Workshop on Early Physics
Opportunities at the LHC
“Min-Bias” and the “Underlying Event”
Rick Field
University of Florida
Outline of Talk
 The QCD Monte-Carlo Model tunes.
LBNL May 6, 2009
Outgoing Parton
 The Pythia MPI energy scaling
PT(hard)
Initial-State Radiation
parameter PARP(90).
Proton
AntiProton
Underlying Event
 “Min-Bias” and the “underlying
event” at the LHC.
Outgoing Parton
 The “underlying event” in Drell-Yan
Underlying Event
Final-State
Radiation
lepton-pair production.
 LHC predictions!
 Summary & Conclusions.
 Early LHC Thesis Projects.
Workshop on Early LHC Physics
May 6, 2009
CDF Run 2
Rick Field – Florida/CDF/CMS
CMS at the LHC
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!
Workshop on Early LHC Physics
May 6, 2009
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.
Workshop on Early LHC Physics
May 6, 2009
Rick Field – Florida/CDF/CMS
Page 3
Tuning PYTHIA:
Multiple Parton Interaction Parameters
Parameter
Default
Description
PARP(83)
0.5
Double-Gaussian: Fraction of total hadronic
matter within PARP(84)
PARP(84)
0.2
Double-Gaussian: Fraction of the overall hadron
radius containing the fraction PARP(83) of the
total hadronic matter.
Multiple Parton Interaction
Color String
Color String
PARP(86)
PARP(89)
PARP(90)
PARP(67)
0.33
0.66
1 TeV
0.16
1.0
Probability that the MPI produces two gluons
with color connections to the “nearest neighbors.
Multiple PartonDetermine
Interactionby comparing
with 630 GeV data!
Probability that the MPI produces two gluons
either as described by PARP(85) or as a closed
gluon
loop.
remaining
fraction consists of
Affects
the The
amount
of
quark-antiquark
pairs.
initial-state radiation!
Color String
Hard-Scattering Cut-Off PT0
5
Determines the reference energy E0.
Determines the energy dependence of the cut-off
PT0 as follows PT0(Ecm) = PT0(Ecm/E0)e with
e = PARP(90)
A scale factor that determines the maximum
parton virtuality for space-like showers. The
larger the value of PARP(67) the more initialstate radiation.
PYTHIA 6.206
e = 0.25 (Set A))
4
PT0 (GeV/c)
PARP(85)
Take E0 = 1.8 TeV
3
2
e = 0.16 (default)
1
100
1,000
10,000
100,000
CM Energy W (GeV)
Reference point
at 1.8 TeV
Workshop on Early LHC Physics
May 6, 2009
Rick Field – Florida/CDF/CMS
Page 4
“Transverse” Cones
vs “Transverse” Regions
“Cone Analysis”
2
2
Transverse
Cone:
(0.7)2=0.49
Away Region
Transverse
Region

(Tano, Kovacs, Huston, Bhatti)
Cone 1

Leading
Jet
Leading
Jet
Toward Region
Transverse
Region:
2/3=0.67
Transverse
Region
Cone 2
Away Region
0
0
-1
h
+1
-1
h
+1
 Sum the PT of charged particles in two cones of radius
0.7 at the same h as the leading jet but with |DF| = 90o.
 Plot the cone with the maximum and minimum PTsum
versus the ET of the leading (calorimeter) jet.
Workshop on Early LHC Physics
May 6, 2009
Rick Field – Florida/CDF/CMS
Page 5
Energy Dependence
of the “Underlying Event”
“Cone Analysis”
(Tano, Kovacs, Huston, Bhatti)
630 GeV
1,800 GeV
PYTHIA 6.115
PT0 = 1.4 GeV
PYTHIA 6.115
PT0 = 2.0 GeV
 Sum the PT of charged particles (pT > 0.4 GeV/c) in two cones of radius 0.7 at the same h as the leading
jet but with |DF| = 90o. Plot the cone with the maximum and minimum PTsum versus the ET of the
leading (calorimeter) jet.
 Note that PYTHIA 6.115 is tuned at 630 GeV with PT0 = 1.4 GeV and at 1,800 GeV with PT0 = 2.0 GeV.
This implies that e = PARP(90) should be around 0.30 instead of the 0.16 (default).
