The “Underlying Event” in Run 2 (CDF)
Outgoing Parton
PT(hard)
The “underlying event” consists of
hard initial & final-state radiation
plus the “beam-beam remnants” and
possible multiple parton interactions.
Initial-State Radiation
Proton
AntiProton
Underlying Event
Underlying Event
Studying the “Underlying Event”






Outgoing Parton
Final-State
Radiation
Two Classes of Events: “Leading Jet” and “Back-to-Back”.
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”.
 Studying the “Underlying Event” in Drell-Yan Production.
 Extrapolations to the LHC. UE&MB@CMS
Florida-Perugia
Drell-Yan Production
Lepton
Proton
AntiProton
Underlying Event
Underlying Event
Initial-State
Radiation
CMS at the LHC
University of Perugia - Lecture 2
March 31, 2006
Rick Field – Florida/CDF/CMS
Anti-Lepton
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
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
Df
“Toward”
“Transverse”
“Transverse”
“Away”
Transverse
Region 1
Df
“Toward”
“Trans 1”
f
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 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).
University of Perugia - Lecture 2
March 31, 2006
Rick Field – Florida/CDF/CMS
Page 2
Particle Densities
DhDf = 4p = 12.6
2p
f
31 charged
charged particles
particle
Charged Particles
pT > 0.5 GeV/c |h| < 1
CDF Run 2 “Min-Bias”
CDF Run 2 “Min-Bias”
Observable
Average
Nchg
Number of Charged Particles
(pT > 0.5 GeV/c, |h| < 1)
3.17 +/- 0.31
0.252 +/- 0.025
PTsum
(GeV/c)
Scalar pT sum of Charged Particles
(pT > 0.5 GeV/c, |h| < 1)
2.97 +/- 0.23
0.236 +/- 0.018
Average Density
per unit h-f
chg/dhdf = 1/4p
3/4p = 0.08
0.24
dNchg
13 GeV/c PTsum
0
-1
h
+1
Divide by 4p
dPTsum/dhdf = 1/4p
3/4p GeV/c = 0.08
0.24 GeV/c
 Study the charged particles (pT > 0.5 GeV/c, |h| < 1) and form the charged
particle density, dNchg/dhdf, and the charged scalar pT sum density,
dPTsum/dhdf.
University of Perugia - Lecture 2
March 31, 2006
Rick Field – Florida/CDF/CMS
Page 3
“Transverse” Particle Densities
Charged Particles
pT > 0.5 GeV/c |h| < 1
2p
Away Region
Jet #1 Direction
Df
Transverse
Region 1
f
Leading
Jet
AVE “transverse”
(Trans 1 + Trans 2)/2
Area = 4p/6
“Toward”
“Trans 1”
“Trans 2”
Toward Region
Transverse
Region 2
“Away”
1 charged particle in the
“transverse 2” region
Away Region
0
-1
h
+1
dNchg/dhdf = 1/(4p/6) = 0.48
 Study the charged particles (pT > 0.5 GeV/c, |h| < 1) in the “Transverse 1” and
“Transverse 2” and form the charged particle density, dNchg/dhdf, and the charged
scalar pT sum density, dPTsum/dhdf.
 The average “transverse” density is the average of “transverse 1” and “transverse 2”.
University of Perugia - Lecture 2
March 31, 2006
Rick Field – Florida/CDF/CMS
Page 4
Charged Particle Density Df Dependence
Log Scale!
Jet #1 Direction
Charged Particle Density: dN/dhdf
10.0
“Toward”
“Transverse”
“Transverse”
Jet #3
“Away”
“Away-Side”
“Away-Side”
Jet Jet
Charged Particle Density
Df
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-f
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.
University of Perugia - Lecture 2
March 31, 2006
Rick Field – Florida/CDF/CMS
Page 5
Charged Particle Density Df Dependence
Refer to this as a
“Leading Jet” event
Jet #1 Direction
Charged
Particle Density:
Density: dN/dhdf
dN/dhdf
Charged Particle
Df
10.0
10.0
Subset
“Transverse”
“Transverse”
“Away”
Refer to this as a
“Back-to-Back” event
Jet #1 Direction
Df
“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
Df (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” (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.
