Physics and Techniques
of Event Generators
IPPP Durham, April 18-20, 2007
Min-Bias and the Underlying Event
at the TEVATRON and the LHC
Rick Field
University of Florida
(for the CDF & CMS Collaborations)
2nd Lecture
UE&MB@CMS
 A more detailed study of the
“underlying event” in Run 2 at
CDF. and extrapolations to the LHC.
Outgoing Parton
 Using lepton-pair production to
PT(hard)
Initial-State Radiation
Proton
study the “underlying event” in Run
CMS at the LHC
2 at CDF and the LHC.
CDF Run 2
MCnet07 - Durham - Part 2
April 18-20, 2007
Rick Field – Florida/CDF/CMS
AntiProton
Underlying Event
Outgoing Parton
Underlying Event
Final-State
Radiation
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  Correlations
pT > 0.5 GeV/c |h| < 1
2p
Look at the charged
particle density in the
“transverse” region!
Away Region
“Toward-Side” Jet
Jet #1 Direction

“Toward”
“Transverse”
“Transverse”
“Away”
Transverse
Region 1

“Toward”
“Trans 1”

Leading
Jet
“Trans 2”
Toward Region
Transverse
Region 2
“Away”
Away Region
“Away-Side” Jet
0
-1
h
+1
 Look at charged particle correlations in the azimuthal angle relative to the leading

calorimeter jet (JetClu R = 0.7, |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).
MCnet07 - Durham - Part 2
April 18-20, 2007
Rick Field – Florida/CDF/CMS
Page 2
Charged Particle Density 
Dependence
Log Scale!
Jet #1 Direction
Charged Particle Density: dN/dhd
10.0
“Toward”
“Transverse”
“Transverse”
Jet #3
“Away”
“Away-Side”
“Away-Side”
Jet Jet
Charged Particle Density

30 < ET(jet#1) < 70 GeV
CDF Preliminary
“Toward-Side” Jet
data uncorrected
"Transverse"
Region
1.0
Jet#1
Charged Particles
(|h|<1.0, PT>0.5 GeV/c)
0.1
0
30
60
90
120
Min-Bias
0.25 per unit h-
150
180
210
 (degrees)
240
270
300
Leading Jet
330
360
 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
“leading jet” events 30 < ET(jet#1) < 70 GeV.
 Also shows charged particle density, dNchg/dhd, for charged particles in the range pT >
0.5 GeV/c and |h| < 1 for “min-bias” collisions.
MCnet07 - Durham - Part 2
April 18-20, 2007
Rick Field – Florida/CDF/CMS
Page 3
Charged Particle Density 
Dependence
Refer to this as a
“Leading Jet” event
Jet #1 Direction
Charged
Particle Density:
Density: dN/dhd
dN/dhd
Charged Particle

10.0
10.0
Subset
“Transverse”
“Transverse”
“Away”
Refer to this as a
“Back-to-Back” event
Jet #1 Direction

“Toward”
“Transverse”
“Transverse”
Charged Particle
Particle Density
Density
Charged
“Toward”
CDF
CDF Preliminary
Preliminary
30 << ET(jet#1)
ET(jet#1) << 70
70 GeV
GeV
30
Back-to-Back
data
data uncorrected
uncorrected
Leading Jet
Min-Bias
"Transverse"
"Transverse"
Region
Region
1.0
1.0
Jet#1
Jet#1
Charged
Charged Particles
Particles
(|h|<1.0,
(|h|<1.0, PT>0.5
PT>0.5 GeV/c)
GeV/c)
0.1
0.1
00
30
30
60
60
90
120
“Away”
150
180
210
210
240
240
270
270
300
300
330
330
360
360
 (degrees)
Jet #2 Direction
 Look at the “transverse” region as defined by the leading jet (JetClu R = 0.7, |h| < 2) 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 Jet#1 and Jet#2 nearly “back-to-back” (12 > 150o) with almost equal
transverse energies (ET(jet#2)/ET(jet#1) > 0.8) and with ET(jet#3) < 15 GeV.
 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.
MCnet07 - Durham - Part 2
April 18-20, 2007
Rick Field – Florida/CDF/CMS
Page 4
Charged Particle Density 
Dependence
“Leading Jet”
Jet #1 Direction
Charged Particle Density: dN/dhd

272
CDF Preliminary
“Toward”
252
256
260
264 268
276 280
284
288
292
248
296
244
data uncorrected
30 < ET(jet#1) < 70 GeV
300
240
304
236
308
232
“Transverse”
312
228
“Transverse”
316
224
320
220
324
Jet#1
216
328
212
“Away”
332
208
336
204
340
200
“Back-to-Back”
344
196
348
192
Jet #1 Direction
352
188

"Transverse"
Region
184
180
356
"Transverse"
Region
360
4
176
“Toward”
8
172
12
0.5
168
16
164
“Transverse”
“Transverse”
20
160
24
1.0
156
28
Leading Jet
152
“Away”
Back-to-Back
36
148
1.5
144
140
40
44
136
48
132
Jet #2 Direction
52
2.0
128
Polar Plot
32
Charged Particles
(|h|<1.0, PT>0.5 GeV/c)
124
56
60
120
64
116
68
112
108
104
100
96
88
84
80
76
72
92
 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.
MCnet07 - Durham - Part 2
April 18-20, 2007
Rick Field – Florida/CDF/CMS
Page 5
“Transverse” PTsum Density versus
ET(jet#1)
Jet #1 Direction

“Toward”
“Transverse”
“Transverse”
“Away”
“Back-to-Back”
Jet #1 Direction

“Toward”
“Transverse”
"AVE Transverse" PTsum Density: dPT/dhd
1.4
“Transverse”
"Transverse" PTsum Density (GeV/c)
“Leading Jet”
uncorrected
datadata
uncorrected
theory + CDFSIM
PY Tune A
1.0
Hard Radiation!
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-
 Shows the average charged PTsum density, dPTsum/dhd, 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.
MCnet07 - Durham - Part 2
April 18-20, 2007
Rick Field – Florida/CDF/CMS
Page 6
“Transverse” PTsum Density versus
ET(jet#1)
Jet #1 Direction

Charged PTsum Density: dPT/dhd
100.0
“Transverse”
“Transverse”
“Away”
"AVE Transverse" PTsum Density: dPT/dhd
Leading Jet
CDF Run 2 Preliminary
1.2
data uncorrected
1.0
CDF Preliminary
95 < ET(jet#1) < 130 GeV
30 < ET(jet#1) < 70 GeV
data uncorrected
Leading Jet
Min-Bias
10.0
"Transverse"
Region
1.0
Charged Particles
(|h|<1.0, PT>0.5 GeV/c)
Jet#1
0.1
0
0.8
30
60
90
120
150
180
210
240
270
300
330
360
 (degrees)
0.6
30-70 GeV
0.4
Charged PTsum Density: dPT/dhd
95-130 GeV
Back-to-Back
0.2
1.96 TeV
50
100
ET(jet#1) (GeV)
Jet #1 Direction

“Toward”
“Transverse”
95 < ET(jet#1) < 130 GeV
Very little dependence on
ET(jet#1) in the “transverse”
200
250
region150
for “back-to-back”
events!10.0
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
0.0
0
100.0
Charged PTsum Density (GeV/c)
"Transverse" PTsum Density (GeV/c)
1.4
Charged PTsum Density (GeV/c)
“Toward”
“Transverse”
Back-to-Back
30 < ET(jet#1) < 70 GeV
Min-Bias
Charged Particles
(|h|<1.0, PT>0.5 GeV/c)
1.0
CDF Preliminary
Jet#1
data uncorrected
"Transverse" Region
0.1
“Away”
0
30
60
90
120
150
180
210
240
270
300
330
360
 (degrees)
Jet #2 Direction
MCnet07 - Durham - Part 2
April 18-20, 2007
Rick Field – Florida/CDF/CMS
Page 7
“TransMIN” PTsum Density versus
ET(jet#1)
“Leading Jet”
Jet #1 Direction

"MIN Transverse" PTsum Density: dPT/dhd
“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

Leading Jet
Jet
Leading
PY Tune A
0.4
“Toward”
“Back-to-Back”
Jet #1 Direction

“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/dhd, for pT > 0.5 GeV/c, |h| < 1
versus ET(jet#1) for “Leading Jet” and “Back-to-Back” events.
MCnet07 - Durham - Part 2
April 18-20, 2007
Rick Field – Florida/CDF/CMS
Page 8
“Transverse” PTsum Density
PYTHIA Tune A vs HERWIG
“Leading Jet”
Jet #1 Direction

"AVE Transverse" PTsum Density: dPT/dhd
“Toward”
“Transverse”
“Transverse”
“Away”
“Back-to-Back”
Jet #1 Direction