 For the MIN cone 0.25 GeV/c in radius R = 0.7 implies a PTsum density of dPTsum/dhd = 0.16 GeV/c
and 1.4 GeV/c in the MAX cone implies dPTsum/dhd = 0.91 GeV/c (average PTsum density of 0.54
GeV/c per unit h-).
Workshop on Early LHC Physics
May 6, 2009
Rick Field – Florida/CDF/CMS
Page 6
“Transverse” Charged Densities
Energy Dependence
"Transverse" Charged PTsum Density: dPTsum/dhd
"Min Transverse" PTsum Density: dPTsum/dhd
0.60
0.3
Charged PTsum Density (GeV)
Charged PTsum Density (GeV)
e = 0.25
HERWIG 6.4
0.40
e = 0.16
e=0
0.20
HERWIG 6.4
e = 0.25
0.2
Increasing e produces less energy
dependence for the
UE resulting
in
e = 0.16
e=0
less UE activity at the LHC!
CTEQ5L
Pythia 6.206 (Set A)
Pythia 6.206 (Set A)
630 GeV |h|<1.0 PT>0.4 GeV
0.1
CTEQ5L
630 GeV |h|<1.0 PT>0.4 GeV
0.0
0.00
0
5
10
15
20
25
30
35
40
45
50
0
5
10
20
25
30
35
40
45
50
PT(charged jet#1) (GeV/c)
PT(charged jet#1) (GeV/c)
Lowering PT0 at 630 GeV (i.e.
increasing e) increases UE activity
charged
PTsum density
resulting in
less energy dependence.
(|h|<1, PT>0.4 GeV) versus PT(charged jet#1) at 630
GeV predicted by HERWIG 6.4 (PT(hard) > 3
GeV/c, CTEQ5L) and a tuned version of PYTHIA
6.206 (PT(hard) > 0, CTEQ5L, Set A, e = 0, e = 0.16
(default) and e = 0.25 (preferred)).
 Also shown are the PTsum densities (0.16 GeV/c and
0.54 GeV/c) determined from the Tano cone
analysis at 630 GeV
Hard-Scattering Cut-Off PT0
5
PYTHIA 6.206
e = 0.25 (Set A))
4
PT0 (GeV/c)
 Shows the “transverse”
15
3
2
e = 0.16 (default)
1
Rick Field Fermilab MC Workshop
Reference point
October 4, 2002!
E = 1.8 TeV
100
1,000
10,000
100,000
CM Energy W (GeV)
0
Workshop on Early LHC Physics
May 6, 2009
Rick Field – Florida/CDF/CMS
Page 7
All use LO as
with L = 192 MeV!
PYTHIA 6.2 Tunes
UE Parameters
ISR Parameter
Parameter
Tune AW
Tune DW
Tune D6
PDF
CTEQ5L
CTEQ5L
CTEQ6L
MSTP(81)
1
1
1
MSTP(82)
4
4
4
PARP(82)
2.0 GeV
1.9 GeV
1.8 GeV
PARP(83)
0.5
0.5
0.5
PARP(84)
0.4
0.4
0.4
PARP(85)
0.9
1.0
1.0
PARP(86)
0.95
1.0
1.0
PARP(89)
1.8 TeV
1.8 TeV
1.8 TeV
PARP(90)
0.25
0.25
0.25
PARP(62)
1.25
1.25
1.25
PARP(64)
0.2
0.2
0.2
PARP(67)
4.0
2.5
2.5
MSTP(91)
1
1
1
PARP(91)
2.1
2.1
2.1
PARP(93)
15.0
15.0
15.0
Uses CTEQ6L
Tune A energy dependence!
Intrinsic KT
Workshop on Early LHC Physics
May 6, 2009
Rick Field – Florida/CDF/CMS
Page 8
All use LO as
with L = 192 MeV!
PYTHIA 6.2 Tunes
UE Parameters
Tune A
ISR Parameter
Parameter
Tune DWT
Tune D6T
ATLAS
PDF
CTEQ5L
CTEQ6L
CTEQ5L
MSTP(81)
1
1
1
MSTP(82)
4
4
4
PARP(82)
1.9409 GeV
1.8387 GeV
1.8 GeV
PARP(83)
0.5
0.5
0.5
ATLAS energy dependence!
