Early LHC Physics
Early Physics Measurements
Rick Field
University of Florida
Outline of Talk
 Studying “min-bias” collisions and
the “underlying event” at CDF.
 The QCD Monte-Carlo model tunes.
University of Florida October 2009
Outgoing Parton
 The PYTHIA MPI energy scaling
parameter PARP(90).
PT(hard)
CDF Run 2
Initial-State Radiation
Proton
Proton
Underlying Event
 The “underlying event” at STAR.
Extrapolations to RHIC.
Outgoing Parton
Underlying Event
Final-State
Radiation
 LHC predictions!
 Summary & Conclusions.
UF High Energy Physics Seminar
October 27 & 30, 2009
CMS at the LHC
Rick Field – Florida/CDF/CMS
UE&MB@CMS
Page 1
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
UF High Energy Physics Seminar
October 27 & 30, 2009
Rick Field – Florida/CDF/CMS
Page 2
Inelastic Non-Diffractive Cross-Section
Inelastic Non-Diffractive Cross-Section: sHC
Inelastic Non-Diffractive Cross-Section: sHC
Number of Inelastic ND Events
in 1/nb
70
70
60
Cross-Section (mb)
RDF Preliminary
py Tune DW generator level
py Tune DW generator level
50
60,000,000
Number of Events
Cross-Section (mb)
70,000,000
RDF Preliminary
60
40
30
20
10
0
0
2
4
K-Factor = 1.2
My guess!
50,000,000
40,000,000
RDF Preliminary
py Tune DW generator level
50
40
30
20
10
K-Factor = 1.2
Lots of events!
K-Factor = 1.2
0
30,000,000
6
8
10
12
0.1
14
1.0
10.0
100.0
Inelastic Non-Diffractive Events
Center-of-Mass Energy (TeV)
Center-of-Mass Energy (TeV)
20,000,000
0
Linear scale!
2
4
6
8Log scale!
10
12
14
Center-of-Mass Energy (TeV)
stot = sEL + sSD +sDD +sHC
 The inelastic non-diffractive cross section versus center-of-mass energy from PYTHIA (×1.2).
sHC varies slowly.
Only a 13% increase between 7 TeV (≈ 58 mb) and 14 teV (≈ 66 mb). Linear
on a log scale!
UF High Energy Physics Seminar
October 27 & 30, 2009
Rick Field – Florida/CDF/CMS
Page 3
Particle Densities
DhD = 4 = 12.6
2

31 charged
charged particles
particle
Charged Particles
pT > 0.5 GeV/c |h| < 1
CDF Run 2 “Min-Bias”
CDF Run 2 “Min-Bias”
Observable
Average
Nchg
Number of Charged Particles
(pT > 0.5 GeV/c, |h| < 1)
3.17 +/- 0.31
0.252 +/- 0.025
PTsum
(GeV/c)
Scalar pT sum of Charged Particles
(pT > 0.5 GeV/c, |h| < 1)
2.97 +/- 0.23
0.236 +/- 0.018
Average Density
per unit h-
dNchg
chg/dhd = 1/4
3/4 = 0.08
0.24
13 GeV/c PTsum
0
-1
h
+1
Divide by 4
dPTsum/dhd = 1/4
3/4 GeV/c = 0.08
0.24 GeV/c
Study the charged particles (pT > 0.5 GeV/c, |h| < 1) and form the charged
particle density, dNchg/dhd, and the charged scalar pT sum density,
dPTsum/dhd.
UF High Energy Physics Seminar
October 27 & 30, 2009
Rick Field – Florida/CDF/CMS
Page 4
CDF Run 1 “Min-Bias” Data
Charged Particle Density
Charged Particle Density: dN/dhd
Charged Particle Pseudo-Rapidity Distribution: dN/dh
1.0
7
CDF Published
CDF Published
6
0.8
dN/dhd
dN/dh
5
4
3
0.6
0.4
2
0.2
CDF Min-Bias 630 GeV
CDF Min-Bias 1.8 TeV
1
CDF Min-Bias 1.8 TeV
all PT
CDF Min-Bias 630 GeV
all PT
0.0
0
-4
-3
-2
-1
0
1
2
3
4
-4
-3
-1
0
1
2
3
4
Pseudo-Rapidity h
Pseudo-Rapidity h
<dNchg/dh> = 4.2
-2
<dNchg/dhd> = 0.67
 Shows CDF “Min-Bias” data on the number of charged particles per unit pseudo-rapidity
at 630 and 1,800 GeV. There are about 4.2 charged particles per unit h in “Min-Bias”
collisions at 1.8 TeV (|h| < 1, all pT).
DhxD = 1
 Convert to charged particle density, dNchg/dhd, by dividing by 2.
D = 1
There are about 0.67 charged particles per unit h- in “Min-Bias”
0.25
0.67
collisions at 1.8 TeV (|h| < 1, all pT).
 There are about 0.25 charged particles per unit h- in “Min-Bias”
Dh = 1
collisions at 1.96 TeV (|h| < 1, pT > 0.5 GeV/c). <dNchg/dh> = 1.6!
UF High Energy Physics Seminar
October 27 & 30, 2009
Rick Field – Florida/CDF/CMS
Page 5
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!
UF High Energy Physics Seminar
October 27 & 30, 2009
Rick Field – Florida/CDF/CMS
Page 6
MPI, Pile-Up, and Overlap
MPI: Multiple Parton Interactions
Outgoing Parton
PT(hard)
Initial-State Radiation
Proton
Proton
Underlying Event
 MPI: Additional 2-to-2 parton-parton
scatterings within a single hadron-hadron
collision.
Underlying Event
Outgoing Parton
Final-State
Radiation
Proton
Pile-Up
Pile-Up
Proton
Proton
Proton
Primary
Interaction Region Dz
 Pile-Up: More than one hadron-hadron collision in the beam
crossing.
Overlap
 Overlap: An experimental timing issue where a hadron-hadron
collision from the next beam crossing gets included in the hadronhadron collision from the current beam crossing because the next
crossing happened before the event could be read out.
UF High Energy Physics Seminar
October 27 & 30, 2009
Rick Field – Florida/CDF/CMS
Page 7
CDF Run 1: Evolution of Charged Jets
“Underlying Event”
Charged Particle D Correlations
PT > 0.5 GeV/c |h| < 1
Charged Jet #1
Direction
“Transverse” region
very sensitive to the
“underlying event”!
Look at the charged
particle density in the
“transverse” region!
