Lake Louise Winter Institute
Extrapolating from the Tevatron to the LHC
Rick Field
University of Florida
Outgoing Parton
Outline of Talk 2
PT(hard)
Chateau Lake Louise
February 2010
Initial-State Radiation
 The latest “underlying event”
Proton
AntiProton
Underlying Event
studies at CDF for “leading Jet”
and Z-boson events. Data
corrected to the particle level.
Outgoing Parton
Underlying Event
Final-State
Radiation
CDF Run 2
 Min-Bias and the “underlying event”.
 Studying <pT> versus Nchg in
UE&MB@CMS
“min-bias” collisions and in Drell-Yan.
 UE studies at 900 GeV from CMS and
CMS at the LHC
ATLAS coming soon!
 LHC predictions!
Lake Louise Winter Institute
February 16, 2010
Rick Field – Florida/CDF/CMS
Page 1
QCD Monte-Carlo Models:
High Transverse Momentum Jets
Hard Scattering
Initial-State Radiation
Hard Scattering “Jet”
Initial-State Radiation
“Jet”
Outgoing Parton
PT(hard)
Outgoing Parton
PT(hard)
Proton
“Hard Scattering” Component
AntiProton
Final-State Radiation
Outgoing Parton
Underlying Event
Underlying Event
Proton
“Jet”
Final-State Radiation
AntiProton
Underlying Event
Outgoing Parton
Underlying Event
“Underlying Event”
 Start with the perturbative 2-to-2 (or sometimes 2-to-3) parton-parton scattering and add initial and finalstate 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).
The “underlying
event” is“jet”
an unavoidable
 Of course the outgoing colored partons fragment
into hadron
and inevitably “underlying event”
background to most collider observables
observables receive contributions from initial
and final-state radiation.
and having good understand of it leads to
more precise collider measurements!
Lake Louise Winter Institute
February 16, 2010
Rick Field – Florida/CDF/CMS
Page 2
QCD Monte-Carlo Models:
Lepton-Pair Production
Lepton-Pair
Production
High
PT Z-Boson
Production
Anti-Lepton
Outgoing Parton
Initial-State
Initial-State Radiation
Radiation
High P
T Z-Boson Production
Lepton-Pair
Production
Initial-State
Initial-StateRadiation
Radiation
“Jet”
Proton
Proton
Final-State Radiation
Outgoing
Parton
Anti-Lepton
Final-State Radiation
“Hard Scattering” Component
AntiProton
AntiProton
Underlying Event
Lepton
Z-boson
Underlying Event
Proton
Lepton
Z-boson
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-state radiation.
Lake Louise Winter Institute
February 16, 2010
Rick Field – Florida/CDF/CMS
Page 3
“Towards”, “Away”, “Transverse”
Look at the charged
particle density, the
charged PTsum density
and the ETsum density in
all 3 regions!
 Correlations relative to the leading jet
Jet #1 Direction
“Transverse” region is
very sensitive to the
“underlying event”!
Charged particles pT > 0.5 GeV/c || < 1
Calorimeter towers ET > 0.1 GeV || < 1
“Toward-Side” Jet
2
Away Region
Z-Boson
Direction
Jet #1 Direction


Transverse
Region
“Toward”
“Toward”
“Transverse”
“Transverse”
“Away”
“Transverse”
“Transverse”

Leading
Jet
Toward Region
“Away”
Transverse
Region
“Away-Side” Jet
Away Region
0
-1

+1
 Look at correlations in the azimuthal angle relative to the leading charged particle jet (|| <
1) or the leading calorimeter jet (|| < 2).
 Define || < 60o as “Toward”, 60o < || < 120o as “Transverse ”, and || > 120o as “Away”.
o
Each of the three regions have area  = 2×120 = 4/3.
Lake Louise Winter Institute
February 16, 2010
Rick Field – Florida/CDF/CMS
Page 4
Event Topologies
 “Leading Jet” events correspond to the leading
calorimeter jet (MidPoint R = 0.7) in the region || < 2
with no other conditions.
 “Inclusive 2-Jet Back-to-Back” events are selected to
have at least two jets with Jet#1 and Jet#2 nearly “backto-back” (12 > 150o) with almost equal transverse
energies (PT(jet#2)/PT(jet#1) > 0.8) with no other
conditions .
 “Exclusive 2-Jet Back-to-Back” events are selected to
have at least two jets with Jet#1 and Jet#2 nearly “backto-back” (12 > 150o) with almost equal transverse
energies (PT(jet#2)/PT(jet#1) > 0.8) and PT(jet#3) < 15
GeV/c.
 “Leading ChgJet” events correspond to the leading
charged particle jet (R = 0.7) in the region || < 1 with
no other conditions.
 “Z-Boson” events are Drell-Yan events
with 70 < M(lepton-pair) < 110 GeV
with no other conditions.
Lake Louise Winter Institute
February 16, 2010
Rick Field – Florida/CDF/CMS
Jet #1 Direction

“Leading Jet”
“Toward”
“Transverse”
“Transverse”
subset
“Away”
Jet #1 Direction

“Inc2J Back-to-Back”
“Toward”
subset
“Transverse”
“Transverse”
“Away”
“Exc2J Back-to-Back”
Jet #2 Direction
ChgJet #1 Direction

“Charged Jet”
“Toward”
“Transverse”
“Transverse”
“Away”
Z-Boson Direction

“Toward”
Z-Boson
“Transverse”
“Transverse”
“Away”
Page 5
“transMAX” & “transMIN”
Jet #1 Direction
Z-Boson
Direction
Jet #1 Direction

Area = 4/6
“transMIN” very sensitive to
the “beam-beam remnants”!
“Toward-Side” Jet

“Toward”
“TransMAX”
“Toward”
“TransMIN”
“TransMAX”
“Away”
“TransMIN”
Jet #3
“Away”
“Away-Side” Jet
 Define the MAX and MIN “transverse” regions (“transMAX” and “transMIN”) on an
event-by-event basis with MAX (MIN) having the largest (smallest) density. Each of the
two “transverse” regions have an area in - space of 4/6.
 The “transMIN” region is very sensitive to the “beam-beam remnant” and the soft
multiple parton interaction components of the “underlying event”.
 The difference, “transDIF” (“transMAX” minus “transMIN”), is very sensitive to the
“hard scattering” component of the “underlying event” (i.e. hard initial and final-state
radiation).
 The overall “transverse” density is the average of the “transMAX” and “transMIN”
densities.
Lake Louise Winter Institute
February 16, 2010
Rick Field – Florida/CDF/CMS
Page 6
Observables at the
Particle and Detector Level
“Leading Jet”
Jet #1 Direction
Observable
Particle Level
Detector Level
dNchg/dd
Number of charged particles
per unit -
(pT > 0.5 GeV/c, || < 1)
Number of “good” charged tracks
per unit -
(pT > 0.5 GeV/c, || < 1)
dPTsum/dd
Scalar pT sum of charged particles
per unit -
(pT > 0.5 GeV/c, || < 1)
Scalar pT sum of “good” charged tracks per
unit -
(pT > 0.5 GeV/c, || < 1)
<pT>
Average pT of charged particles
(pT > 0.5 GeV/c, || < 1)
Average pT of “good” charged tracks
(pT > 0.5 GeV/c, || < 1)
PTmax
Maximum pT charged particle
(pT > 0.5 GeV/c, || < 1)
Require Nchg ≥ 1
Maximum pT “good” charged tracks
(pT > 0.5 GeV/c, || < 1)
Require Nchg ≥ 1
dETsum/dd
Scalar ET sum of all particles
per unit -
(all pT, || < 1)
Scalar ET sum of all calorimeter towers
per unit -
(ET > 0.1 GeV, || < 1)
PTsum/ETsum
Scalar pT sum of charged particles
(pT > 0.5 GeV/c, || < 1)
divided by the scalar ET sum of
all particles (all pT, || < 1)
Scalar pT sum of “good” charged tracks
(pT > 0.5 GeV/c, || < 1)
divided by the scalar ET sum of
calorimeter towers (ET > 0.1 GeV, || < 1)

“Toward”
“Transverse”
“Transverse”
“Away”
Jet #1 Direction

“Toward”
“Transverse”
“Transverse”
“Away”
Jet #2 Direction
“Back-to-Back”
Lake Louise Winter Institute
February 16, 2010
Rick Field – Florida/CDF/CMS
Page 7
Overall Totals (|| < 1)
ETsum = 775 GeV!
“Leading Jet”
Overall Totals versus PT(jet#1)
ETsum = 330 GeV
1000
CDF Run 2 Preliminary
ETsum (GeV)
data corrected
pyA generator level
Jet #1 Direction

PTsum (GeV/c)
Average
100
“Overall”
Nchg
"Leading Jet"
MidPoint R=0.7 |(jet#1)|<2
10
PTsum = 190 GeV/c
Charged Particles (||<1.0, PT>0.5 GeV/c)
Stable Particles (||<1.0, all PT)
1
0
50
Nchg = 30
100
150
200
250
300
350
400
PT(jet#1) (GeV/c)
 Data at 1.96 TeV on the overall number of charged particles (pT > 0.5 GeV/c, || < 1) and the overall
scalar pT sum of charged particles (pT > 0.5 GeV/c, || < 1) and the overall scalar ET sum of all
particles (|| < 1) for “leading jet” events as a function of the leading jet pT. The data are corrected to
the particle level (with errors that include both the statistical error and the systematic uncertainty) and
are compared with PYTHIA Tune A at the particle level (i.e. generator level)..
Lake Louise Winter Institute
February 16, 2010
Rick Field – Florida/CDF/CMS
Page 8
“Towards”, “Away”, “Transverse”
“Leading Jet”
Jet #1 Direction