PARP(84)
0.4
0.4
Tune
B 0.5
Tune
AW
Tune BW
These are 1.0
“old” PYTHIA
6.2
PARP(85)
1.0
0.33 tunes!
are new 6.420
tunes
PARP(86)There 1.0
1.0
0.66 by
PARP(89)
1.96 TeV
TeV
1.0 TeV
Peter Skands
(Tune1.96S320,
update
of S0)
PARP(90)
0.16
0.16 N324,0.16
Peter Skands
(Tune
N0CR)
PARP(62)
1.25
1.25
1.0
Hendrik Hoeth (Tune P329, “Professor”)
PARP(64)
0.2
0.2
1.0
PARP(67)
2.5
2.5
1.0
MSTP(91)
1
1
1
PARP(91)
Tune D
PARP(93)
Tune 2.1
DW
15.0
2.1
15.0
5.0
Tune D6T
Intrinsic KT
Workshop on Early LHC Physics
May 6, 2009
1.0
Tune D6
Rick Field – Florida/CDF/CMS
Page 9
Peter’s Pythia Tunes WEBsite
 http://home.fnal.gov/~skands/leshouches-plots/
Workshop on Early LHC Physics
May 6, 2009
Rick Field – Florida/CDF/CMS
Page 10
1st Workshop on Energy Scaling
in Hadron-Hadron Collisions
Peter Skands!
Renee Fatemi gave a talk on the
“underlying event at ATAR!
“On the Boarder” restaurant, Aurora, IL
April 27, 2009
Workshop on Early LHC Physics
May 6, 2009
Rick Field – Florida/CDF/CMS
Page 11
The “Underlying Event” at STAR
 At STAR they have measured the “underlying event at W = 200 GeV (|h| < 1, pT > 0.2 GeV)
and compared with Pythia Tune A.
Workshop on Early LHC Physics
May 6, 2009
Rick Field – Florida/CDF/CMS
Page 12
Proton-AntiProton Collisions
at the Tevatron
Elastic Scattering
The CDF “Min-Bias” trigger
picks up most of the “hard
core” cross-section plus a
Double
Diffraction
small
amount of single &
double diffraction.
M2
M1
Single Diffraction
M
stot = sEL +sIN
SD +sDD +sHC
1.8 TeV: 78mb
= 18mb
The “hard core” component
contains both “hard” and
“soft” collisions.
+ 9mb
+ (4-7)mb + (47-44)mb
CDF “Min-Bias” trigger
1 charged particle in forward BBC
AND
1 charged particle in backward BBC
Hard Core
“Inelastic Non-Diffractive Component”
“Hard” Hard Core (hard scattering)
Outgoing Parton
“Soft” Hard Core (no hard scattering)
Proton
AntiProton
PT(hard)
Beam-Beam Counters
3.2 < |h| < 5.9
Proton
AntiProton
Underlying Event
Underlying Event
Initial-State
Radiation
Final-State
Radiation
Outgoing Parton
Workshop on Early LHC Physics
May 6, 2009
Rick Field – Florida/CDF/CMS
Page 13
Charged Particle Density: dN/dh
Charged Particle Density: dN/dh
Charged Particle Density: dN/dh
5.0
2.0
PY Tune A
generator level
4.0
3.0
2.0
PY64 Tune S320
PY64 Tune P329
1.0
Min-Bias
1.96 TeV
Charged Particles (all PT)
PY64 Tune P329
RDF Preliminary
Charged Particle Density
Charged Particle Density
RDF Preliminary
generator level
1.5
PY Tune A
1.0
PY64 Tune S320
0.5
Min-Bias
1.96 TeV
Charged Particles (PT>0.5 GeV/c)
0.0
0.0
-8
-6
-4
-2
0
2
4
6
8
-8
-6
PseudoRapidity h
-4
-2
0
2
4
6
8
PseudoRapidity h
Charged particle (all pT) pseudo-rapidity Charged particle (pT>0.5 GeV/c) pseudodistribution, dNchg/dhd, at 1.96 TeV for
inelastic non-diffractive collisions from
PYTHIA Tune A, Tune S320, and Tune
P324.
Workshop on Early LHC Physics
May 6, 2009
rapidity distribution, dNchg/dhd, at 1.96
TeV for inelastic non-diffractive collisions
from PYTHIA Tune A, Tune S320, and
Tune P324.
Rick Field – Florida/CDF/CMS
Page 14
Charged Particle Density: dN/dh
RDF LHC Prediction!