2
“Toward-Side” Jet
D
“Toward”
CDF Run 1 Analysis
Away Region
Charged Jet #1
Direction
D
Transverse
Region
“Toward”
“Transverse”

Leading
Jet
“Transverse”
Toward Region
“Transverse”
“Transverse”
Transverse
Region
“Away”
“Away”
Away Region
“Away-Side” Jet
0
-1
h
+1
 Look at charged particle correlations in the azimuthal angle D relative to the leading charged
particle jet.
 Define |D| < 60o as “Toward”, 60o < |D| < 120o as “Transverse”, and |D| > 120o as “Away”.
 All three regions have the same size in h- space, DhxD = 2x120o = 4/3.
UF High Energy Physics Seminar
October 27 & 30, 2009
Rick Field – Florida/CDF/CMS
Page 8
PYTHIA 6.206 Defaults
MPI constant
probability
scattering
PYTHIA default parameters
6.115
6.125
6.158
6.206
MSTP(81)
1
1
1
1
MSTP(82)
1
1
1
1
PARP(81)
1.4
1.9
1.9
1.9
PARP(82)
1.55
2.1
2.1
1.9
PARP(89)
1,000
1,000
1,000
PARP(90)
0.16
0.16
0.16
4.0
1.0
1.0
PARP(67)
4.0
1.00
"Transverse" Charged Density
Parameter
"Transverse" Charged Particle Density: dN/dhd
CDF Data
Pythia 6.206 (default)
MSTP(82)=1
PARP(81) = 1.9 GeV/c
data uncorrected
theory corrected
0.75
0.50
0.25
1.8 TeV |h|<1.0 PT>0.5 GeV
0.00
0
5
10
15
20
25
30
35
40
45
50
PT(charged jet#1) (GeV/c)
CTEQ3L
CTEQ4L
CTEQ5L
CDF Min-Bias
CDF JET20
 Plot shows the “Transverse” charged particle density versus PT(chgjet#1) compared to the
QCD hard scattering predictions of PYTHIA 6.206 (PT(hard) > 0) using the default
parameters for multiple parton interactions and CTEQ3L, CTEQ4L, and CTEQ5L.
Note Change
PARP(67) = 4.0 (< 6.138)
PARP(67) = 1.0 (> 6.138)
UF High Energy Physics Seminar
October 27 & 30, 2009
Default parameters give
very poor description of
the “underlying event”!
Rick Field – Florida/CDF/CMS
Page 9
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.
UF High Energy Physics Seminar
October 27 & 30, 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 10
Run 1 PYTHIA Tune A
CDF Default!
PYTHIA 6.206 CTEQ5L
"Transverse" Charged Particle Density: dN/dhd
Parameter
Tune B
Tune A
MSTP(81)
1
1
MSTP(82)
4
4
PARP(82)
1.9 GeV
2.0 GeV
PARP(83)
0.5
0.5
PARP(84)
0.4
0.4
PARP(85)
1.0
0.9
"Transverse" Charged Density
1.00
CDF Preliminary
0.75
1.0
0.95
PARP(89)
1.8 TeV
1.8 TeV
PARP(90)
0.25
0.25
PARP(67)
1.0
4.0
New PYTHIA default
(less initial-state radiation)
UF High Energy Physics Seminar
October 27 & 30, 2009
Run 1 Analysis
0.50
0.25
CTEQ5L
PYTHIA 6.206 (Set B)
PARP(67)=1
1.8 TeV |h|<1.0 PT>0.5 GeV
0.00
0
PARP(86)
PYTHIA 6.206 (Set A)
PARP(67)=4
data uncorrected
theory corrected
5
10
15
20
25
30
35
40
45
50
PT(charged jet#1) (GeV/c)
 Plot shows the “transverse” charged particle density
versus PT(chgjet#1) compared to the QCD hard
scattering predictions of two tuned versions of PYTHIA
6.206 (CTEQ5L, Set B (PARP(67)=1) and Set A
(PARP(67)=4)).
Old PYTHIA default
(more initial-state radiation)
Rick Field – Florida/CDF/CMS
Page 11
Run 1 Charged Particle Density
“Transverse” pT Distribution
"Transverse" Charged Particle Density: dN/dhd
Charged Particle Density
Charged Particle Jet #1
Direction
"Transverse"
PT(chgjet#1) > 5 GeV/cD
1.0E+00
CDF Min-Bias
CDF Run 1
CDF JET20
data uncorrected
0.75
0.50
Factor of 2!
0.25
1.8 TeV |h|<1.0 PT>0.5 GeV/c
0.00
0
5
10
15
20
25
30
35
40
45
PT(charged jet#1) (GeV/c)
PT(charged jet#1) > 30 GeV/c
“Transverse” <dNchg/dhd> = 0.56
“Min-Bias”
50
Charged Density dN/dhddPT (1/GeV/c)
"Transverse" Charged Density
1.00
CDF Run 1
data uncorrected
1.0E-01
“Toward”
"Transverse"
PT(chgjet#1) > 30 GeV/c
1.0E-02
“Transverse”
“Transverse”
1.0E-03
“Away”
1.0E-04
Min-Bias
1.0E-05
1.8 TeV |h|<1 PT>0.5 GeV/c
1.0E-06
CDF Run 1 Min-Bias data
<dNchg/dhd> = 0.25
0
2
4
6
8
10
12
14
PT(charged) (GeV/c)
 Compares the average “transverse” charge particle density with the average “Min-Bias”
charge particle density (|h|<1, pT>0.5 GeV). Shows how the “transverse” charge particle
density and the Min-Bias charge particle density is distributed in pT.
UF High Energy Physics Seminar
October 27 & 30, 2009
Rick Field – Florida/CDF/CMS
Page 12
CDF Run 1 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.
UF High Energy Physics Seminar
October 27 & 30, 2009
Rick Field – Florida/CDF/CMS
Page 13
CDF Run 1 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!).
UF High Energy Physics Seminar
October 27 & 30, 2009
Rick Field – Florida/CDF/CMS
Page 14
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).
UF High Energy Physics Seminar
October 27 & 30, 2009
Rick Field – Florida/CDF/CMS
Page 15
25
20
25
“Transverse” Charged Density
PTmax Direction
D
"Transverse" Charged Particle Density: dN/dhd
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 (|h|<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, |h| < 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).
UF High Energy Physics Seminar
October 27 & 30, 2009
Rick Field – Florida/CDF/CMS
Page 16
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/dhd
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 h
 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/dhddPT (1/GeV/c)
dN/dhd
Pythia 6.206 Set A
1.8 TeV |h|<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)!
UF High Energy Physics Seminar
October 27 & 30, 2009
Rick Field – Florida/CDF/CMS
Page 17
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
“Semi-hard” partonparton collision
(pT < ≈2 GeV/c)
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”.