“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/dhd, 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.
MCnet07 - Durham - Part 2
April 18-20, 2007
Rick Field – Florida/CDF/CMS
Page 10
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/dhd
Charged PTsum Density: dPT/dhd
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
 (degrees)
150
180
210
240
270
300
330
360
330
360
 (degrees)
Data - Theory: Charged PTsum Density dPT/dhd
Data - Theory: Charged PTsum Density dPT/dhd
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
60
120
150
180
210
240
270
300
 (degrees)
 (degrees)
MCnet07 - Durham - Part 2
April 18-20, 2007
90
Rick Field – Florida/CDF/CMS
Page 11
Charged PTsum Density
PYTHIA Tune A vs HERWIG
Data - Theory: Charged PTsum Density dPT/dhd
Data - Theory: Charged PTsum Density dPT/dhd
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)
Data - Theory (GeV/c)
CDF Preliminary
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
0
360
30
60
90
120
210
240
270
300
330
360
330
360
2
CDF Preliminary
 Add 0.2 GeV/c per unit h- to HERWIG
scalar PTsum density, dPTsum/dhd.
 This corresponds to 0.2 × 4p = 2.5 GeV/c
in the entire range pT > 0.5 GeV/c, |h| < 1.
MCnet07 - Durham - Part 2
April 18-20, 2007
180
Data - Theory: Charged PTsum Density dPT/dhd
dPT/dhd + 0.2 GeV/c
Data - Theory (GeV/c)
308 MeV in
R = 0.7 cone!
150
 (degrees)
 (degrees)
data uncorrected
theory + CDFSIM
1
30 < ET(jet#1) < 70 GeV
Back-to-Back
HERWIG + 0.2 GeV/c
0
-1
"Transverse"
Region
Charged Particles
(|h|<1.0, PT>0.5 GeV/c)
Jet#1
-2
0
30
60
Rick Field – Florida/CDF/CMS
90
120
150
180
210
240
270
300
 (degrees)
Page 12
“Transverse” PTmax versus ET(jet#1)
Jet #1 Direction
“Leading Jet”

“TransMIN”
Highest“TransMAX”
pT particle
in the
“transverse” region!
“Back-to-Back”
“Away”
Jet #1 Direction

“Toward”
“TransMAX”
PTmaxT
PTmaxT
“TransMIN”
“Away”
"Transverse" PTmax (GeV/c)
Jet #1 Direction
“Toward”
PTmaxT
"Transverse" Charged PTmax
3.0
CDF Run 2 Preliminary
1.96 TeV

2.5
data uncorrected
Leading Jet
2.0
“Toward”
1.5
“TransMAX”
1.0
“TransMIN”
0.5“Away”
Min-Bias
Back-to-Back
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
0.0
0
50
100
150
200
250
ET(jet#1) (GeV)
Jet #2 Direction
Min-Bias
 Use the leading jet to define the “transverse” region and look at the maximum pT
charged particle in the “transverse” region, PTmaxT.
 Shows the average PTmaxT, in the “transverse” region (pT > 0.5 GeV/c, |h| < 1) versus
ET(jet#1) for “Leading Jet” and “Back-to-Back” events compared with the average
maximum pT particle, PTmax, in “min-bias” collisions (pT > 0.5 GeV/c, |h| < 1).
MCnet07 - Durham - Part 2
April 18-20, 2007
Rick Field – Florida/CDF/CMS
Page 15
Back-to-Back “Associated”
Charged Particle Densities
Maximum pT particle in
the “transverse” region!
PTmaxT
Direction
“Associated” densities do
not include PTmaxT!
Jet #1 Direction


“Toward”
“TransMAX”
PTmaxT

“TransMIN”
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  dependence of the “associated” charged particle and PTsum densities,
dNchg/dhd and dPTsum/dhd 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).
MCnet07 - Durham - Part 2
April 18-20, 2007
Rick Field – Florida/CDF/CMS
Page 16
Back-to-Back “Associated”
Charged Particle Densities
“Associated” densities do
not include PTmaxT!
PTmaxT
Direction
Associated Particle Density

Jet#2
Region
Charged Particles
(|h|<1.0, PT>0.5 GeV/c)
CDF Preliminary
Jet #3
Jet #2
Associated Particle Density: dN/dhd
10.0
Jet #1
Jet#1
Region
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
Log Scale!
120
150
180
210
240
270
300
330
360
 (degrees)
 Look at the  dependence of the “associated” charged particle density, dNchg/dhd 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).
MCnet07 - Durham - Part 2
April 18-20, 2007
Rick Field – Florida/CDF/CMS
Page 17
Back-to-Back “Associated”
Charged Particle Densities
“Back-to-Back”
charge density
Charged Particle Density: dN/dhd
Jet #1 Direction

2
CDF Preliminary
346
350
354
358
6
10
14
18
342
22
338
26
334
data uncorrected
“Toward”
30 < ET(jet#1) < 70 GeV
Back-to-Back
30
330
34
326
38
322
42
318
46
314
“Transverse”
“Transverse”
50
310
54
Jet#1
306
58
302
62
298
“Away”
66
294
70
290
“Back-to-Back”
“associated” density
74
286
78
"Transverse"
Region
282
Jet #2 Direction
278
274
82
PTmaxT
270
86
"Transverse"
Region
90
94
266

Jet#1
Region
98
262
102
0.5
258
106
254
110
250
PTmaxT
Direction
114
1.0
246
118
242
122
238
Jet#2
Region
126
234
130
1.5
230
134
226
138
222
142
2.0
218
Polar Plot
Charged Particles
(|h|<1.0, PT>0.5 GeV/c)
214
154
206
158
202
162
198
194
190
186
Associated Density
PTmaxT not included
146
150
210
178
174
170
166
182
 Shows the  dependence of the “associated” charged particle density, dNchg/dhd, pT > 0.5
GeV/c, |h| < 1 (not including PTmaxT) relative to PTmaxT (rotated to 180o) and the charged
particle density, dNchg/dhd, 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.
MCnet07 - Durham - Part 2
April 18-20, 2007
Rick Field – Florida/CDF/CMS
Page 20
Back-to-Back “Associated”
Charged Particle Densities
“Back-to-Back”
charge density
Charged Particle Density: dN/dhd
Jet #1 Direction

2
CDF Preliminary
346
350
354
358
6
10
14
18
342
22
338
26
334
data uncorrected
“Toward”
30 < ET(jet#1) < 70 GeV
Back-to-Back
30
330
34
326
38
322
42
318
46
314
“Transverse”
“Transverse”
50
310
54
Jet#1
306
58
302
“Away”
62
298
66
294
70
290
“Back-to-Back”
“associated” density
74
286
Jet #2 Direction
78
"Transverse"
Region
282
278
82
PTmaxT
270
86
"Transverse"
Region
274
90
94
266

Jet#1
Region
98
262
102
0.5
258
106
254
PTmaxT
Direction
110
250
114
1.0
246
118
242
122
238
Jet#2
Region
126
1.5
234
230
130
134
226
138
222
Polar Plot
Associated Density
PTmaxT > 2 GeV/c
(not included)
142
2.0
218
Charged Particles
(|h|<1.0, PT>0.5 GeV/c)
214
146
150
210
154
206
158
202
162
198
194
190
186
178
174
170
166
182
 Shows the  dependence of the “associated” charged particle density, dNchg/dhd, 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/dhd, 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.
MCnet07 - Durham - Part 2
April 18-20, 2007
Rick Field – Florida/CDF/CMS
Page 21
Jet Topologies
QCDThree
Four
Jet
QCD
Jet Topology
Topology Charged Particle Density: dN/dhd
QCD
2-to-4
Scattering
Multiple
Parton
Interactions
2
CDF
Preliminary
Final-State
Jet #1
data uncorrected
Radiation
Outgoing Parton
346
6
10
14
30 < ET(jet#1) < 70 GeV
Outgoing Parton
Outgoing PartonBack-to-Back
18
30
330
34
326
38
322
42
318
46
Jet #1
PT(hard)
50
54
Jet#1
306
58
PT(hard)
302
298
Proton
Proton
358
26
334
310
Jet #3
354
22
338
314
Jet#1
Region
350
342
62
66
294
Jet #4
PTmaxT
Direction
70
290
74
286
78
Jet #4
AntiProton
AntiProton
"Transverse"
Jet #3
Region
282
278
82
274
Jet#2
Region
Underlying Event
Underlying Event
PTmaxT
270
86
"Transverse"
Region
90
94
266
98
Underlying Event
262
Jet #2
102
0.5
258
Underlying Event
106
254
110
Jet #2
250
114
1.0
246
118
242
238
126
1.5
234
230
130
134
226
138
222
Final-State
Radiation
Outgoing Parton
Charged Particles
(|h|<1.0, PT>0.5 GeV/c)
Associated Density
PTmaxT > 2 GeV/c
(not included)
142
2.0
218
Polar Plot
Initial-State
Radiation
122
214
146
150
210
154
206
158
202
162
198
194
190
186
178
174
170
166
182
Outgoing
 Shows the  dependence
ofParton
the “associated” charged particleOutgoing
density,Parton
dNchg/dhd, 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/dhd, 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.
MCnet07 - Durham - Part 2
April 18-20, 2007
Rick Field – Florida/CDF/CMS
Page 22
“Back-to-Back” vs “Min-Bias”
“Associated” Charge Density
“Back-to-Back”
“Associated” Density
“Birth” of jet#3 in the
“transverse” region!
PTmaxT
Direction
Associated Particle Density: dN/dhd

