The “Underlying Event”
in Run 2 at CDF
The “underlying event” consists of
hard initial & final-state radiation
plus the “beam-beam remnants” and
possible multiple parton interactions.
CERN MC4LHC Workshop
Outgoing Parton
July 2003
During the workshop the theorists, ATLAS/CMS
Proton
experimenters, and I constructed a “wish list” of data
Underlying Event
from CDF relating to “min-bias” and the
“underlying event” and I promisedMuch
to do themore
analysisnew Run 2
and make the data available.
PT(hard)
Initial-State Radiation
AntiProton
Underlying Event
results than I can show here!
I will show a few plots
New CDF Run 2 results! of each type and give a
 Two Classes of Events:preview
“LeadingofJet”
andto“Back-to-Back”.
more
come!
Outgoing Parton





Final-State
Radiation
Two “Transverse” regions: “transMAX”, “transMIN”, “transDIF”.
PTmax and PTmaxT distributions and averages.
Df Distributions: “Density” and “Associated Density”.
<pT> versus charged multiplicity: “min-bias” and the “transverse” region.
Correlations between the two “transverse” regions: “trans1” vs “trans2”.
HERA/LHC Workshop
October 11, 2004
Rick Field - Florida/CDF
Page 1
The “Transverse” Regions
as defined by the Leading Jet
Jet #1 Direction
“Transverse” region is
very sensitive to the
“underlying event”!
Charged Particle Df Correlations
2p
pT > 0.5 GeV/c |h| < 1
Away Region
“Toward-Side” Jet
Df
Look at the charged
particle density in the
“transverse” region!
Jet #1 Direction
Transverse
Region 1
Df
“Toward”
“Toward”
“Transverse”
“Transverse”
“Away”
“Trans 1”
f
Leading
Jet
“Trans 2”
Toward Region
Transverse
Region 2
“Away”
“Away-Side” Jet
Away Region
0
-1
h
+1
 Look at charged particle correlations in the azimuthal angle Dfrelative to the leading

calorimeter jet (JetClu R = 0.7, |h| < 2).
o
o
o
o
o
Define |Df| < 60 as “Toward”, 60 < -Df < 120 and 60 < Df < 120 as “Transverse 1” and
o
“Transverse 2”, and |Df| > 120 as “Away”. Each of the two “transverse” regions have
o
area DhDf = 2x60 = 4p/6. The overall “transverse” region is the sum of the two
o
transverse regions (DhDf = 2x120 = 4p/3).
HERA/LHC Workshop
October 11, 2004
Rick Field - Florida/CDF
Page 2
Charged Particle Density
Df Dependence Run 2
Charged Particle Density: dN/dhdf
Log Scale!
Jet #1 Direction
10.0
30 < ET(jet#1) < 70 GeV
Df
“Toward”
“Transverse”
“Transverse”
Jet #3
“Away”
Charged Particle Density
CDF Preliminary
“Toward-Side” Jet
data uncorrected
"Transverse"
Region
1.0
Jet#1
Charged Particles
(|h|<1.0, PT>0.5 GeV/c)
“Away-Side”
“Away-Side”
Jet Jet
0.1
0
30
60
90
Min-Bias
0.25 per unit h-f
120
150
180
210
Df (degrees)
240
270
300
Leading Jet
330
360
 Shows the Df dependence of the charged particle density, dNchg/dhdf, for charged
particles in the range pT > 0.5 GeV/c and |h| < 1 relative to jet#1 (rotated to 270o) for
“leading jet” events 30 < ET(jet#1) < 70 GeV.
 Also shows charged particle density, dNchg/dhdf, for charged particles in the range pT >
