The LHC Physics Environment
Talk 2: Extrapolations from the
Tevatron to RHIC and the LHC
University of Wisconsin, Madison
June 24th – July 2nd, 2009
Rick Field
University of Florida
Outline of Talk
 The PYTHIA MPI energy scaling parameter

PARP(90).
The “underlying event” at STAR.
Extrapolations to RHIC.
Outgoing Parton
 LHC predictions for the “underlying
event” (hard scattering QCD &
Drell-Yan).
PT(hard)
Initial-State Radiation
Proton
CDF Run 2
 “Min-bias” and “pile-up” at the LHC.
 Correlations: charged particle <pT>
Outgoing Parton
versus the charged multiplicity in “minbias” and Drell-Yan.
 Summary & Conclusions.
 Early LHC Thesis Projects.
2009 CTEQ Summer School
July 1, 2009
AntiProton
Underlying Event
CMS at the LHC
Rick Field – Florida/CDF/CMS
Underlying Event
Final-State
Radiation
UE&MB@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!
2009 CTEQ Summer School
July 1, 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.
2009 CTEQ Summer School
July 1, 2009
Rick Field – Florida/CDF/CMS
Page 3
Particle Densities
DD = 4 = 12.6
2

31 charged
charged particles
particle
Charged Particles
pT > 0.5 GeV/c || < 1
CDF Run 2 “Min-Bias”
CDF Run 2 “Min-Bias”
Observable
Average
Nchg
Number of Charged Particles
(pT > 0.5 GeV/c, || < 1)
3.17 +/- 0.31
0.252 +/- 0.025
PTsum
(GeV/c)
Scalar pT sum of Charged Particles
(pT > 0.5 GeV/c, || < 1)
2.97 +/- 0.23
0.236 +/- 0.018
Average Density
per unit -
dNchg
chg/dd = 1/4
3/4 = 0.08
0.24
13 GeV/c PTsum
0
-1

+1
Divide by 4
dPTsum/dd = 1/4
3/4 GeV/c = 0.08
0.24 GeV/c
Study the charged particles (pT > 0.5 GeV/c, || < 1) and form the charged
particle density, dNchg/dd, and the charged scalar pT sum density,
dPTsum/dd.
2009 CTEQ Summer School
July 1, 2009
Rick Field – Florida/CDF/CMS
Page 4
“Transverse” Charged Density
PTmax Direction
D
"Transverse" Charged Particle Density: dN/dd
0.8
“Transverse”
“Transverse”
“Away”
ChgJet#1 Direction
D
“Toward”
“Transverse”
“Transverse”
“Away”
"Transverse" Charged Density
“Toward”
RDF Preliminary
1.96 TeV
py Tune A generator level
0.6
0.6
0.4
Jet#1
ChgJet#1
0.2
PTmax
Charged Particles (||<1.0, PT>0.5 GeV/c)
0.0
Jet#1 Direction
D
0
5
10
15
20
25
30
PT(jet#1) or PT(chgjet#1) or PTmax (GeV/c)
“Toward”
“Transverse”
“Transverse”
“Away”
 Shows the charged particle density in the “transverse” region for charged particles (pT > 0.5
GeV/c, || < 1) at 1.96 TeV as defined by PTmax, PT(chgjet#1), and PT(jet#1) from PYTHIA
Tune A at the particle level (i.e. generator level).
2009 CTEQ Summer School
July 1, 2009
Rick Field – Florida/CDF/CMS
Page 5
Tuning PYTHIA:
Multiple Parton Interaction Parameters
Parameter
Default
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.
Determines the energy
Probability
that of
thethe
MPI
produces two gluons
dependence
MPI!
with color connections to the “nearest neighbors.
0.33
PARP(86)
0.66
PARP(89)
PARP(82)
PARP(90)
PARP(67)
1 TeV
1.9
GeV/c
0.16
1.0
Multiple Parton Interaction
Color String
Color String
Multiple PartonDetermine
Interactionby comparing
Probability thatAffects
the MPI
theproduces
amount two
of gluons
either as described
by PARP(85)
or as a closed
initial-state
radiation!
gluon loop. The remaining fraction consists of
quark-antiquark pairs.
with 630 GeV data!
Color String
Hard-Scattering Cut-Off PT0
Determines the reference energy E0.
The cut-off PT0 that regulates the 2-to-2
scattering divergence 1/PT4→1/(PT2+PT02)2
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.
2009 CTEQ Summer School
July 1, 2009
Rick Field – Florida/CDF/CMS
5
PYTHIA 6.206
e = 0.25 (Set A))
4
PT0 (GeV/c)
PARP(85)
Description
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
Page 6
“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

+1
-1

+1
 Sum the PT of charged particles in two cones of radius
0.7 at the same  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.