Charged Particle Density: dN/dh
Charged Particle Density: dN/dh
8.0
5.0
generator level
4.0
3.0
2.0
PY64 Tune S320
PY64 Tune P329
1.0
PY64 Tune P329
RDF Preliminary
PY Tune A
Charged Particle Density
Charged Particle Density
RDF Preliminary
Min-Bias
1.96 TeV
Charged Particles (all PT)
generator level
6.0
4.0
PY Tune A
PY64 Tune S320
2.0
0.0
0.0
-8
-6
-4
-2
0
2
4
6
8
-8
-6
-4
-2
0
2
4
6
PseudoRapidity h
PseudoRapidity h
“Minumum Bias” Collisions
Proton
Min-Bias
14 TeV
Charged Particles (all PT)
“Minumum Bias” Collisions
AntiProton
Tevatron
Proton
Proton
LHC
Charged particle (all pT) pseudo-rapidity distribution, dNchg/dhd, at 1.96 TeV for
inelastic non-diffractive collisions from PYTHIA Tune A, Tune S320, and Tune P324.
Extrapolations of PYTHIA Tune A, Tune S320, and Tune P329 to the LHC.
Workshop on Early LHC Physics
May 6, 2009
Rick Field – Florida/CDF/CMS
Page 15
8
Charged Particle Density: dN/dh
RDF LHC Prediction!
Charged Particle Density: dN/dh
2.0
PY64 Tune P329
RDF Preliminary
RDF Preliminary
Charged Particle Density
Charged Particle Density
Charged Particle Density: dN/dh
4.0
generator level
1.5
PY Tune A
1.0
PY64 Tune S320
0.5
Min-Bias
1.96 TeV
Charged Particles (PT>0.5 GeV/c)
PY64 Tune P329
generator level
3.0
PY64 Tune S320
2.0
PY Tune A
1.0
0.0
0.0
-8
-6
-4
-2
0
2
4
6
8
-8
-6
-4
-2
0
2
4
6
8
PseudoRapidity h
PseudoRapidity h
“Minumum Bias” Collisions
Proton
Min-Bias
14 TeV
Charged Particles (PT>0.5 GeV/c)
“Minumum Bias” Collisions
AntiProton
Tevatron
Proton
Proton
LHC
Charged particle (pT > 0.5 GeV/c) pseudo-rapidity distribution, dNchg/dhd, at 1.96 TeV
for inelastic non-diffractive collisions from PYTHIA Tune A, Tune S320, and Tune P324.
Extrapolations of PYTHIA Tune A, Tune S320, and Tune P329 to the LHC.
Workshop on Early LHC Physics
May 6, 2009
Rick Field – Florida/CDF/CMS
Page 16
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 (|h|<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, |h| < 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).
Workshop on Early LHC Physics
May 6, 2009
Rick Field – Florida/CDF/CMS
Page 17
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 (|h|<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
Workshop on Early LHC Physics
May 6, 2009
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 18
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 (|h|<1.0, PT>0.4 GeV/c)
0.6
ChargedParticles
Particles(|h|<1.0,
(|h|<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, |h| <
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, |h| < 1, excluding the lepton-pair) for for Drell-Yan production (70 < M(pair) < 110 GeV) at CDF Run 2.
Workshop on Early LHC Physics
May 6, 2009
Rick Field – Florida/CDF/CMS
Page 19
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 (|h|<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
Workshop on Early LHC Physics
May 6, 2009
Rick Field – Florida/CDF/CMS
Page 20
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 (|h|<1.0, PT>0.5 GeV/c)
excluding the lepton-pair
ATLAS
ATLAS
Charged
Charged Particles
Particles (|h|<1.0,
(|h|<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, |h| < 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, |h| < 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).
Workshop on Early LHC Physics
May 6, 2009
Rick Field – Florida/CDF/CMS
Page 21
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
(|h|<1.0,
PT>0.5
GeV/c)
Charged
Charged Particles
Particles (|h|<1.0,
(|h|<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 (|h|<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
|h|GeV/c,
< 1, |h|
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).
Workshop on Early LHC Physics
May 6, 2009
Rick Field – Florida/CDF/CMS
Page 22
Min-Bias: Average PT versus Nchg
RDF LHC Prediction!