UF High Energy Physics Seminar
October 27 & 30, 2009
Proton
+
+
Proton
Proton
Rick Field – Florida/CDF/CMS
Proton
Proton
+…
Multiple-parton
interactions (MPI)!
Page 18
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
+…
UF High Energy Physics Seminar
October 27 & 30, 2009
Rick Field – Florida/CDF/CMS
Multiple-parton
interactions (MPI)!
Page 19
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
“Semi-hard” partonparton collision
(pT < ≈2 GeV/c)
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”.
UF High Energy Physics Seminar
October 27 & 30, 2009
Proton
+
+
Proton
Proton
Rick Field – Florida/CDF/CMS
Proton
Proton
+…
Multiple-parton
interactions (MPI)!
Page 20
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
CDF Run 2 <Nchg>=4.5
1.0E-02
Probability
Probability
1.0E-02
CDF Run 2 Preliminary
1.0E-01
1.0E-03
1.0E-04
1.0E-05
py Tune A <Nchg> = 4.3
pyAnoMPI <Nchg> = 2.6
1.0E-03
1.0E-04
1.0E-05
1.0E-06
1.0E-06
Min-Bias 1.96
1.0E-07
Min-Bias 1.96
1.0E-07
Charged Particles (|h|<1.0, PT>0.4 GeV/c)
Normalized to 1
Normalized to 1
Charged Particles (|h|<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
10
Number of Charged Particles
“Minumum Bias” Collisions
Proton
15
20
25
30
35
40
45
50
Number of Charged Particles
No MPI!
Tune A!
AntiProton
 Data at 1.96 TeV on the charged particle multiplicity (pT > 0.4 GeV/c, |h| < 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).
UF High Energy Physics Seminar
October 27 & 30, 2009
Rick Field – Florida/CDF/CMS
Page 21
55
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).
UF High Energy Physics Seminar
October 27 & 30, 2009
Rick Field – Florida/CDF/CMS
Page 22
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
UF High Energy Physics Seminar
October 27 & 30, 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 23
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 (|h|<1.0, PT>0.4 GeV/c)
Charged Particles (|h|<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, |h| < 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.
UF High Energy Physics Seminar
October 27 & 30, 2009
Rick Field – Florida/CDF/CMS
Page 24
55
LHC Predictions: 900 GeV
Charged Multiplicity Distribution
Charged Multiplicity Distribution
1.0E+00
0.16
RDF Preliminary
RDF Preliminary
pyA <Nchg> = 5.0 STdev = 4.5
1.0E-01
pyDW 900 GeV <Nchg> = 5.3
0.12
Probability
pyS320 900 GeV <Nchg> = 5.2
pyP329 900 GeV <Nchg> = 5.3
1.0E-02
pyDWT 900 GeV <Nchg> = 5.0
Probability
pyA <Nchg> = 5.0 STdev = 4.5
pyDW 900 GeV <Nchg> = 5.3
1.0E-03
pyS320 900 GeV <Nchg> = 5.2
pyP329 900 GeV <Nchg> = 5.3
pyDWT 900 GeV <Nchg> = 5.0
0.08
Charged Particles (|h|<2.0, PT>0.5 GeV/c)
0.04
1.0E-04
Min-Bias 900 GeV
Normalized to 1
1.0E-05
0.00
0
Min-Bias 900 GeV
2
1.0E-06
4
6
8
10
12
14
16
18
20
Number of Charged Particles
Normalized to 1 Charged Particles (|h|<2.0, PT>0.5 GeV/c)
1.0E-07
0
sHC!
5
10
15
20
25
30
35
40
45
50
55
Number of Charged Particles
“Minumum Bias” Collisions
Proton
“Minumum Bias” Collisions
Proton
Proton
Proton
 Charged multiplicity distributions for proton-proton collisions at 900 GeV
(pT > 0.5 GeV/c, |h| < 2) from PYTHIA Tune A, Tune DW, Tune DWT, Tune
S320, and Tune P329.
UF High Energy Physics Seminar
October 27 & 30, 2009
Rick Field – Florida/CDF/CMS
Page 25
LHC Predictions: 900 GeV
Charged Multiplicity Distribution
Average
0.16
7
RDF Preliminary
Charged
Charged
Particle
ChargedParticle
ParticleMultiplicity
Multiplicity
Number of Charged
Particles
0.40
0.160
0.25
pyA <Nchg> = 5.0 STdev = 4.5
0.140
0.20
0.30
0.120
pyDW 900 GeV <Nchg> = 5.3
generator level
pyS320 900 GeV <Nchg> = 5.2
0.08
0.04
Min-Bias 900 GeV
Normalized to 1
Probability
Probability
pyDW
6
Average Nchg
Probability
0.12
RDF
Preliminary
RDFPreliminary
Preliminary
RDF
pyP329 900 GeV <Nchg> = 5.3
Charged Particles (|h|<2.0, PT>0.5 GeV/c)
0
2
4
6
Charged
Particles
(|h|<2.0,
PT>0.5
GeV/c)
Charged
Particles
(|h|<2.0,
PT>0.5
GeV/c)
Charged
Particles
(|h|<2.0,
PT>0.5
GeV/c)
Min-Bias
900 900
GeV
Min-Bias
Min-Bias
900GeV
GeV
0.10
0.060
Normalized
to 1 to 1
Normalized
Normalized to 1
0.10
0.040
0.05
0.020
pyA
pyDWT
4
0.00
0.100
0.15
1000 events
<Nchg> = 5.1
STdev = 4.6
10
100events
events<Nchg>
<Nchg>= =5.2
4.9STdev
STdev= =3.8
4.9
pyA <Nchg>==5.0
5.0 STdev==4.5
4.5
pyA
pyA <Nchg>
<Nchg> = 5.0 STdev
STdev = 4.5
0.20
0.080
pyDWT 900 GeV <Nchg> = 5.0
5
generator
generator
level level
generator
level
RDF Preliminary
0.00
0.00
0.000
8
10
12
14
Min-Bias
900
Number of Charged
Particles
16
GeV
18
00 0
20
22
445
66
88
10
1010
1212
14
1415 16
16
18
18
20
20
20
Charged Particles (|h|<2.0, PT>0.5
GeV/c)
Number
of
Number
ofofCharged
Charged
Particles
Number
ChargedParticles
Particles
3
1
10
100
1000
Number
of Events
1,000
events
100
events
10 events
sHC!
24/mb!
2.4/mb!
LLL===0.24/mb!