“Min-Bias”
“Associated” Density
Associated Particle Density
Jet#2
Region
10.0
Jet#1
Region
PTmax Direction

PTmaxT > 2.0 GeV/c
PTmax > 2.0 GeV/c
Charged Particles
Particles
Charged
(|h|<1.0, PT>0.5
PT>0.5 GeV/c)
GeV/c)
(|h|<1.0,
3030< <ET(jet#1)
ET(jet#1)< <7070GeV
GeV
1.0
Min-Bias x 1.65
PTmaxT
PTmaxT
PTmax
PTmax
Min-Bias
PTmaxT,
PTmaxT,PTmax
PTmaxnot
notincluded
included
CDFPreliminary
Preliminary
CDF
data
uncorrected
data
uncorrected
0.1
Correlations in 
0
30
60
90
120
150
180
210
240
270
300
330
360
 (degrees)
Log Scale!
“Birth” of jet#1 in
 Shows the  dependence of the “associated” charged particle density,“min-bias”
dNchg/dhd
for
collisions!
pT > 0.5 GeV/c, |h| < 1 (not including PTmaxT) relative to PTmaxT (rotated to 180o) for
PTmaxT > 2.0 GeV/c, for “back-to-back” events with 30 < ET(jet#1) < 70 GeV.
 Shows the data on the  dependence of the “associated” charged particle density,
dNchg/dhd, pT > 0.5 GeV/c, |h| < 1 (not including PTmax) relative to PTmax (rotated to
180o) for “min-bias” events with PTmax > 2.0 GeV/c.
MCnet07 - Durham - Part 2
April 18-20, 2007
Rick Field – Florida/CDF/CMS
Page 24
“Associated” PTsum Density
PYTHIA Tune A vs HERWIG
HERWIG (without multiple parton
interactions) does not produce
enough “associated” PTsum in the
direction of PTmaxT!
Associated PTsum Density: dPT/dhd
PTmaxT > 0.5 GeV/cAssociated PTsum Density: dPT/dhd
10.0
Associated PTsum Density (GeV/c)
Associated PTsum Density (GeV/c)
10.0
Charged Particles
(|h|<1.0, PT>0.5 GeV/c)
PTmaxT not included
1.0
PTmaxT > 0.5 GeV/c
Back-to-Back
30 < ET(jet#1) < 70 GeV
PY Tune A
CDF Preliminary
PTmaxT
data uncorrected
theory + CDFSIM
"Jet#1"
Region
0.1
Charged Particles
(|h|<1.0, PT>0.5 GeV/c)
PTmaxT not included
1.0
PTmaxT > 0.5 GeV/c
HERWIG
CDF Preliminary
30
60
90
120
150
180
210
240
270
300
330
360
0
30
60
90
120
 (degrees)
"Jet#1"
Region
2
CDF Preliminary
And HERWIG (without multiple
parton interactions) does not 2
Charged Particles
Back-to-Back
produce
enough PTsum in the
(|h|<1.0, PT>0.5 GeV/c) 30 < ET(jet#1) < 70 GeV
direction
opposite of PTmaxT!1
PTmaxT not included
PYTHIA Tune A
Data - Theory (GeV/c)
data uncorrected
theory + CDFSIM
150
180
210
240
270
300
330
360
 (degrees)
Data - Theory: Associated PTsum Density dPT/dhd
Data - Theory: Associated PTsum Density dPT/dhd
Data - Theory (GeV/c)
PTmaxT
data uncorrected
theory + CDFSIM
0.1
0
1
Back-to-Back
30 < ET(jet#1) < 70 GeV
0
-1
PTmaxT
CDF Preliminary
data uncorrected
theory + CDFSIM
Charged Particles
(|h|<1.0, PT>0.5 GeV/c)
Back-to-Back
30 < ET(jet#1) < 70 GeV
PTmaxT not included
0
-1
PTmaxT
HERWIG
"Jet#1"
Region
"Jet#1"
Region
-2
-2
0
30
60
90
120
150
180
210
240
270
300
330
360
0
30
60
MCnet07 - Durham - Part 2
April 18-20, 2007
90
120
150
180
210
240
270
300
330
360
 (degrees)
 (degrees)
Rick Field – Florida/CDF/CMS
Page 26
“Associated” PTsum Density
For PTmaxT > 2.0 GeV both
PYTHIA and HERWIG produce
PYTHIA Tune A vs HERWIG
slightly too much “associated” PTsum
in the direction of PTmaxT!
PTmaxT > 2 GeV/c Associated PTsum Density: dPT/dhd
Associated PTsum Density: dPT/dhd
10.0
Charged Particles
(|h|<1.0, PT>0.5 GeV/c)
PTmaxT not included
Associated PTsum Density (GeV/c)
Associated PTsum Density (GeV/c)
10.0
1.0
PTmaxT > 2.0 GeV/c
Back-to-Back
30 < ET(jet#1) < 70 GeV
PY Tune A
CDF Preliminary
PTmaxT
data uncorrected
theory + CDFSIM
"Jet#1"
Region
0.1
Charged Particles
(|h|<1.0, PT>0.5 GeV/c)
PTmaxT not included
1.0
PTmaxT > 2.0 GeV/c
CDF Preliminary
PTmaxT
data uncorrected
theory + CDFSIM
"Jet#1"
Region
0.1
0
30
60
90
120
150
180
210
240
270
300
330
360
0
30
60
90
120
 (degrees)
CDF Preliminary
240
270
300
330
360
Data - Theory
PTmaxT
0
Charged Particles
(|h|<1.0, PT>0.5 GeV/c)
"Jet#1"
Region
PTmaxT > 2.0 GeV/c (not included)
Back-to-Back
30 < ET(jet#1) < 70 GeV
HERWIG
data uncorrected
theory + CDFSIM
-1
Charged Particles
(|h|<1.0, PT>0.5 GeV/c)
210
Data - Theory: Associated Particle Density dN/dhd
1
0.0
-1.0
180
2
PYTHIA Tune A
theory + CDFSIM
1.0
150
 (degrees)
But HERWIG (without multiple
Data - Theory: Associated
Particleinteractions)
Density dN/dhd
parton
produces
too few particles
in the
Back-to-Back
CDF Preliminary
direction
opposite
of
PTmaxT!
30
<
ET(jet#1)
<
70 GeV
data uncorrected
2.0
Data - Theory
Back-to-Back
30 < ET(jet#1) < 70 GeV
HERWIG
PTmaxT
"Jet#1"
Region
PTmaxT > 2.0 GeV/c (not included)
-2.0
-2
0
30
60
90
120
150
180
210
240
270
300
330
360
0
30
60
 (degrees)
MCnet07 - Durham - Part 2
April 18-20, 2007
90
120
150
180
210
240
270
300
330
360
 (degrees)
Rick Field – Florida/CDF/CMS
Page 27
Jet Multiplicity
Max pT in the
“transverse” region!
Jet Multiplicity
50%
Jet #1 Direction

“Away”
Jet #2 Direction
HERWIG (without
multiple parton
interactions) does not have equal
amounts of 3 and 4 jet topologies!
Percent of Events
PTmaxT
“TransMIN”
data uncorrected
theory + CDFSIM
PY
HERWIG
Tune A
40%
“Toward”
“TransMAX”
CDF Run 2 Pre-Preliminary
Data
Data
Data
Back-to-Back
30 < ET(jet#1) < 70 GeV
PTmaxT > 2.0 GeV/c
30%
20%
10%
0%
0
1
2
3
Data have about equal amounts
of 3 and 4 jet topologies!
4
5
6
7
8
9
10
Number of Jets
 Shows the data on the number of jets (JetClu, R = 0.7, |h| < 2, ET(jet) > 3 GeV)
for “back-to-back” events with 30 < ET(jet#1) < 70 GeV and PTmaxT > 2.0
GeV/c.
PYTHIA Tune
after CDFSIM.
 Compares the (uncorrected) data with HERWIG
afterACDFSIM.
MCnet07 - Durham - Part 2
April 18-20, 2007
Rick Field – Florida/CDF/CMS
Page 28
“Transverse” <pT> versus
“Transverse” Nchg
“Leading Jet”
Jet #1 Direction
"Transverse" Average PT versus Nchg