2009 CTEQ Summer School
July 1, 2009
Rick Field – Florida/CDF/CMS
Page 7
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  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/dd = 0.16 GeV/c
and 1.4 GeV/c in the MAX cone implies dPTsum/dd = 0.91 GeV/c (average PTsum density of 0.54
GeV/c per unit -).
2009 CTEQ Summer School
July 1, 2009
Rick Field – Florida/CDF/CMS
Page 8
“Transverse” Charged Densities
Energy Dependence
"Transverse" Charged PTsum Density: dPTsum/dd
"Min Transverse" PTsum Density: dPTsum/dd
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 ||<1.0 PT>0.4 GeV
0.1
CTEQ5L
630 GeV ||<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
Lowering PT0 at 630 GeV (i.e.
increasing e) increases UE activity
charged
PTsum density
resulting in
less energy dependence.
40
45
50
Hard-Scattering Cut-Off PT0
5
PYTHIA 6.206
e = 0.25 (Set A))
4
PT0 (GeV/c)
(||<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, Kovacs,
Huston, and Bhatti “transverse” cone analysis at
630 GeV.
3
2
e = 0.16 (default)
1
100
1,000
Rick Field Fermilab MC Workshop
Reference point
E = 1.8 TeV
October 4, 2002!
2009 CTEQ Summer School
July 1, 2009
35
PT(charged jet#1) (GeV/c)
PT(charged jet#1) (GeV/c)
 Shows the “transverse”
15
Rick Field – Florida/CDF/CMS
10,000
100,000
CM Energy W (GeV)
0
Page 9
All use LO as
with L = 192 MeV!
UE Parameters
ISR Parameter
PYTHIA 6.2 Tunes
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!
(not the default)
Intrinsic KT
2009 CTEQ Summer School
July 1, 2009
Rick Field – Florida/CDF/CMS
Page 10
All use LO as
with L = 192 MeV!
UE Parameters
Tune A
ISR Parameter
PYTHIA 6.2 Tunes
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
0.4
0.4
0.5
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
1.0
Tune D6
5.0
Tune D6T
Intrinsic KT
2009 CTEQ Summer School
July 1, 2009
ATLAS energy dependence!
(PYTHIA default)
Tune B
Tune AW
PARP(85)
1.0
0.33 tunes!
These are 1.0
“old” PYTHIA
6.2
PARP(86)
1.0
0.66
There 1.0
are new 6.420
tunes
by
Tune BW
PARP(89)
1.96 TeV
1.96 TeV
1.0 TeV
Peter Skands (Tune S320, update of S0)
PARP(90)
0.16
0.16
0.16
Peter
Skands
(Tune
N324,
N0CR)
PARP(62)
1.25
1.25
1.0
Hendrik
Hoeth
(Tune0.2P329, “Professor”)
PARP(64)
0.2
1.0
PARP(84)
Rick Field – Florida/CDF/CMS
Page 11
Peter’s Pythia Tunes WEBsite
 http://home.fnal.gov/~skands/leshouches-plots/
2009 CTEQ Summer School
July 1, 2009
Rick Field – Florida/CDF/CMS
Page 12
Min-Bias “Associated”
Charged Particle Density
35% more at RHIC means
"Transverse" Charged Particle Density: dN/dd
26% less at the LHC!
1.6
RDF Preliminary
"Transverse" Charged Density
0.3
"Transverse" Charged Density
"Transverse" Charged Particle Density: dN/dd
PY Tune DW
generator level
0.2
~1.35
PY Tune DWT
0.1
Min-Bias
0.2 TeV
Charged Particles (||<1.0, PT>0.5 GeV/c)
RDF Preliminary
PY Tune DWT
generator level
1.2
~1.35
0.8
PY Tune DW
0.4
Min-Bias
14 TeV
Charged Particles (||<1.0, PT>0.5 GeV/c)
0.0
0.0
0
2
4
6
8
10
12
14
16
18
20
0
2
4
6
8
PTmax Direction
D
“Toward”
“Transverse”
12
14
16
18
20
PTmax (GeV/c)
PTmax (GeV/c)
RHIC
10
PTmax Direction
0.2 TeV → 14 TeV
(~factor of 70 increase)
“Transverse”
“Away”
D
“Toward”
LHC
“Transverse”
“Transverse”
“Away”
 Shows the “associated” charged particle density in the “transverse” regions 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 and 14 TeV from PYTHIA Tune DW and Tune DWT at the particle level (i.e. generator
level). The STAR data from RHIC favors Tune DW!
2009 CTEQ Summer School
July 1, 2009
Rick Field – Florida/CDF/CMS
Page 13
Min-Bias “Associated”
Charged Particle Density
About a factor of 2.7 increase in
Associated Charged Particle Density: dN/dd
the “transverse” region!