University of Perugia - Lecture 2
March 31, 2006
Rick Field – Florida/CDF/CMS
Page 6
Charged Particle Density Df Dependence
“Leading Jet”
Jet #1 Direction
Charged Particle Density: dN/dhdf
Df
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
Df
"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 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.
University of Perugia - Lecture 2
March 31, 2006
Rick Field – Florida/CDF/CMS
Page 7
“Transverse” PTsum Density versus ET(jet#1)
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
CDF Run
2 Preliminary
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.
University of Perugia - Lecture 2
March 31, 2006
Rick Field – Florida/CDF/CMS
Page 8
“Transverse” PTsum Density versus ET(jet#1)
Jet #1 Direction
Df
Charged PTsum Density: dPT/dhdf
100.0
“Transverse”
“Transverse”
“Away”
"AVE Transverse" PTsum Density: dPT/dhdf
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
Df (degrees)
0.6
30-70 GeV
0.4
Charged PTsum Density: dPT/dhdf
95-130 GeV
Back-to-Back
0.2
1.96 TeV
50
100
ET(jet#1) (GeV)
Jet #1 Direction
Df
“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
Df (degrees)
Jet #2 Direction
University of Perugia - Lecture 2
March 31, 2006
Rick Field – Florida/CDF/CMS
Page 9
“TransDIF” PTsum Density versus ET(jet#1)
“Leading Jet”
Jet #1 Direction
"MAX-MIN Transverse" PTsum Density: dPT/dhdf
Df
“Toward”
“TransMAX”
"Transverse" PTsum Density (GeV/c)
2.0
CDF Run 2 Preliminary
CDF Run 2 PreliminaryPY Tune A
Jet #1 Direction
data uncorrected
“TransMIN”
“Away”
data uncorrected
theory + CDFSIM
theory + CDFSIM
Df
1.5
LeadingJet
“Toward”
1.0
“Back-to-Back”
Jet #1 Direction
Df
“Toward”
“TransMAX”
0.5
“TransMIN”
Back-to-Back
“Away”
1.96 TeV
HW
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
0.0
“TransMAX”
“TransMIN”
“Away”
Jet #2 Direction
0
50
“MAX-MIN” is very sensitive to
the “hard scattering” 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 PTsum density.
 Shows the “transDIF” = MAX-MIN charge PTsum density, dPTsum/dhdf, for pT > 0.5
GeV/c, |h| < 1 versus ET(jet#1) for “Leading Jet” and “Back-to-Back” events.
University of Perugia - Lecture 2
March 31, 2006
Rick Field – Florida/CDF/CMS
Page 10
“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.
University of Perugia - Lecture 2
March 31, 2006
Rick Field – Florida/CDF/CMS
Page 11
“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.
University of Perugia - Lecture 2
March 31, 2006
Rick Field – Florida/CDF/CMS
Page 12
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
60
120
150
180
210
240
270
300
Df (degrees)
Df (degrees)
University of Perugia - Lecture 2
March 31, 2006
90
Rick Field – Florida/CDF/CMS
Page 13
“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”
“Away”
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
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.
University of Perugia - Lecture 2
March 31, 2006
Rick Field – Florida/CDF/CMS
Page 16
“Transverse” PTmax versus ET(jet#1)
Jet #1 Direction
“Leading Jet”
Df
“TransMIN”
Highest“TransMAX”
pT particle
in the
“transverse” region!
“Back-to-Back”
“Away”
Jet #1 Direction
Df
“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
Df
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).
University of Perugia - Lecture 2
March 31, 2006
Rick Field – Florida/CDF/CMS
Page 17
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
Df
Df
“Toward”
“TransMAX”
PTmaxT
Df
“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 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).
University of Perugia - Lecture 2
March 31, 2006
Rick Field – Florida/CDF/CMS
Page 18
Back-to-Back “Associated”
Charged Particle Densities
“Associated” densities do
not include PTmaxT!
PTmaxT
Direction
Associated Particle Density
Df
Jet#2
Region
Charged Particles
(|h|<1.0, PT>0.5 GeV/c)
CDF Preliminary
Jet #3
Jet #2
Associated Particle Density: dN/dhdf
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
Df (degrees)
 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).