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

“Toward”
“Transverse”
“Transverse”
“Away”
Average PT (GeV/c)
data uncorrected
“Transverse”

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
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.
MCnet07 - Durham - Part 2
April 18-20, 2007
Rick Field – Florida/CDF/CMS
Page 29
“Transverse 1” Region vs
“Transverse 2” Region
Jet #1 Direction

Jet #1 Direction
“Toward”
“Trans 1”
“Trans 2”
“Away”
“Back-to-Back”
Jet #1 Direction

“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

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.
MCnet07 - Durham - Part 2
April 18-20, 2007
Rick Field – Florida/CDF/CMS
Page 30
“Transverse 1” Region vs
“Transverse 2” Region
"Transverse 1" vs "Transverse 2"
"Transverse 1" vs "Transverse 2"
3.5
3.0
"Transverse 2" Nchg
data uncorrected
theory + CDFSIM
Leading Jet
30 < ET(jet#1) < 70 GeV
CDF Run 2 Preliminary
"Transverse 2" Nchg
CDF Run 2 Preliminary
3.0
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
MCnet07 - Durham - Part 2
April 18-20, 2007
2
4
6
8
10
12
"Transverse 1" Nchg
Rick Field – Florida/CDF/CMS
Page 31
Recent CDF Run 2
“Underlying Event” Results
Jet #1 Direction

“Toward”
“Trans 1”
The “underlying event” consists of
hard initial & final-state radiation
plus the “beam-beam remnants” and
possible multiple parton interactions.
Outgoing Parton
“Trans 2”
PT(hard)
Initial-State Radiation
“Away”
Proton
AntiProton
Underlying Event
“Transverse” region is
very sensitive to the
“underlying event”!
Outgoing Parton
Underlying Event
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.
MCnet07 - Durham - Part 2
April 18-20, 2007
Rick Field – Florida/CDF/CMS
Page 32
“Transverse” Observables
Particle and Detector Level
“Leading Jet”
Jet #1 Direction
Observable
Particle Level
Detector Level
dNchg/dhd
Number of charged particles
per unit h-
(pT > 0.5 GeV/c, |h| < 1)
Number of “good” charged tracks
per unit h-
(pT > 0.5 GeV/c, |h| < 1)
dPTsum/dhd
Scalar pT sum of charged
particles per unit h-
(pT > 0.5 GeV/c, |h| < 1)
Scalar pT sum of “good” charged tracks
per unit h-
(pT > 0.5 GeV/c, |h| < 1)
<pT>
Average pT of charged particles
(pT > 0.5 GeV/c, |h| < 1)
Average pT of “good” charged tracks
(pT > 0.5 GeV/c, |h| < 1)
PTmax
Maximum pT charged particle
(pT > 0.5 GeV/c, |h| < 1)
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)
Rick Field – Florida/CDF/CMS
Page 33

“Toward”
“Transverse”
“Transverse”
“Away”
Jet #1 Direction

“Toward”
“Transverse”
“Transverse”
“Away”
Jet #2 Direction
“Back-to-Back”
MCnet07 - Durham - Part 2
April 18-20, 2007
“TransMAX/MIN” Nchg Density
PYTHIA Tune A vs HERWIG
“Leading Jet”
“Back-to-Back”
Jet #1 Direction
Jet #1 Direction
“TransMIN”
“Away”
CDF Run 2 Preliminary
“Toward”
“TransMAX”
“TransMIN”
“Away”
"Transverse" Charged Density
“TransMAX”
1.4


“Toward”
"TransMAX" Charged Particle Density: dN/dhd
"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)
MCnet07 - Durham - Part 2
April 18-20, 2007
Rick Field – Florida/CDF/CMS
Page 34
“Transverse” <PT> and <PTmax>
PYTHIA Tune A vs HERWIG
Jet #1 Direction

Jet #1 Direction
Jet”
“Leading
“Back-to-Back”
“Transverse”
“Transverse”
“Transverse”
“Away”
"Transverse" Charged <PT> (GeV/c)
“Toward”
“Toward”
"Transverse" Charged Particle Mean PT
2.0
“Transverse”
“Away”
Jet #2 Direction
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"
HW
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
0.5
 Shows the average transverse
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.
MCnet07 - Durham - Part 2
April 18-20, 2007
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)

0
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/CMS
100
150
200
250
300
350
400
450
PT(jet#1) (GeV/c)
Page 36
“TransMAX/MIN” ETsum Density
PYTHIA Tune A vs HERWIG
“Leading Jet”
“Back-to-Back”
Jet #1 Direction
Jet #1 Direction
“Toward”
“TransMAX”
“TransMIN”
“Away”
“Toward”
“TransMAX”
“TransMIN”
“Away”
"Transverse" ETsum Density (GeV)


"TransMAX" ETsum Density: dET/dhd
7.0
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)
MCnet07 - Durham - Part 2
April 18-20, 2007
Rick Field – Florida/CDF/CMS
Page 37
“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.
MCnet07 - Durham - Part 2
April 18-20, 2007
Rick Field – Florida/CDF/CMS
Page 39
“TransMAX/MIN” ETsum Density
PYTHIA Tune A vs JIMMY
“Leading Jet”
“Back-to-Back”
Jet #1 Direction
Jet #1 Direction
“TransMAX”
“TransMIN”
“Away”
“Toward”
“TransMAX”
“TransMIN”
“Away”
"Transverse" ETsum Density (GeV)
“Toward”
7.0


"TransMAX" ETsum Density: dET/dhd
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.
MCnet07 - Durham - Part 2
April 18-20, 2007
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/CMS
150
200
250
PT(jet#1) (GeV/c)
300
350
400
450
JIMMY
Runs with HERWIG and adds
multiple parton interactions!
Page 40
“TransMAX/MIN” PTsum Density
PYTHIA Tune A vs JIMMY
“Leading Jet”
“Back-to-Back”
Jet #1 Direction
Jet #1 Direction
“Toward”
“TransMAX”
“TransMIN”
“Away”
“Toward”
“TransMAX”
“TransMIN”
“Away”
"Transverse" PTsum Density (GeV/c)


"TransMAX" Charged PTsum Density: dPT/dhd
3.0
Jet #2 Direction
MCnet07 - Durham - Part 2
April 18-20, 2007
"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/CMS
100
150
200
250
300
350
400
450
PT(jet#1) (GeV/c)
Page 41
“TransMAX/MIN” Nchg Density
PYTHIA Tune A vs JIMMY
“Leading Jet”
“Back-to-Back”
Jet #1 Direction
Jet #1 Direction

“Toward”
“TransMAX”
“TransMIN”
“Away”
CDF Run 2 Preliminary
“Toward”
“TransMAX”
“TransMIN”
“Away”
"Transverse" Charged Density

"TransMAX" Charged Particle Density: dN/dhd
1.4
"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,
MCnet07 - Durham - Part 2
April 18-20, 2007
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
100
Rick Field – Florida/CDF/CMS
150
200
250
300
350
400
450
PT(jet#1) (GeV/c)
Page 42
“Transverse” <PT>
PYTHIA Tune A vs JIMMY
“Leading Jet”
“Back-to-Back”
Jet #1 Direction
Jet #1 Direction
“Toward”
“TransMAX”
“TransMIN”
“Away”
“Toward”
“TransMAX”
“TransMIN”
“Away”
"Transverse" Charged <PT> (GeV/c)