1.2
1.6
py Tune DW generator level
RDF Preliminary
Min-Bias
1.96 TeV
Charged Particle Density
RDF Preliminary
Charged Particle Density
Associated Charged Particle Density: dN/dd
1.2
"Toward"
"Away"
0.8
"Transverse"
0.4
py Tune DW generator level
Min-Bias
0.2 TeV
"Away"
0.8
"Toward"
0.4
"Transverse"
Charged Particles (||<1.0, PT>0.5 GeV/c)
Charged Particles (||<1.0, PT>0.5 GeV/c)
0.0
0.0
0
2
4
6
8
10
12
16
18
20
0
2
4
6
8
10
PTmax (GeV/c)
PTmax (GeV/c)
PTmax Direction
PTmax Direction
D
“Toward”
Tevatron
14
“Transverse”
1.96 TeV ← 0.2 TeV
(~factor of 10 increase)
“Transverse”
12
14
D
“Toward”
RHIC
“Transverse”
“Transverse”
“Away”
“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, || < 1, not including PTmax) for
“min-bias” events at 1.96 TeV and at 0.2 TeV from PYTHIA Tune DW at the particle level (i.e.
generator level).
2009 CTEQ Summer School
July 1, 2009
Rick Field – Florida/CDF/CMS
Page 14
Min-Bias “Associated”
Charged Particle Density
About a factor of 2 increase in the
Associated Charged Particle Density: dN/dd
“transverse” region!
1.6
py Tune DW generator level
Min-Bias
14 TeV
RDF Preliminary
Min-Bias
1.96 TeV
Charged Particle Density
RDF Preliminary
Charged Particle Density
Charged Particle Density: dN/dd
2.5
1.2
"Toward"
"Away"
0.8
"Transverse"
0.4
py Tune DW generator level
2.0
"Toward"
"Away"
1.5
"Transverse"
1.0
0.5
Charged Particles (||<1.0, PT>0.5 GeV/c)
Charged Particles (||<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
Tevatron
“Transverse”
25
PTmax Direction
PTmax Direction
“Toward”
20
PTmax (GeV/c)
PTmax (GeV/c)
D
15
1.96 TeV → 14 TeV
(~factor of 7 increase)
“Transverse”
D
“Toward”
LHC
“Transverse”
“Transverse”
“Away”
“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, || < 1, not including PTmax) for
“min-bias” events at 1.96 TeV and at 14 TeV from PYTHIA Tune DW at the particle level (i.e.
generator level).
2009 CTEQ Summer School
July 1, 2009
Rick Field – Florida/CDF/CMS
Page 15
Min-Bias “Associated”
Charged Particle Density
"Transverse" Charged Particle Density: dN/dd
"Transverse" Charged Density
1.2
RDF Preliminary
14 TeV
Min-Bias
py Tune DW generator level
0.8
~1.9
0.4
1.96 TeV
~2.7
0.2 TeV
Charged Particles (||<1.0, PT>0.5 GeV/c)
0.0
0
5
10
15
20
25
PTmax (GeV/c)
PTmax Direction
D
“Toward”
RHIC
“Transverse”
“Transverse”
0.2 TeV → 1.96 TeV
(UE increase ~2.7 times)
Tevatron
“Away”
PTmax Direction
D
“Toward”
“Transverse”
PTmax Direction
1.96 TeV → 14 TeV
(UE increase ~1.9 times)
LHC
“Transverse”
“Away”
D
“Toward”
“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, 1.96 TeV and 14 TeV predicted by PYTHIA Tune DW at the particle level (i.e. generator
level).
2009 CTEQ Summer School
July 1, 2009
Rick Field – Florida/CDF/CMS
Page 16
The “Underlying Event” at STAR
 At STAR they have measured the “underlying event at W = 200 GeV (|| < 1, pT > 0.2 GeV)
and compared their uncorrected data with PYTHIA Tune A + STAR-SIM.