University of Perugia - Lecture 2
March 31, 2006
Rick Field – Florida/CDF/CMS
Page 19
Back-to-Back “Associated”
Charged Particle Densities
“Back-to-Back”
charge density
Jet #1 Direction
Df
Charged Particle Density: dN/dhdf
10.0
“Toward”
“Transverse”
“Away”
“Back-to-Back”
“associated” density
Df
Jet #2 Direction
Jet#1
Region
Charged Particle Density
“Transverse”
CDF Preliminary
data uncorrected
Charged Particles
(|h|<1.0, PT>0.5 GeV/c)
"Transverse"
Region
1.0
Associated Density
PTmaxT not included
PTmaxT
Back-to-Back
PTmaxT > 0.5 GeV/c
PTmaxT
Direction
30 < ET(jet#1) < 70 GeV
Jet#1
0.1
Jet#2
Region
0
30
60
90
120
150
180
210
240
270
300
330
360
Df (degrees)
 Shows 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
It is
more probable
to find
a
GeV/c, for “back-to-back”
events with 30
< ET(jet#1) < 70 GeV.
particle accompanying
PTmaxT
than itof
is the
to find
a particle
in the
Shows Df dependence
charged
particle
density, dNchg/dhdf for charged particles
“transverse”
region!
(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.
University of Perugia - Lecture 2
March 31, 2006
Rick Field – Florida/CDF/CMS
Page 21
Back-to-Back “Associated”
Charged Particle Densities
“Back-to-Back”
charge density
Charged Particle Density: dN/dhdf
Jet #1 Direction
Df
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
Df
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 Df dependence of the “associated” charged particle density, dNchg/dhdf, pT > 0.5
GeV/c, |h| < 1 (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.
University of Perugia - Lecture 2
March 31, 2006
Rick Field – Florida/CDF/CMS
Page 22
Back-to-Back “Associated”
Charged Particle Densities
“Back-to-Back”
charge density
Charged Particle Density: dN/dhdf
Jet #1 Direction
Df
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
Df
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 Df dependence of the “associated” charged particle density, 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.
University of Perugia - Lecture 2
March 31, 2006
Rick Field – Florida/CDF/CMS
Page 23
Jet Topologies
QCDThree
Four
Jet
QCD
Jet Topology
Topology Charged Particle Density: dN/dhdf
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 #3Df
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 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.
University of Perugia - Lecture 2
March 31, 2006
Rick Field – Florida/CDF/CMS
Page 24
Back-to-Back “Associated”
Charged Particle Density
Associated Particle Density: dN/dhdf
PTmaxT
Direction
10.0
Df
Jet#2
Region
Jet#1
Region
Associated Particle Density
CDF Preliminary
Charged Particles
(|h|<1.0, PT>0.5 GeV/c)
data uncorrected
Back-to-Back
1.0
Jet#2
Region
95 < ET(jet#1) < 130 GeV
30 < ET(jet#1) < 70 GeV
"Jet#1"
Region
PTmaxT
PTmaxT > 2.0 GeV/c (not included)
0.1
Log Scale!
0
30
60
90
120
150
180
210
240
270
300
330
360
Df (degrees)
 Look at the Df dependence of the “associated” charged particle density, dNchg/dhdf, 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 and 95 < ET(jet#1) <
130 GeV.
 Very little dependence on ET(jet#1) in the “transverse” region for “back-to-back”
events!
University of Perugia - Lecture 2
March 31, 2006
Rick Field – Florida/CDF/CMS
Page 25
“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/dhdf
Df
“Min-Bias”
“Associated” Density
Associated Particle Density
Jet#2
Region
10.0
Jet#1
Region
PTmax Direction
Df
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 f
0
30
60
90
120
150
180
210
240
270
300
330
360
Df (degrees)
Log Scale!
“Birth” of jet#1 in
 Shows the Df dependence of the “associated” charged particle density,“min-bias”
dNchg/dhdf
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 Df dependence of the “associated” charged particle density,
dNchg/dhdf, 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.