“Toward”
“Transverse”
“Transverse”
“Away”
ETsum
Density
(GeV)
Charged
PTsum
Density
(GeV/c)
Average
Charged
Density
Charged
Particle
Density:
dN/dd
Charged
PTsum
Density:
dPT/dd
ETsum
Density:
dET/dd
5
100.0
100.0
CDFCDF
RunRun
2 Preliminary
2 Preliminary
4
data corrected
data"Toward"
corrected
pyA generator level
pyA generator level
10.0
3
"Toward"
"Away"
"Away"
Factor of ~13
"Toward"
"Transverse"
Factor of ~16
"Away"
"Transverse" "Leading Jet"
Factor of MidPoint
~4.5 R=0.7 |(jet#1)|<2
2
1.0
1.0
1
0 0.1
0.1
0 0
0
"Transverse"
CDF Run 2 Preliminary
data corrected
pyA generator level
50 50
50
100100
100
150
150
150
"Leading Jet"
"Leading Jet"
MidPoint R=0.7 |(jet#1)|<2
MidPoint R=0.7 |(jet#1)|<2
ChargedStable
Particles
(||<1.0,
PT>0.5
GeV/c)
Charged
Particles
(||<1.0,
PT>0.5
GeV/c)
Particles
(||<1.0,
all
PT)
200
200
200
250
250
250
300
300
300
350
350
350
400
400
400
PT(jet#1)
PT(jet#1)(GeV/c)
(GeV/c)
PT(jet#1)
(GeV/c)
 Data
Data at
at 1.96
1.96 TeV
TeV on
on the
the charged
density ofparticle
charged
particles,
dN/dd,
p > 0.5 GeV/c
and || < 1 for

pT sum
density, with
dPT/dd,
and“leading
||
T > 0.5 GeV/c

Data at
1.96 TeV
on the
particle scalar
ETscalar
sum density,
dET/dd,
forT|| < with
1 for p“leading
jet” events
as<a1
jet” events as a function of the leading jet p for the “toward”, “away”, and “transverse” regions. The
for “leading
jet”
eventsjet
as pa function
of the Tleading
jet pand
the “toward”,
“away”,The
anddata
“transverse”
T for“transverse”
function
of the
leading
“toward”,
“away”,
regions.
are corrected
T for the
data
are
corrected
to
the
particle
level
(with
errors
that
include
both
the
statistical
error
and
the systematic
regions.
The
data
are
corrected
to
the
particle
level
(with
errors
that
include
both
the
statistical
errorand
andare
to the particle level (with errors that include both the statistical error and the systematic uncertainty)
uncertainty)
and
are
compared
with
PYTHIA
Tune
A
at
the
particle
level
(i.e.
generator
level).
the systematic
and A
are
with
PYTHIA
Tune Alevel).
at the particle level (i.e. generator
compared
withuncertainty)
PYTHIA Tune
at compared
the particle
level
(i.e. generator
level).
Lake Louise Winter Institute
February 16, 2010
Rick Field – Florida/CDF/CMS
Page 9
Charged Particle Density
HERWIG + JIMMY
Tune
(PTJIM
= 3.6)
Charged
ParticleParticle
Density:Density:
dN/dd
"Transverse"
Charged
dN/ddCharged Particle Density:"Away"
Charged
Particle
Density:
dN/dd
"Away"
dN/dd
Charged
Particle
Density:
dN/dd
3
CDF Run 2 Preliminary
data corrected
data corrected
generator level theory
pyAW generator level
0.9
2
"Drell-Yan Production"
70 < M(pair) < 110 GeV
0.6
1
20
20
40
60
generator level theory
2
40
80
100
0
60
120
0
"Drell-Yan Production"
70 < M(pair) < 110 GeV
80
160
20
140
180
PT(Z-Boson)
(GeV/c)(GeV/c)
PT(jet#1)
or PT(Z-Boson)
Z-Boson Direction

High PT Z-Boson Production
CDF
CDFRun
Run22Preliminary
Preliminary
100
200
40
"Leading Jet"
data
datacorrected
corrected
pyA generator
generator
levellevel
theory
pyAW
Charged Particles
Particles (||<1.0,
(||<1.0, PT>0.5
PT>0.5
GeV/c)
HW
Charged
GeV/c)
excluding the lepton-pair
"Toward"
0
0.0
00
"Leading
Jet"
"Away" data corrected
1
"Transverse"
"Z-Boson"
0.3
44
Average
Density
"Away" Charged
Charged Density
CDFRun
Run22Preliminary
Preliminary
CDF
"Away" Charged Density
"Transverse"
ChargedDensity
Density
Average Charged
3
1.2
33
"Away"
"Toward"
22
JIM
11
"Leading Jet"
MidPoint R=0.7 |(jet#1)|<2
"Z-Boson""Transverse"
Charged Particles (||<1.0, PT>0.5 GeV/c)
excluding the lepton-pair
Charged Particles (||<1.0, PT>0.5 GeV/c)
Charged Particles (||<1.0, PT>0.5 GeV/c)
00
00
60
20
20
40
40
60
60
80
80
80
100
100
100
120
120
140
140
Jet #1 Direction
“Transverse”
PT(hard)
“Toward”
AntiProton
“Transverse”
“Transverse”
200
200
Outgoing Parton

Initial-State Radiation
“Toward”
Proton
180
180
PT(jet#1)
or PT(Z-Boson)
PT(jet#1)
(GeV/c) (GeV/c)
PT(Z-Boson) (GeV/c)
Outgoing Parton
160
160
“Transverse”
Initial-State Radiation
Proton
AntiProton
Underlying Event
Underlying Event
“Away”
“Away”
Outgoing Parton
Z-boson
Final-State
Radiation
 Data at 1.96 TeV on the density of charged particles, dN/dd, with pT > 0.5 GeV/c and || < 1 for “Z-Boson”
and “Leading Jet” events as a function of the leading jet pT or PT(Z) for the “toward”, “away”, and
“transverse” regions. The data are corrected to the particle level (with errors that include both the statistical
error and the systematic uncertainty) and are compared with PYTHIA Tune AW and Tune A, respectively, at the
particle level (i.e. generator level).
Lake Louise Winter Institute
February 16, 2010
Rick Field – Florida/CDF/CMS
Page 10
The “TransMAX/MIN” Regions
"TransDIF"
Charged
Particle
Density:
dN/dd
"TransDIF" Charged
Particle
Density:
dN/dd
Charged
Particle
Density:
dN/dd
"TransMAX/MIN"
Charged
Particle
Density:
dN/dd Charged Particle"TransMAX/MIN"
"TransMAX/MIN"
Charged
Particle
Density:
dN/dd
"TransDIF"
Density:
dN/dd
"Drell-Yan
Production"
"Drell-Yan
Production"
"Drell-Yan
Production"
70
M(pair)
110
GeV
70
M(pair)
110
GeV
70
<<<
M(pair)
<<<
110
GeV
"transMAX"
"transMAX"
0.6
0.8
0.8
ATLAS
0.9
0.6
pyDW
JIM
HW
"transMIN"
"transMIN"
0.3
0.4
0.4
ATLAS
HW
Charged Particles (||<1.0, PT>0.5 GeV/c)
excluding the lepton-pair
0.0
0.0
00
20
20
"Z-Boson"
0.3
0.0
60
60 0
40
40
80 40
20 80
PT(Z-Boson)
PT(Z-Boson) (GeV/c)
(GeV/c)
Z-Boson Direction

High PT Z-Boson Production
TransMAX
- TransMIN
"Transverse"
Charged Density
Density
Charged Particles
Particles (||<1.0,
(||<1.0,
PT>0.5
GeV/c)
Charged
PT>0.5
GeV/c)
CDF Run
2 Preliminary
excluding the
the lepton-pair
lepton-pair
excluding
data
corrected
pyAW
pyDW
pyAW
JIM
generator level theory
datacorrected
corrected
data
corrected
data
generatorlevel
leveltheory
theory
generator
level
theory
generator
0.9
1.2
1.2
1.6
1.2
1.2
CDFRun
Run222Preliminary
Preliminary
CDF
Run
Preliminary
CDF
"TransDIF" Charged Density
TransMAX - TransMIN
"Transverse"
Charged
"Transverse"
Charged Density
Density
1.2
1.6
1.6
100 80
60100
CDF Run
Run 22 Preliminary
Preliminary
CDF
"Leading
Jet"
data corrected
1.2
0.9
HW
HW
"transMIN"
0.4
0.3
"Leading Jet"
MidPoint R=0.7 |(jet#1)|<2
Charged Particles (||<1.0, PT>0.5 GeV/c) Charged Particles (||<1.0, PT>0.5 GeV/c)
Charged Particles (||<1.0, PT>0.5 GeV/c)
0.0
0.0
0
100
0
120 50
160
50 140 100
100
150
180
150
200
200
200
250
250
Jet #1 Direction
Initial-State Radiation
300
300
350
350
400
400
PT(jet#1)
PT(jet#1) (GeV/c)
(GeV/c)
Outgoing Parton