“Minumum Bias” Collisions
Proton
10000
“Minumum Bias” Collisions
Proton
Proton
Proton
 Charged multiplicity distributions for proton-proton collisions at 900 GeV
(pT > 0.5 GeV/c, |h| < 2) from PYTHIA Tune A, Tune DW, Tune DWT, Tune
S320, and Tune P329.
UF High Energy Physics Seminar
October 27 & 30, 2009
Rick Field – Florida/CDF/CMS
Page 26
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.
UF High Energy Physics Seminar
October 27 & 30, 2009
Rick Field – Florida/CDF/CMS
Page 27
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.
UF High Energy Physics Seminar
October 27 & 30, 2009
Rick Field – Florida/CDF/CMS
Page 28
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
UF High Energy Physics Seminar
October 27 & 30, 2009
Rick Field – Florida/CDF/CMS
Page 29
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).
UF High Energy Physics Seminar
October 27 & 30, 2009
Rick Field – Florida/CDF/CMS
Page 30
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
10
20
30
40
Number of Charged Particles
Lepton
Proton
AntiProton
Underlying Event
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).
UF High Energy Physics Seminar
October 27 & 30, 2009
Rick Field – Florida/CDF/CMS
Page 31
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.
UF High Energy Physics Seminar
October 27 & 30, 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 32
“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.
UF High Energy Physics Seminar
October 27 & 30, 2009
Rick Field – Florida/CDF/CMS
Page 33
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-).
UF High Energy Physics Seminar
October 27 & 30, 2009
Rick Field – Florida/CDF/CMS
Page 34
“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
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)
(|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, 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!
UF High Energy Physics Seminar
October 27 & 30, 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 35
CDF Run 1 PT(Z)
Parameter
Tune A
Tune AW
UE Parameters MSTP(81)
1
1
MSTP(82)
4
4
PARP(82)
2.0 GeV
2.0 GeV
PARP(83)
0.5
0.5
PARP(84)
0.4
0.4
PARP(85)
0.9
0.9
PARP(86)
0.95
0.95
PARP(89)
1.8 TeV
1.8 TeV
PARP(90)
0.25
0.25
PARP(62)
1.0
1.25
PARP(64)
1.0
0.2
PARP(67)
4.0
4.0
MSTP(91)
1
1
PARP(91)
1.0
2.1
PARP(93)
5.0
15.0
ISR Parameters
Z-Boson Transverse Momentum
0.12
PT Distribution 1/N dN/dPT
PYTHIA 6.2 CTEQ5L
Tune used by the
CDF-EWK group!
CDF Run 1 Data
PYTHIA Tune A
PYTHIA Tune AW
CDF Run 1
published
0.08
1.8 TeV
Normalized to 1
0.04
0.00
0
2
4
6
8
10
12
14
16
18
Z-Boson PT (GeV/c)
 Shows the Run 1 Z-boson pT distribution (<pT(Z)>
≈ 11.5 GeV/c) compared with PYTHIA Tune A
(<pT(Z)> = 9.7 GeV/c), and PYTHIA Tune AW
(<pT(Z)> = 11.7 GeV/c).
Effective Q cut-off, below which space-like showers are not evolved.
Intrensic KT
The Q2 = kT2 in as for space-like showers is scaled by PARP(64)!
UF High Energy Physics Seminar
October 27 & 30, 2009
20
Rick Field – Florida/CDF/CMS
Page 36
Jet-Jet Correlations (DØ)
Jet#1-Jet#2 D Distribution
D Jet#1-Jet#2
 MidPoint Cone Algorithm (R = 0.7, fmerge = 0.5)
 L = 150 pb-1 (Phys. Rev. Lett. 94 221801 (2005))
 Data/NLO agreement good. Data/HERWIG agreement
good.
 Data/PYTHIA agreement good provided PARP(67) =
1.0→4.0 (i.e. like Tune A, best fit 2.5).
UF High Energy Physics Seminar
October 27 & 30, 2009
Rick Field – Florida/CDF/CMS
Page 37
CDF Run 1 PT(Z)
PYTHIA 6.2 CTEQ5L
Tune DW
Tune AW
UE Parameters MSTP(81)
1
1
MSTP(82)
4
4
PARP(82)
1.9 GeV
2.0 GeV
PARP(83)
0.5
0.5
PARP(84)
0.4
0.4
PARP(85)
1.0
0.9
PARP(86)
1.0
0.95
PARP(89)
1.8 TeV
1.8 TeV
PARP(90)
0.25
0.25
PARP(62)
1.25
1.25
PARP(64)
0.2
0.2
PARP(67)
2.5
4.0
MSTP(91)
1
1
PARP(91)
2.1
2.1
PARP(93)
15.0
15.0
ISR Parameters
PT Distribution 1/N dN/dPT
Parameter
Z-Boson Transverse Momentum
0.12
CDF Run 1 Data
PYTHIA Tune DW
HERWIG
CDF Run 1
published
0.08
1.8 TeV
Normalized to 1
0.04
0.00
0
2
4
6
8
10
12
14
16
18
20
Z-Boson PT (GeV/c)
 Shows the Run 1 Z-boson pT distribution (<pT(Z)>
≈ 11.5 GeV/c) compared with PYTHIA Tune DW,
and HERWIG.
Tune DW uses D0’s perfered value of PARP(67)!
Intrensic KT
Tune DW has a lower value of PARP(67) and slightly more MPI!
UF High Energy Physics Seminar
October 27 & 30, 2009
Rick Field – Florida/CDF/CMS
Page 38
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!
(not the default)
Intrinsic KT
UF High Energy Physics Seminar
October 27 & 30, 2009
Rick Field – Florida/CDF/CMS
Page 39
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!
(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)
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
5.0
Tune D6T
Intrinsic KT
UF High Energy Physics Seminar
October 27 & 30, 2009
1.0
Tune D6
Rick Field – Florida/CDF/CMS
Page 40
Peter’s Pythia Tunes WEBsite
 http://home.fnal.gov/~skands/leshouches-plots/
UF High Energy Physics Seminar
October 27 & 30, 2009
Rick Field – Florida/CDF/CMS
Page 41
Min-Bias “Associated”
Charged Particle Density
35% more at RHIC means
"Transverse" Charged Particle Density: dN/dhd
26% less at the LHC!
1.6
RDF Preliminary
"Transverse" Charged Density
0.3
"Transverse" Charged Density
"Transverse" Charged Particle Density: dN/dhd
PY Tune DW
generator level
0.2
~1.35
PY Tune DWT
0.1
Min-Bias
0.2 TeV
Charged Particles (|h|<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 (|h|<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, |h| < 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!
