Toward an Understanding of
Hadron-Hadron Collisions
From Feynman-Field to the LHC
Rick Field
University of Florida
Outline of Talk
 The early days of Feynman-Field
Phenomenology.
 Studying “min-bias” collisions and
Rutgers University October 2009
the “underlying event” at CDF.
 Studying the formation of the “underlying
event”.
Outgoing Parton
PT(hard)
CDF Run 2
 The PYTHIA MPI energy scaling
Initial-State Radiation
Proton
Proton
Underlying Event
Underlying Event
parameter PARP(90).
 The “underlying event” at STAR.
Outgoing Parton
Final-State
Radiation
Extrapolations to RHIC.
 LHC predictions!
 Summary & Conclusions.
Rutgers High Energy Physics Seminar
October 13, 2009
CMS at the LHC
Rick Field – Florida/CDF/CMS
UE&MB@CMS
Page 1
Toward and Understanding of
Hadron-Hadron Collisions
Feynman-Field Phenomenology1
Feynman
From 7 GeV/c
and
st
hat!
Field
Outgoing Parton
p0’s
to 600 GeV/c
Jets. The early days of trying to
understand and simulate hadronhadron collisions.
PT(hard)
Initial-State Radiation
Proton
AntiProton
Underlying Event
Outgoing Parton
Rutgers High Energy Physics Seminar
October 13, 2009
Rick Field – Florida/CDF/CMS
Underlying Event
Final-State
Radiation
Page 2
Hadron-Hadron Collisions
FF1 1977
 What happens when two hadrons
collide at high energy?
Hadron
Hadron
Feynman quote from FF1
???
“The model we shall choose is not a popular one,
 Most of the time the hadrons
ooze
so that we will not duplicate too much of the
through each other andwork
fall apart
(i.e.who are similarly analyzing
of others
no hard scattering). The
outgoing
various
models (e.g. constituent interchange
particles continue in roughly
the same
model, multiperipheral
models, etc.). We shall
Parton-Parton Scattering Outgoing Parton
assume
direction as initial proton
andthat the high PT particles arise from
“Soft” constituent
Collision (no large transverse momentum)
direct hard collisions between
antiproton.
quarks in the incoming particles, which
Hadron
Hadron
 Occasionally there will
be a large
fragment
or cascade down
into several hadrons.”
transverse momentum meson.
Question: Where did it come from?
 We assumed it came from quark-quark
elastic scattering, but we did not know
how to calculate it!
Outgoing Parton
high PT meson
“Black-Box Model”
Rutgers High Energy Physics Seminar
October 13, 2009
Rick Field – Florida/CDF/CMS
Page 3
Quark-Quark Black-Box Model
No gluons!
FF1 1977
Quark Distribution Functions
determined from deep-inelastic
lepton-hadron collisions
Feynman quote from FF1
“Because of the incomplete knowledge of
our functions some things can be predicted
with more certainty than others. Those
experimental results that are not well
predicted can be “used up” to determine
these functions in greater detail to permit
better predictions of further experiments.
Our papers will be a bit long because we
wish to discuss this interplay in detail.”
Quark-Quark Cross-Section
Unknown! Deteremined from
hadron-hadron collisions.
Rutgers High Energy Physics Seminar
October 13, 2009
Rick Field – Florida/CDF/CMS
Quark Fragmentation Functions
determined from e+e- annihilations
Page 4
Quark-Quark Black-Box Model
Predict
particle ratios
FF1 1977
Predict
increase with increasing
CM energy W
“Beam-Beam
Remnants”
Predict
overall event topology
(FFF1 paper 1977)
7 GeV/c p0’s!
Rutgers High Energy Physics Seminar
October 13, 2009
Rick Field – Florida/CDF/CMS
Page 5
Feynman Talk at Coral Gables
(December 1976)
1st transparency
Last transparency
“Feynman-Field
Jet Model”
Rutgers High Energy Physics Seminar
October 13, 2009
Rick Field – Florida/CDF/CMS
Page 6
QCD Approach: Quarks & Gluons
Quark & Gluon Fragmentation
Functions
Q2 dependence predicted from QCD
Parton Distribution Functions
Q2 dependence predicted from
QCD
FFF2 1978
Feynman quote from FFF2
“We investigate whether the present
experimental behavior of mesons with
large transverse momentum in hadron-hadron
collisions is consistent with the theory of
quantum-chromodynamics (QCD) with
asymptotic freedom, at least as the theory
is now partially understood.”
Quark & Gluon Cross-Sections
Calculated from QCD
Rutgers High Energy Physics Seminar
October 13, 2009
Rick Field – Florida/CDF/CMS
Page 7
A Parameterization of
the Properties of Jets
Field-Feynman 1978
Secondary Mesons
(after decay)
continue
 Assumed that jets could be analyzed on a “recursive”
principle.