PT(hard)
Initial-State Radiation
“Toward”
Proton
“TransMAX”
"Leading Jet"
MidPoint R=0.7 |(jet#1)|<2
PY Tune A
PY Tune A
0.8
0.6
PT(jet#1) or PT(Z-Boson) (GeV/c)
Outgoing Parton
"transMAX"
data corrected
generatorlevel
leveltheory
theory
generator
AntiProton
“Toward”
Proton
AntiProton
Underlying Event
“TransMIN”
“TransMAX”
“Away”
“TransMIN”
“Away”
Outgoing Parton
Z-boson
Underlying Event
Final-State
Radiation

particle
density,
dN/dd,
withwith
pT > p0.5
GeV/c and || < 1 for “Z-Boson” and
Data
Dataat
at1.96
1.96TeV
TeVon
onthe
thecharged
density of
charged
particles,
dN/dd,
T > 0.5 GeV/c and || < 1 for “leading
“Leading
Jet”
as aof
function
of PTjet
(Z)por
the leading jet pT for the
“transMIN” regions.
jet” events
as aevents
function
the leading
as“transMAX”,
a function of Pand
T and for Z-Boson events
T(Z) for “TransDIF” =
The
data are corrected
to the particle
level (with
errors
includeto
both
statistical
the that
systematic
“transMAX”
minus “transMIN”
regions.
The data
arethat
corrected
thethe
particle
levelerror
(withand
errors
include
uncertainty)
and
are
compared
with
PYTHIA
Tune
AW
and
Tune
A,
respectively,
at
the
particle
level
(i.e.
both the statistical error and the systematic uncertainty) and are compared with PYTHIA Tune A and HERWIG
generator
level).at the particle level (i.e. generator level).
(without MPI)
Lake Louise Winter Institute
February 16, 2010
Rick Field – Florida/CDF/CMS
Page 12
Charged Particle <pT>
"Toward" Average PT Charged
"Transverse" Average PT
1.6
CDF Run 2 Preliminary
CDF Run 2 Preliminary
data corrected
generator level theory
"Toward" <PT> (GeV/c)
"Transverse" Average PT (GeV/c)
2.0
PY Tune A
1.5
1.0
"Leading Jet"
MidPoint R=0.7 |(jet#1)|<2
HW
data corrected
generator level theory
"Drell-Yan Production"
70 < M(pair) < 110 GeV
pyDW
pyAW
1.2
0.8
ATLAS
JIM
HW
Charged Particles (||<1.0, PT>0.5 GeV/c)
excluding the lepton-pair
Charged Particles (||<1.0, PT>0.5 GeV/c)
0.4
0.5
0
50
100
150
200
250
300
350
400
0
20
40
60
PT(jet#1) (GeV/c)
Jet #1 Direction
100
Z-BosonDirection


“Toward”
“Transverse”
80
PT(Z-Boson) (GeV/c)
“Toward”
“Transverse”
“Transverse”
“Away”
“Transverse”
“Away”
 Data at 1.96 TeV on the charged particle average pT, with pT > 0.5 GeV/c and || < 1 for the “toward”
region for “Z-Boson” and the “transverse” region for “Leading Jet” events as a function of the
leading jet pT or PT(Z). The data are corrected to the particle level (with errors that include both the
statistical error and the systematic uncertainty) and are compared with PYTHIA Tune AW and Tune A,
respectively, at the particle level (i.e. generator level). The Z-Boson data are also compared with
PYTHIA Tune DW, the ATLAS tune, and HERWIG (without MPI)
Lake Louise Winter Institute
February 16, 2010
Rick Field – Florida/CDF/CMS
Page 14
Z-Boson: “Towards”, Transverse”,
& “TransMIN” Charge Density
Charged
Particle
Density:
dN/dd
Charged
Particle
Density:
dN/dd
"TransMIN"
Charged
Particle
Density:
dN/dd
"Toward"
Charged
Particle
Density:
dN/dd
"TransMIN" Charged Particle Density:
dN/dd
High
PT Z-Boson
Production
Outgoing Parton
datagenerator
correctedlevel
pyAW
generator level theory
"Toward"
0.3
0.3
"Drell-Yan Production"
Production"
"Drell-Yan
70 << M(pair)
M(pair) <
70
< 110
110 GeV
GeV
HW
20
20
0.6
pyDW
data corrected
generator level theory
0.4
0.2
pyAW
Charged
Charged Particles
Particles (||<1.0,
(||<1.0, PT>0.5
PT>0.5 GeV/c)
GeV/c)
"Z-Boson"
excluding
excluding the
the lepton-pair
lepton-pair
0.0
0.0
00
CDF Run 2 Preliminary
"Transverse
ATLAS
JIM
0.6
0.6
0.0
60
60 0
40
40
PT(Z-Boson)
PT(Z-Boson) (GeV/c)
(GeV/c)
Initial-State Radiation
0.9
0.6
0.8
Charged
Density
"TransMIN"
Charged
Density
CDF Run 2 Preliminary
CDF Run
2 Preliminary
data corrected
"TransMIN" Charged Density
Charged
Density
"Toward"
Charged
Density
0.9
0.9
Initial-State Radiation
CDF Run 2 Preliminary
data corrected
Proton
generator
level theory
pyAW
generator
level
0.6
0.4
"Leading Jet"
"Drell-Yan Production"
"Drell-Yan Production"
70 < M(pair) < 110 GeV
70 < M(pair) < 110 GeV
AntiProtonpyDW
ATLAS
JIM
"Toward"
0.3
0.2
Z-boson
Z-boson
"transMIN"
Charged
Charged Particles
Particles (||<1.0,
(||<1.0, PT>0.5
PT>0.5 GeV/c)
GeV/c)
pyAW
HW
excluding
excluding the
the lepton-pair
lepton-pair
Charged Particles (||<1.0, PT>0.5 GeV/c)
0.0
80 40
20 80
100 80
60 100
1000
120
20
140
PT(jet#1) or PT(Z-Boson) (GeV/c)
160
40
180
60
200
100
PT(Z-Boson) (GeV/c)
Z-Boson Direction
Z-BosonDirection


“Toward”
“Toward”
“Transverse”
80
“TransMAX”
“Transverse”
“TransMIN”
“Away”
“Away”
 Data at 1.96 TeV on the density of charged particles, dN/dd, with pT > 0.5 GeV/c and || < 1 for “ZBoson” events as a function of PT(Z) for the “toward” and “transverse” regions. The data are
corrected to the particle level (with errors that include both the statistical error and the systematic
uncertainty) and are compared with PYTHIA Tune AW and HERWIG (without MPI) at the particle
level (i.e. generator level).
Lake Louise Winter Institute
February 16, 2010
Rick Field – Florida/CDF/CMS
Page 15
Z-Boson: “Towards” Region
"Toward" Charged Particle Density: dN/dd
"Toward" Charged Particle Density: dN/dd
CDF Run 2 Preliminary
CDF Run 2 Preliminary
generator level theory
data corrected
generator level theory
1.5
0.6
1.0
2.0
0.9
"Drell-Yan Production"
pyDWT LHC14
70 < M(pair) pyDW
< 110 GeV
ATLAS
JIM
HW Tevatron
pyDWT Tevatron
HW LHC14
DWT
0.3
pyAW
0.5
"Drell-Yan Production"
70 < M(pair) < 110 GeV
HW
Charged
ChargedParticles
Particles(||<1.0,
(||<1.0,PT>0.5
PT>0.5GeV/c)
GeV/c)
excluding
excludingthe
thelepton-pair
lepton-pair
0.0
0.0
00
2520
50
40
75
60
100
80125
"Toward"Charged
ChargedDensity
Density
"Toward"
"Toward" Charged Density
0.9
2.0
CDF Run 2 Preliminary
CDF Run
2 Preliminary
data corrected
pyDWT
datagenerator
correctedlevel
HW generator level
1.5
LHC14
1.0
Tevatron
LHC10
0.3
0.5
LHC10
Tevatron
Charged
Charged Particles
Particles (||<1.0,
(||<1.0, PT>0.5
PT>0.5 GeV/c)
GeV/c)
excluding
excluding the
the lepton-pair
lepton-pair
0.0
0.0
100
150
00
25 20
50
75
40
60 100
80125
PT(Z-Boson)
PT(Z-Boson) (GeV/c)
(GeV/c)
Z-BosonDirection
Z-BosonDirection


“Transverse”
"Drell-Yan
Production"
70 < M(pair)
< 110 GeV
70 < M(pair) < 110 GeV
0.6
PT(Z-Boson)
PT(Z-Boson) (GeV/c)
(GeV/c)
“Toward”
"Drell-Yan Production"
LHC14
HW without MPI
“Toward”
“Transverse”
“Transverse”
“Transverse”
“Away”
“Away”
 Data at 1.96 TeV on the density of charged particles, dN/dd, with pT > 0.5 GeV/c and || < 1 for “ZBoson” events as a function of PT(Z) for the “toward” region. The data are corrected to the particle
level (with errors that include both the statistical error and the systematic uncertainty) and are
compared with PYTHIA Tune AW and HERWIG (without MPI) at the particle level (i.e. generator
level).
Lake Louise Winter Institute
February 16, 2010
Rick Field – Florida/CDF/CMS
Page 17
150
100
Z-Boson: “Towards” Region
"Toward" Average PT Charged
"Toward" Average PT Charged
1.6
1.6
data corrected
generator level theory
CDF Run 2 Preliminary
"Drell-Yan Production"
70 < M(pair) < 110 GeV
pyDW
"Toward" <PT> (GeV/c)
"Toward" <PT> (GeV/c)
CDF Run 2 Preliminary
pyAW
1.2
0.8
ATLAS
JIM
HW
"Drell-Yan Production"
70 < M(pair) < 110 GeV
1.2
DWT
0.8
HW LHC14
HW Tevatron
pyDWT Tevatron
Charged Particles (||<1.0, PT>0.5 GeV/c)
excluding the lepton-pair
0.4
pyDWT LHC14
data corrected
generator level theory
Charged Particles (||<1.0, PT>0.5 GeV/c)
excluding the lepton-pair
0.4
0
20
40
60
80
100
0
20
PT(Z-Boson) (GeV/c)
40
60
Z-BosonDirection