"Transverse" Charged Particle Mean PT
2.0
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)
MCnet07 - Durham - Part 2
April 18-20, 2007
Rick Field – Florida/CDF/CMS
Page 43
Possible Scenario??
 PYTHIA Tune A fits the charged particle
"Transverse" pT Distribution: dN/dpT
1.0E+01
"Transverse" PT Distribution
Sharp Rise at
Low PT?
PTsum density for pT > 0.5 GeV/c, but it
does not produce enough ETsum for
towers with ET > 0.1 GeV.
Possible Scenario??
But I cannot get any
of the Monte-Carlo to
do this perfectly!
1.0E+00
1.0E-01
 It is possible that there is a sharp rise in
Multiple
Parton
Interactions
the number of particles in the “underlying
event” at low pT (i.e. pT < 0.5 GeV/c).
1.0E-02
Beam-Beam
Remnants
1.0E-03
 Perhaps there are two components, a vary
1.0E-04
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
pT All Particles (GeV/c)
MCnet07 - Durham - Part 2
April 18-20, 2007
4.0
4.5
5.0
“soft” beam-beam remnant component
(Gaussian or exponential) and a “hard”
multiple interaction component.
Rick Field – Florida/CDF/CMS
Page 44
CDF Run 1 PT(Z)
PYTHIA 6.2 CTEQ5L
UE Parameters
Tune A
Tune A25
Tune A50
MSTP(81)
1
1
1
MSTP(82)
4
4
4
PARP(82)
2.0 GeV
2.0 GeV
2.0 GeV
PARP(83)
0.5
0.5
0.5
PARP(84)
0.4
0.4
0.4
PARP(85)
0.9
0.9
0.9
PARP(86)
0.95
0.95
0.95
1.8 TeV
1.8 TeV
1.8 TeV
PARP(90)
0.25
0.25
0.25
PARP(67)
4.0
4.0
4.0
MSTP(91)
1
1
1
PARP(91)
1.0
2.5
5.0
PARP(93)
5.0
15.0
25.0
s = 1.0
CDF Run 1 Data
PYTHIA Tune A
PYTHIA Tune A25
PYTHIA Tune A50
s = 2.5
0.08
CDF Run 1
published
1.8 TeV
s = 5.0
Normalized to 1
0.04
0.00
0
ISR Parameter PARP(89)
Z-Boson Transverse Momentum
0.12
PT Distribution 1/N dN/dPT
Parameter
2
4
6
8
10
12
14
16
18
Z-Boson PT (GeV/c)
 Shows the Run 1 Z-boson pT distribution
(<pT(Z)> ≈ 11.5 GeV/c) compared with PYTHIA
Tune A (<pT(Z)> = 9.7 GeV/c), Tune A25
(<pT(Z)> = 10.1 GeV/c), and
Tune A50
(<pT(Z)> = 11.2 GeV/c).
Vary the intrensic KT!
Intrensic KT
MCnet07 - Durham - Part 2
April 18-20, 2007
20
Rick Field – Florida/CDF/CMS
Page 45
CDF Run 1 PT(Z)
PYTHIA 6.2 CTEQ5L
Tune used by the
CDF-EWK group!
Z-Boson Transverse Momentum
Parameter
Tune A
Tune AW
UE Parameters MSTP(81)
1
1
MSTP(82)
4
4
PARP(82)
2.0 GeV
2.0 GeV
PARP(83)
0.5
0.5
PARP(84)
0.4
0.4
PARP(85)
0.9
0.9
PARP(86)
0.95
0.95
PARP(89)
1.8 TeV
1.8 TeV
PARP(90)
0.25
0.25
PARP(62)
1.0
1.25
PARP(64)
1.0
0.2
PARP(67)
4.0
4.0
MSTP(91)
1
1
PARP(91)
1.0
2.1
PARP(93)
5.0
15.0
PT Distribution 1/N dN/dPT
0.12
CDF Run 1 Data
PYTHIA Tune A
PYTHIA Tune AW
published
0.08
1.8 TeV
Normalized to 1
0.04
0.00
0
ISR Parameters
CDF Run 1
2
4
6
8
10
12
14
16
18
Z-Boson PT (GeV/c)
 Shows the Run 1 Z-boson pT distribution (<pT(Z)>
≈ 11.5 GeV/c) compared with PYTHIA Tune A
(<pT(Z)> = 9.7 GeV/c), and PYTHIA Tune AW
(<pT(Z)> = 11.7 GeV/c).
Effective Q cut-off, below which space-like showers are not evolved.
Intrensic KT
The Q2 = kT2 in as for space-like showers is scaled by PARP(64)!
MCnet07 - Durham - Part 2
April 18-20, 2007
20
Rick Field – Florida/CDF/CMS
Page 46
Jet-Jet Correlations (DØ)
Jet#1-Jet#2  Distribution
 Jet#1-Jet#2
 MidPoint Cone Algorithm (R = 0.7, fmerge = 0.5)
 L = 150 pb-1 (Phys. Rev. Lett. 94 221801 (2005))
 Data/NLO agreement good. Data/HERWIG
agreement good.
 Data/PYTHIA agreement good provided PARP(67)
= 1.0→4.0 (i.e. like Tune A, best fit 2.5).
MCnet07 - Durham - Part 2
April 18-20, 2007
Rick Field – Florida/CDF/CMS
Page 47
CDF Run 1 PT(Z)
PYTHIA 6.2 CTEQ5L
Z-Boson Transverse Momentum
Parameter
Tune DW
Tune AW
UE Parameters MSTP(81)
1
1
MSTP(82)
4
4
PARP(82)
1.9 GeV
2.0 GeV
PARP(83)
0.5
0.5
PARP(84)
0.4
0.4
PARP(85)
1.0
0.9
PARP(86)
1.0
0.95
PARP(89)
1.8 TeV
1.8 TeV
PARP(90)
0.25
0.25
PARP(62)
1.25
1.25
PARP(64)
0.2
0.2
PARP(67)
2.5
4.0
MSTP(91)
1
1
PARP(91)
2.1
2.1
PARP(93)
15.0
15.0
PT Distribution 1/N dN/dPT
0.12
CDF Run 1 Data
PYTHIA Tune DW
HERWIG
published
0.08
1.8 TeV
Normalized to 1
0.04
0.00
0
ISR Parameters
CDF Run 1
2
4
6
8
10
12
14
16
18
20
Z-Boson PT (GeV/c)
 Shows the Run 1 Z-boson pT distribution (<pT(Z)>
≈ 11.5 GeV/c) compared with PYTHIA Tune DW,
and HERWIG.
Tune DW uses D0’s perfered value of PARP(67)!
Intrensic KT
Tune DW has a lower value of PARP(67) and slightly more MPI!
MCnet07 - Durham - Part 2
April 18-20, 2007
Rick Field – Florida/CDF/CMS
Page 48
“Transverse” Nchg Density
ISR Parameter
Intrensic KT
Parameter
Tune AW
Tune DW
Tune BW
MSTP(81)
1
1
1
MSTP(82)
4
4
4
PARP(82)
2.0 GeV
1.9 GeV
1.8 GeV
PARP(83)
0.5
0.5
0.5
PARP(84)
0.4
0.4
0.4
PARP(85)
0.9
1.0
1.0
PARP(86)
0.95
1.0
1.0
PARP(89)
1.8 TeV
1.8 TeV
1.8 TeV
PARP(90)
0.25
0.25
0.25
PARP(62)
1.25
1.25
1.25
PARP(64)
0.2
0.2
0.2