(bk) (ka)
 Let f(h)dh be the probability that the rank 1 meson leaves
fractional momentum h to the remaining cascade, leaving
Rank 2
Rank 1
quark “b” with momentum P1 = h1P0.
 Assume that the mesons originating from quark “b” are
distributed in presisely the same way as the mesons which
(cb)
(ba)
Primary Mesons
came from quark a (i.e. same function f(h)), leaving quark
“c” with momentum P2 = h2P1 = h2h1P0.
cc pair bb pair
Calculate F(z)
from f(h) and b i!
Original quark with
flavor “a” and
momentum P0
Rutgers High Energy Physics Seminar
October 13, 2009
 Add in flavor dependence by letting bu = probabliity of
producing u-ubar pair, bd = probability of producing ddbar pair, etc.
 Let F(z)dz be the probability of finding a meson
(independent of rank) with fractional mementum z of the
original quark “a” within the jet.
Rick Field – Florida/CDF/CMS
Page 8
Feynman-Field Jet Model
R. P. Feynman
ISMD, Kaysersberg,
France, June 12, 1977
Feynman quote from FF2
“The predictions of the model are reasonable
enough physically that we expect it may
be close enough to reality to be useful in
designing future experiments and to serve
as a reasonable approximation to compare
to data. We do not think of the model
as a sound physical theory, ....”
Rutgers High Energy Physics Seminar
October 13, 2009
Rick Field – Florida/CDF/CMS
Page 9
High PT Jets
CDF (2006)
Feynman, Field, & Fox (1978)
Predict
large “jet”
cross-section
30 GeV/c!
Feynman quote from FFF
600writing,
GeV/c Jets!
“At the time of this
there is
still no sharp quantitative test of QCD.
An important test will come in connection
with the phenomena of high PT discussed here.”
Rutgers High Energy Physics Seminar
October 13, 2009
Rick Field – Florida/CDF/CMS
Page 10
Monte-Carlo Simulation
of Hadron-Hadron Collisions
FF1-FFF1 (1977)
“Black-Box” Model
F1-FFF2 (1978)
QCD Approach
FFFW “FieldJet” (1980)
QCD “leading-log order” simulation
of hadron-hadron collisions
my early days
yesterday
today
FF2 (1978)
Monte-Carlo
simulation of “jets”
“FF” or “FW”
Fragmentation
ISAJET
HERWIG
PYTHIA
(“FF” Fragmentation)
(“FW” Fragmentation)
(“String” Fragmentation)
SHERPA
Rutgers High Energy Physics Seminar
October 13, 2009
PYTHIA 6.4
Rick Field – Florida/CDF/CMS
HERWIG++
Page 11
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!
Rutgers High Energy Physics Seminar
October 13, 2009
Rick Field – Florida/CDF/CMS
Page 12
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.
Rutgers High Energy Physics Seminar
October 13, 2009
Rick Field – Florida/CDF/CMS
Page 13
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
Rutgers High Energy Physics Seminar
October 13, 2009
Rick Field – Florida/CDF/CMS
Page 14
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!
Rutgers High Energy Physics Seminar
October 13, 2009
Rick Field – Florida/CDF/CMS
Page 15
Particle Densities
DhD = 4p = 12.6
2p

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 = 1/4p
3/4p = 0.08
0.24
13 GeV/c PTsum
0
-1
h
+1
Divide by 4p
dPTsum/dhd = 1/4p
3/4p GeV/c = 0.08
0.24 GeV/c
Study the charged particles (pT > 0.5 GeV/c, |h| < 1) and form the charged
particle density, dNchg/dhd, and the charged scalar pT sum density,
dPTsum/dhd.
Rutgers High Energy Physics Seminar
October 13, 2009
Rick Field – Florida/CDF/CMS
Page 16
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 2p.
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!
Rutgers High Energy Physics Seminar
October 13, 2009
Rick Field – Florida/CDF/CMS
Page 17
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!
2p
“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 = 4p/3.
Rutgers High Energy Physics Seminar
October 13, 2009
Rick Field – Florida/CDF/CMS
Page 18
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)
Rutgers High Energy Physics Seminar
October 13, 2009
Default parameters give
very poor description of
the “underlying event”!
Rick Field – Florida/CDF/CMS
Page 19
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)
Rutgers High Energy Physics Seminar
October 13, 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 20
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.
Rutgers High Energy Physics Seminar
October 13, 2009
Rick Field – Florida/CDF/CMS
Page 21
PYTHIA Tune A Min-Bias
“Soft” + ”Hard”
Tuned to fit the CDF Run 1
“underlying event”!