“Transverse”
“Transverse”
100
PT(Z-Boson) (GeV/c)
Z-BosonDirection
“Toward”
80
HW (without MPI)
almost no change!
“Toward”
“Transverse”
“Transverse”
“Away”
“Away”
 Data at 1.96 TeV on the average pT of charged particles with pT > 0.5 GeV/c and || < 1 for “Z-Boson”
events as a function of PT(Z) for the “toward” region. The data are corrected to the particle level
(with errors that include both the statistical error and the systematic uncertainty) and are compared
with PYTHIA Tune AW and HERWIG (without MPI) at the particle level (i.e. generator level).
Lake Louise Winter Institute
February 16, 2010
Rick Field – Florida/CDF/CMS
Page 18
Z-Boson: “Towards” Region
RDF LHC
Prediction!
"Toward" Charged Particle Density:
dN/dd
"Toward" Charged Particle Density: dN/dd
1.6
RDF Preliminary
PY Tune AW
PY Tune DW
generator level
RDF Preliminary
Drell-Yan
1.96 TeV
"Toward" Charged Density
"Toward" Charged Density
0.8
0.6
0.4
PY64 Tune P329
PY64 Tune S320
0.2
70 < M(pair) < 110 GeV
Charged Particles (||<1.0, PT>0.5 GeV/c)
0.0
PY Tune DWT
PY Tune DW
generator level
1.2
0.8
PY64 Tune P329
PY64 Tune S320
70 < M(pair) < 110 GeV
0.4
Drell-Yan
14 TeV
Charged Particles (||<1.0, PT>0.5 GeV/c)
0.0
0
25
50
75
100
125
150
0
25
Lepton-Pair PT (GeV/c)
50
75


“Toward”
“Toward”
“Transverse”
125
Z-BosonDirection
Z-BosonDirection
“Transverse”
100
Lepton-Pair PT (GeV/c)
Tevatron
LHC
“Transverse”
“Transverse”
“Away”
“Away”
 Data at 1.96 TeV on the density of charged particles, dN/dd, with pT > 0.5 GeV/c and || < 1 for “Z-
Boson” events as a function of PT(Z) for the “toward” region from PYTHIA Tune AW, Tune DW, Tune
S320, and Tune P329 at the particle level (i.e. generator level).
 Extrapolations of PYTHIA Tune AW, Tune DW, Tune DWT, Tune S320, and Tune P329 to the LHC.
Lake Louise Winter Institute
February 16, 2010
Rick Field – Florida/CDF/CMS
Page 19
150
Z-Boson: “Towards” Region
RDF LHC Prediction!
"Toward" Charged PTsum Density: dN/dd
"Toward" Charged PTsum Density: dN/dd
2.0
1.0
generator level
0.8
PY Tune DW
0.6
0.4
PY64 Tune P329
70 < M(pair) < 110 GeV
0.2
Drell-Yan
1.96 TeV
RDF Preliminary
PY Tune AW
"Toward" PTsum Density
"Toward" PTsum Density
RDF Preliminary
PY64 Tune S320
Charged Particles (||<1.0, PT>0.5 GeV/c)
PY Tune DWT
generator level
1.6
1.2
PY Tune DW
0.8
PY64 Tune P329
0.4
70 < M(pair) < 110 GeV
PY64 Tune S320
Drell-Yan
14 TeV
Charged Particles (||<1.0, PT>0.5 GeV/c)
0.0
0.0
0
25
50
75
100
125
150
0
25
50
75
Z-BosonDirection
Z-BosonDirection