University of Perugia - Lecture 2
March 31, 2006
Rick Field – Florida/CDF/CMS
Page 26
“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/dhdf
PTmaxT > 0.5 GeV/cAssociated PTsum Density: dPT/dhdf
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
Df (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
Df (degrees)
Data - Theory: Associated PTsum Density dPT/dhdf
Data - Theory: Associated PTsum Density dPT/dhdf
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
University of Perugia - Lecture 2
March 31, 2006
90
120
150
180
210
240
270
300
330
360
Df (degrees)
Df (degrees)
Rick Field – Florida/CDF/CMS
Page 28
Jet Multiplicity
Max pT in the
“transverse” region!
Jet Multiplicity
50%
Jet #1 Direction
Df
“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.
University of Perugia - Lecture 2
March 31, 2006
Rick Field – Florida/CDF/CMS
Page 30
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
f
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/dhdf, and the charged scalar pT sum density, dPTsum/dhdf, by
dividing by the area in h-f space.
University of Perugia - Lecture 2
March 31, 2006
Rick Field – Florida/CDF/CMS
Page 33
CDF Run 1 PT(Z)
PYTHIA 6.2 CTEQ5L
Parameter
Tune A
Tune A25
Tune A50
MSTP(81)
1
1
1
MSTP(82)
s = 1.0
4
4
4
PARP(82)
2.0 GeV
2.0 GeV
2.0 GeV
PARP(83)
0.5
0.5
0.5
PARP(84)
0.4
0.4
0.4
PARP(85)
0.9
0.9
0.9
PARP(86)
0.95
0.95
0.95
PARP(89)
1.8 TeV
1.8 TeV
1.8 TeV
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
Z-Boson Transverse Momentum
0.12
PT Distribution 1/N dN/dPT
UE Parameters
0.08
CDF Run 1
published
1.8 TeV
s = 5.0
Normalized to 1
0.04
0.00
0
2
4
6
8
10
12
14
16
18
20
Z-Boson PT (GeV/c)
ISR Parameter
Intrensic KT
University of Perugia - Lecture 2
March 31, 2006
CDF Run 1 Data
PYTHIA Tune A
PYTHIA Tune A25
PYTHIA Tune A50
s = 2.5
 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).
Rick Field – Florida/CDF/CMS
Page 34
CDF Run 1 PT(Z)
PYTHIA 6.2 CTEQ5L
Parameter
Tune A
Tune AW
MSTP(81)
1
1
MSTP(82)
4
4
PARP(82)
2.0 GeV
2.0 GeV
PARP(83)
0.5
0.5
PARP(84)
0.4
0.4
PARP(85)
0.9
0.9
PARP(86)
0.95
0.95
PARP(89)
1.8 TeV
1.8 TeV
PARP(90)
0.25
0.25
PARP(62)
1.0
1.25
PARP(64)
1.0
0.2
PARP(67)
4.0
4.0
MSTP(91)
1
1
PARP(91)
1.0
2.1
PARP(93)
5.0
15.0
Z-Boson Transverse Momentum
0.12
ISR Parameters
Intrensic KT
PT Distribution 1/N dN/dPT
UE Parameters
CDF Run 1 Data
PYTHIA Tune AW
0.08
CDF Run 1
published
s = 2.1
1.8 TeV
Normalized to 1
0.04
0.00
0
2
4
6
8
10
12
14
16
18
20
Z-Boson PT (GeV/c)
University of Perugia - Lecture 2
March 31, 2006
 Shows the Run 1 Z-boson pT distribution (<pT(Z)> ≈
11.5 GeV/c) compared with PYTHIA Tune AW
(<pT(Z)> = 11.7 GeV/c).
Effective Q cut-off, below which space-like showers are not evolved.
The Q2 = kT2 in as for space-like showers is scaled by PARP(64)!