Average PT versus Nchg
Average PT versus Nchg
1.4
1.6
RDF Preliminary
generator level
PY Tune A
1.2
Average PT (GeV/c)
Average PT (GeV/c)
RDF Preliminary
PY64 Tune P329
PY Tune DW
1.0
PY64 Tune S320
0.8
PY64 Tune N324
Min-Bias
1.96 TeV
1.4
PY Tune A
1.2
PY64 Tune P329
1.0
PY64 Tune S320
0.8
Min-Bias
14 TeV
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
0.6
PY Tune DW
generator level
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
0.6
0
5
10
15
20
25
30
35
0
5
Number of Charged Particles
10
15
“Minumum Bias” Collisions
Proton
20
25
30
35
40
Number of Charged Particles
“Minumum Bias” Collisions
Proton
AntiProton
Tevatron
Proton
LHC
The average pT of charged particles versus the number of charged particles (pT > 0.5
GeV/c, |h| < 1) for “min-bias” collisions at 1.96 TeV from PYTHIA Tune A, Tune DW,
Tune S320, Tune N324, and Tune P324.
Extrapolations of PYTHIA Tune A, Tune DW, Tune S320, and Tune P324 to the
LHC.
Workshop on Early LHC Physics
May 6, 2009
Rick Field – Florida/CDF/CMS
Page 23
CDF Run 2 Min-Bias “Associated”
Charged Particle Density
“Associated” densities do
not include PTmax!
Highest pT
charged particle!
Charged Particle Density: dN/dhd
PTmax Direction
PTmax Direction
0.5
D
Correlations in 
Charged Particle Density
CDF Preliminary
Associated Density
PTmax not included
data uncorrected
0.4
D
Charge Density
0.3
0.2
0.1
Min-Bias
Correlations
in 
Charged Particles
(|h|<1.0, PT>0.5 GeV/c)
PTmax
0.0
0
30
60
90
120
150
180
210
240
270
300
330
360
D (degrees)
 Use the maximum pT charged particle in the event, PTmax, to define a direction and look
It is more probable
to find
a particle
at the the “associated”
density, dN
chg/dhd,
in “min-bias” collisions (pT > 0.5 GeV/c, |h| <
accompanying
PTmax
than
it
is
to
1).
find a particle in the central region!
 Shows the data
on the D dependence of the “associated” charged particle density,
dNchg/dhd, for charged particles (pT > 0.5 GeV/c, |h| < 1, not including PTmax) relative
to PTmax (rotated to 180o) for “min-bias” events. Also shown is the average charged
particle density, dNchg/dhd, for “min-bias” events.
Workshop on Early LHC Physics
May 6, 2009
Rick Field – Florida/CDF/CMS
Page 24
CDF Run 2 Min-Bias “Associated”
Charged Particle Density Rapid rise in the particle
density in the “transverse”
region as PTmax increases!
Associated Particle Density: dN/dhd
PTmaxDirection
Direction
PTmax
D
“Toward”
“Transverse”
“Transverse”
Correlations in 
“Away”
Associated Particle Density
Jet #1
D
PTmax > 2.0 GeV/c
1.0
PTmax > 2.0 GeV/c
PTmax > 1.0 GeV/c
0.8
Charged Particles
(|h|<1.0, PT>0.5 GeV/c)
CDF Preliminary
data uncorrected
PTmax > 0.5 GeV/c
Transverse
Region
0.6
Transverse
Region
0.4
0.2
Jet #2
PTmax
PTmax not included
Min-Bias
0.0
0
30
60
90
120
150
180
210
240
270
300
330
360
D (degrees)
Ave Min-Bias
0.25 per unit h-
PTmax > 0.5 GeV/c
 Shows the data on the D dependence of the “associated” charged particle density,
dNchg/dhd, for charged particles (pT > 0.5 GeV/c, |h| < 1, not including PTmax) relative
to PTmax (rotated to 180o) for “min-bias” events with PTmax > 0.5, 1.0, and 2.0 GeV/c.
 Shows “jet structure” in “min-bias” collisions (i.e. the “birth” of the leading two jets!).