“Toward”
“Toward”
“Transverse”
125
Lepton-Pair PT (GeV/c)
Lepton-Pair PT (GeV/c)
“Transverse”
100
Tevatron
LHC
“Transverse”
“Transverse”
“Away”
“Away”
 Data at 1.96 TeV on the charged PTsum density, dPT/dd, with pT > 0.5 GeV/c and || < 1 for “Z-Boson”
events as a function of PT(Z) for the “toward” region from PYTHIA Tune AW, Tune DW, Tune S320, and
Tune P329 at the particle level (i.e. generator level).
 Extrapolations of PYTHIA Tune AW, Tune DW, Tune DWT, Tune S320, and Tune P329 to the LHC.
Lake Louise Winter Institute
February 16, 2010
Rick Field – Florida/CDF/CMS
Page 20
150
Charged Particle Multiplicity
Charged Multiplicity Distribution
Charged Multiplicity Distribution
1.0E+00
1.0E+00
CDF Run 2 Preliminary
CDF Run 2 Preliminary
1.0E-01
1.0E-01
CDF Run 2 <Nchg>=4.5
CDF Run 2 <Nchg>=4.5
1.0E-02
1.0E-02
1.0E-03
1.0E-03
py64 Tune A <Nchg> = 4.1
Probability
Probability
pyAnoMPI <Nchg> = 2.6
1.0E-04
1.0E-05
1.0E-04
1.0E-05
1.0E-06
1.0E-06
HC 1.96 TeV
Min-Bias 1.96 TeV
1.0E-07
1.0E-07
Normalized to 1
Normalized to 1 Charged Particles (||<1.0, PT>0.4 GeV/c)
Charged Particles (||<1.0, PT>0.4 GeV/c)
1.0E-08
1.0E-08
0
5
10
15
20
25
30
35
40
45
50
55
0
5
20
25
30
35
40
No MPI!
“Minumum Bias” Collisions
Proton
15
45
50
55
Number of Charged Particles
Number of Charged Particles
7 decades!
10
Tune A!
AntiProton
 Data at 1.96 TeV on the charged particle multiplicity (pT > 0.4 GeV/c, || < 1) for “min-bias”
collisions at CDF Run 2.
 The data are compared with PYTHIA Tune A and Tune A without multiple parton
interactions (pyAnoMPI).
Lake Louise Winter Institute
February 16, 2010
Rick Field – Florida/CDF/CMS
Page 21
PYTHIA Tune A Min-Bias
“Soft” + ”Hard”
Tuned to fit the CDF Run 1
“underlying event”!
PYTHIA Tune A
CDF Run 2 Charged
DefaultParticle Density
Charged Particle Density: dN/dd
1.0
CDF Published
1.0E+00
0.8
CDF Min-Bias Data
1.0E-01
0.6
0.4
0.2
Pythia 6.206 Set A
1.8 TeV all PT
CDF Min-Bias 1.8 TeV
0.0
-4
-3
-2
-1
0
1
2
3
4
Pseudo-Rapidity 
 PYTHIA regulates the perturbative 2-to-2
parton-parton cross sections with cut-off
parameters
which allows one to run with
Lots of “hard” scattering in
PT“Min-Bias”
(hard) > 0.
One
can simulate both “hard”
at the
Tevatron!
and “soft” collisions in one program.
Charged Density dN/dddPT (1/GeV/c)
dN/dd
Pythia 6.206 Set A
1.8 TeV ||<1
1.0E-02
12% of “Min-Bias” events
have PT(hard) > 5 GeV/c!
PT(hard) > 0 GeV/c
1.0E-03
1% of “Min-Bias” events
have PT(hard) > 10 GeV/c!
1.0E-04
1.0E-05
CDF Preliminary
1.0E-06
0
2
4
6
8
10
12
14
PT(charged) (GeV/c)
 The relative amount of “hard” versus “soft” depends on the cut-off and can be tuned.
 This PYTHIA fit predicts that 12% of all “Min-Bias” events are a result of a hard 2-to-2
parton-parton scattering with PT(hard) > 5 GeV/c (1% with PT(hard) > 10 GeV/c)!
Lake Louise Winter Institute
February 16, 2010
Rick Field – Florida/CDF/CMS
Page 22
PYTHIA Tune A
LHC Min-Bias Predictions
Hard-Scattering in Min-Bias Events
Charged Particle Density
50%
12% of “Min-Bias”
events
have||<1
PT(hard) > 10 GeV/c!
1.0E+00
Pythia 6.206 Set A
Pythia 6.206 Set A
40%
% of Events
Charged Density dN/dddPT (1/GeV/c)
1.0E-01
1.0E-02
PT(hard) > 5 GeV/c
PT(hard) > 10 GeV/c
30%
20%
1.8 TeV
1.0E-03
10%
14 TeV
1.0E-04
0%
100
1,000
10,000
100,000
CM Energy W (GeV)
630 GeV
LHC?
1.0E-05
 Shows the center-of-mass energy dependence
CDF Data
1.0E-06
0
2
4
6
8
PT(charged) (GeV/c)
1% of “Min-Bias” events
have PT(hard) > 10 GeV/c!
10
12
14
of the charged particle density,
dNchg/dddPT, for “Min-Bias” collisions
compared with PYTHIA Tune A with
PT(hard) > 0.
 PYTHIA Tune A predicts that 1% of all “Min-Bias” events at 1.8 TeV are a result of a hard
2-to-2 parton-parton scattering with PT(hard) > 10 GeV/c which increases to 12% at 14 TeV!
Lake Louise Winter Institute
February 16, 2010
Rick Field – Florida/CDF/CMS
Page 23
Charged Particle Multiplicity
Charged Multiplicity DistributionCharged
0.20
1.0E+00
0.20
CDF Run 2 Preliminary
CDF
1.0E-01
CDF Run 2 <Nchg>=4.5
0.15
py64 Tune A <Nchg> = 4.1
0.15
HC 1.96 TeV
0.05
Normalized to 1
0
2
4
CDF Run 2 Preliminary
CDF Run 2 <Nchg>=4.5
CDF Run 2 <Nchg>=4.5
pyS320 <Nchg> = 4.2
py64 Tune A <Nchg> = 4.1
Charged Particles (||<1.0, PT>0.4 GeV/c)
0.10
HC 1.96 TeV
0.05
0.00
Run 2 Preliminary
1.0E-02
pyAnoMPI <Nchg> = 2.6
Probability
0.10
Probability
Probability
Charged Multiplicity Distribution
Multiplicity Distribution
1.0E-03
py64DW <Nchg> = 4.2
1.0E-04
pyS320 <Nchg> = 4.2
pyP329 <Nchg> = 4.4
1.0E-05
1.0E-06
Normalized
to 1 14
12
16
Charged
Particles (||<1.0, PT>0.4 GeV/c)
Number of Charged
Particles
1.0E-07
6
8
10
HC 1.96 TeV
Normalized to 1
0.00
0
2
4
6
8 1.0E-08 10
0
12
5
Tune A!Number of Charged Particles
No MPI!
10
Charged Particles (||<1.0, PT>0.4 GeV/c)
14
15
20
16
25
30
35
40
45
50
55
Number of Charged Particles
“Minumum Bias” Collisions
Proton
Tune S320!
AntiProton
 Data at 1.96 TeV on the charged particle multiplicity (pT > 0.4 GeV/c, || < 1) for “min-bias”
collisions at CDF Run 2.
 The data are compared with PYTHIA Tune A and Tune A without multiple parton
interactions (pyAnoMPI).
Lake Louise Winter Institute
February 16, 2010
Rick Field – Florida/CDF/CMS
Page 24
The “Underlying Event”
Select inelastic non-diffractive events
that contain a hard scattering
Proton
Hard parton-parton
collisions is hard
(pT > ≈2 GeV/c)
Proton
The “underlying-event” (UE)!
Proton
Given that you have one hard
scattering it is more probable to
have MPI! Hence, the UE has
more activity than “min-bias”.
Lake Louise Winter Institute
February 16, 2010
“Semi-hard” partonparton collision
(pT < ≈2 GeV/c)
Proton
+
+
Proton
Proton
Rick Field – Florida/CDF/CMS
Proton
Proton
+…
Multiple-parton
interactions (MPI)!
Page 25
The Inelastic Non-Diffractive
Cross-Section
Occasionally one of
the parton-parton
collisions is hard
(pT > ≈2 GeV/c)
Proton
Proton
Majority of “minbias” events!
Proton
“Semi-hard” partonparton collision
(pT < ≈2 GeV/c)
Proton
+
Proton
+
Proton
Proton
Proton
+
Proton
Proton
+…
Lake Louise Winter Institute
February 16, 2010
Rick Field – Florida/CDF/CMS
Multiple-parton
interactions (MPI)!
Page 26
The “Underlying Event”
Select inelastic non-diffractive events
that contain a hard scattering
Proton
Hard parton-parton
collisions is hard
(pT > ≈2 GeV/c)
Proton
The “underlying-event” (UE)!
Proton
Given that you have one hard
scattering it is more probable to
have MPI! Hence, the UE has
more activity than “min-bias”.
Lake Louise Winter Institute
February 16, 2010
“Semi-hard” partonparton collision
(pT < ≈2 GeV/c)
Proton
+
+
Proton
Proton
Rick Field – Florida/CDF/CMS
Proton
Proton
+…
Multiple-parton
interactions (MPI)!
Page 27
Min-Bias Correlations
Average PT versus Nchg
Average PT (GeV/c)
1.4
CDF Run 2 Preliminary
pyDW
data corrected
generator level theory
“Minumum Bias” Collisions
1.2
Min-Bias
1.96 TeV
pyA
Proton
1.0
AntiProton
ATLAS
0.8
Charged Particles (||<1.0, PT>0.4 GeV/c)
0.6
0
10
20
30
40
50
Number of Charged Particles
 Data at 1.96 TeV on the average pT of charged particles versus the number of charged
particles (pT > 0.4 GeV/c, || < 1) for “min-bias” collisions at CDF Run 2. The data are
corrected to the particle level and are compared with PYTHIA Tune A at the particle
level (i.e. generator level).
Lake Louise Winter Institute
February 16, 2010
Rick Field – Florida/CDF/CMS
Page 28
Min-Bias: Average PT versus Nchg
 Beam-beam remnants (i.e. soft hard core) produces
Average PT versus Nchg
Average PT (GeV/c)
1.4
CDF Run 2 Preliminary
Min-Bias
1.96 TeV
data corrected
generator level theory
1.2
low multiplicity and small <pT> with <pT>
independent of the multiplicity.
 Hard scattering (with no MPI) produces large
pyA
multiplicity and large <pT>.
pyAnoMPI
1.0
 Hard scattering (with MPI) produces large
0.8
multiplicity and medium <pT>.
ATLAS
Charged Particles (||<1.0, PT>0.4 GeV/c)
0.6
0
5
10
15
20
25
30
35
40
This observable is sensitive
to the MPI tuning!
Number of Charged Particles
“Hard” Hard Core (hard scattering)
Outgoing Parton
“Soft” Hard Core (no hard scattering)
PT(hard)
CDF “Min-Bias”
=
Proton
+
AntiProton
Proton
AntiProton
Underlying Event
Underlying Event
Initial-State
Radiation
Final-State
Radiation
Multiple-Parton Interactions
+
Proton
AntiProton
Underlying Event
Outgoing Parton
Lake Louise Winter Institute
February 16, 2010
Outgoing Parton
PT(hard)
Initial-State
Radiation
The CDF “min-bias” trigger
picks up most of the “hard
core” component!
Outgoing Parton
Underlying Event
Final-State
Radiation
Rick Field – Florida/CDF/CMS
Page 29
QCD Monte-Carlo Models:
Lepton-Pair Production
Lepton-Pair
Production
High
PT Z-Boson
Production
Anti-Lepton
Outgoing Parton
Initial-State
Initial-State Radiation
Radiation
High P
T Z-Boson Production
Lepton-Pair
Production
Initial-State
Initial-StateRadiation
Radiation
“Jet”
Proton
Proton
Final-State Radiation
Outgoing
Parton
Anti-Lepton
Final-State Radiation
“Hard Scattering” Component
AntiProton
AntiProton
Underlying Event
Lepton
Z-boson
Underlying Event
Proton
Lepton
Z-boson
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-state radiation.
Lake Louise Winter Institute
February 16, 2010
Rick Field – Florida/CDF/CMS
Page 30
Average PT versus Nchg
Average PT
PT versus
versus Nchg
Nchg
Average
Average PT versus Nchg
2.5
2.5
CDF Run 2 Preliminary
data corrected
generator level theory
1.2
CDFRun
Run22Preliminary
Preliminary
CDF
Min-Bias
1.96 TeV
Average
Average PT
PT (GeV/c)
(GeV/c)
Average PT (GeV/c)
1.4
pyA
pyAnoMPI
1.0
0.8
ATLAS
data corrected
generator
level theory
generator level theory
2.0
2.0
HW
HW
pyAW
pyAW
"Drell-YanProduction"
Production"
"Drell-Yan
70<<M(pair)
M(pair)<<110
110GeV
GeV
70
1.5
1.5
JIM
JIM
1.0
1.0
ATLAS
ATLAS
Charged Particles (||<1.0, PT>0.4 GeV/c)
0.6
ChargedParticles
Particles(||<1.0,
(||<1.0,PT>0.5
PT>0.5GeV/c)
GeV/c)
Charged
excludingthe
thelepton-pair
lepton-pair
excluding
0.5
0.5
0
5
10
15
20
25
30
35
40
00
55
10
10
Number of Charged Particles
15
15
20
20
25
25
30
30
Numberof
ofCharged
ChargedParticles
Particles
Number
Drell-Yan Production
Lepton
“Minumum Bias” Collisions
Proton
AntiProton
Proton
AntiProton
Underlying Event
Underlying Event
Anti-Lepton
 Data at 1.96 TeV on the average pT of charged particles versus the number of charged particles (pT > 0.4 GeV/c, || <
1) for “min-bias” collisions at CDF Run 2. The data are corrected to the particle leveland are compared with PYTHIA
Tune A, Tune DW, and the ATLAS tune at the particle level (i.e. generator level).
 Particle level predictions for the average pT of charged particles versus the number of charged particles (pT > 0.5
GeV/c, || < 1, excluding the lepton-pair) for for Drell-Yan production (70 < M(pair) < 110 GeV) at CDF Run 2.
Lake Louise Winter Institute
February 16, 2010
Rick Field – Florida/CDF/CMS
Page 31
35
35
Average PT versus Nchg
 Z-boson production (with low pT(Z) and no MPI)
No MPI!
Average PT versus Nchg
produces low multiplicity and small <pT>.
2.5
Average PT (GeV/c)
CDF Run 2 Preliminary
data corrected
generator level theory
2.0
HW
 High pT Z-boson production produces large
pyAW
multiplicity and high <pT>.
"Drell-Yan Production"
70 < M(pair) < 110 GeV
 Z-boson production (with MPI) produces large
1.5
multiplicity and medium <pT>.
JIM
1.0
ATLAS
Charged Particles (||<1.0, PT>0.5 GeV/c)
excluding the lepton-pair
0.5
0
5
10
15
20
25
30
35
Number of Charged Particles
Drell-Yan Production (no MPI)
High PT Z-Boson Production
Lepton
Initial-State Radiation
Outgoing Parton
Final-State Radiation
Drell-Yan
=
Proton
AntiProton
Underlying Event
Underlying Event
Anti-Lepton
+
+
Drell-Yan Production (with MPI)
Proton
Proton
Lepton
AntiProton
Z-boson
AntiProton
Underlying Event
Underlying Event
Anti-Lepton
Lake Louise Winter Institute
February 16, 2010
Rick Field – Florida/CDF/CMS
Page 32
Average PT(Z) versus Nchg
No MPI!
Average PT versus Nchg
PT(Z-Boson)
PT(Z-Boson) versus
versus Nchg
Nchg
80
80
2.5
data corrected
generator level theory
2.0
CDF
CDF Run
Run 22 Preliminary
Preliminary
HW
Average PT(Z) (GeV/c)
Average PT (GeV/c)
CDF Run 2 Preliminary
pyAW
"Drell-Yan Production"
70 < M(pair) < 110 GeV
1.5
JIM
1.0
ATLAS
generator
level theory
data corrected
generator level theory
60
60
pyAW
pyAW
HW
HW
"Drell-Yan
"Drell-Yan Production"
Production"
70
70 << M(pair)
M(pair) << 110
110 GeV
GeV
40
40
JIM
JIM
20
20
Charged Particles (||<1.0, PT>0.5 GeV/c)
excluding the lepton-pair
ATLAS
ATLAS
Charged
Charged Particles
Particles (||<1.0,
(||<1.0, PT>0.5
PT>0.5 GeV/c)
GeV/c)
excluding
excluding the
the lepton-pair
lepton-pair
00
0.5
0
5
10
15
20
25
30
35
00
55
Outgoing Parton
Lepton
Initial-State Radiation
Proton
Proton
AntiProton
Underlying Event
Underlying Event
15
15
20
20
25
25
30
30
35
35
40
40
Number
Number of
of Charged
Charged Particles
Particles
Number of Charged Particles
High PDrell-Yan
Production
T Z-BosonProduction
10
10
 Predictions for the average PT(Z-Boson) versus
the number of charged particles (pT > 0.5
GeV/c, || < 1, excluding the lepton-pair) for for
Drell-Yan production (70 < M(pair) < 110 GeV)
at CDF Run 2.
Anti-Lepton
Z-boson
 Data on the average pT of charged particles versus the number of charged particles (pT > 0.5 GeV/c, || < 1,
excluding the lepton-pair) for for Drell-Yan production (70 < M(pair) < 110 GeV) at CDF Run 2. The data are
corrected to the particle level and are compared with various Monte-Carlo tunes at the particle level (i.e.
generator level).
Lake Louise Winter Institute
February 16, 2010
Rick Field – Florida/CDF/CMS
Page 33
Average PT versus Nchg
PT(Z) < 10 GeV/c
Average
Charged
PT
versus
Nchg
Average
Average Charged
Charged PT
PT versus
versus Nchg
Nchg
CDF
Run
Preliminary
CDF
CDF Run
Run 22
2 Preliminary
Preliminary
data corrected
generator
level
generator
level theory
theory
generator level theory
1.2
1.2
1.2
pyAW
pyAW
pyAW
1.0
1.0
1.0
HW
HW
HW
0.8
0.8
0.8
"Drell-Yan
Production"
"Drell-Yan
"Drell-Yan Production"
Production"
70
M(pair)
110
GeV
70
70 <<
< M(pair)
M(pair) <<
< 110
110 GeV
GeV
PT(Z)
10
GeV/c
PT(Z)
PT(Z) <<
< 10
10 GeV/c
GeV/c
CDF Run 2 Preliminary
JIM
JIM
Average PT (GeV/c)
Average
PT
(GeV/c)
AveragePT
PT(GeV/c)
(GeV/c)
Average
1.4
1.4
1.4
Average PT versus Nchg
1.4
ATLAS
ATLAS
Drell-Yan PT > 0.5 GeV PT(Z) < 10 GeV/c
data corrected
generator level theory
1.2
pyAW
No MPI!
1.0
Min-Bias PT > 0.4 GeV/c
0.8
Charged
Particles
(||<1.0,
PT>0.5
GeV/c)
Charged
Charged Particles
Particles (||<1.0,
(||<1.0, PT>0.5
PT>0.5 GeV/c)
GeV/c)
excluding
the
lepton-pair
excluding
excluding the
the lepton-pair
lepton-pair
Charged Particles (||<1.0)
pyA
0.6
0.6
0.6
0.6
00
0
55
5
10
10
10
15
15
15
20
20
20
25
25
25
30
30
30
35
35
35
0
Number
of
Charged
Particles
Number
Number of
of Charged
Charged Particles
Particles
Drell-Yan Production
Proton
20
30
40
Number of Charged Particles
Lepton
AntiProton
Underlying Event
10
Underlying Event
Remarkably similar behavior!
Perhaps indicating that MPIProton
playing an important role in
both processes.
“Minumum Bias” Collisions
AntiProton
Anti-Lepton
 Predictions
for thepTaverage
pT ofparticles
chargedversus
particles
theofnumber
charged(p
particles
(pT > 0.5
Data the average
of charged
theversus
number
chargedofparticles
||GeV/c,
< 1, ||
T > 0.5 GeV/c,
<
1, excluding
the lepton-pair)
forDrell-Yan
for Drell-Yan
production
< M(pair)
110 GeV,
PT(pair)
10 GeV/c)
at
excluding
the lepton-pair)
for for
production
(70 <(70
M(pair)
< 110< GeV,
PT(pair)
< 10<GeV/c)
at CDF
CDF
Run
Run 2.
The2.data are corrected to the particle level and are compared with various Monte-Carlo tunes at the
particle level (i.e. generator level).
Lake Louise Winter Institute
February 16, 2010
Rick Field – Florida/CDF/CMS
Page 34
Charged Particle Multiplicity
Charged Multiplicity Distribution
Charged Multiplicity Distribution
1.0E+00
1.0E+00
CDF Run 2 Preliminary
1.0E-01
CDF Run 2 <Nchg>=4.5
pyAnoMPI <Nchg> = 2.6
1.0E-03
CDF Run 2 <Nchg>=4.5
1.0E-02
py Tune A <Nchg> = 4.3
Probability
Probability
1.0E-02
CDF Run 2 Preliminary
1.0E-01
1.0E-04
1.0E-05
py Tune A <Nchg> = 4.3
pyA 900 GeV <Nchg> = 3.3
1.0E-03
1.0E-04
1.0E-05
1.0E-06
1.0E-06
Min-Bias 1.96
1.0E-07
Normalized to 1
Min-Bias
1.0E-07
Normalized to 1
Charged Particles (||<1.0, PT>0.4 GeV/c)
Charged Particles (||<1.0, PT>0.4 GeV/c)
1.0E-08
1.0E-08
0
5
No MPI!
10
15
20
25
30
35
40
45
50
55
0
5
Tune A prediction at
900 GeV!
Number of Charged Particles
“Minumum Bias” Collisions
Proton
10
15
20
25
30
35
40
45
50
Number of Charged Particles
“Minumum Bias” Collisions
Tune A!
AntiProton
Proton
Proton
 Data at 1.96 TeV on the charged particle multiplicity (pT > 0.4 GeV/c, || < 1) for “min-bias”
collisions at CDF Run 2.
 The data are compared with PYTHIA Tune A and Tune A without multiple parton interactions
(pyAnoMPI).
 Prediction from PYTHIA Tune A for proton-proton collisions at 900 GeV.
Lake Louise Winter Institute
February 16, 2010
Rick Field – Florida/CDF/CMS
Page 35
55
LHC Predictions: 900 GeV
Charged Multiplicity Distribution
Charged Multiplicity Distribution
Charged Multiplicity Distribution
Distribution
Momentum
Transverse Momentum
Charged Transverse
Charged
Distribution
0.08
0.16
1.0E+00
RDF Preliminary
30
1.0E+02
py64DW <Nchg> = 14.4 <pT> = 787 MeV/c
RDF
0.06
0.12
1.0E+01
MeV/c
787MeV/c
<pT>==795
14.4<pT>
<Nchg>==14.7
py64DW
pyP329 <Nchg>
20
1.0E+00
HC 900 GeV
1.0E-05
Normalized to 1
1.0E-06
0
10
20
0.02
0.04
HC HC
900900
GeVGeV
Charged Particles (||<2.0)
Normalized
to 1 to 1
Normalized
RDF Preliminary
00
HC 900
HC GeV
900 GeV
0
1.0E-03
0.0 0.0 0.2
40
50
0.4
1.0
60
Number of Charged Particles
70
0.6
25
10
4
15
6
20
8
25
10
30
12
35
14
40
16
Number of Charged Particles
Charged Particles (||<2.0) Number of Charged Particles
802.0
0.8
1.0
3.0
1.2 4.0 1.4
(GeV/c)
Momentum
Transverse
Transverse
Momentum
(GeV/c)
“Minumum Bias” Collisions
Charged Particles (||<2.0, all pT)
0.00
0.00
1.0E-02
Proton
Charged Particles (||<2.0, PT>0.5 GeV/c)
pyP329 <Nchg> = 14.7 <pT> = 795 MeV/c
10
30
0.04
pyDW
900
GeV<Nchg>
<Nchg>== 14.2
5.3
pyA
900
GeV
pyDW
14.4
pyS320900
900GeV
GeV<Nchg>
<Nchg> == 5.2
pyS320
900 GeV
GeV<Nchg>
<Nchg>
= 14.2
pyP329 900
= 5.3
pyP329 900 GeV <Nchg> = 14.7
0.08
<Nchg> = 14.2 <pT> = 778 MeV/c
pyS320
All pT
<Nchg> ~ 14
pT > 0.5 geV/c
<Nchg> ~ 5 1.0E-01
1.0E-04
Preliminary
pyS320 <Nchg> = 14.2 <pT> = 778 MeV/c
Probability
Probability
Probability
1.0E-03
d<Nchg>/dpT
d<Nchg>/dpT1/(GeV/c)
1/(GeV/c)
1.0E-01
1.0E-02
RDF
Preliminary
pyA <Nchg>
= 5.0 STdev = 4.5
RDF Preliminary
Charged Particles (||<2.0)
1.6
5.0
“Minumum Bias” Collisions
Proton
Proton
Proton
 Charged multiplicity distributions for proton-proton collisions at 900 GeV
(|| < 2) from PYTHIA Tune A, Tune DW, Tune S320, and Tune P329.
Lake Louise Winter Institute
February 16, 2010
Rick Field – Florida/CDF/CMS
Page 36
LHC Predictions: 900 GeV
Charged Particle Density: dN/d
Charged Particle Density: dN/d
5
5
RDF Preliminary
Charged Particle Density
Charged Particle Density
RDF Preliminary
4
3
2
ALICE INEL
UA5 INEL
INEL = HC+DD+SD
900 GeV
1
pyDW INEL (2.67)
4
3
2
1
pyS320 INEL (2.70)
Charged Particles (all pT)
UA5
ALICE
NSD = HC+DD
900 GeV
pyDW_10mm (3.04)
pyS320_10mm (3.09)
0
0
-3.0
-2.5
-2.0
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
2.0
2.5
3.0
-3.0
-2.5
-2.0
-1.0
-0.5
0.0
0.5
1.0
1.5
2.0
2.5
PseudoRapidity 
PseudoRapidity 
“Minumum Bias” Collisions
“Minumum Bias” Collisions
Proton
-1.5
Proton
Proton
Proton
 Compares the 900 GeV data with my favorite PYTHIA Tunes (Tune DW and Tune
S320 Perugia 0). Tune DW uses the old Q2-ordered parton shower and the old
MPI model. Tune S320 uses the new pT-ordered parton shower and the new MPI
model. The numbers in parentheses are the average value of dN/d for the region
|| < 0.6.
Lake Louise Winter Institute
February 16, 2010
Rick Field – Florida/CDF/CMS
Page 37
3.0
LHC Predictions: 900 GeV
Off by 11%!
CMS dN/d
Charged
Particle Density: dN/d
Charged Particle Density: dN/d
4
5
Charged Particle Density
Charged Particle Density
times 1.11
4
3
2
ALICE INEL
UA5 INEL
pyDW times 1.11 (2.97)
pyS320 times 1.11 (3.00)
INEL = HC+DD+SD
900 GeV
1
Charged Particles (all pT)
0
-3.0
Only HC
RDF Preliminary
RDF Preliminary
900 GeV
3
pyDW HC (3.30)
pyS320 HC (3.36)
pyDW SD (0.61)
2
pyS320 SD (0.53)
pyDW DD (0.59)
Only DD
pyS320 DD (0.53)
Only SD
1
Charged Particles (all pT)
0
-2.5
-2.0
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
2.0
2.5
3.0
-6
-5
-4
PseudoRapidity 
-2
-1
0
1
2
3
4
5
PseudoRapidity 
“Minumum Bias” Collisions
“Minumum Bias” Collisions
Proton
-3
Proton
Proton
Proton
 Shows the individual HC, DD, and SD predictions of PYTHIA Tune DW and Tune
S320 Perugia 0. The numbers in parentheses are the average value of dN/d for the
region || < 0.6. I do not trust PYTHIA to model correctly the DD and SD
contributions! I would like to know how well these tunes model the HC component.
We need to look at observables where only HC contributes!
Lake Louise Winter Institute
February 16, 2010
Rick Field – Florida/CDF/CMS
Page 38
6
“Transverse” Charged Density
"Transverse" Charged Particle Multiplicity
"Transverse" Charged Particle Density: dN/dd
0.18
RDF Preliminary
generator level
py64DW <Nchg> = 3.5 <NchgDen> = 0.42
pyS320 <Nchg> = 3.4 <NchgDen> = 0.41
pyDW
0.4
Probability
"Transverse" Charged Density
0.6
pyS320
0.2
0.12
RDF Preliminary
generator level
0.06
HC 900 GeV PTmax > 5 GeV/c
HC 900 GeV
Charged Particles (||<2.0, PT>0.5 GeV/c)
Charged Particles (||<2.0, PT>0.5 GeV/c)
0.0
0.00
0
2
4
6
8
10
12
14
16
18
20
0
1
PTmax (GeV/c)
2
3
4
5
6
PTmax Direction
8
9
10
11
12
13
14
PTmax Direction