2009 CTEQ Summer School
July 1, 2009
Rick Field – Florida/CDF/CMS
Page 17
The “Underlying Event” at STAR
Charged PTsum Density
Charged PTsum
"Transverse"
PTsumDensity
Density (GeV/c)
(GeV/c)
"Transverse"
PTsum Density:
dPT/dd
ChargedCharged
PTsum Density:
dPT/dd
2.0
100.0
1.6
“Back-to-Back”
Charged Particles (||<1.0, PT>0.2 GeV/c)
Data uncorrected
PYTHIA Tune A + STAR-SIM
CDF
Run
2 Preliminary
CDF
Run
2 Preliminary
data corrected
particle level
datatocorrected
10.0
1.2
pyA
generator level
1.96
TeV
"Leading Jet"
"Toward"
PY Tune A
"Away"
“Toward”
"Transverse"
0.8
1.0
"Back-to-Back"
"Leading Jet"
MidPoint R=0.7 |(jet#1)|<2
0.4
0.1
0.0
0
0
50
“Away”
MidPoint
R = Particles
0.7 |(jet#1)
< 2 PT>0.5 GeV/c)
Charged
(||<1.0,
Charged Particles (||<1.0, PT>0.5 GeV/c)
HW
50
0.55
100
150
200
250
100
150
200
250
300
300
350
350
400
400
450
Preliminary
~1.5
PT(jet#1) (GeV/c)
PT(jet#1) (GeV/c)
Jet #1 Direction
D
D
“Leading Jet”
“Toward”
“Transverse”
“Transverse”
“Away”
“Transverse”
Jet #1 Direction
0.37
“Toward”
“Transverse”
PT(jet#1) (GeV/c)
“Transverse”
“Away”
“Back-to-Back”
Jet #2 Direction
 Data on the charged particle scalar pT sum density, dPT/dd, as a function of the leading jet pT for the
“toward”, “away”, and “transverse” regions compared with PYTHIA Tune A.
2009 CTEQ Summer School
July 1, 2009
Rick Field – Florida/CDF/CMS
Page 18
Min-Bias “Associated”
Charged Particle Density
RDF LHC Prediction!
"Transverse" Charged Particle Density: dN/dd
"Transverse" Charged Particle Density: dN/dd
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 (||<1.0, PT>0.5 GeV/c)
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)
If the LHC data are not in
the range shown here then
we learn new (QCD) physics!
0.0
0
2
4
6
8
10
12
14
16
18
20
0
5
10
PTmax (GeV/c)
PTmax Direction
D
“Transverse”
20
25
PTmax Direction
D
“Toward”
“Toward”
“Transverse”
15
PTmax (GeV/c)
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, || < 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, Tune P329, and pyATLAS to the
LHC.
2009 CTEQ Summer School
July 1, 2009
Rick Field – Florida/CDF/CMS
Page 19
Z-Boson: “Towards” Region
RDF LHC
Prediction!
"Toward" Charged Particle Density:
dN/dd
"Toward" Charged Particle Density: dN/dd
RDF Preliminary
PY Tune AW
PY Tune DW
generator level
RDF Preliminary
Drell-Yan
1.96 TeV
"Toward" Charged Density
"Toward" Charged Density
PY ATLAS
1.6
0.8
0.6
0.4
PY64 Tune P329
PY64 Tune S320
0.2
70 < M(pair) < 110 GeV
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
If the LHC data are not in
the range shown here then
we learn new (QCD) physics!
Charged Particles (||<1.0, PT>0.5 GeV/c)
Charged Particles (||<1.0, PT>0.5 GeV/c)
0.0
0.0
0
25
50
75
100
125
150
0
25
D
“Transverse”
100
125
Z-BosonDirection
D
“Toward”
“Toward”
“Transverse”
75
Lepton-Pair PT (GeV/c)
Lepton-Pair PT (GeV/c)
Z-BosonDirection
50
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, and pyATLAS to
the LHC.
2009 CTEQ Summer School
July 1, 2009
Rick Field – Florida/CDF/CMS
Page 20
150
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 < || < 5.9
Proton
AntiProton
Underlying Event
Underlying Event
Initial-State
Radiation
Final-State
Radiation
Outgoing Parton
2009 CTEQ Summer School
July 1, 2009
Rick Field – Florida/CDF/CMS
Page 21
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!
2009 CTEQ Summer School
July 1, 2009
Rick Field – Florida/CDF/CMS
Page 22
Charged Particle Density: dN/d
Charged Particle Density: dN/d
Charged Particle Density: dN/d
5.0
2.0
Charged Particle Density
Charged Particle Density
generator level
4.0
3.0
PY Tune DW
2.0
PY64 Tune S320
PY64 Tune P329
1.0
PY64 Tune P329
PY Tune A
RDF Preliminary
Min-Bias
1.96 TeV
Charged Particles (all PT)
RDF Preliminary
generator level
1.5
PY Tune DW
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 
-4
-2
0
2
4
6
8
PseudoRapidity 
Charged particle (all pT) pseudo-rapidity Charged particle (pT>0.5 GeV/c) pseudodistribution, dNchg/dd, at 1.96 TeV for
inelastic non-diffractive collisions from
PYTHIA Tune A, Tune DW, Tune S320, and
Tune P324.
2009 CTEQ Summer School
July 1, 2009
rapidity distribution, dNchg/dd, at 1.96
TeV for inelastic non-diffractive collisions
from PYTHIA Tune A, Tune DW, Tune
S320, and Tune P324.