UF High Energy Physics Seminar
October 27 & 30, 2009
Rick Field – Florida/CDF/CMS
Page 42
Min-Bias “Associated”
Charged Particle Density
"Transverse" Charged Particle Density: dN/dhd
"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 (|h|<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, |h| < 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).
UF High Energy Physics Seminar
October 27 & 30, 2009
Rick Field – Florida/CDF/CMS
Page 43
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 their uncorrected data with PYTHIA Tune A + STAR-SIM.
UF High Energy Physics Seminar
October 27 & 30, 2009
Rick Field – Florida/CDF/CMS
Page 44
The “Underlying Event” at STAR
Charged PTsum Density
Charged PTsum
"Transverse"
PTsumDensity
Density (GeV/c)
(GeV/c)
"Transverse"
PTsum Density:
dPT/dhd
ChargedCharged
PTsum Density:
dPT/dhd
2.0
100.0
1.6
“Back-to-Back”
Charged Particles (|h|<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 |h(jet#1)|<2
0.4
0.1
0.0
0
0
50
“Away”
MidPoint
R = Particles
0.7 |h(jet#1)
< 2 PT>0.5 GeV/c)
Charged
(|h|<1.0,
Charged Particles (|h|<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/dhd, as a function of the leading jet pT for the
“toward”, “away”, and “transverse” regions compared with PYTHIA Tune A.
UF High Energy Physics Seminar
October 27 & 30, 2009
Rick Field – Florida/CDF/CMS
Page 45
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 ATLAS
RDF Preliminary
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 (|h|<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
PY Tune DWT
0.0
0
2
4
6
8
10
12
14
16
18
20
0
5
10
PTmax (GeV/c)
D
25
D
“Toward”
“Toward”
“Transverse”
20
PTmax Direction
PTmax Direction
“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, |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, Tune P329, and pyATLAS to the
LHC.
UF High Energy Physics Seminar
October 27 & 30, 2009
Rick Field – Florida/CDF/CMS
Page 46
“Transverse” Charged Density
PTmax Direction
"Transverse" Charged Particle Density: dN/dhd
D
1.6
“Transverse”
“Transverse”
“Away”
ChgJet#1 Direction
D
“Toward”
“Transverse”
“Transverse”
“Away”
"Transverse" Charged Density
“Toward”
RDF Preliminary
7 TeV
py Tune DW generator level
1.2
PTmax
0.8
ChgJet#1
DY(muon-pair)
70 < M(pair) < 110 GeV
0.4
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
0.0
Muon-Pair Direction
D
0
5
10
15
20
25
30
35
40
45
50
PT(chgjet#1) or PTmax or PT(pair) (GeV/c)
“Toward”
“Transverse”
“Transverse”
“Away”
 Shows the charged particle density in the “transverse” region for charged particles (pT > 0.5
GeV/c, |h| < 1) at 7 TeV as defined by PTmax, PT(chgjet#1), and PT(muon-pair) from PYTHIA
Tune DW at the particle level (i.e. generator level). Charged particle jets are constructed using
the Anti-KT algorithm with d = 0.5.
UF High Energy Physics Seminar
October 27 & 30, 2009
Rick Field – Florida/CDF/CMS
Page 47
Min-Bias “Associated”
Charged Particle Density
"Transverse" Charged Particle Density: dN/dhd
"Transverse" Charged Particle Density: dN/dhd
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 (|h|<1.0, PT>0.5 GeV/c)
RDF Preliminary
LHC14
py Tune DW generator level
0.8
LHC10
LHC7
Tevatron
900 GeV
0.4
PTmax = 5.25 GeV/c
RHIC
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
0.0
0.0
0
5
10
15
20
0
25
2
D
“Toward”
RHIC
“Transverse”
“Transverse”
0.2 TeV → 1.96 TeV
(UE increase ~2.7 times)
Tevatron
“Away”
6
8
10
12
14
Center-of-Mass Energy (TeV)
PTmax (GeV/c)
PTmax Direction
4
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, |h| < 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
Linear scale!
(i.e. generator level).
UF High Energy Physics Seminar
October 27 & 30, 2009
Rick Field – Florida/CDF/CMS
Page 48
Min-Bias “Associated”
Charged Particle Density
"Transverse" Charged Particle Density: dN/dhd
"Transverse" Charged Particle Density: dN/dhd
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 (|h|<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 (|h|<1.0, PT>0.5 GeV/c)
0.0
0.0
0
5
10
15
20
25
0.1
D
“Toward”
LHC7
“Transverse”
100.0
PTmax Direction
7 TeV → 14 TeV
(UE increase ~20%)
D
“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, |h| < 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).
UF High Energy Physics Seminar
October 27 & 30, 2009
Rick Field – Florida/CDF/CMS
Page 49
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 |h| < 1)
0.8
0.4
500,000
Charged Particles (PTmax > 5 GeV/c |h| < 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
|h| < 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
 The inelastic non-diffractive PTmax > 5 GeV/c cross section 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!
UF High Energy Physics Seminar
October 27 & 30, 2009
Rick Field – Florida/CDF/CMS
Page 50
“Transverse” Charged Density
Differential Cross-Section: ds/dPT
"Transverse" Charged Particle Density: dN/dhd
Number of Events in 1 GeV/c
Bin with 1/nb
1.0E+02
10,000,000
RDF Preliminary
7 TeV
0.8
0.4
0.0
0
5
10
py Tune DW generator level
1.0E+00
1,000,000
PTmax
15
1.0E+01
RDF Preliminary
ds/dPT (mb/GeV/c)
1.2
100,000
ChgJet#1
10,000
PTmax
30
35
40
ChgJet#1
1.0E-02
PTmax
K-Factor = 1.2
K-Factor = 1.2
100
25
ChgJet#1
1.0E-01
1.0E-03
1,000
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
20
With 1/nb of “min-bias” data at
7 TeV
we could study7 TeV
the UE out
py Tune DW generator
level
to
PTmax
=
25
GeV/c
or
7 TeV
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
PT(chgjet#1) = 45 GeV/c !
RDF Preliminary
py Tune DW generator level
Number of Events
"Transverse" Charged Density
1.6
1.0E-04
45
0
50
5
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
PT(chgjet#1) or PTmax (GeV/c)
10
15
20
25
30
35
40
45
PT(chgjet#1) or PTmax (GeV/c)
10
0
5
10
15
20
25
30
35
40
45
50
PT(chgjet#1)
or PTmax
(GeV/c)for charged particles (p > 0.5
 Shows the charged particle density in the
“transverse”
region
T
GeV/c, |h| < 1) at 7 TeV as defined by PTmax and PT(chgjet#1) from PYTHIA Tune DW at the
particle level (i.e. generator level). Charged particle jet are constructed using the Anti-KT
algorithm with d = 0.5.