“Toward”
“Transverse”
7
Number of Charged Particles
“Toward”
“Transverse”
“Transverse”
“Away”
“Transverse”
PTmax > 5 GeV/c!
“Away”
 Shows the charged particle density in the “transverse” region for charged particles (pT > 0.5
GeV/c, || < 2) at 900 GeV as defined by PTmax from PYTHIA Tune DW and Tune S320 at the
particle level (i.e. generator level).
 Shows the charged particle multiplicity distribution in the “transverse” region (pT > 0.5 GeV/c,
|| < 2) at 900 GeV as defined by PTmax from PYTHIA Tune DW and Tune S320 at the particle
level (i.e. generator level).
Lake Louise Winter Institute
February 16, 2010
Rick Field – Florida/CDF/CMS
Page 39
Charged Particle Multiplicity
NchgDen = 0.21
The “underlying event” is twice as
active as an average HC collision!
Charged Multiplicity Distribution
"Transverse" Charged Particle Multiplicity
0.18
0.16
RDF Preliminary
py64DW <Nchg> = 3.5 <NchgDen> = 0.42
pyA <Nchg> = 5.0 STdev = 4.5
pyDW 900 GeV <Nchg> = 5.3
pyS320 <Nchg> = 3.4 <NchgDen> = 0.41
0.12
Probability
Probability
0.12
RDF Preliminary
generator level
0.06
pyS320 900 GeV <Nchg> = 5.2
pyP329 900 GeV <Nchg> = 5.3
0.08
Charged Particles (||<2.0, PT>0.5 GeV/c)
0.04
HC 900 GeV PTmax > 5 GeV/c
HC 900 GeV
Normalized to 1
Charged Particles (||<2.0, PT>0.5 GeV/c)
0.00
0.00
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
0
2
4
6
8
10
12
14
Number of Charged Particles
Number of Charged Particles
PTmax Direction
“Minumum Bias” Collisions