PARP(67)
4.0
2.5
1.0
MSTP(91)
1
1
1
PARP(91)
2.5
2.5
2/5
PARP(93)
15.0
15.0
15.0
Three different amounts of ISR!
MCnet07 - Durham - Part 2
April 18-20, 2007
"Transverse" Charged
Charged Particle
Particle Density:
Density: dN/dhd
dN/dhd
"Transverse"
1.0
1.0
"Transverse"
"Transverse"Charged
ChargedDensity
Density
UE Parameters
Three different amounts of MPI!
PYTHIA 6.2 CTEQ5L
RDF Preliminary
Preliminary
RDF
PY Tune BW
generator level
level
generator
0.8
0.8
PYPY
Tune
DW
Tune
DW
PY-ATLAS
PY Tune A
0.6
0.6
0.4
0.4
PY Tune AW
HERWIG
HERWIG
1.96 TeV
TeV
1.96
0.2
0.2
Leading Jet
Jet (|h|<2.0)
(|h|<2.0)
Leading
Charged Particles
Particles (|h|<1.0,
(|h|<1.0, PT>0.5
PT>0.5 GeV/c)
GeV/c)
Charged
0.0
0.0
00
50
50
100
100
150
150
200
200
250
250
300
300
350
350
400
400
450
450
500
500
PT(particle jet#1)
jet#1) (GeV/c)
(GeV/c)
PT(particle
 Shows the “transverse” charged particle
density, dN/dhd, versus PT(jet#1) for “leading
jet” events at 1.96 TeV for PYTHIA Tune A,
Tune AW, Tune DW, Tune BW, and HERWIG
(without MPI).
 Shows the “transverse” charged particle
density, dN/dhd, versus PT(jet#1) for “leading
jet” events at 1.96 TeV for Tune DW, ATLAS,
and HERWIG (without MPI).
Rick Field – Florida/CDF/CMS
Page 49
“Transverse” PTsum Density
Three different amounts of MPI!
PYTHIA 6.2 CTEQ5L
UE Parameters
ISR Parameter
Intrensic KT
Tune AW
Tune DW
Tune BW
MSTP(81)
1
1
1
MSTP(82)
4
4
4
PARP(82)
2.0 GeV
1.9 GeV
1.8 GeV
PARP(83)
0.5
0.5
0.5
PARP(84)
0.4
0.4
0.4
PARP(85)
0.9
1.0
1.0
PARP(86)
0.95
1.0
1.0
PARP(89)
1.8 TeV
1.8 TeV
1.8 TeV
PARP(90)
0.25
0.25
0.25
PARP(62)
1.25
1.25
1.25
PARP(64)
0.2
0.2
0.2
PARP(67)
4.0
2.5
1.0
MSTP(91)
1
1
1
PARP(91)
2.5
2.5
2/5
PARP(93)
15.0
15.0
15.0
Three different amounts of ISR!
MCnet07 - Durham - Part 2
April 18-20, 2007
"Transverse" PTsum Density: dPT/dhd
"Transverse" PTsum
PTsum Density
Density (GeV/c)
(GeV/c)
"Transverse"
Parameter
1.6
RDF Preliminary
generator level
1.2
PY Tune BW
PY Tune A
PY-ATLAS
0.8
PY Tune AW
PY Tune DW
1.96 TeV
0.4
HERWIG
Leading Jet (|h|<2.0)
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
HERWIG
0.0
0
50
100
150
200
250
300
350
400
450
PT(particle jet#1) (GeV/c)
 Shows the “transverse” charged PTsum
density, dPT/dhd, versus PT(jet#1) for
“leading jet” events at 1.96 TeV for PYTHIA
Tune A, Tune AW, Tune DW, Tune BW, and
HERWIG (without MPI).
 Shows the “transverse” charged PTsum
density, dPT/dhd, versus PT(jet#1) for
“leading jet” events at 1.96 TeV for Tune DW,
ATLAS, and HERWIG (without MPI).
Rick Field – Florida/CDF/CMS
Page 50
500
PYTHIA 6.2 Tunes
s(MPI) at 1.96 TeV
s(MPI) at 14 TeV
Tune A
309.7 mb
484.0 mb
Tune DW
351.7 mb
549.2 mb
Tune DWT
351.7 mb
829.1 mb
324.5 mb
CDF Run 2 Data!
768.0 mb
PYTHIA 6.2 CTEQ5L
Parameter
Tune A
Tune DW
Tune DWT
ATLAS
MSTP(81)
1
1
1
1
MSTP(82)
4
PARP(82)
2.0 GeV
4
1.7GeV
1.9
PARP(83)
0.5
ATLAS
1.8 GeV
"Leading Jet"
"Transverse"
Charged
Particle
Average
pT
"Transverse"
Charged
Particle
Density:
dN/dhd
"Transverse"
PTsum
Density:
dPT/dhd
0.5 data corrected
0.5 to particle level
0.5
1.5
0.4
0.5
PY Tune0.4
A, DW
PARP(85)
0.9
1.0
1.3
1.0
PARP(86)
0.95
PARP(89)
1.8 TeV
PARP(90)
0.25
PARP(62)
1.0
PARP(64)
1.0
0.2
PARP(67)
4.0
MSTP(91)
1
0.72.5
0
1
1.8
1.1 TeV
0.25
1.0
0.33
1.0
0.66
1.96 TeV
1.0 TeV
0.16
0.16
1.25
1.0
1.25
0.9
1.96 TeV
0.2
2.5
50
1
100
HERWIG
1.0
1.0
150
1
PARP(91)
1.0
2.1
2.1
1.0
PARP(93)
5.0
15.0
15.0
5.0
Identical to DW at 1.96 TeV but uses
ATLAS extrapolation to the LHC!
MCnet07 - Durham - Part 2
April 18-20, 2007
"Transverse"
Charged
PTDensity
(GeV/c)
"Transverse"
Charged
"Transverse"
PTsum
Density
(GeV/c)
0.4
1.9409 GeV
Charged Average PT
CDF Run 2 Preliminary
"Transverse" <PT> (GeV/c)
PARP(84)
4"Transverse"
4
1.6
1.0
1.5
RDF
RDFPreliminary
Preliminary
RDF
Preliminary
generator
generatorlevel
level
generator
level
0.8
1.2
1.3
PY Tune DW
PY Tune DW
0.6
PY Tune DW
PY Tune A
PY Tune A
PY-ATLAS
PY-ATLAS
0.8
1.1
PY-ATLAS
0.4
PY Tune A
MidPoint R = 0.7 |h(jet#1) <PY-ATLAS
2
1.96TeV
TeV
1.96
1.96 TeV
HERWIG
0.4
0.9
HERWIGPT>0.5 GeV/c)
Charged
Particles (|h|<1.0,
0.2
Leading
JetJet
(|h|<2.0)
Leading
(|h|<2.0)
Leading
Jet (|h|<2.0)
Charged
Particles
(|h|<1.0,
PT>0.5
GeV/c)
Charged
Particles
(|h|<1.0,
PT>0.5
GeV/c)
Charged
Particles
(|h|<1.0,
PT>0.5
GeV/c)
HERWIG
0.0
0.0
200 0.7 250
00
0
50
50
50
300
100
100
100
PT(jet#1) (GeV/c)
350
150
150
150
400
200
200
200
250
250
250
450
300
300
300
350
350
350
400
400
400
450
450
450
500
500
500
PT(particle
jet#1)
PT(particle jet#1)
jet#1) (GeV/c)
(GeV/c)
PT(particle
(GeV/c)
Shows
Showsthe
the“transverse”
“transverse”charged
chargedPTsum
particledensity,