0.5 GeV/c and |h| < 1 for “min-bias” collisions.
HERA/LHC Workshop
October 11, 2004
Rick Field - Florida/CDF
Page 3
Refer to this as a
“Leading Jet” event
Charged Particle Density
Df Dependence Run 2
Jet #1 Direction
Df
Particle Density:
Density: dN/dhdf
dN/dhdf
Charged Particle
“Toward”
“Transverse”
CDF Preliminary
“Transverse”
“Away”
Refer to this as a
“Back-to-Back” event
Jet #1 Direction
Df
“Toward”
“Transverse”
Density
Charged Particle Density
Subset
10.0
10.0
data uncorrected
30 << ET(jet#1)
ET(jet#1)<<70
70GeV
GeV
30
Back-to-Back
Leading Jet
Min-Bias
"Transverse"
"Transverse"
Region
Region
1.0
1.0
Jet#1
Jet#1
Charged Particles
Charged
(|h|<1.0, PT>0.5 GeV/c)
(|h|<1.0,
“Transverse”
0.1
0.1
“Away”
00
30
60
90
120
150
180
180
210
210
240
240
270
270
300
300
330
330 360
360
Df (degrees)
(degrees)
Jet #2 Direction
 Look at the “transverse” region as defined by the leading jet or by the leading two jets

(JetClu R = 0.7, |h| < 2). “Back-to-Back” events are selected to have at least two jets
with ET > 15 GeV with Jet#1 and Jet#2 nearly “back-to-back” (Df12 > 150o) with almost
equal transverse energies (ET(jet#2)/ET(jet#1) > 0.8) and with ET(jet#3) < 15 GeV.
Shows the Df dependence of the charged particle density, dNchg/dhdf, 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.
HERA/LHC Workshop
October 11, 2004
Rick Field - Florida/CDF
Page 4
“Transverse” PTsum Density
versus ET(jet#1) Run 2
Jet #1 Direction
Df
“Toward”
“Transverse”
“Transverse”
“Away”
“Back-to-Back”
Jet #1 Direction
Df
“Toward”
“Transverse”
"AVE Transverse" PTsum Density: dPT/dhdf
1.4
“Transverse”
"Transverse" PTsum Density (GeV/c)
“Leading Jet”
uncorrected
datadata
uncorrected
theory + CDFSIM
PY Tune A
1.0
0.8
0.6
0.4
Back-to-Back
HW
0.2
1.96 TeV
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
0.0
0
50
“Away”
Jet #2 Direction
Leading Jet
2 Preliminary
CDF Run
Preliminary
1.2
100
150
200
250
ET(jet#1) (GeV)
Min-Bias
0.24 GeV/c per unit h-f
 Shows the average charged PTsum density, dPTsum/dhdf, in the “transverse” region (pT
> 0.5 GeV/c, |h| < 1) versus ET(jet#1) for “Leading Jet” and “Back-to-Back” events.
 Compares the (uncorrected) data with PYTHIA Tune A and HERWIG after CDFSIM.
HERA/LHC Workshop
October 11, 2004
Rick Field - Florida/CDF
Page 5
“TransMIN” PTsum Density
versus ET(jet#1)
“Leading Jet”
Jet #1 Direction
Df
"MIN Transverse" PTsum Density: dPT/dhdf
“Toward”
“TransMAX”
"Transverse" PTsum Density (GeV/c)
0.6
CDF Run 2 Preliminary
Jet #1 Direction
“TransMIN”
“Away”
1.96 TeV
data uncorrected
theory + CDFSIM
Df
Leading Jet
Jet
Leading
PY Tune A
0.4
“Toward”
“Back-to-Back”
Jet #1 Direction
Df
“Toward”
“TransMAX”
“TransMIN”
“Away”
Jet #2 Direction
“TransMAX”
0.2
“TransMIN”
Min-Bias
“Away”
Back-to-Back
Back-to-Back
HW
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
0.0
0
50
“transMIN” is very sensitive to the
“beam-beam remnant” component
of the “underlying event”!
100
150
200
250
ET(jet#1) (GeV)
 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 particle density.
 Shows the “transMIN” charge particle density, dNchg/dhdf, for pT > 0.5 GeV/c, |h| < 1
versus ET(jet#1) for “Leading Jet” and “Back-to-Back” events.
HERA/LHC Workshop
October 11, 2004
Rick Field - Florida/CDF
Page 6
“Transverse” PTsum Density
PYTHIA Tune A vs HERWIG
“Leading Jet”
Jet #1 Direction
Df
"AVE Transverse" PTsum Density: dPT/dhdf
“Toward”
“Transverse”
“Transverse”
“Away”
“Back-to-Back”
Jet #1 Direction
Df
“Toward”
“Transverse”
“Transverse”
"Transverse" PTsum Density (GeV/c)
1.4
Leading Jet
CDF Preliminary
1.2
data uncorrected
theory + CDFSIM
PY Tune A
1.0
0.8
0.6
0.4
Back-to-Back
HW
0.2
1.96 TeV
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
0.0
0
50
100
150
200
250
ET(jet#1) (GeV)
“Away”
Jet #2 Direction
Now look in detail at “back-to-back” events in
the region 30 < ET(jet#1) < 70 GeV!
