 3.25
GeV/c) at the particle level.
CDF Run 2 Preliminary
CDF Run 2 Preliminary
JIM
data corrected to particle level
1.6
1.96 TeV
"Leading Jet"
PY Tune A
1.2
0.8
"Back-to-Back"
0.4
MidPoint R = 0.7 |h(jet#1) < 2
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
0.0
0
50
100
150
200
250
300
350
400
450
PT(jet#1) (GeV/c)
TeV4LHC - Fermilab
October 21, 2005
Rick Field - Florida/CDF
Page 18
Summary
 Particle Level Data: CDF has new data on the
“underlying event” that is corrected to the particle level
so that it can be used to tune the QCD Monte-Carlo
models without requiring CDF detector simulation!
“Hard” Scattering
Outgoing Parton
PT(hard)
Proton
AntiProton
Underlying Event
Underlying Event
Initial-State
Radiation
Final-State
Radiation
Outgoing Parton
 Interesting Physics: We see interesting dependence of the “underlying event” on the
transverse momentum of the leading jet (i.e. the Q2 of the hard scattering). For the
“leading jet” case the “transMAX” densities rise with increasing PT(jet#1), while for the
“back-to-back” case they fall. The rise in the “leading jet” case is due to hard initial and
final-state radiation, which has been suppressed in the “back-to-back” events. The “backto-back” data show a decrease in the “transMIN” densities with increasing PT(jet#1)
which is very interesting.
 PYTHIA Tune A does not produce enough energy in the “underlying event”! JIMMY 325
(PTJIM = 3.25 GeV/c) fits the energy in the “underlying event” but does so by producing
too many particles (i.e. it is too soft).
 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 “underlying event”!
TeV4LHC - Fermilab
October 21, 2005
Rick Field - Florida/CDF
Page 19
The Future
Much more QCD physics to
come from the Tevatron!
Some CDF-QCD Group Analyses!
 Jet Cross Sections and Correlations: MidPoint and KT algorithms
with L = 1 fb-1!
 DiJet Mass Distributions:  distribution, compositness.
 Heavy Flavor Jets: b-jet and b-bbar jet cross sections and
correlations.
 Z and W Bosons plus Jets: including b-jets.
 Jets Fragmentation: jet shapes, momentum distributions, twoparticle correlations.
 Underlying Event Studies: distributions as well as averages for
charged particles and energy for jet, jet+jet, g+jet, Z+jet, and
Drell-Yan.
 Pile-Up Studies: modeling of pile-up.
 Monte-Carlo Tuning: New Run 2 PYTHIA tune?, tuned JIMMY,
PYTHIA 6.3, Sherpa, etc..
Analyses using 1fb-1 of data by Winter 2006!
TeV4LHC - Fermilab
October 21, 2005
Rick Field - Florida/CDF
Page 20