Rick Field – Florida/CDF/CMS
Page 23
Charged Particle Density: dN/d
RDF LHC Prediction!
Charged Particle Density: dN/d
Charged Particle Density: dN/d
5.0
8.0
Charged Particle Density
Charged Particle Density
PY Tune A
RDF Preliminary
generator level
4.0
PY ATLAS
3.0
PY Tune DW
2.0
PY64 Tune S320
PY64 Tune P329
1.0
Min-Bias
1.96 TeV
Charged Particles (all PT)
0.0
PY64 Tune P329
RDF Preliminary
generator level
PY Tune DWT
6.0
PY ATLAS
4.0
PY Tune DW
PY Tune A
PY64 Tune S320
2.0
Min-Bias
14 TeV
Charged Particles (all PT)
If the LHC data are not in
the range shown here then
we learn new (QCD) physics!
0.0
-8
-6
-4
-2
0
2
4
6
8
-8
-6
-4
-2
PseudoRapidity 
“Minumum Bias” Collisions
Proton
2
4
6
PseudoRapidity 
AntiProton
Tevatron
0
Proton
“Minumum Bias” Collisions
Proton
LHC
Charged particle (all pT) pseudo-rapidity distribution, dNchg/dd, at 1.96 TeV for
inelastic non-diffractive collisions from PYTHIA Tune A, Tune DW, Tune S320, and
Tune P324.
Extrapolations (all pT) of PYTHIA Tune A, Tune DW, Tune S320, Tune P324. and
ATLAS to the LHC.
2009 CTEQ Summer School
July 1, 2009
Rick Field – Florida/CDF/CMS
Page 24
8
Charged Particle Density: dN/d
RDF LHC Prediction!
Charged Particle Density: dN/d
Charged
ChargedParticle
Particle Density:
Density:dN/d
dN/d
4.0
generator
generatorlevel
level
1.5
1.5
PY
PYTune
TuneDW
DW
PY ATLAS
PY64
PY64Tune
TuneS320
S320
0.5
0.5
Min-Bias
Min-Bias
1.96
1.96TeV
TeV
Charged
ChargedParticles
Particles(PT>0.5
(PT>0.5GeV/c)
GeV/c)
0.0
0.0
PY ATLAS
RDF Preliminary
PY
PYTune
TuneAA
1.0
1.0
PY Tune DWT
PY64
PY64Tune
TuneP329
P329
RDF
RDFPreliminary
Preliminary
Charged Particle Density
Charged Particle
Particle Density
Density
Charged
2.0
2.0
PY64 Tune P329
generator level
3.0
PY64 Tune S320
2.0
PY Tune A
PY Tune DW
1.0
Min-Bias
14 TeV
Charged Particles (PT>0.5 GeV/c)
If the LHC data are not in
the range shown here then
we learn new (QCD) physics!
0.0
-8
-8
-6
-6
-4
-4
-2
-2
00
22
44
66
88
-8
-6
-4
-2
PseudoRapidity
PseudoRapidity
“Minumum Bias” Collisions
Proton
2
4
6
8
PseudoRapidity 
AntiProton
Tevatron
0
Proton
“Minumum Bias” Collisions
Proton
LHC
Charged particle (pT > 0.5 GeV/c) pseudo-rapidity distribution, dNchg/dd, at 1.96 TeV
for inelastic non-diffractive collisions from PYTHIA Tune A, Tune DW, Tune S320, and
Tune P324.
Extrapolations (pT > 0.5 GeV/c) of PYTHIA Tune A, Tune DW, Tune S320, Tune P324.
and ATLAS to the LHC.
2009 CTEQ Summer School
July 1, 2009
Rick Field – Florida/CDF/CMS
Page 25
MPI, Pile-Up, and Overlap
MPI: Multiple Parton Interactions
Outgoing Parton
PT(hard)
Initial-State Radiation
Proton
AntiProton
Underlying Event
 MPI: Additional 2-to-2 parton-parton
scatterings within a single protonantiproton collision.
Underlying Event
Outgoing Parton
Final-State
Radiation
Proton
Pile-Up
Pile-Up
AntiProton Proton
AntiProton
Primary
Interaction Region Dz
 Pile-Up: More than one proton-antiproton collision in the
beam crossing.
Overlap
 Overlap: An experimental timing issue where a proton-antiproton
collision from the next beam crossing gets included in the protonantiproton collision from the current beam crossing because the next
crossing happened before the event could be read out.
2009 CTEQ Summer School
July 1, 2009
Rick Field – Florida/CDF/CMS
Page 26
Studying Pile-Up at CDF
High PT Jet
CDF Run 2
Proton
AntiProton
Primary
Pile-Up
60 cm
396 ns
MB
 The primary vertex is the highest PTsum of charged particles pointing towards it.