 Shows the average charged PTsum density, dPTsum/dhdf, in the “transverse” region (pT

> 0.5 GeV/c, |h| < 1) versus ET(jet#1) for “Leading Jet” and “Back-to-Back” events.
Compares the (uncorrected) data with PYTHIA Tune A and HERWIG after CDFSIM.
HERA/LHC Workshop
October 11, 2004
Rick Field - Florida/CDF
Page 7
Charged PTsum Density
PYTHIA Tune A vs HERWIG
HERWIG (without multiple parton
interactions) does not produces
enough PTsum in the “transverse”
region for 30 < ET(jet#1) < 70 GeV!
Charged PTsum Density: dPT/dhdf
Charged PTsum Density: dPT/dhdf
100.0
Charged Particles
30 < ET(jet#1) < 70 GeV
(|h|<1.0, PT>0.5 GeV/c)
Back-to-Back
PY Tune A
Charged PTsum Density (GeV/c)
Charged PTsum Density (GeV/c)
100.0
10.0
1.0
CDF Preliminary
Jet#1
"Transverse"
Region
data uncorrected
theory + CDFSIM
Charged Particles
30 < ET(jet#1) < 70 GeV
(|h|<1.0, PT>0.5 GeV/c)
Back-to-Back
HERWIG
10.0
"Transverse"
Region
1.0
CDF Preliminary
0.1
0.1
0
30
60
90
120
150
180
210
240
270
300
330
360
0
30
60
90
120
Df (degrees)
150
180
210
240
270
300
330
360
330
360
Df (degrees)
Data - Theory: Charged PTsum Density dPT/dhdf
Data - Theory: Charged PTsum Density dPT/dhdf
2
2
data uncorrected
theory + CDFSIM
1
Back-to-Back
30 < ET(jet#1) < 70 GeV
PYTHIA Tune A
CDF Preliminary
Data - Theory (GeV/c)
CDF Preliminary
Data - Theory (GeV/c)
Jet#1
data uncorrected
theory + CDFSIM
0
-1
"Transverse"
Region
Charged Particles
(|h|<1.0, PT>0.5 GeV/c)
data uncorrected
theory + CDFSIM
1
30 < ET(jet#1) < 70 GeV
Back-to-Back
HERWIG
0
-1
"Transverse"
Region
Charged Particles
(|h|<1.0, PT>0.5 GeV/c)
Jet#1
Jet#1
-2
-2
0
30
60
90
120
150
180
210
240
270
300
330
360
0
30
90
120
150
180
210
240
270
300
Df (degrees)
Df (degrees)
HERA/LHC Workshop
October 11, 2004
60
Rick Field - Florida/CDF
Page 8
Summary
“Leading Jet”
Jet #1 Direction
Jet #1 Direction
Df
“Back-to-Back”
Df
“Toward”
“Toward”
“Transverse”
“Transverse”
“Transverse”
“Transverse”
“Away”
“Away”
Jet #2 Direction
 “Back-to-Back” events have less “hard scattering” (initial and final state
radiation) component in the “transverse” region which allows for a closer look at
the “beam-beam remnant” and multiple parton scattering component of the
“underlying” event.
 PYTHIA Tune A (with multiple parton scattering) does a much better job in
describing the “back-to-back” events than does HERWIG (without multiple
parton scattering).
HERA/LHC Workshop
October 11, 2004
Rick Field - Florida/CDF
Page 9
Min-Bias “Associated”
Highest pT
charged particle!
Charged Particle Density
“Associated” densities do
not include PTmax!
Charged Particle Density: dN/dhdf
PTmax Direction
0.5
PTmax
Direction
Df
Correlations in f
Charged Particle Density
CDF Preliminary
Associated Density
PTmax not included
data uncorrected
0.4
Df
Charge Density
0.3
0.2
0.1
Min-Bias
Correlations
in f
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
Df (degrees)
 Use the maximum pT charged particle in the event, PTmax, to define a direction and

is “associated”
more probable
to finddN
a chg
particle
look at the It
the
density,
/dhdf, in “min-bias” collisions (pT > 0.5
PTmax than it is to
GeV/c, |h| <accompanying
1).
find a particle in the central region!
Shows the data on the Df dependence of the “associated” charged particle density,
dNchg/dhdf, 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/dhdf, for “min-bias” events.
HERA/LHC Workshop
October 11, 2004
Rick Field - Florida/CDF
Page 10
Min-Bias “Associated”
Rapid rise in the particle
density in the “transverse”
region as PTmax increases!