 Shows the leading charged particle jet, chgjet#1, and the leading charged particle, PTmax,
differential cross section, ds/dPT (pT > 0.5 GeV/c, |h| < 1) from PYTHIA Tune DW at the
particle level (i.e. generator level). Charged particle jet are constructed using the Anti-KT
algorithm with d = 0.5.
UF High Energy Physics Seminar
October 27 & 30, 2009
Rick Field – Florida/CDF/CMS
Page 51
50
The Drell-Yan Cross Section
Drell-Yan
Cross Section
Z-Bosonm+mProduction
at theRatio
LHC
Z-Boson
Production
at the
Tevatron
Drell-Yan
m+m- Cross
Section
1000.0
60%
RDF
RDFPreliminary
Preliminary
1.0E+02
Tune DW
generator
generator
levellevel
Drell-Yan 1.96 TeV proton-antiproton
1.0E+01
Percent of Events
ds/dMPercent
(pb/GeV)
of Events
50%
Pythia Tune AW
40%
1.0E+00
70 < M(m+m-) < 110 GeV
|h(m-pair)| < 6
30%
1.0E-01
5.8% heavy flavor at the
Tevatron!
1.0E-02
20%
1.0E-03
1.0E-04
LHC
0%
1.0E-05
40%
30%
u ubar
d dbar
1.0E-06
s sbar
c cbar
Tevatron Run2
0
250
500
750
1000
1250
1500
m+m- Mass (GeV)
+ -
22.2% heavy flavor at
the LHC!
10.0
1.0
0
250
500
750
1000
m+m- Mass (GeV)
u ubar
1.0E-07
70 < M(m m ) < 110 GeV
|h(m-pair)| < 6
0%
b bbar
Drell-Yan 14 TeV proton-proton
20%
10%
10%
RDF
RDFPreliminary
Preliminary
generator
level level
Tune DW
generator
50%
Pythia Tune AW
100.0
LHC/Tevatron Run 2
1.0E+03
60%
d dbar
s sbar
c cbar
b bbar
 Shows the ratio (LHC/Tevatron) of the DrellYan Lepton-Pair (m+m-) cross section, ds/dM,
versus the lepton-pair invariant mass from
PYTHIA Tune AW.
 Shows the Drell-Yan Lepton-Pair (m+m-) cross
section, ds/dM, at the 1.96 TeV (Tevatron Run
2) and at 14 TeV (LHC) versus the lepton-pair
invariant mass from PYTHIA Tune AW.
UF High Energy Physics Seminar
October 27 & 30, 2009
Rick Field – Florida/CDF/CMS
Page 52
Drell-Yan Production
Tevatron vs LHC
Lepton-Pair
Drell-Yan Production
Lepton-Pair Transverse
Momentum
PT(pair)
Proton
AntiProton
Underlying Event
<pT(m+m-)> is much
larger at the LHC!
Underlying Event
Initial-State
Radiation
Shapes of the pT(m+m-)
distribution at the Z-boson mass.
Final-State
Radiation
Outgoing Parton
Drell-Yan PT(m+m-) Distribution
Lepton-Pair Transverse1.0E+02
Momentum
80
Drell-Yan
generator level
1.0E+01
LHC
40
20
Z
0
1/N dN/dPT (1/GeV)
60
ds/dPT (pb/GeV)
Average Pair PT
Drell-Yan PT(m+m-) Distribution
RDF Preliminary
generator level
Drell-Yan
0.10
1.0E+00
Tevatron Run 2
1.0E-01
generator level
Tevatron Run2
0.08
Pythia Tune AW (solid)
Herwig (dashed)
PY Tune DW (solid)
HERWIG (dashed)
0.06
70 < M(m-pair) < 110 GeV
|h(m-pair)| < 6
0.04
LHC
0.02
PY Tune DW (solid)
HERWIG
1.0E-02(dashed)
LHC
Normalized to 1
0.00
0
100
200
300
400
500
600
700
800
900
1000
1.0E-03
Lepton-Pair Invariant Mass (GeV)
70 < M(m-pair) < 110 GeV
|h(m-pair)| < 6
0
5
10
15
20
25
30
35
40
PT(m+m-) (GeV/c)
Tevatron Run2
1.0E-04
 Average Lepton-Pair transverse
momentum  Shape of the Lepton-Pair pT distribution at the
0
50
100
150
250
Z-boson
mass 200
at the Tevatron
and the LHC for
at the Tevatron and the LHC for PYTHIA
PT (m+m-) (GeV/c)
PYTHIA Tune DW and HERWIG (without MPI).
Tune DW and HERWIG (without MPI).
UF High Energy Physics Seminar
October 27 & 30, 2009
Rick Field – Florida/CDF/CMS
Page 53
Drell-Yan Muon-Pair Cross-Section
Drell-Yan Muon-Pair Cross Section
2,500
Drell-Yan Muon-Pair Events in 10/pb
25,000
RDF Preliminary
RDF Preliminary
py Tune DW generator level
20,000
Number of Events
Cross-Section (pb)
2,000
py Tune DW generator level
70 < M(pair) < 110 GeV
1,500
1,000
500
70 < M(pair) < 110 GeV
15,000
10,000
5,000
K-Factor = 1.3
K-Factor = 1.3
0
0
0
2
4
6
8
10
12
14
0
Center-of-Mass Energy (TeV)
2
4
6
8
10
12
Center-of-Mass Energy (TeV)
Linear scale!
 The Drell-Yan muon-pair cross section 70 < M(pair) < 110 GeV versus center-of-mass energy
from PYTHIA (×1.3).
 The Drell-Yan cross-section varies rapidly. Factor of 2.2 increase between 7 TeV (≈ 0.9 nb) and
14 teV (≈ 2 nb). Linear on a linear scale!
Note nb not mb!
UF High Energy Physics Seminar
October 27 & 30, 2009
Rick Field – Florida/CDF/CMS
Page 54
14
Drell-Yan Muon-Pair Cross-Section
Drell-Yan Muon-Pair Cross Section
2,500
Drell-Yan Muon-Pair Events in 10/pb
25,000
RDF Preliminary
RDF Preliminary
py Tune DW generator level
20,000
Number of Events
2,000
Cross-Section (pb)
py Tune DW generator level
70 < M(pair) < 110 GeV
1,500
pT(muon) > 5 GeV/c
|h(muon)| < 2.4
1,000
500
70 < M(pair) < 110 GeV
15,000
pT(muon) > 5 GeV/c
|h(muon)| < 2.4
10,000
5,000
K-Factor = 1.3
K-Factor = 1.3
0
0
0
2
4
6
8
10
12
14
0
2
6
8
10
12
Center-of-Mass Energy (TeV)
Center-of-Mass Energy (TeV)
Linear scale!