“Toward”
“Transverse”
Proton
Proton
“Transverse”
“Away”
 Shows the charged particle multiplicity distribution in the “transverse” region (pT > 0.5 GeV/c,
|| < 2) at 900 GeV as defined by PTmax from PYTHIA Tune DW and Tune S320 at the particle
level (i.e. generator level).
 Shows the charged particle multiplicity distribution in HC collisions (pT > 0.5 GeV/c, || < 2) at
900 GeV PYTHIA Tune A, Tune DW, Tune S320, and Tune P329 at the particle level (i.e.
generator level).
Lake Louise Winter Institute
February 16, 2010
Rick Field – Florida/CDF/CMS
Page 40
16
Min-Bias “Associated”
Charged Particle Density
"Transverse" Charged Particle Density: dN/dd
"Transverse" Charged Particle Density: dN/dd
1.2
RDF Preliminary
14 TeV
Min-Bias
"Transverse" Charged Density
"Transverse" Charged Density
1.2
py Tune DW generator level
10 TeV
7 TeV
0.8
1.96 TeV
0.9 TeV
0.4
0.2 TeV
Charged Particles (||<1.0, PT>0.5 GeV/c)
RDF Preliminary
py Tune DW generator level
LHC14
LHC10
LHC7
0.8
Tevatron
0.4
900 GeV
RHIC
PTmax = 5.25 GeV/c
Charged Particles (||<1.0, PT>0.5 GeV/c)
0.0
0.0
0
5
10
15
20
25
0.1

“Toward”
LHC7
“Transverse”
100.0
PTmax Direction
7 TeV → 14 TeV
(UE increase ~20%)

“Toward”
LHC14
“Transverse”
“Away”
10.0
Center-of-Mass Energy (TeV)
PTmax (GeV/c)
PTmax Direction
1.0
Linear on a log plot!
“Transverse”
“Transverse”
“Away”
 Shows the “associated” charged particle density in the “transverse” region as a function of PTmax
for charged particles (pT > 0.5 GeV/c, || < 1, not including PTmax) for “min-bias” events at 0.2
TeV, 0.9 TeV, 1.96 TeV, 7 TeV, 10 TeV, 14 TeV predicted by PYTHIA Tune DW at the particle level
Log scale!
(i.e. generator level).
Lake Louise Winter Institute
February 16, 2010
Rick Field – Florida/CDF/CMS
Page 41
“Transverse” Charge Density
"Transverse" Charged Particle Density: dN/dd
"Transverse" Charged Particle Density: dN/dd
1.2
"Transverse" Charged Density
"Transverse" Charged Density
0.6
RDF Preliminary
generator level
pyDW
0.4
pyS320
0.2
HC 900 GeV
Charged Particles (||<2.0, PT>0.5 GeV/c)
RDF Preliminary
py Tune DW generator level
7 TeV
0.8
factor of 2!
900 GeV
0.4
Charged Particles (||<2.0, PT>0.5 GeV/c)
0.0
0.0
0
2
4
6
8
10
12
14
16
18
20
0
2
4

LHC
900 GeV
“Toward”
“Transverse”
8
10
12
14
16
18
20
PTmax (GeV/c)
PTmax (GeV/c)
PTmax Direction
6
PTmax Direction
900 GeV → 7 TeV
(UE increase ~ factor of 2.1)
“Transverse”
“Away”