Charged Particle Density
Associated Particle Density: dN/dhdf
PTmaxDirection
Direction
PTmax
Df
“Toward”
“Transverse”
“Transverse”
Correlations in f
“Away”
Associated Particle Density
Jet #1
Df
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
Df (degrees)
Ave Min-Bias
0.25 per unit h-f
PTmax > 0.5 GeV/c
 Shows the data on the Df dependence of the “associated” charged particle density,
dNchg/dhdf, 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!).
HERA/LHC Workshop
October 11, 2004
Rick Field - Florida/CDF
Page 11
Back-to-Back “Associated”
Charged Particle Densities
Maximum pT particle in
the “transverse” region!
Jet #1 Direction
PTmaxT
Direction
“Associated” densities do
not include PTmaxT!
Df
Df
“Toward”
“TransMAX”
PTmaxT
“TransMIN”
Df
PTmaxT
Direction
Jet#1
Region
Jet#2
Region
Jet#1
Region
Jet#2
Region
“Away”
Jet #2 Direction
 Use the leading jet in “back-to-back” events to define the “transverse” region and look
at the maximum pT charged particle in the “transverse” region, PTmaxT.
 Look at the Df dependence of the “associated” charged particle and PTsum densities,
dNchg/dhdf and dPTsum/dhdf for charged particles (pT > 0.5 GeV/c, |h| < 1, not including
PTmaxT) relative to PTmaxT.
 Rotate so that PTmaxT is at the center of the plot (i.e. 180o).
HERA/LHC Workshop
October 11, 2004
Rick Field - Florida/CDF
Page 14
Back-to-Back “Associated”
Charged Particle Density
“Associated” densities do
not include PTmaxT!
PTmaxT
Direction
Jet #1
Jet#1
Region
Associated Particle Density
Df
Jet #2
Charged Particles
(|h|<1.0, PT>0.5 GeV/c)
CDF Preliminary
Jet #3
Jet#2
Region
Associated Particle Density: dN/dhdf
10.0
data uncorrected
Back-to-Back
30 < ET(jet#1) < 70 GeV
PTmaxT not included
1.0
Jet#2
Region
PTmaxT > 2.0 GeV/c
PTmaxT > 1.0 GeV/c
Jet #4??
"Jet#1"
Region
PTmaxT
PTmaxT > 0.5 GeV/c
0.1
0
30
60
90
120
150
180
210
240
270
300
330
360
Df (degrees)
Log Scale!
 Look at the Df dependence of the “associated” charged particle density, dNchg/dhdf for
charged particles (pT > 0.5 GeV/c, |h| < 1, not including PTmaxT) relative to PTmaxT
(rotated to 180o) for PTmaxT > 0.5 GeV/c, PTmaxT > 1.0 GeV/c and PTmaxT > 2.0
GeV/c, for “back-to-back” events with 30 < ET(jet#1) < 70 GeV .
 Shows “jet structure” in the “transverse” region (i.e. the “birth” of the 3rd & 4th jet).
HERA/LHC Workshop
October 11, 2004
Rick Field - Florida/CDF
Page 15
Jet Topologies
QCDThree
Four
Jet
QCD
Jet Topology
Topology Charged Particle Density: dN/dhdf
QCD
2-to-4
Scattering
Multiple Parton Interactions
2
Preliminary
CDF
Final-State
Jet #1
data uncorrected
Radiation
Outgoing Parton
346
10
14
30 < ET(jet#1) < 70 GeV
Outgoing Parton
Outgoing PartonBack-to-Back
18
30
34
38
326
42
322
46
318
Jet #1
PT(hard)
50
54
Jet#1
306
58
PT(hard)
302
298
PTmaxT
Proton
Direction
Proton
6
358
26
330
310
Jet #3Df
354
22
334
314
Jet#1
Region
350
342
338
62
66
70
294
Jet #4
74
290
78
286
Jet #4
AntiProton
AntiProton
"Transverse"
Jet #3
Region
282
278
274
Jet#2
Region
Underlying Event
Underlying Event
PTmaxT
270
86
90
94
98
266
Underlying Event
102
262
Jet #2
0.5
258
Underlying Event
106
254
110
Jet #2
250
114
1.0
246
118
126
238
1.5
234
230
130
134
138
226
Particles
ChargedFinal-State
GeV/c)
(|h|<1.0, PT>0.5
Radiation
Associated Density
PTmaxT > 2 GeV/c
(not included)
142
222
2.0
218
214
146
150
154
210
Polar Plot
Initial-State
Radiation
122
242

82
"Transverse"
Region
158
206
162
202
198
194
190
178
186
174
170
166
182
Parton
Outgoing
Outgoing
Shows the Df dependence
ofParton
the “associated” charged particleOutgoing
density,Parton
dNchg/dhdf, pT > 0.5
GeV/c, |h| < 1, PTmaxT > 2.0 GeV/c (not including PTmaxT) relative to PTmaxT (rotated to
180o) and the charged particle density, dNchg/dhdf, pT > 0.5 GeV/c, |h| < 1, relative to jet#1
(rotated to 270o) for “back-to-back events” with 30 < ET(jet#1) < 70 GeV.