Rick Field – Florida/CDF/CMS
Page 35
Drell-Yan Production
at the Tevatron
Lepton-Pair
Drell-Yan Production
Lepton-Pair Transverse
Momentum
Proton
<PT(pair)> versus M(pair)
PT(pair)
AntiProton
Underlying Event
Underlying Event
Initial-State
Radiation
Final-State
Radiation
Outgoing Parton
Lepton-Pair Transverse Momentum
Lepton-Pair Transverse Momentum
20
20
RDF Preliminary
RDF Preliminary
PY Tune AW
15
Average Pair PT
Average Pair PT
HERWIG
generator level
generator level
10
PY Tune A
5
15
10
PY Tune AW
5
Drell-Yan
1.96 TeV
Z
Drell-Yan
1.96 TeV
Z
0
0
0
50
100
150
200
250
0
50
Lepton-Pair Invariant Mass (GeV)
100
150
200
250
Lepton-Pair Invariant Mass (GeV)
 Shows the lepton-pair average PT versus the  Shows the lepton-pair average PT versus the
lepton-pair invariant mass at 1.96 TeV for
lepton-pair invariant mass at 1.96 TeV for
PYTHIA Tune AW and HERWIG.
PYTHIA Tune AW and PYTHIA Tune A.
University of Perugia - Lecture 2
March 31, 2006
Rick Field – Florida/CDF/CMS
Page 36
Drell-Yan Production
at the LHC
Lepton-Pair
Drell-Yan Production
Lepton-Pair Transverse
Momentum
Proton
<PT(pair)> versus M(pair)
PT(pair)
AntiProton
Underlying Event
The lepton-pair <PT>
much larger at the LHC!
Underlying Event
Initial-State
Radiation
Final-State
Radiation
Outgoing Parton
Lepton-Pair Transverse Momentum
Lepton-Pair Transverse Momentum
40
20
RDF Preliminary
HERWIG
RDF Preliminary
15
10
Average Pair PT
Average Pair PT
LHC
generator level
generator level
PY Tune AW
30
HERWIG
CDF
20
10
5
Drell-Yan
1.96 TeV
Z
Z
PY Tune AW
Drell-Yan
0
0
0
50
100
150
200
250
0
50
100
150
200
250
Lepton-Pair Invariant Mass (GeV)
Lepton-Pair Invariant Mass (GeV)
 Shows the lepton-pair average PT versus the  Shows the lepton-pair average PT versus the
lepton-pair invariant mass at 14 TeV for
lepton-pair invariant mass at 1.96 TeV for
PYTHIA Tune AW and HERWIG.
PYTHIA Tune AW and HERWIG.
University of Perugia - Lecture 2
March 31, 2006
Rick Field – Florida/CDF/CMS
Page 37
The “Underlying Event” in
Drell-Yan Production (Tevatron)
Drell-Yan Production
Lepton
The “Underlying Event”
Proton
Underlying Event
Charged particle density
versus M(pair)
AntiProton
Underlying Event
HERWIG (without MPI)
is much less active than
PY Tune AW (with MPI)!
Initial-State
Radiation
Anti-Lepton
Charged Particle Density: dN/dhdf
Charged Particle Density: dN/dhdf
1.0
1.0
RDF Preliminary
generator level
Charged Particle Density
Charged Particle Density
RDF Preliminary
PY Tune AW
0.8
0.6
0.4
PY Tune A
Drell-Yan
1.96 TeV
0.2
Z
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
0.0
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 )
0.0
0
50
100
150
200
250
0
50
Lepton-Pair Invariant Mass (GeV)
100
150
200
250
Lepton-Pair Invariant Mass (GeV)
 Shows the charged particle density versus the  Shows the charged particle density versus the
lepton-pair invariant mass at 1.96 TeV for
lepton-pair invariant mass at 1.96 TeV for
PYTHIA Tune AW and PYTHIA Tune A.
PYTHIA Tune AW and HERWIG (with no MPI).
University of Perugia - Lecture 2
March 31, 2006
Rick Field – Florida/CDF/CMS
Page 38
The “Underlying Event” in
Drell-Yan Production (LHC)
Drell-Yan Production
Lepton
The “Underlying Event”
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” much
more active at the LHC!