 Normally one only includes those charged particles which point back to the primary
vertex.
 The primary vertex is presumably the collision that satisfied the trigger. Maybe not
for “min-bias” events?
 How well do we understand the pile-up at CDF?
Is the pile-up biased?
Is the pile-up the same for all triggers?
Does pile-up conspire to help satisfy your trigger?
How well do we model pile-up?
2009 CTEQ Summer School
July 1, 2009
Rick Field – Florida/CDF/CMS
Page 27
Pile-Up at the LHC
Tune DWT “Hard-Core” No
Trigger (ct =10mm)
Charged Particle Multiplicity Distribution
Charged Particle PseuoRapidity Distribution
4
Generator Level
HCMB 14 TeV
0.04
Charged Particles (||<2.0, all pT)
Mean = 24.39
0.03
Generator Level
HCMB 14 TeV
pyDWT <Nchg> = 81.7
<Nchg> in 0.4 bin
Probability per 1 Particle
0.05
pyDWT <Nchg> = 24.39
0.02
Npile = 1
3
2
1
0.01
Charged Particles (all pT)
0
0.00
0
10
20
30
40
50
60
70
80
90
100
-8
-6
-2
0
2
4
6
8
PseudoRapidity 
Number of Charged Particles: Nchg
 Shows the charged multiplicity distribution (||
< 2, all pT) for Npile = 1 (i.e. shows, on the
average, what one event looks like). The plot
shows the probability of finding 0, 1, 2, … etc.
charged particles. The sum of the points is
equal to one. The mean is 24.39 charged
particles and s = 19.7.
2009 CTEQ Summer School
July 1, 2009
-4
 Shows the charged particle pseudo-rapidity
distribution (all pT) for Npile = 1 (i.e. shows,
on the average, what one event looks like). The
plot shows the <Nchg> in a 0.4 bin (i.e. not
divided by bin size). The sum of the points
with || < 2 is 24.39.
Rick Field – Florida/CDF/CMS
Page 28
Pile-Up at the LHC
Charged Particle Multiplicity Distribution
“Central Limit Theorem”:
<Nchg> ~ Npile, s ~ sqrt(Npile)!
Charged Particle Multiplicity Distribution
0.16
Generator Level
HCMB 14 TeV
Duh!
0.06
Charged Particles (||<2.0, all pT)
pyDWT <Nchg> = 243.9
Mean = 243.9
0.04
Npile = 1 with Nchg->10*Nchg
Npile = 10
0.02
0.00
Probability per 50 Particles
Probability per 10 Particles
0.08
Generator Level
HCMB 14 TeV
0.12
True
for any
P(||<2.0,
cut!
Charged
Particles
all pT)
T(min)
pyDWT <Nchg> = 1219.5
0.08
Npile = 10 with Nchg->5*Nchg
Npile = 1 with Nchg->50*Nchg
0.04
Npile = 50
0.00
0
100
200
300
400
500
600
700
800
900
1000
0
500
Number of Charged Particles: Nchg
1000
1500
2000
2500
3000
3500
4000
4500
5000
Number of Charged Particles: Nchg
 Shows the charged multiplicity distribution (||
 Shows the charged multiplicity distribution
< 2, all pT) for Npile = 50 (i.e. shows, on the
(|| < 2, all pT) for Npile = 10 (i.e. shows, on
average, what 50 events looks like). The plot
the average, what 10 events looks like). The
shows the probability of finding 0, 50, 100, …
plot shows the probability of finding 0, 10, 20,
etc. charged particles. The sum of the points is
… etc. charged particles. The sum of the
equal to one. The mean is 1219.5 charged
points is equal to one. The mean is 243.9
particles and s = 138.9. Also shown is the
charged particles and s = 62.3. Also shown
Npile = 1 distribution scaled by a factor of 50
is the Npile = 1 distribution scaled by a
(i.e. Nchg → 50×Nchg) and the Npile = 10
factor of 10 (i.e. Nchg → 10×Nchg).
distribution scaled by a factor of 5 (i.e. Nchg →
5×Nchg).
2009 CTEQ Summer School
July 1, 2009
Rick Field – Florida/CDF/CMS
Page 29
Pile-Up at the LHC
Log-Scale!