Shows
the
“transverse”
charged
average
pdensity,

T,
dN/dhd,
versus
PPTT(jet#1)
“leading
versus
PT(jet#1)
“leading
jet”
eventsjet”
at 1.96
dPT/dhd,
versusfor
(jet#1) for
for
“leading
jet”
events
1.96A,
TeV
forATLAS,
TuneA,
A,and
DW,HERWIG
ATLAS,and
and
TeV
foratatTune
DW,
events
1.96
TeV
for
Tune
DW,
ATLAS,
HERWIG
(withoutMPI).
MPI).
(without
MPI).
HERWIG
(without
Rick Field – Florida/CDF/CMS
Page 51
The “Underlying Event” in
High PT Jet Production (LHC)
High PT Jet Production
Outgoing Parton
PT(hard)
Initial-State
Radiation
The “Underlying Event” Proton
Underlying Event
Underlying Event
“Underlying event” much
more active at the LHC!
Final-State
Radiation
Outgoing Parton
"Transverse" Charged Particle Density: dN/dhd
"Transverse" Charged Particle Density: dN/dhd
1.0
2.0
RDF Preliminary
LHC
RDF Preliminary
generator level
0.8
0.6
PY Tune AW
HERWIG
0.4
1.96 TeV
0.2
"Leading Jet"
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
0.0
"Transverse" Charged Density
"Transverse" Charged Density
Charged particle density
versus PT(jet#1)
AntiProton
generator level
1.5
PY Tune AW
HERWIG
1.0
CDF
0.5
"Leading Jet"
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
0.0
0
50
100
150
200
250
300
350
400
450
500
0
250
500
PT(particle jet#1) (GeV/c)
750
1000
1250
1500
1750
2000
2250
2500
PT(particle jet#1) (GeV/c)
 Charged particle density in the “Transverse”  Charged particle density in the “Transverse”
region versus PT(jet#1) at 1.96 TeV for PY
region versus PT(jet#1) at 14 TeV for PY Tune
Tune AW and HERWIG (without MPI).
AW and HERWIG (without MPI).
MCnet07 - Durham - Part 2
April 18-20, 2007
Rick Field – Florida/CDF/CMS
Page 52
MIT Search Scheme: Vista/Sleuth
Exclusive 3 Jet Final State Challenge
At least 1 Jet (“trigger” jet)
(PT > 40 GeV/c, |h| < 1.0)
CDF Data
Normalized to 1
PYTHIA
Tune A
Exactly 3 jets
(PT > 20 GeV/c, |h| < 2.5)
R(j2,j3)
Order Jets by PT
Jet1 highest PT, etc.
Bruce Knuteson
Khaldoun
Makhoul
Georgios
Choudalakis
MCnet07 - Durham - Part 2
April 18-20, 2007
Markus
Klute
Conor
Henderson
Rick Field – Florida/CDF/CMS
Ray
Culbertson
Gene
Flanagan
Page 53
Exc3J: R(j2,j3) Normalized
The data have more
3 jet events with
small R(j2,j3)!?
 Let Ntrig40 equal the number of events
Exclusive 3-Jet Production: R(j2,j3)
with at least one jet with PT > 40 geV and
|h| < 1.0 (this is the “offline” trigger).
0.16
 Let N3Jexc20 equal the number of events
0.12
with exactly three jets with PT > 20 GeV/c
and |h| < 2.5 which also have at least one
jet with PT > 40 GeV/c and |h| < 1.0.
 Let N3JexcFr = N3Jexc20/Ntrig40. The is
the fraction of the “offline” trigger events
that are exclusive 3-jet events.
Initial-State Radiation
0.08
Normalized to
N3JexcFr
0.04
0.00
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
Underlying Event
 PARP(67) affects the initial-state radiation which
contributes primarily to the region R(j2,j3) > 1.0.
“Jet 3”
Outgoing Parton
Initial-State Radiation
“Jet 2”
R > 1.0
MCnet07 - Durham - Part 2
April 18-20, 2007
5.0
R(j2,j3)
with PYTHIA Tune AW (PARP(67)=4), Tune DW
(PARP(67)=2.5), Tune BW (PARP(67)=1).
AntiProton
Underlying Event
Data R(j2,j3)
pyAW
pyDW
pyBW
data uncorrected
generator level theory
 The CDF data on dN/dR(j2,j3) at 1.96 TeV compared
Outgoing Parton
“Jet 1”
Proton
dN/dR(j2,j3)
CDF Run 2 Preliminary
Rick Field – Florida/CDF/CMS
Page 54
3Jexc R(j2,j3) Normalized
 Let Ntrig40 equal the number of events
Exclusive
Exclusive 3-Jet
3-Jet Production:
Production: R(j2,j3)
R(j2,j3)
0.16
0.80
0.16
with at least one jet with PT > 40 geV and
|h| < 1.0 (this is the “offline” trigger).
0.12
0.60
0.12
dN/dR(j2,j3)
dN/dR(j2,j3)
dN/dR(j2,j3)
 Let N3Jexc20 equal the number of events
CDF Run
Run 22 Preliminary
Preliminary
CDF
with exactly three jets with PT > 20 GeV/c
0.08
0.40
0.08
I do not understand
the
and |h| < 2.5 which also have at least one
excess number
of events
0.04
jet with PT > 40 GeV/c and |h| < 1.0.
0.20
0.04
data
uncorrected
datauncorrected
uncorrected
data
generator
level
theory
generatorlevel
leveltheory
theory
generator
CDF Data
Data
Data R(j2,j3)
R(j2,j3)
hw05
pyDW
pyDW
pyDW
pyDWnoFSR
hw05
pyBW
Normalized to
N3JexcFr
with R(j2,j3) < 1.0.
Normalized to 1
 Let N3JexcFr = N3Jexc20/Ntrig40.
The is this0.00
Perhaps
is
related
to the
0.00
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
the fraction of the “offline” trigger“soft
eventsenergy”
0.0 problem??
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
R(j2,j3)
R(j2,j3)
that are exclusive 3-jet events.
For now the best tune is
 The Tune
CDF data
PYTHIA
DW.on dN/dR(j2,j3) at 1.96 TeV compared
Final-State Radiation
Outgoing Parton
“Jet 1”
with PYTHIA Tune DW (PARP(67)=2.5) and
HERWIG (without MPI).
Proton
AntiProton
Underlying Event
Underlying Event
Outgoing Parton
Final-State Radiation
“Jet “Jet
2” 3”
R < 1.0
MCnet07 - Durham - Part 2
April 18-20, 2007
 Final-State radiation contributes to the region R(j2,j3)
< 1.0.
 If you ignore the normalization and normalize all the
distributions to one then the data prefer Tune BW, but
I believe this is misleading.
Rick Field – Florida/CDF/CMS
Page 55
QCD Monte-Carlo Models:
Lepton-Pair Production
Lepton-Pair Production
Anti-Lepton
Initial-State Radiation
Lepton-Pair Production
Initial-State Radiation
“Jet”
Proton
Anti-Lepton
“Hard Scattering” Component
AntiProton
Lepton
Underlying Event
Underlying Event
Proton
Lepton
AntiProton
Underlying Event
Underlying Event
“Underlying Event”

Start with the perturbative Drell-Yan muon pair production and add initial-state gluon radiation (in the
leading log approximation or modified leading log approximation).
 The “underlying event” consists of the “beam-beam remnants” and from particles arising from soft or
semi-soft multiple parton interactions (MPI).
 Of course the outgoing colored partons fragment into hadron “jet” and inevitably “underlying event”
observables receive contributions from initial and final-state radiation.
MCnet07 - Durham - Part 2
April 18-20, 2007
Rick Field – Florida/CDF/CMS
Page 56
The “Central” Region
in Drell-Yan Production
Drell-Yan Production
Look at the charged
particle density and the
PTsum density in the
“central” region!
Charged Particles (pT > 0.5 GeV/c, |h| < 1)
Lepton
2p
Proton
AntiProton
Underlying Event
Underlying Event
Initial-State
Radiation