“Toward”
LHC
7 TeV
“Transverse”
“Transverse”
“Away”
 Shows the charged particle density in the “transverse” region for charged particles (pT > 0.5
GeV/c, || < 2) at 900 GeV as defined by PTmax from PYTHIA Tune DW and Tune S320 at the
particle level (i.e. generator level).
Lake Louise Winter Institute
February 16, 2010
Rick Field – Florida/CDF/CMS
Page 42
sHC: PTmax > 5 GeV/c
Inelastic HC Cross-Section: PTmax > 5 GeV/c
Inelastic HC Cross-Section: PTmax > 5 GeV/c
Number
of Events Fraction
in 1/nb: PTmax
>>55GeV/c
HC
Cross-Section:
PTmax
GeV/c
1.6
1.5
1,500,000
2.0%
py Tune DW generator level
py Tune
generator
level level
py DW
Tune
DW generator
K-Factor = 1.2
1.0
0.5
0.0
0
2
Numberof
ofEvents
Events
Percent
Cross-Section (mb)
RDF Preliminary
RDF RDF
Preliminary
Preliminary
1.5%
1,000,000
K-Factor = 1.2
Still lots of events!
1.0%
1.2
K-Factor = 1.2
Charged Particles (PTmax > 5 GeV/c || < 1)
0.8
0.4
500,000
Charged Particles (PTmax > 5 GeV/c || < 1)
0.5%
4
0.0
6
8
10
12
14
0.1
1.0
10.0
100.0
Charged Particles (PTmax > 5 GeV/c
|| < 1)
Center-of-Mass
Energy (TeV)
Center-of-Mass Energy (TeV)
0
0.0%
Linear scale!
Cross-Section (mb)
RDF Preliminary
py Tune DW generator level
0
0
2
2
4 4
6 6
88
1010
Log scale!
12
12
14
14
Center-of-Mass
Energy
(TeV)
Center-of-Mass
Energy
(TeV)
stot = sEL +sSD +sDD +sHC
In 1,000,000 HC collisions at
900 GeV you get 940 with
PTmax > 5 GeV/c!
 The inelastic non-diffractive PTmax > 5 GeV/c cross section (|| < 1) versus center-of-mass
energy from PYTHIA (×1.2).
sHC(PTmax > 5 GeV/c) varies more rapidly. Factor of 2.3 increase between 7 TeV (≈ 0.56 mb)
and 14 teV (≈ 1.3 mb). Linear on a linear scale!
Lake Louise Winter Institute
February 16, 2010
Rick Field – Florida/CDF/CMS
Page 43
PTmax Cross-Section 900 GeV
Number of Events with PTmax > PT0
Differential Cross-Section: ds/dPTmax
1.0E+02
1,000,000
RDF Preliminary
pyDW 1,885 Events with PTmax > 5 GeV/c
generator level
Charged Particles (||<2.0, PT>0.5 GeV/c)
1.0E+00
1.0E-01
pyS320
1.0E-02
1.0E-03
HC 900 GeV
1.0E-04
RDF Preliminary
generator level
10,000
1,000
HC 900 GeV
100
pyDW
K-Factor = 1.2
pyS320 3,160 Events with PTmax > 5 GeV/c
100,000
Number of Events
ds/dPT (mb/GeV/c)
1.0E+01
1,000,000 HC Collisions
1.0E-05
Charged Particles (||<2.0)
10
0
2
4
6
8
10
12
14
16
18
20
0
1
2
PTmax (GeV/c)
3
4
5
6
7
8
9
10
11
12
13
14
15
PT0 (GeV/c)
stot = sEL +sSD +sDD +sHC
In 1,000,000 HC collisions at
900 GeV you get ~3,000 with
PTmax > 5 GeV/c!
 The inelastic non-diffractive PTmax > 5 GeV/c cross section (|| < 2) at 900 GeV from PYTHIA
Tune DW and Tune S320.
 Number of events with PTmax > PT0 (|| < 2) for 1,000,000 HC collisions at 900 GeV from
PYTHIA Tune DW and Tune S320.
Lake Louise Winter Institute
February 16, 2010
Rick Field – Florida/CDF/CMS
Page 44
“Transverse” Charged Particle Density
"Transverse" Charged PTsum Density: dPT/dd
"Transverse" Charged Particle Density: dN/dd
0.8
RDF Preliminary
RDF Preliminary
Fake Data
pyDW generator level
ChgJet#1
PTsum Density (GeV/c)
"Transverse" Charged Density
0.8
0.6
PTmax
0.4
0.2
361,595 events
900 GeV
ChgJet#1
Fake Data
pyDW generator level
0.6
PTmax
0.4
0.2
900 GeV
Charged Particles (||<2.0, PT>0.5 GeV/c)
Charged Particles (||<2.0, PT>0.5 GeV/c)
0.0
0.0
0
2
4
6
8
10
12
14
16
18
0
2
4
6
8
10
12
14
16
18
PTmax or PT(chgjet#1) (GeV/c)
PTmax or PT(chgjet#1) (GeV/c)
 Fake data (from MC) at 900 GeV on the
 Fake data (from MC) at 900 GeV on the
“transverse” charged particle density,
“transverse” charged PTsum density,
dN/dd, as defined by the leading charged
dPT/dd, as defined by the leading charged
particle (PTmax) and the leading charged
particle (PTmax) and the leading charged
particle jet (chgjet#1) for charged particles
particle jet (chgjet#1) for charged particles
with pT > 0.5 GeV/c and || < 2. The fake
with pT > 0.5 GeV/c and || < 2. The fake
data (from PYTHIA Tune DW) are generated
data (from PYTHIA Tune DW) are generated
at the particle level (i.e. generator level)
at the particle level (i.e. generator level)
assuming 0.5 M min-bias events at 900 GeV
assuming 0.5 M min-bias events at 900 GeV
(361,595 events in the plot).
(361,595 events in the plot).
Lake Louise Winter Institute
February 16, 2010
Rick Field – Florida/CDF/CMS
Page 45
“Transverse” Distributions
"Transverse" Charged PT Distribution
"Transverse" Charged Particle Multiplicity
1.0E+01
1.0E+00
RDF Preliminary
pyDW generator level
Probability
1.0E-01
Fake Data <Nchg> = 2.80 ± 0.01
pyDW <Nchg> = 2.78
1.0E-02
43, 855 events
900 GeV PTmax > 2 GeV/c
1.0E-03
Normalized to 1
(1/N) dNchg/dPT (1/GeV/c)
RDF Preliminary
pyDW generator level
1.0E+00
Fake Data <PT> = 0.958 ± 0.002
pyDW <PT> = 0.904 GeV/c
1.0E-01
1.0E-02
900 GeV PTmax > 2 GeV/c
1.0E-03
Normalized to <Nchg>
1.0E-04
Charged Particles (||<2.0)
Stay tuned! UE studies
at 900 GeV coming soon
from CMS and
ATLAS.
 Fake
data (from MC) at 900 GeV on the
 Fake data (from MC) at 900 GeV on the
Charged Particles (||<2.0, PT>0.5 GeV/c)
1.0E-05
1.0E-04
0
1
2
3
4
5
6
7
8
9 10 11 12 13 14 15 16 17 18 19 20
0.0
2.0
3.0
4.0
5.0
6.0
7.0
PT (GeV/c)
Number of Charged Particles
“transverse” charged particle multiplicity as
defined by the leading charged particle
(PTmax) with PTmax > 2 GeV/c for charged
particles with pT > 0.5 GeV/c and || < 2. The
fake data (from PYTHIA Tune DW) are
generated at the particle level (i.e. generator
level) assuming 0.5 M min-bias events at 900
GeV (43,855 events in the plot).
Lake Louise Winter Institute
February 16, 2010
1.0
“transverse” charged PT distribution as
defined by the leading charged particle
(PTmax) with PTmax > 2 GeV/c for charged
particles with pT > 0.5 GeV/c and || < 2. The
fake data (from PYTHIA Tune DW) are
generated at the particle level (i.e. generator
level) assuming 0.5 M min-bias events at 900
GeV.
Rick Field – Florida/CDF/CMS
Page 46
LHC Predictions
“Minumum Bias” Collisions
Proton
AntiProton
Charged Particle Density: dN/d
4.0
RDF Preliminary
Charged Particle Density
I believe because of the STAR analysis we are now
in a position to make some predictions at the LHC!
PY64 Tune P329
generator level
3.0
PY64 Tune S320
2.0
PY Tune A
1.0
Min-Bias
14 TeV
Charged Particles (PT>0.5 GeV/c)
 The amount of activity in “min-bias” collisions.
Outgoing Parton
Underlying Event
1.6
“Toward”
“Transverse”
“Away”
 The amount of activity in the “underlying event” in hard
scattering events.
Drell-Yan Production
-2
0
2
4
6
8
"Transverse" Charged Particle Density: dN/dd
Stay tuned! UE studies
at 900 GeV and 7 TeV
coming soon!
“Transverse”
Final-State
Radiation
-4
PseudoRapidity 
"Transverse" Charged Density
AntiProton
Outgoing Parton
-6

Initial-State Radiation
Underlying Event
-8
PTmax Direction
PT(hard)
Proton
0.0
PY ATLAS
RDF Preliminary
PY Tune DWT
generator level
1.2
0.8
PY64 Tune P329
PY Tune A
0.4
PY Tune DW
PY64 Tune S320
Min-Bias
14 TeV
Charged Particles (||<1.0, PT>0.5 GeV/c)
0.0
0
5
10
Z-BosonDirection
15
20
25
PTmax (GeV/c)

Lepton
"Toward" Charged Particle Density: dN/dd
“Toward”
Underlying Event
Underlying Event
PY ATLAS
RDF Preliminary
AntiProton
“Transverse”
“Transverse”
“Away”
Anti-Lepton
 The amount of activity in the “underlying event” in DrellYan events.
"Toward" Charged Density
Proton
1.6
PY Tune DWT
generator level
1.2
0.8
PY Tune DW
PY64 Tune P329
PY64 Tune S320
0.4
70 < M(pair) < 110 GeV
Drell-Yan
14 TeV
Charged Particles (||<1.0, PT>0.5 GeV/c)
0.0
0
25
50
75
100
125
150
Lepton-Pair PT (GeV/c)
Lake Louise Winter Institute
February 16, 2010
Rick Field – Florida/CDF/CMS
Page 47