HERA/LHC Workshop
October 11, 2004
Rick Field - Florida/CDF
Page 17
“Associated” Charge Density
PYTHIA Tune A vs HERWIG
HERWIG (without multiple parton
interactions) too few “associated”
particles in the direction of PTmaxT!
Associated Particle Density: dN/dhdf
Associated Particle Density: dN/dhdf
10.0
10.0
data uncorrected
theory + CDFSIM
Charged Particles
(|h|<1.0, PT>0.5 GeV/c)
PTmaxT not included
CDF Preliminary
Back-to-Back
30 < ET(jet#1) < 70 GeV
Associated Particle Density
Associated Particle Density
CDF Preliminary
1.0
PTmaxT > 0.5 GeV/c
PY Tune A
PTmaxT
"Jet#1"
Region
0.1
data uncorrected
theory + CDFSIM
Charged Particles
(|h|<1.0, PT>0.5 GeV/c)
PTmaxT not included
1.0
PTmaxT
PTmaxT > 0.5 GeV/c
HERWIG
"Jet#1"
Region
0.1
0
30
60
90
120
150
180
210
240
270
300
330
360
0
30
60
90
120
Df (degrees)
And HERWIG (without multiple
parton interactions) too few particles
1.0
Back-to-Back
in Tune
the direction
opposite of PTmaxT!
PYTHIA
A
1.0
CDF Preliminary
0.0
-0.5
CDF Preliminary
240
270
300
330
360
PTmaxT
Charged Particles
(|h|<1.0, PT>0.5 GeV/c)
PTmaxT not included
"Jet#1"
Region
-1.0
Back-to-Back
30 < ET(jet#1) < 70 GeV
0.0
-0.5
Charged Particles
(|h|<1.0, PT>0.5 GeV/c)
PTmaxT not included
210
HERWIG
data uncorrected
theory + CDFSIM
0.5
Data - Theory
0.5
180
Data - Theory: Associated Particle Density dN/dhdf
30 < ET(jet#1) < 70 GeV
data uncorrected
theory + CDFSIM
150
Df (degrees)
Data - Theory: Associated Particle Density dN/dhdf
Data - Theory
Back-to-Back
30 < ET(jet#1) < 70 GeV
PTmaxT
"Jet#1"
Region
-1.0
0
30
60
90
120
150
180
210
240
270
300
330
360
0
30
Df (degrees)
HERA/LHC Workshop
October 11, 2004
60
90
120
150
180
210
240
270
300
330
360
Df (degrees)
Rick Field - Florida/CDF
Page 18
“Associated” Charge Density
PYTHIA Tune A vs HERWIG
For PTmaxT > 2.0 GeV both
PYTHIA and HERWIG produce
slightly too many “associated”
particles in the direction of PTmaxT!
Associated Particle Density: dN/dhdf
Associated Particle Density: dN/dhdf
10.0
10.0
data uncorrected
theory + CDFSIM
1.0
Charged Particles
(|h|<1.0, PT>0.5 GeV/c)
PTmaxT not included
data uncorrected
theory + CDFSIM
Charged Particles
(|h|<1.0, PT>0.5 GeV/c)
PTmaxT not included
1.0
PTmaxT
"Jet#1"
Region
PTmaxT
PTmaxT > 2.0 GeV/c
HERWIG
"Jet#1"
Region
0.1
0
30
60
90
120
150
180
210
240
270
300
330
360
0
30
60
90
120
Df (degrees)
1.6
150
180
210
240
270
300
330
360
Df (degrees)
1.0
PYTHIA Tune A
direction
data uncorrected
theory + CDFSIM
Back-to-Back
opposite
of PTmaxT!