Central Region
Anti-Lepton
Multiple Parton Interactions
Proton
Lepton
AntiProton
Underlying Event
0
-1
Underlying Event
Anti-Lepton
h
+1
After removing the leptonpair everything else is the
“underlying event”!
 Look at the “central” region after removing the lepton-pair.
 Study the charged particles (pT > 0.5 GeV/c, |h| < 1) and form the charged particle
density, dNchg/dhd, and the charged scalar pT sum density, dPTsum/dhd, by
dividing by the area in h- space.
MCnet07 - Durham - Part 2
April 18-20, 2007
Rick Field – Florida/CDF/CMS
Page 57
Drell-Yan Production (Run 2 vs LHC)
Drell-Yan Production
Proton
<pT(m+m-)> is much
larger at the LHC!
Lepton-Pair Transverse
Momentum
Lepton
AntiProton
Underlying Event
Underlying Event
Shapes of the pT(m+m-)
distribution at the Z-boson mass.
Initial-State
Radiation
Anti-Lepton
Lepton-Pair Transverse Momentum
Drell-Yan PT(m+m-) Distribution
80
0.10
Drell-Yan
Drell-Yan
LHC
60
1/N dN/dPT (1/GeV)
Average Pair PT
generator level
40
Tevatron Run 2
20
0
0.08
PY Tune DW (solid)
HERWIG (dashed)
0.06
70 < M(m-pair) < 110 GeV
|h(m-pair)| < 6
0.04
0.02
PY Tune DW (solid)
HERWIG (dashed)
Z
generator level
Tevatron Run2
LHC
Normalized to 1
0.00
0
100
200
300
400
500
600
700
800
900
1000
0
5
Lepton-Pair Invariant Mass (GeV)
10
15
20
25
30
35
40
PT(m+m-) (GeV/c)
 Average Lepton-Pair transverse momentum  Shape of the Lepton-Pair pT distribution at the
Z-boson mass at the Tevatron and the LHC for
at the Tevatron and the LHC for PYTHIA
PYTHIA Tune DW and HERWIG (without MPI).
Tune DW and HERWIG (without MPI).
MCnet07 - Durham - Part 2
April 18-20, 2007
Rick Field – Florida/CDF/CMS
Page 58
The “Underlying Event” in
Drell-Yan Production
Drell-Yan Production
The “Underlying Event”
Lepton
Proton
HERWIG (without MPI)
is much less active than
PY Tune AW (with MPI)!
Underlying Event
Charged particle density
versus M(pair)
AntiProton
Underlying Event
“Underlying event” much
more active at the LHC!
Initial-State
Radiation
Anti-Lepton
Charged Particle Density: dN/dhd
Charged Particle Density: dN/dhd
1.5
1.0
RDF Preliminary
generator level
PY Tune AW
0.8
0.6
0.4
HERWIG
0.2
Drell-Yan
1.96 TeV
Z
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
(excluding lepton-pair )
Charged Particle Density
Charged Particle Density
RDF Preliminary
generator level
Z
LHC
1.0
PY Tune AW
CDF
0.5
Drell-Yan
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
(excluding lepton-pair )
HERWIG
0.0
0.0
0
50
100
150
200
250
0
50
100
150
200
250
Lepton-Pair Invariant Mass (GeV)
Lepton-Pair Invariant Mass (GeV)
 Charged particle density versus the lepton-  Charged particle density versus the lepton-pair
invariant mass at 14 TeV for PYTHIA Tune AW
pair invariant mass at 1.96 TeV for PYTHIA
and HERWIG (without MPI).
Tune AW and HERWIG (without MPI).
MCnet07 - Durham - Part 2
April 18-20, 2007
Rick Field – Florida/CDF/CMS
Page 59
Extrapolations to the LHC:
Drell-Yan Production
Drell-Yan Production
Charged particle density
versus M(pair)
Lepton
The “Underlying Event”
Proton
AntiProton
Underlying Event
Tune DW and DWT are
identical at 1.96 TeV, but
have different MPI energy
dependence!
Underlying Event
Initial-State
Radiation
Anti-Lepton
Charged Particle Density: dN/dhd
Charged Particle Density: dN/dhd
1.0
2.5
PY Tune BW
generator level
RDF Preliminary
PY Tune DW
0.8
0.6
0.4
PY Tune A
PY Tune AW
1.96 TeV
0.2
HERWIG
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
(excluding lepton-pair )
Z
0.0
0
50
100
Charged Particle Density
Charged Particle Density
RDF Preliminary
generator level
PY-ATLAS
PY Tune DWT
2.0
1.5
PY Tune DW
1.0
14 TeV
0.5
Z
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
(excluding lepton-pair )
HERWIG
0.0
150
200
250
300
350
400
450
500
0
100
Lepton-Pair Invariant Mass (GeV)
200
300
400
500
600
700
800
900
1000
Lepton-Pair Invariant Mass (GeV)
 Average charged particle density versus the  Average charged particle density versus the
lepton-pair invariant mass at 1.96 TeV for
lepton-pair invariant mass at 14 TeV for
PYTHIA Tune A, Tune AW, Tune BW, Tune
PYTHIA Tune DW, Tune DWT, ATLAS and
DW and HERWIG (without MPI).
HERWIG (without MPI).
MCnet07 - Durham - Part 2
April 18-20, 2007
Rick Field – Florida/CDF/CMS
Page 60
Extrapolations to the LHC:
Drell-Yan Production
Drell-Yan Production
The “Underlying Event”
Charged particle charged
PTsum density versus M(pair)
Lepton
Proton
AntiProton
Underlying Event
The ATLAS tune has a much “softer”
distribution of charged particles than
the CDF Run 2 Tunes!
Underlying Event
Initial-State
Radiation
Anti-Lepton
Charged PTsum Density: dPT/dhd
Charged PTsum Density: dPT/dhd
RDF Preliminary
PY Tune BW
5.0
generator level
0.9
PY Tune A
0.6
PY Tune AW
PY Tune DW
1.96 TeV
0.3
Charged Particles (|h|<1.0, PT>0.9 GeV/c)
(excluding lepton-pair )
HERWIG
Z
0.0
0
50
100
Charged PTsum Density (GeV/c)
Charged PTsum Density (GeV/c)
1.2
RDF Preliminary
PY Tune DWT
generator level
PY Tune DW
4.0
PY-ATLAS
3.0
2.0
14 TeV
1.0
Leading Jet (|h|<2.0)
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
HERWIG
Z
0.0
150
200
250
300
350
400
450
500
0
100
Lepton-Pair Invariant Mass (GeV)
200
300
400
500
600
700
800
900
1000
Lepton-Pair Invariant Mass (GeV)
 Average charged PTsum density versus the  Average charged PTsum density versus the
lepton-pair invariant mass at 14 TeV for PYTHIA
lepton-pair invariant mass at 1.96 TeV for
Tune DW, Tune DWT, ATLAS and HERWIG
PYTHIA Tune A, Tune AW, Tune BW, Tune
(without MPI).
DW and HERWIG (without MPI).
MCnet07 - Durham - Part 2
April 18-20, 2007
Rick Field – Florida/CDF/CMS
Page 61
Extrapolations to the LHC:
Drell-Yan Production
Drell-Yan Production
The “Underlying Event”
The ATLAS tune has a much “softer”
distribution of chargedAntiProton
particles than
Underlying Event
the CDF Run 2 Tunes!
Initial-State
Proton
Charged Particles
(|h|<1.0, pT > 0.5 GeV/c)
Charged particle density
versus M(pair)
Lepton
Underlying Event
Radiation
Charged Particles
(|h|<1.0, pT > 0.9 GeV/c)
Anti-Lepton
Charged Particle Density: dN/dhd
Charged Particle Density: dN/dhd
Drell-Yan
PY Tune DWT
Generator Level
14 TeV
Charged Particle
4.0 Density: dN/dhd
PY-ATLAS
generator level
2.0
1.5
1.0
0.5
Z
HERWIG
100
200
0.0
0
Charged Particle Density
Charged Particle Density
RDF Preliminary
300
1.2
PY-ATLAS
PY Tune DWT
3.0
PY Tune DW
PY Tune DW
2.0
14 TeV
1.0
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
(excluding lepton-pair )
Charged Particle Density
2.5
0.8
Charged Particles (pT > min, |h|<1.0)
(excluding lepton-pair
PY Tune DW )
0.4
PY-ATLAS
70 < M(m+m-) < 110 GeV
Z
Generator Level
14 TeV
HERWIG
Charged Particles (|h|<1.0, PT>0.9 GeV/c)
(excluding lepton-pair )
0.0
400
500
600
HERWIG
700
800
900
1000
0
100
200
300
400
500
600
700
800
900
1000
Lepton-Pair Invariant Mass (GeV)
Lepton-Pair Invariant Mass (GeV)
0.0
particle
0.0
0.2
0.4(pT >0.60.5 0.8  Average
1.0
1.2charged
1.4
1.6
1.8density (pT > 0.9 GeV/c)
 Average charged particle
density
the lepton-pair invariant mass at 14 TeV
GeV/c) versus the lepton-pair invariantMinimum
mass pversus
T (GeV/c)
at 14 TeV for PYTHIA Tune DW, Tune DWT, for PYTHIA Tune DW, Tune DWT, ATLAS and
HERWIG (without MPI).
ATLAS and HERWIG (without MPI).
MCnet07 - Durham - Part 2
April 18-20, 2007
Rick Field – Florida/CDF/CMS
Page 62
Summary and Conclusions
“Minumum Bias” Collisions
 “Min-Bias” is not well defined. What you
see depends on what you trigger on! Every
trigger produces some biases.
Proton
 Very preliminary results seem to show that
pile-up conspires to help give you what you
ask for (i.e. satisfy your “trigger” or your
event selection)!
If true this means the pile-up is not the
same for all processes. It is process (i.e.
trigger) dependent!
Charged Particle Density: dN/dh
10
Charged Particle Density
 We have learned a lot about “Min-Bias” at the
Tevatron, but we do not know what to expect at
the LHC. This will depend on the Min-Bias Trigger!
AntiProton
pyA
pyDW
pyDWT
ATLAS
Generator Level
14 TeV
8
I must double
check my analysis and
6
get it “blessed” before you can trust
4
what I have shown!
 We are making good progress in understanding and
modeling the “underlying event”. However, we do not
yet have a perfect fit to all the features of the CDF
“underlying event” data!
2
Charged Particles (all pT)
0
-10
-8
-6
-4
-2
0
2
4
6
8
10
PseudoRapidity h
Outgoing Parton
PT(hard)
Initial-State Radiation
Proton
AntiProton
Underlying Event
Outgoing Parton
Underlying Event
Final-State
Radiation
 Need to measure “Min-Bias” and the “underlying event” at the LHC as soon
as possible and tune the Monte-Carlo modles and compare with CDF!
MCnet07 - Durham - Part 2
April 18-20, 2007
Rick Field – Florida/CDF/CMS
Page 63
UE&MB@CMS
UE&MB@CMS
“Minimum-Bias” Collisions
Proton
Proton
High PT Jet Production
Outgoing Parton
PT(hard)
Initial-State
Radiation
Proton
Proton
Underlying Event
Outgoing Parton
 Min-Bias Studies: Charged particle distributions and
correlations. Construct “charged particle jets” and look
at “mini-jet” structure and the onset of the “underlying
event”. (requires only charged tracks)
Underlying Event
Final-State
Radiation
Drell-Yan Production
Lepton
Proton
Proton
Underlying Event
Underlying Event
Study charged
particles
 “Underlying
Event”
Studies: The “transverse region” in
and“leading
muons using
the
CMS
detector charged particle jet
Jet” and “back-to-back”
atproduction
the LHC (as
soon
possible)!
and
theas“central
region” in Drell-Yan
production. (requires charged tracks and muons for DrellYan)
Initial-State
Radiation
Anti-Lepton
Drell-Yan Production
Lepton-Pair
PT(pair)
Proton
Proton
Underlying Event
Underlying Event
Initial-State
Radiation
Final-State
Radiation
 Drell-Yan Studies: Transverse momentum distribution of
the lepton-pair versus the mass of the lepton-pair,
<pT(pair)>, <pT2(pair)>, ds/dpT(pair) (only requires
muons). Event structure for large lepton-pair pT (i.e. mm
+jets, requires muons).
Outgoing Parton
MCnet07 - Durham - Part 2
April 18-20, 2007
Rick Field – Florida/CDF/CMS
Page 64