Workshop on Early LHC Physics
May 6, 2009
Rick Field – Florida/CDF/CMS
Page 25
CDF Run 2 Min-Bias “Associated”
Charged Particle Density
PY Tune A
PTmax > 2.0 GeV/c
PTmax Direction
Direction
PTmax
D
“Toward”
“Transverse”
“Transverse”
Correlations in 
“Away”
PTmax > 2.0 GeV/c
Associated Particle Density
D
Associated Particle Density: dN/dhd
1.0
CDF Preliminary
PY Tune A
0.8
data uncorrected
theory + CDFSIM
PTmax > 0.5 GeV/c
PY Tune A
Transverse
Region
0.6
PY Tune A 1.96 TeV
Transverse
Region
0.4
0.2
PTmax
PTmax not included
(|h|<1.0, PT>0.5 GeV/c)
0.0
0
30
60
90
120
PTmax > 0.5 GeV/c
150
180
210
240
270
300
330
360
D (degrees)
 Shows the data on the D dependence of the “associated” charged particle density,
dNchg/dhd, for charged particles (pT > 0.5 GeV/c, |h| < 1, not including PTmax) relative
to PTmax (rotated to 180o) for “min-bias” events with PTmax > 0.5 GeV/c and PTmax >
2.0 GeV/c compared with PYTHIA Tune A (after CDFSIM).
 PYTHIA Tune A predicts a larger correlation than is seen in the “min-bias” data (i.e.
Tune A “min-bias” is a bit too “jetty”).
Workshop on Early LHC Physics
May 6, 2009
Rick Field – Florida/CDF/CMS
Page 26
Min-Bias “Associated”
Charged Particle Density
PTmax Direction
Associated Charged
Charged
Particle
Density:
dN/dhd
Associated
"Transverse"
ChargedParticle
ParticleDensity:
Density:dN/dhd
dN/dhd
D
Associated Charged Particle Density: dN/dhd
10.0
Charged Particle Density
py Tune A generator level
“Toward” Region
PTmax > 2.0 GeV/c
PTmax > 5.0 GeV/c
1.0
PTmax > 10.0 GeV/c
“Transverse”
“Transverse”
0.1
Min-Bias
1.96 TeV
PTmax > 0.5 GeV/c
PTmax > 1.0 GeV/c
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
0.0
Density
"Transverse"
Charged
Density
Charged Particle
1.6
2.5
1.2
RDF Preliminary
RDF Preliminary
RDF Preliminary
py Tune A generator level
py Tune A generator level
1.0
2.0
1.2
0.8
1.5
Min-Bias
Min-Bias
Min-Bias
14 TeV
1.96 TeV
“Toward”
14 TeV
"Toward"
"Away"
"Toward"
“Transverse”
~ factor of "Away"
2!
“Transverse”
0.8
0.6
1.0
0.4
0.4
0.5
0.2
1.96 TeV
"Transverse"
"Transverse"
“Away”
Charged
ChargedParticles
Particles(|h|<1.0,
(|h|<1.0,PT>0.5
PT>0.5 GeV/c)
GeV/c)
Charged
Particles
(|h|<1.0,
PT>0.5
GeV/c)
0.0
0.0
0
30
60
90
120
150
180
210
240
270
300
330
360
00
2
D (degrees)
54
6
8
10
10
12
15
14
16
20
18
PTmax (GeV/c)
(GeV/c)
PTmax
 Shows the D dependence of the “associated” charged particle density, dNchg/dhd, for charged
particles (pT > 0.5 GeV/c, |h| < 1, not including PTmax) relative to PTmax (rotated to 180o) for
“min-bias” events at 1.96 TeV with PTmax > 0.5, 1.0, 2.0, 5.0, and 10.0 GeV/c from PYTHIA
Tune A (generator level).
PTmax Direction
D
“Toward”
“Transverse”
“Transverse”
“Away”
 Shows the “associated” charged particle density in the “toward”, “away” and
“transverse” regions as a function of PTmax for charged particles (pT > 0.5
GeV/c, |h| < 1, not including PTmax) for “min-bias” events at 1.96 TeV from
PYTHIA Tune A (generator level).
Workshop on Early LHC Physics
May 6, 2009
Rick Field – Florida/CDF/CMS
Page 27
25
20
25
Min-Bias “Associated”
Charged Particle Density
RDF LHC Prediction!