30 < ET(jet#1)
< 70 GeV
0.0
-0.8
data uncorrected
theory + CDFSIM
0.5
Data - Theory
0.8
Data - Theory
Back-to-Back
30 < ET(jet#1) < 70 GeV
Next Step
Look at the jet topologies
(2 jet vs 3 jet vs 4 jet etc).
See if there is an excess of
But HERWIG
(without
multipledue to multiple
4
jet
events
parton
interactions)
produces
Data - Theory: Associated Particle Density dN/dhdf
Data - Theory: Associated
Particle
Density dN/dhdf
too few particles
in the interactions!
parton
CDF Preliminary
CDF Preliminary
PTmaxT > 2.0 GeV/c
PY Tune A
0.1
CDF Preliminary
Back-to-Back
30 < ET(jet#1) < 70 GeV
Associated Particle Density
Associated Particle Density
CDF Preliminary
HERWIG
0.0
-0.5
Charged Particles
PTmaxT
(|h|<1.0, PT>0.5 GeV/c)
PTmaxT > 2.0 GeV/c (not included)
Back-to-Back
30 < ET(jet#1) < 70 GeV
Charged Particles
(|h|<1.0, PT>0.5 GeV/c)
"Jet#1"
Region
PTmaxT
"Jet#1"
Region
PTmaxT > 2.0 GeV/c (not included)
-1.6
-1.0
0
30
60
90
120
150
180
210
240
270
300
330
360
0
30
Df (degrees)
HERA/LHC Workshop
October 11, 2004
60
90
120
150
180
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300
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Df (degrees)
Rick Field - Florida/CDF
Page 20
Summary
Max pT in the
“transverse” region!
“Associated” densities do
not include PTmaxT!
Jet #1 Direction
Df
PTmaxT
Direction
PTmax Direction
Df
“Toward”
“TransMAX”
PTmaxT
“TransMIN”
Jet#2
Region
“Away”
Df
Jet#1
Region
Correlations in f
Jet #2 Direction
 The “associated” densities show strong correlations (i.e. jet structure) in the
“transverse” region both for “Leading Jet” and “Back-to-Back” events.
 The “birth” of the 1st jet in “min-bias” collisions looks very similar to the
“birth” of the 3rd jet in the “transverse” region of hard scattering “Back-toBack” events.
Question: Is the topology
3 jet or 4 jet?
HERA/LHC Workshop
October 11, 2004
Rick Field - Florida/CDF
Page 22
“Transverse” <pT> versus
“Transverse” Nchg
“Leading Jet”
Jet #1 Direction
"Transverse" Average PT versus Nchg
Df
2.0
2.0
CDF Run 2 Preliminary
“Toward”
CDF Run 2 Preliminary
Jet #1 Direction
data uncorrected
“Transverse”
“Away”
“Back-to-Back”
Jet #1 Direction
Df
“Toward”
“Transverse”
“Transverse”
Average PT (GeV/c)
data uncorrected
“Transverse”
Df
LeadingJet
Jet
Leading
ET(jet#1)< <7070GeV
GeV
3030< <ET(jet#1)
theory + CDFSIM
1.96
TeV
1.5
1.5
Back-to-Back
Back-to-Back
30
30<<ET(jet#1)
ET(jet#1)<<70
70GeV
GeV
“Toward”
1.0
1.0
“Transverse”
“Transverse”
PYTHIA Tune A 1.96 TeV
Min-Bias
Min-Bias
“Away”
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
0.5
0.5
00
22
44
6
8
10
12
14
16
18
20
22
Number of Charged Particles
“Away”
Min-Bias
Jet #2 Direction
 Look at the <pT> of particles in the “transverse” region (pT > 0.5 GeV/c, |h| < 1) versus
the number of particles in the “transverse” region: <pT> vs Nchg.
 Shows <pT> versus Nchg in the “transverse” region (pT > 0.5 GeV/c, |h| < 1) for “Leading
Jet” and “Back-to-Back” events with 30 < ET(jet#1) < 70 GeV compared with “minbias” collisions.