Charged Particle Multiplicity Distribution
Charged Particle Multiplicity Distribution
Charged Particle PseuoRapidity Distribution
1.0E+00
1.0E+01
0.06
All PT <Nchg> = 24.39
1.0E+00
0.04
0.02
PT > 1 <Nchg> = 11.6
PT > 1 GeV/c <Nchg> = 4.87
PT > 2.5 GeV/c <Nchg> = 0.636
1.0E-01
PT > 5 GeV/cPT
<Nchg>
= 0.0466= 1.3
> 2.5 <Nchg>
PT > 10 GeV/c <Nchg> = 0.0025
1.0E-02
PT > 5 <Nchg> = 0.089
1.0E-03
Probability per 1 Particle
Charged Particles
(||<2.0)= 81.7
All PT <Nchg>
Generator Level
HCMB 14 TeV
<Nchg> in 0.4 bin
Probability per 1 Particle
0.08
Charged Particles (||<2.0)
Generator Level
HCMB 14 TeV
1.0E-01
1.0E-02
1.0E-03
1.0E-04
PT > 10 <Nchg> =0.005
0.00
0
5
10
15
20
25
1.0E-04
30 -8 35
Number of Charged Particles: Nchg
1.0E-05
-6 40
-445
50
-2
0
0
2
PseudoRapidity 
54
10 6 15
8 20
25
30
35
40
45
Number of Charged Particles: Nchg
 Charged multiplicity distribution (|| < 2) for Npile = 1 (i.e. shows, on the average, what one
event looks like). The plot shows the probability of finding 0, 1, 2, … etc. charged particles.
The five curves correspond to pT(min) = 0, 1.0 , 2.5, 5.0, and 10.0 GeV/c.
 Shows the charged particle pseudo-rapidity distribution for Npile = 1 (i.e. shows, on the
average, what one event looks like). The plot shows the <Nchg> in a 0.4 bin (i.e. not divided
by bin size). The five curves correspond to pT(min) = 0, 1.0 , 2.5, 5.0, and 10.0 GeV/c.
2009 CTEQ Summer School
July 1, 2009
Rick Field – Florida/CDF/CMS
Page 30
50
Pile-Up at the LHC
Charged Particle PT Distribution
Average
Average Number
Number of
of Charged
Charged Particles
Particles vs
vs PTmin
PTmin
1.0E+02
100.00
1.0E+02
Generator Level
HCMB 14 TeV
pyDWT <PT> = 693 MeV/c
1.0E-01
Charged Particles (||<2.0)
1.0E-02
1.0E+00
1.0E-02
0.10
1.0E-04
1.0E-03
0
2
4
6
8
10
12
14
16
18
20
pyDWT
pyDWT
fit
fit
1.00
1.0E-01
1.0E-03
1.0E-05
0.01
1.0E-04
0.00
Charged Particles (||<2.0)
Charged Particles (||<2.0)
1
2 1.03
4
5 2.06
7
8 3.09
10
11 4.0
12
13
14 5.0
15
Minimum
T T(GeV/c)
MinimumPP
(GeV/c)
PT (GeV/c)
 Shows the charged particle pT distribution
(|| < 2) for Npile = 1 (i.e. shows, on the
average, what one event looks like). The plot
shows the <Nchg> in a 1.0 GeV/c bin (i.e. not
divided by bin size). The sum of the points
gives 24.39.
2009 CTEQ Summer School
July 1, 2009
Generator
Level
Generator
Level
HCMB
14
TeV
HCMB 14
TeV
Hard-Scattering
Tail!
1.0E+01
10.00
1.0E+00
<Nchg>
<Nchg>
<Nchg> in 1 GeV/c bin
1.0E+01
 Shows the average number of charged particle
the PT-cut (|| < 2) for Npile = 1 (i.e. shows, on
the average, what one event looks like). The
first point corresponds to <Nchg> = 24.39.
The fit corresponds to
<Nchg>=24.39exp(-1.4pT(min)).
Rick Field – Florida/CDF/CMS
Page 31
Pile-Up at the LHC
<AssocNchg>+1 ≈ <Nchg>!
Charged Multiplicity & Associated Multiplicity
<AssocNchg>+1 > > <Nchg>!
Npile = 1 <Nchg> = 0.0466
Generator Level
HCMB 14 TeV
Npile = 1 <AssocNchg> = 0.277
0.8
5.0
<Nchg>
<AssocNchg>
<AssocNchg>+1
4.0
Average Number
1.0
Probability per 1 Particle
Charged Multiplicity & Associated Multiplicity
0.6
Charged Particles (pT > 5 GeV/c, ||<2.0)
0.4
Npile = 1
Generator Level
HCMB 14 TeV
3.0
2.0
1.0
0.2
Charged Particles (pT > 5 GeV/c, ||<2.0)
0.0
0.0
0
1
2
3
4
5
1
11
21
31
41
51
61
71
81
91
101
Number of Pile-Up Events
Nchg or AssocNchg
 Shows the charged multiplicity distribution (pT > 5 GeV/c, || < 2) for Npile = 1 (i.e. shows, on
the average, what one event looks like). The plot shows the probability of finding 0, 1, 2, … etc.
charged particles. The plot also shows the “associated multiplicity” distribution (open squares),
<AssocNchg> = <Nchg> -1, for events with at least one charged particle with pT > 5 GeV/c (i.e.
the overall average multiplicity is <AssocNchg> +1 ) . Note that <AssocNchg> +1 = 1.277 and
<Nchg> = 0.0466. There are many more particles in events with at least one charged particle
with pT > 5 GeV/c, than in an average “min-bias” event. Also, note that the probability of
getting an additional particle in an event with at least one charged particle with pT > 5 GeV/c
(i.e. AssocNchg = 1 is greater than the probability of getting one particle in a typical “min-bias”
event, Nchg = 1).