4
4,700 events in 10/pb!
CMS acceptance!
 The Drell-Yan muon-pair cross section 70 < M(pair) < 110 GeV (|h(m)| < 2.4, pT(m) > 5 GeV/c)
versus center-of-mass energy from PYTHIA (×1.3).
 The CMS Drell-Yan cross-section varies rapidly. Factor of 1.9 increase between 7 TeV (≈ 0.5
nb) and 14 TeV (≈ 0.9 nb). Linear on a linear scale!
UF High Energy Physics Seminar
October 27 & 30, 2009
Rick Field – Florida/CDF/CMS
Page 55
14
“Transverse” Charged Density
Note at CMS “min-bias” is pre-scaled
by a factor of 5,000 so this really
Differential Cross-Section: ds/dPT
"Transverse"
Charged
Particle
Density:
dN/dhd
corresponds
to 5/pb
delivered
! Number
of Events in1.0E+01
1 GeV/c Bin
With 10/pb of data at 7 TeV we could
RDF Preliminary
1.0E+00
study the UE in Drell-Yan production
RDF Preliminary
10,000,000
7 TeV
py Tune DW generator level
7 TeV RDF Preliminary
py Tune DW generator level
1.0E-01
out
to
PT(pair)
=
15
GeV/c
!
7 TeV
0.8
0.0
0
5
10
15
PTmax
1/nb
100,000
DY(muon-pair)
70 < M(pair) < 110 GeV
0.4
py Tune DW generator level
1.0E-02
1,000,000
PTmax
ds/dPT (mb/GeV/c)
1.2
Number of Events
"Transverse" Charged Density
1.6
ChgJet#1
10,000
ChgJet#1
Charged
(|h|<1.0, PT>0.5 GeV/c)
1.0E-03 Particles
PTmax
1.0E-04
1.0E-05
ChgJet#1
1/nb
1.0E-06
1.0E-07
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
1,000
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
DY(CMS muon-pair)
70 < M(pair) < 110 GeV
10/pb
1.0E-08
DY(CMS muon-pair)
70 < M(pair) < 110 GeV
1.0E-09
20
25100 30
35
40
45
0
50
5
10
15
20
25
30
35
40
45
50
PT(chgjet#1) or PTmax or PT(pair) (GeV/c)
PT(chgjet#1) or PTmax or PT(pair) (GeV/c)
10
0
5
10
15
20
25
30
35
40
45
50
PT(chgjet#1)
or PTmax orregion
PT(pair)for
(GeV/c)
 Shows the charged particle density in
the “transverse”
charged particles (pT > 0.5
GeV/c, |h| < 1) at 7 TeV as defined by PTmax, PT(chgjet#1), and PT(muon-pair) for PYTHIA
Tune DW at the particle level (i.e. generator level). Charged particle jet are constructed using the
Anti-KT algorithm with d = 0.5.
 Shows the leading charged particle jet, chgjet#1, and the leading charged particle, PTmax,
differential cross section, ds/dPT (pT > 0.5 GeV/c, |h| < 1), and the Drell-Yan differential crosssection (70 < M(pair) < 110 GeV) from PYTHIA Tune DW at the particle level (i.e. generator
level). Charged particle jet are constructed using the Anti-KT algorithm with d = 0.5.
UF High Energy Physics Seminar
October 27 & 30, 2009
Rick Field – Florida/CDF/CMS
Page 56
Z-Boson: “Towards” Region
RDF LHC
Prediction!
"Toward" Charged Particle Density:
dN/dhd
"Toward" Charged Particle Density: dN/dhd
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 (|h|<1.0, PT>0.5 GeV/c)
Charged Particles (|h|<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/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, and pyATLAS to
the LHC.
UF High Energy Physics Seminar
October 27 & 30, 2009
Rick Field – Florida/CDF/CMS
Page 57
150
Drell-Yan Charged Multiplicity
Charged
Charged Particle
Particle Multiplicity
Multiplicity
Charged Particle Multiplicity
Average Number of0.07
Charged Particles
0.25
0.040
0.040
35
0.035
RDF Preliminary
Average Nchg
0.020
0.015
0.010
0.005
generator
level
pyDW
<Nchg> =
22.1 STdev = 12.9
pyS320 <Nchg> = 18.5 STdev = 12.1
pyDWT <Nchg> = 25.6 STdev = 14.7
Probability
Probability
30
0.025
pyDWT
7 TeV Drell-Yan
70 < M(pair) < 110 GeV
25
pyDW
It would be nice to have 2/pb
at 7 TeV (acquired)
15
which might mean
10
3-4/pb
(delivered)!
1
10
100
1000
20
pyS320
Charged Particles (|h|<2.0, PT>0.5 GeV/c)
(excluding lepton-pair )
0.000
RDF Preliminary
Preliminary
Charged Particles (|h|<2.0, PT>0.5 GeV/c) RDFgenerator
RDF
Preliminary
level
generator level
(excluding
lepton-pair
)
generator level
7 TeV Drell-Yan
1000 events <Nchg> = 22.0 STdev = 12.9
100 events <Nchg> = 21.7 STdev = 12.6
70 < M(pair) < 110 GeV
10 events
<Nchg>
= STdev
27.5 STdev
= 13.8
pyDW
<Nchg>
= 22.1
= 12.9
pyDW <Nchg> = 22.1 STdev = 12.9
pyDW
<Nchg>
=
22.1
STdev
=
12.9
0.025
7 TeV Drell-Yan
0.15
0.04
7 TeV<Drell-Yan
70 < M(pair)
110 GeV
7 TeV Drell-Yan
0.020
70 < M(pair)
< 110 GeV
70
<
M(pair)
< 110 GeV
Charged
Particles
(|h|<2.0,
PT>0.5
GeV/c)
0.03
0.10
Charged
Particleslepton-pair
(|h|<2.0, PT>0.5
GeV/c)
0.015
(excluding
)
(excluding lepton-pair )
0.02
0.010
0.05
0.01
0.005
0.035
0.06
0.20
0.030
0.05
generator level
0.030
Probability
RDF Preliminary
0.00
0.00
0.000
0
5
10
15
20
25
30
35
40
45
50
55
60
65
Number of Charged Particles
70
75
80
000 555 10
10
15
20
25
30
35
40
45
50
55 60
60 65
65 70
70 75
75 80
80 85
85 90
90 95
95
10 15
15 20
20 25
25 30
30 35
35 40
40 45
45 50
50 55
90
95
Charged
Particles
(|h|<2.0,
PT>0.5
GeV/c)
Number
Number
of
Charged
Particles
Number
ofCharged
ChargedParticles
Particles
(excluding lepton-pair
) of
Drell-Yan Production Lepton-Pair Production
Lepton
Proton
10000
1,000
100
events
events
Number
of Events
10
events
LLL===210/nb!