HERA/LHC Workshop
October 11, 2004
Rick Field - Florida/CDF
Page 23
“Transverse 1” Region vs
“Transverse 2” Region
Jet #1 Direction
Df
Jet #1 Direction
“Toward”
“Trans 1”
“Trans 2”
“Away”
“Back-to-Back”
Jet #1 Direction
Df
“Toward”
“Trans 1”
"Transverse 1" vs "Transverse 2"
3.5
1.8
“Trans 2”
"Transverse
"Transverse
2" <PT>
2" Nchg
(GeV/c)
“Leading Jet”
CDF
CDFRun
Run22Preliminary
Preliminary 3030< <ET(jet#1)
ET(jet#1)< <7070GeV
GeV
Df
3.0
1.6
data
datauncorrected
uncorrected
2.5
1.4
Leading Jet
Leading Jet
1.96 TeV
“Toward”
2.0
1.2
“Trans1.51”
“Trans 2”
1.96 TeV
1.0
1.0
Back-to-Back
Back-to-Back
Charged
ChargedParticles
Particles(|h|<1.0,
(|h|<1.0,PT>0.5
PT>0.5GeV/c)
GeV/c)
“Away”
0.5
0.8
0
2
4
6
8
10
12
14
"Transverse 1" Nchg
“Away”
Jet #2 Direction
 Use the leading jet to define two “transverse” regions and look at the correlations
between “transverse 1” and “transverse 2”.
 Shows the average
of charged
particles
the “transverse
2” region
average number
pT of charged
particles
in thein“transverse
2” region
versusversus
the the
number of charged particles in the “transverse 1” region for pTT > 0.5 GeV/c and |h| < 1
for “Leading Jet” and “Back-to-Back” events.
HERA/LHC Workshop
October 11, 2004
Rick Field - Florida/CDF
Page 24
“Transverse 1” Region vs
“Transverse 2” Region
"Transverse 1" vs "Transverse 2"
"Transverse 1" vs "Transverse 2"
3.5
3.0
"Transverse 2" Nchg
3.0
data uncorrected
theory + CDFSIM
Leading Jet
30 < ET(jet#1) < 70 GeV
CDF Run 2 Preliminary
"Transverse 2" Nchg
CDF Run 2 Preliminary
PY Tune A
2.5
1.96 TeV
2.0
HW
1.5
data uncorrected
theory + CDFSIM
2.5
PY Tune A
2.0
1.5
HW
1.0
1.0
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
0.5
0.5
0
2
4
6
8
10
12
14
0
2
4
"Transverse 1" Nchg
6
8
10
12
"Transverse 1" Nchg
"Transverse 1" vs "Transverse 2"
"Transverse 1" vs "Transverse 2"
1.8
1.50
CDF Run 2 Preliminary
data uncorrected
theory + CDFSIM
1.6
PY Tune A
1.96 TeV
1.4
Leading Jet
30 < ET(jet#1) < 70 GeV
"Transverse 2" <PT> (GeV/c)
"Transverse 2" <PT> (GeV/c)
Back-to-Back
30 < ET(jet#1) < 70 GeV
1.2
HW
1.0
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
CDF Run 2 Preliminary
data uncorrected
theory + CDFSIM
1.25
Back-to-Back
30 < ET(jet#1) < 70 GeV
1.00
PY Tune A
0.75
HW
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
0.8
0.50
0
2
4
6
8
10
12
14
0
"Transverse 1" Nchg
HERA/LHC Workshop
October 11, 2004
2
4
6
8
10
12
"Transverse 1" Nchg
Rick Field - Florida/CDF
Page 25
Summary
“Leading Jet”
Jet #1 Direction
Df
Jet #1 Direction
“Back-to-Back”
“Toward”
“Toward”
“Trans 1”
Df
“Trans 1”
“Trans 2”
“Trans 2”
“Away”
“Away”
Jet #2 Direction
 There are some interesting correlations between the “transverse 1” and
“transverse 2” regions both for “Leading-Jet” and “Back-to-Back” events!
 PYTHIA Tune A (with multiple parton scattering) does a much better job in
describing these correlations than does HERWIG (without multiple parton
scattering).
Question: Is this a probe of
multiple parton interactions?
HERA/LHC Workshop
October 11, 2004
Rick Field - Florida/CDF
Page 26
The Universality of
PYTHIA Tune A
DirectZ-boson
Photon
Production
“Hard”
Scattering
Production
Multiple
Parton
Interactions
“Flavor
Creation”
Photon
Z-boson
Outgoing
Parton
Outgoing
Parton
b-quark
 We would like to have a
PT()
PT(hard)
PT(hard)
PT(Z)
“universal” tune of PYTHIA!