2009 CTEQ Summer School
July 1, 2009
Rick Field – Florida/CDF/CMS
Page 32
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).
2009 CTEQ Summer School
July 1, 2009
Rick Field – Florida/CDF/CMS
Page 34
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
2009 CTEQ Summer School
July 1, 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 35
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.
2009 CTEQ Summer School
July 1, 2009
Rick Field – Florida/CDF/CMS
Page 36
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
2009 CTEQ Summer School
July 1, 2009
Rick Field – Florida/CDF/CMS
Page 37
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).
2009 CTEQ Summer School
July 1, 2009
Rick Field – Florida/CDF/CMS
Page 38
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).
2009 CTEQ Summer School
July 1, 2009
Rick Field – Florida/CDF/CMS
Page 39
Min-Bias: Average PT versus Nchg
RDF LHC Prediction!
Average PT versus Nchg
Average PT versus Nchg
1.6
1.4
PY Tune DW
1.0
0.8
1.4
Average PT (GeV/c)
Average PT (GeV/c)
Average PT (GeV/c)
PY Tune A
1.2
1.2
1.0
PY64 Tune S320
PY64 Tune N324
Min-Bias
1.96 TeV
0.8
Min-Bias
Charged Particles (||<1.0,
PT>0.5 GeV/c)
0.6
5
RDF Preliminary
PY64 Tune P329
py Tune A generator level
generator level
0
1.6
RDF Preliminary
RDF Preliminary
10
15
0.6
20
25
0
5
Number of Charged Particles
30
10
Average PT versus Nchg
1.4
14 TeV
PY Tune DW
generator level
1.2
1.96 TeV
PY64 Tune P329
1.0
PY64 Tune S320
0.8
Min-Bias
Charged Particles
(||<1.0, PT>0.5 GeV/c)
14 TeV
0.6
35
15
20
0
25
5
10
30
Number of Charged Particles
15
Charged Particles (||<1.0, PT>0.5 GeV/c)
20
25
35
40
Number of Charged Particles
“Minumum Bias” Collisions
Proton
PY Tune A
30
35
40
“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, || < 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.
2009 CTEQ Summer School
July 1, 2009
Rick Field – Florida/CDF/CMS
Page 40
LHC Predictions
“Minumum Bias” Collisions
Proton
AntiProton
Charged Particle Density: dN/d
8.0
Charged Particle Density
I believe because of the STAR analysis we are now
in a position to make some predictions at the LHC!
 The amount of activity in “min-bias” collisions.
Outgoing Parton
Underlying Event
Final-State
Radiation
PY Tune DW
PY Tune A
PY64 Tune S320
2.0
-8
“Away”
scattering events.
-6
-4
-2
0
2
4
6
8
PseudoRapidity 
"Transverse" Charged Particle Density: dN/dd
“Toward”
“Transverse”
Min-Bias
14 TeV
Charged Particles (all PT)
1.6
 The amount of activity in the “underlying event” in hard
Drell-Yan Production
4.0
If the LHC data are not in
the range shown here then
we learn new (QCD) physics!
“Transverse”
Outgoing Parton
PY ATLAS
0.0
"Transverse" Charged Density
AntiProton
PY Tune DWT
6.0
D
Initial-State Radiation
Underlying Event
generator level
PTmax Direction
PT(hard)
Proton
PY64 Tune P329
RDF Preliminary
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)
D
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)
2009 CTEQ Summer School
July 1, 2009
Rick Field – Florida/CDF/CMS
Page 41
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”. RHIC data at 200 GeV are very important!
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
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.
 The new and old PYTHIA tunes are beginning to
converge and I believe we are finally in a position to make
some legitimate predictions at the LHC!
5
3
2
e = 0.16 (default)
1
 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 my
“T” tunes and the ATLAS 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!
2009 CTEQ Summer School
July 1, 2009
Rick Field – Florida/CDF/CMS
100
1,000
10,000
100,000
CM Energy W (GeV)
UE&MB@CMS
Page 42
Early LHC Thesis Projects
Thesis 1: Measure dNchg/d 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
2009 CTEQ Summer School
July 1, 2009
Rick Field – Florida/CDF/CMS
Page 43