"Transverse" Charged Particle Density: dN/dhd
"Transverse" Charged Particle Density: dN/dhd
1.6
RDF Preliminary
PY64 Tune P329
"Transverse" Charged Density
"Transverse" Charged Density
0.8
generator level
0.6
0.4
PY Tune A
PY64 Tune N324
0.2
PY64 Tune S320
Min-Bias
1.96 TeV
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
PY Tune DWT
RDF Preliminary
generator level
1.2
0.8
PY64 Tune P329
PY Tune A
PY Tune DW
PY64 Tune S320
0.4
Min-Bias
14 TeV
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
0.0
0.0
0
2
4
6
8
10
12
14
16
18
20
0
5
10
15
PTmax Direction
PTmax Direction
D
D
“Toward”
“Toward”
“Transverse”
25
PTmax (GeV/c)
PTmax (GeV/c)
“Transverse”
20
Tevatron
LHC
“Transverse”
“Transverse”
“Away”
“Away”
 Shows the “associated” charged particle density in the “transverse” region as a function of PTmax
for charged particles (pT > 0.5 GeV/c, |h| < 1, not including PTmax) for “min-bias” events at 1.96
TeV from PYTHIA Tune A, Tune S320, Tune N324, and Tune P329 at the particle level (i.e.
generator level).
 Extrapolations of PYTHIA Tune A, Tune DW, Tune DWT, Tune S320, and Tune P329 to the LHC.
Workshop on Early LHC Physics
May 6, 2009
Rick Field – Florida/CDF/CMS
Page 30
Charged Particle Density
HERWIG + JIMMY
Tune
(PTJIM
= 3.6)
Charged
ParticleParticle
Density:Density:
dN/dhd
"Transverse"
Charged
dN/dhdCharged Particle Density:"Away"
Charged
Particle
Density:
dN/dhd
"Away"
dN/dhd
Charged
Particle
Density:
dN/dhd
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
"Toward"
0
0.0
00
20
20
40
60
"Leading
Jet"
"Away" data corrected
generator level theory
2
"Drell-Yan Production"
70 < M(pair) < 110 GeV
40
80
Charged Particles
Particles (|h|<1.0,
(|h|<1.0, PT>0.5
PT>0.5
GeV/c)
HW
Charged
GeV/c)
excluding the lepton-pair
100
0
60
120
0
80
160
20
140
180
PT(Z-Boson)
(GeV/c)(GeV/c)
PT(jet#1)
or PT(Z-Boson)
Z-Boson Direction
D
High PT Z-Boson Production
CDF
CDFRun
Run22Preliminary
Preliminary
100
200
40
"Leading Jet"
data
datacorrected
corrected
pyA generator
generator
levellevel
theory
pyAW
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 |h(jet#1)|<2
"Z-Boson""Transverse"
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
excluding the lepton-pair
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
Charged Particles (|h|<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
D
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/dhd, with pT > 0.5 GeV/c and |h| < 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).
Workshop on Early LHC Physics
May 6, 2009
Rick Field – Florida/CDF/CMS
Page 31
Z-Boson: “Towards”, Transverse”,
& “TransMIN” Charge Density
Charged
Particle
Density:
dN/dhd
Charged
Particle
Density:
dN/dhd
"TransMIN"
Charged
Particle
Density:
dN/dhd
"Toward"
Charged
Particle
Density:
dN/dhd
"TransMIN" Charged Particle Density:
dN/dhd
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 (|h|<1.0,
(|h|<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 (|h|<1.0,
(|h|<1.0, PT>0.5
PT>0.5 GeV/c)
GeV/c)
pyAW
HW
excluding
excluding the
the lepton-pair
lepton-pair
Charged Particles (|h|<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
D
D
“Toward”
“Toward”
“Transverse”
80
“TransMAX”
“Transverse”
“TransMIN”
“Away”
“Away”
 Data at 1.96 TeV on the density of charged particles, dN/dhd, with pT > 0.5 GeV/c and |h| < 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).
Workshop on Early LHC Physics
May 6, 2009
Rick Field – Florida/CDF/CMS
Page 33
Z-Boson: “Towards” Region
RDF LHC
Prediction!
"Toward" Charged Particle Density:
dN/dhd
"Toward" Charged Particle Density: dN/dhd
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 (|h|<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 (|h|<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
D
D
“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/dhd, with pT > 0.5 GeV/c and |h| < 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.
Workshop on Early LHC Physics
May 6, 2009
Rick Field – Florida/CDF/CMS
Page 34
150
Z-Boson: “Towards” Region
RDF LHC Prediction!
"Toward" Charged PTsum Density: dN/dhd
"Toward" Charged PTsum Density: dN/dhd
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 (|h|<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 (|h|<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
D
D
“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/dhd, with pT > 0.5 GeV/c and |h| < 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.