2.1/pb!
21/nb!
Proton
Underlying Event
Underlying Event
Anti-Lepton
 Prediction from PYTHIA Tune DW, Tune S320, and Tune P329 for Drell-Yan muon-pair production (70
< M(pair) < 110 GeV) for proton-proton collisions at 7 TeV for the number of charged particles with pT
> 0.5 GeV and |h| < 2 (excluding the lepton-pair).
UF High Energy Physics Seminar
October 27 & 30, 2009
Rick Field – Florida/CDF/CMS
Page 58
Charged Particle Density: dN/dh
Charged Particle Density: dN/dh
Charged Particle Density: dN/dh
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 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 DW, Tune S320, and
Tune P324.
UF High Energy Physics Seminar
October 27 & 30, 2009
rapidity distribution, dNchg/dhd, 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 59
Charged Particle Density: dN/dh
RDF LHC Prediction!
Charged Particle Density: dN/dh
Charged Particle Density: dN/dh
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
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 h
“Minumum Bias” Collisions
Proton
Min-Bias
14 TeV
Charged Particles (all PT)
2
4
6
PseudoRapidity h
AntiProton
Tevatron
0
Proton
“Minumum Bias” Collisions
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 DW, Tune S320, and
Tune P324.
Extrapolations (all pT) of PYTHIA Tune A, Tune DW, Tune S320, Tune P324. and
ATLAS to the LHC.
UF High Energy Physics Seminar
October 27 & 30, 2009
Rick Field – Florida/CDF/CMS
Page 60
8
Charged Particle Density: dN/dh
RDF LHC Prediction!
Charged Particle Density: dN/dh
Charged
ChargedParticle
Particle Density:
Density:dN/dh
dN/dh
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
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
PseudoRapidityhh
“Minumum Bias” Collisions
Proton
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
2
4
6
8
PseudoRapidity h
AntiProton
Tevatron
0
Proton
“Minumum Bias” Collisions
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 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.
UF High Energy Physics Seminar
October 27 & 30, 2009
Rick Field – Florida/CDF/CMS
Page 61
Min-Bias “Charged Particle Density
Charged Particle Density: dN/dh
Charged Particle Density (h = 0): dN/dh
3.0
3.0
14 TeV
7 TeV
2.0
1.96 TeV
0.9 TeV
1.0
LHC14
RDF Preliminary
Min-Bias
Charged Density (h = 0)
Charged Particle Density
RDF Preliminary
py Tune DW generator level
0.2 TeV
py Tune DW generator level
LHC7
2.0
Tevatron
900 GeV
RHIC
1.0
Min-Bias
Charged particles pT > 0.5 GeV/c
Charged Particles (PT>0.5 GeV/c)
0.0
0.0
-8
-6
-4
-2
0
2
4
6
0
8
2
PseudoRapidity h
6
8
RHIC
12
14
1.96 TeV → 14 TeV
(dN/dh increase ~1.58 times)
“Minumum Bias” Collisions
“Minumum Bias” Collisions
“Minumum Bias” Collisions
Proton
10
Center-of-Mass Energy (TeV)
0.2 TeV → 1.96 TeV
(dN/dh increase ~1.63 times)
Proton
4
Proton
AntiProton
Tevatron
Proton
Proton
LHC
 Shows the “min-bias” charged particle density, dN/dh, for charged particles (pT > 0.5 GeV/c) for at
0.2 TeV, 0.9 TeV, 1.96 TeV and 14 TeV predicted by PYTHIA Tune DW at the particle level (i.e.
generator level).
Linear scale!
UF High Energy Physics Seminar
October 27 & 30, 2009
Rick Field – Florida/CDF/CMS
Page 62
Min-Bias “Charged Particle Density
Charged Particle Density (h = 0): dN/dh
Charged Particle Density: dN/dh
3.0
3.0
14 TeV
RDF Preliminary
Min-Bias
Charged Density (h = 0)
Charged Particle Density
RDF Preliminary
py Tune DW generator level
7 TeV
2.0
1.96 TeV
0.9 TeV
1.0
0.2 TeV
LHC14
LHC10
LHC7
py Tune DW generator level
2.0
Tevatron
900 GeV
1.0
RHIC
Min-Bias
Charged particles pT > 0.5 GeV/c
Charged Particles (PT>0.5 GeV/c)
0.0
0.0
-8
-6
-4
-2
0
2
4
6
8
0.1
PseudoRapidity h
7 TeV → 14 TeV
(dN/dh ≈ 19% increase)
“Minumum Bias” Collisions
Proton
10.0
100.0
Log scale!
“Minumum Bias” Collisions
Proton
AntiProton
LHC7
1.0
Center-of-Mass Energy (TeV)
Proton
Linear on a log plot!
LHC14
 Shows the “min-bias” charged particle density, dN/dh, for charged particles (pT > 0.5 GeV/c) for at
0.2 TeV, 0.9 TeV, 1.96 TeV and 14 TeV predicted by PYTHIA Tune DW at the particle level (i.e.
generator level).
UF High Energy Physics Seminar
October 27 & 30, 2009
Rick Field – Florida/CDF/CMS
Page 63
LHC Predictions
“Minumum Bias” Collisions
Proton
AntiProton
Charged Particle Density: dN/dh
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 h
"Transverse" Charged Particle Density: dN/dhd
“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 (|h|<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/dhd
“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 (|h|<1.0, PT>0.5 GeV/c)
0.0
0
25
50
75
100
125
150
Lepton-Pair PT (GeV/c)
UF High Energy Physics Seminar
October 27 & 30, 2009
Rick Field – Florida/CDF/CMS
Page 64
Summary & Conclusions
 We are making good progress in understanding and modeling the
“underlying event”. RHIC data at 200 GeV are very important!
Outgoing Parton
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!
Py64 S320 = LHC “Reference Tune”!
Proton
Underlying Event
Outgoing Parton
Final-State
Radiation
Hard-Scattering Cut-Off PT0
5
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!
Underlying Event
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!
UF High Energy Physics Seminar
October 27 & 30, 2009
Rick Field – Florida/CDF/CMS
100
1,000
10,000
100,000
CM Energy W (GeV)
UE&MB@CMS
Page 65