 QCD Hard Scattering
 Direct Photon Production
 Z-Boson Production
 Heavy Flavor Production
Proton
Proton
Proton
Proton
AntiProton
AntiProton
AntiProton
AntiProton
Underlying
UnderlyingEvent
Event
Underlying
Event
Underlying Event
Underlying
Event
Underlying
Event
Underlying
Event
Underlying Event
Initial-State
Initial-State
Initial-State
Radiation
Radiation
Radiation
b-quark
Outgoing
Parton
Final-State
Radiation
Radiation
Outgoing Parton
 I working on a “universal” PYTHIA Run 2 tune!




Must specify the PDF!
Must specify MPI parameters!
Must specify Q2 scale!
Must specify intrinsic kT!
HERA/LHC Workshop
October 11, 2004
Rick Field - Florida/CDF
Page 27
New CDF Run 2 Analysis
Photon and Z-boson
Refer to this as a
“Leading Photon” event
Refer to this as a
“Leading Jet” event
Jet #1 Direction
Df
“Toward”
“Transverse”
“Transverse”
“Away”
Z-boson
Direction
Photon #1
Direction
Df
Df
“Toward”
“Transverse”
“Transverse”
“Away”
Refer to this as a “Zboson” event
“Toward”
“Transverse”
“Transverse”
“Away”
 Study the Df distribution of the charged particle density, dNchg/dhdf, and the charged
scalar pT sum density, dPTsum/dhdf, for charged particles in the region pT > 0.5 GeV/c,
|h| < 1) in “leading jet” events. and “leading photon” events! and “Z-boson” events!
 Study the average charged particle and PTsum density in the “toward”, “transverse”, and
“away” regions versus ET(jet#1) in “leading jet” events.and “leading photon” events!
and “Z-boson” events!
HERA/LHC Workshop
October 11, 2004
Rick Field - Florida/CDF
Page 28
Charged Particle Density
Df Dependence
rdfsoft!
PY Tune A
Jet #1 Direction
Df
Charged Particle Density: dN/dhdf
“Toward”
“Transverse”
10.0
RDF Preliminary
“Transverse”
Leading Jet
“Away”
Photon #1
Direction
Df
“Toward”
“Transverse”
“Transverse”
Z-boson
Direction
Df
“Away”
Charged Particle Density
PYTHIA Tune A
Z-boson
1.0
“Toward”
“Transverse”
Leading Photon
Charged Particles
(|h|<1.0, PT>0.5 GeV/c)
“Transverse”
Jet#1
Photon
Z-boson
"Transverse"
Region
0.1
“Away”
0
30
60
90
120
150
180
210
240
270
300
330
360
Df (degrees)
 Shows the Df dependence of the density, dNchg/dhdf, for charged particles in the range


pT > 0.5 GeV/c and |h| < 1 relative to jet#1 (rotated to 270o) for ET(jet#1) > 30 GeV for
“Leading Jet” events from PYTHIA Tune A.
Shows the Df dependence of the density, dNchg/dhdf, for charged particles in the range
pT > 0.5 GeV/c and |h| < 1 relative to pho#1 (rotated to 270o) for PT(pho#1) > 30 GeV
for “Leading Photon” events from PYTHIA Tune A.
Shows the Df dependence of the density, dNchg/dhdf, for charged particles in the range
pT > 0.5 GeV/c and |h| < 1 relative to the Z (rotated to 270o) for PT(Z) > 30 GeV for “Zboson” events from PYTHIA Tune A.
HERA/LHC Workshop
October 11, 2004
Rick Field - Florida/CDF
Page 29
Summary
Outgoing Parton
Direct Photon Production
PT(hard)
Z-boson Production
Photon
PT()
Z-boson
PT(Z)
Initial-State Radiation
Proton
AntiProton
Underlying Event
Underlying Event
Proton
AntiProton
Underlying Event
Underlying Event
Proton
AntiProton
Underlying Event
Underlying Event
Initial-State
Radiation
Outgoing Parton
Final-State
Radiation
Initial-State
Radiation
Final-State
Radiation
Outgoing Parton
Final-State
Radiation
Outgoing Parton
 I am working on a “universal” PYTHIA Run 2 tune: QCD jets, direct photons,


Z and W bosons, Drell-Yan, heavy flavor production, etc..
I am just getting started, but so far I have seen no major problems with
PYTHIA Tune A except that I should have included a larger intrinsic kT (I used
the default).
In addition to specifying the PDF and the MPI parameters, one will have to
specify the Q2 scale for each process. For Tune A Q2 = 4pT2 for QCD jets and
direct photons and Q2 = Mz2 for Z-boson production.
HERA/LHC Workshop
October 11, 2004
Rick Field - Florida/CDF
Page 31