Workshop on Early LHC Physics
May 6, 2009
Rick Field – Florida/CDF/CMS
Page 35
150
LHC Predictions
“Minumum Bias” Collisions
Proton
AntiProton
Charged Particle Density: dN/dh
4.0
RDF Preliminary
Charged Particle Density
I believe 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/dhd
If the LHC data are not in
the range shown here then
we learn new physics!
“Transverse”
Final-State
Radiation
-4
PseudoRapidity h
"Transverse" Charged Density
AntiProton
Outgoing Parton
-6
D
Initial-State Radiation
Underlying Event
-8
PTmax Direction
PT(hard)
Proton
0.0
PY Tune DWT
RDF Preliminary
generator level
1.2
0.8
PY64 Tune P329
PY Tune A
PY Tune DW
PY64 Tune S320
0.4
Min-Bias
14 TeV
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
0.0
0
5
10
15
20
25
PTmax (GeV/c)
Z-BosonDirection
D
Lepton
"Toward" Charged Particle Density: dN/dhd
“Toward”
RDF Preliminary
AntiProton
Underlying Event
Underlying Event
“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
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 (|h|<1.0, PT>0.5 GeV/c)
0.0
0
25
50
75
100
125
150
Lepton-Pair PT (GeV/c)
Workshop on Early LHC Physics
May 6, 2009
Rick Field – Florida/CDF/CMS
Page 36
Summary & Conclusions
However, I believe that the
better fits to the LEP
fragmentation data at high z
will lead to small improvements
Outgoing Parton
of Tune A at the
Tevatron!
 We are making good progress in understanding and modeling the
“underlying event”.
PT(hard)
Initial-State Radiation
Proton
 The new Pythia pT ordered tunes (py64 S320 and py64 P329)
are very similar to Tune A, Tune AW, and Tune DW. At present
the new tunes do not fit the data better than Tune AW and Tune
DW. However, the new tune are theoretically preferred!
AntiProton
Underlying Event
Underlying Event
Outgoing Parton
Final-State
Radiation
Hard-Scattering Cut-Off PT0
 All tunes with the default value PARP(90) = 0.16
are wrong and are overestimating the activity of
min-bias and the underlying event at the LHC!
This includes all the ATLAS tunes and all my “T”
tunes!
 Need to measure “Min-Bias” and the “underlying
event” at the LHC as soon as possible to see if there is
new QCD physics to be learned!
Workshop on Early LHC Physics
May 6, 2009
Rick Field – Florida/CDF/CMS
PYTHIA 6.206
e = 0.25 (Set A))
4
PT0 (GeV/c)
 It is clear now that the default value PARP(90) = 0.16 is
not correct and the value should be closer to the Tune A
value of 0.25.
5
3
2
e = 0.16 (default)
1
100
1,000
10,000
100,000
CM Energy W (GeV)
UE&MB@CMS
Page 37
Early LHC Thesis Projects
Thesis 1: Measure dNchg/dh and <PT> versus Nchg
in “min-bias” collisions.
“Minumum Bias” Collisions
Proton
Proton
PTmax Direction
Thesis 2: Measure the “toward”, “away”, and “transverse”
region as a function of PTmax in “min-bias” collisions.
ChgJet#1 Direction
Z-Boson Direction
D
D
D
“Toward”
“Toward”
“Transverse”
“Transverse”
“Transverse”
“Toward”
“Transverse”
“Transverse”
“Away”
“Away”
Thesis 3: Measure the “toward”, “away”, and “transverse”
region as a function of PT(chgjet#1).
“Away”
Outgoing Parton
PT(hard)
Initial-State Radiation
Proton
Proton
Underlying Event
Thesis 4: Measure the “toward”, “away”, and “transverse”
region as a function of PT(Z) for Z-boson production.
Underlying Event
Outgoing Parton
Final-State
Radiation
Drell-Yan Production
Proton
Thesis 5: Measure PT(Z) and <pT> versus Nchg
for Z-boson production (all PT(Z), PT(Z) < 10 GeV/c).
“Transverse”
Lepton
Proton
Underlying Event
Underlying Event
Anti-Lepton
Workshop on Early LHC Physics
May 6, 2009
Rick Field – Florida/CDF/CMS
Page 38