Underlying Event
Initial-State
Radiation
Anti-Lepton
Charged Particle Density: dN/dhdf
Charged Particle Density: dN/dhdf
1.5
1.0
RDF Preliminary
generator level
PY Tune AW
0.8
0.6
0.4
HERWIG
0.2
Drell-Yan
1.96 TeV
Z
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
(excluding lepton-pair )
Charged Particle Density
Charged Particle Density
RDF Preliminary
generator level
Z
LHC
1.0
PY Tune AW
CDF
0.5
Drell-Yan
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
(excluding lepton-pair )
HERWIG
0.0
0.0
0
50
100
150
200
250
0
50
100
150
200
250
Lepton-Pair Invariant Mass (GeV)
Lepton-Pair Invariant Mass (GeV)
 Charged particle density versus the lepton-  Charged particle density versus the lepton-pair
invariant mass at 14 TeV for PYTHIA Tune AW
pair invariant mass at 1.96 TeV for PYTHIA
and HERWIG (without MPI).
Tune AW and HERWIG (without MPI).
University of Perugia - Lecture 2
March 31, 2006
Rick Field – Florida/CDF/CMS
Page 39
The “Underlying Event” in
High PT Jet Production (LHC)
The “Underlying Event”
High PT Jet Production
Outgoing Parton
Charged particle density
versus PT(jet#1)
AntiProton
PT(hard)
Initial-State
Radiation
Proton
Underlying Event
Underlying Event
Final-State
Radiation
Outgoing Parton
"Transverse" Charged Particle Density: dN/dhdf
"Transverse" Charged Particle Density: dN/dhdf
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
“Underlying event” much
more active at the LHC!
generator level
1.5
PY Tune AW
HERWIG
1.0
CDF
0.5
"Leading Jet"
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
0.0
0
50
100
150
200
250
300
350
400
450
500
0
250
500
PT(particle jet#1) (GeV/c)
750
1000
1250
1500
1750
2000
2250
2500
PT(particle jet#1) (GeV/c)
 Charged particle density in the “Transverse”  Charged particle density in the “Transverse”
region versus PT(jet#1) at 1.96 TeV for PY
region versus PT(jet#1) at 14 TeV for PY Tune
Tune AW and HERWIG (without MPI).
AW and HERWIG (without MPI).
University of Perugia - Lecture 2
March 31, 2006
Rick Field – Florida/CDF/CMS
Page 40
UE&MB@CMS
UE&MB@CMS
Rick Field (Florida)
Darin Acosta (Florida)
Paolo Bartalini (Florida)
Albert De Roeck (CERN)
Livio Fano' (INFN/Perugia at CERN)
Filippo Ambroglini (INFN/Perugia at CERN)
Khristian Kotov (UF Student, Acosta)
Me at CMS!
 Measure Min-Bias and the “Underlying Event” at CMS
 The plan involves two phases.
 Phase 1 would be to measure min-bias and the “underlying event”
as soon as possible (when the luminosity is low), perhaps during
commissioning. We would then tune the QCD Monte-Carlo models
for all the other CMS analyses. Phase 1 would be a service to the
rest of the collaboration. As the measurements become more
reliable we would re-tune the QCD Monte-Carlo models if
necessary and begin Phase 2.
 Phase 2 is “physics” and would include comparing the min-bias and
“underlying event” measurements at the LHC with the
measurements we have done (and am doing now) at CDF and then
writing a physics publication.
Darin
UE&MB@CMS
University of Perugia - Lecture 2
March 31, 2006
Rick Field – Florida/CDF/CMS
Page 42
UE&MB@CMS
UE&MB@CMS
“Minimum-Bias” Collisions
Proton
Proton
High PT Jet Production
Outgoing Parton
PT(hard)
Initial-State
Radiation
Proton
 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)
Proton
Underlying Event
Outgoing Parton
Underlying Event
Final-State
Radiation
Drell-Yan Production
Lepton
Proton
 “Underlying Event” Studies: The “transverse region” in
“leading
Jet” and
“back-to-back” charged particle jet
Study
charged
particles
production
the “central
and muons
using and
the CMS
detectorregion” in Drell-Yan
production.
(requires charged tracks and muons for Drellat the LHC!
Yan)
Proton
Underlying Event
Underlying Event
Initial-State
Radiation
Anti-Lepton
Drell-Yan Production
Lepton-Pair
PT(pair)
Proton
Proton
Underlying Event
 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).
Underlying Event
Initial-State
Radiation
Final-State
Radiation
Outgoing Parton
University of Perugia - Lecture 2
March 31, 2006
Rick Field – Florida/CDF/CMS
Page 43