PYTHIA Tune A
CDF Run 2 Charged
DefaultParticle Density
Charged Particle Density: dN/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)!
Rutgers High Energy Physics Seminar
October 13, 2009
Rick Field – Florida/CDF/CMS
Page 22
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
+…
Rutgers High Energy Physics Seminar
October 13, 2009
Rick Field – Florida/CDF/CMS
Multiple-parton
interactions (MPI)!
Page 23
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”.
Rutgers High Energy Physics Seminar
October 13, 2009
Proton
+
+
Proton
Proton
Rick Field – Florida/CDF/CMS
Proton
Proton
+…
Multiple-parton
interactions (MPI)!
Page 24
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.
Rutgers High Energy Physics Seminar
October 13, 2009
Rick Field – Florida/CDF/CMS
Page 25
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!).
Rutgers High Energy Physics Seminar
October 13, 2009
Rick Field – Florida/CDF/CMS
Page 26
Min-Bias “Associated”
Charged Particle Density
PTmax Direction
Associated Charged
Charged
Particle
Density:
dN/dhd
Associated
"Transverse"
ChargedParticle
ParticleDensity:
Density:dN/dhd
dN/dhd
D
Associated Charged Particle Density: dN/dhd
10.0
Charged Particle Density
py Tune A generator level
“Toward” Region
PTmax > 2.0 GeV/c
PTmax > 5.0 GeV/c
1.0
PTmax > 10.0 GeV/c
“Transverse”
“Transverse”
0.1
Min-Bias
1.96 TeV
PTmax > 0.5 GeV/c
PTmax > 1.0 GeV/c
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
0.0
Density
"Transverse"
Charged
Density
Charged Particle
1.6
2.5
1.2
RDF Preliminary
RDF Preliminary
RDF Preliminary
py Tune A generator level
py Tune A generator level
1.0
2.0
1.2
0.8
1.5
Min-Bias
Min-Bias
Min-Bias
14 TeV
1.96 TeV
“Toward”
14 TeV
"Toward"
"Away"
"Toward"
“Transverse”
~ factor of "Away"
2!
“Transverse”
0.8
0.6
1.0
0.4
0.4
0.5
0.2
1.96 TeV
"Transverse"
"Transverse"
“Away”
Charged
ChargedParticles
Particles(|h|<1.0,
(|h|<1.0,PT>0.5
PT>0.5 GeV/c)
GeV/c)
Charged
Particles
(|h|<1.0,
PT>0.5
GeV/c)
0.0
0.0
0
30
60
90
120
150
180
210
240
270
300
330
360
00
2
D (degrees)
54
6
8
10
10
12
15
14
16
20
18
PTmax (GeV/c)
(GeV/c)
PTmax
 Shows the D dependence of the “associated” charged particle density, dNchg/dhd, for charged
particles (pT > 0.5 GeV/c, |h| < 1, not including PTmax) relative to PTmax (rotated to 180o) for
“min-bias” events at 1.96 TeV with PTmax > 0.5, 1.0, 2.0, 5.0, and 10.0 GeV/c from PYTHIA
Tune A (generator level).
PTmax Direction
D
“Toward”
“Transverse”
“Transverse”
“Away”
 Shows the “associated” charged particle density in the “toward”, “away” and
“transverse” regions as a function of PTmax for charged particles (pT > 0.5
GeV/c, |h| < 1, not including PTmax) for “min-bias” events at 1.96 TeV from
PYTHIA Tune A (generator level).
Rutgers High Energy Physics Seminar
October 13, 2009
Rick Field – Florida/CDF/CMS
Page 27
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).
Rutgers High Energy Physics Seminar
October 13, 2009
Rick Field – Florida/CDF/CMS
Page 28
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.
Rutgers High Energy Physics Seminar
October 13, 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 29
“Transverse” Cones
vs “Transverse” Regions
“Cone Analysis”
2p
2p
Transverse
Cone:
p(0.7)2=0.49p
Away Region
Transverse
Region

(Tano, Kovacs, Huston, Bhatti)
Cone 1

Leading
Jet
Leading
Jet
Toward Region
Transverse
Region:
2p/3=0.67p
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.
Rutgers High Energy Physics Seminar
October 13, 2009
Rick Field – Florida/CDF/CMS
Page 30
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-).
Rutgers High Energy Physics Seminar
October 13, 2009
Rick Field – Florida/CDF/CMS
Page 31
“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!
Rutgers High Energy Physics Seminar
October 13, 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 32
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)!
Rutgers High Energy Physics Seminar
October 13, 2009
20
Rick Field – Florida/CDF/CMS
Page 33
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).
Rutgers High Energy Physics Seminar
October 13, 2009
Rick Field – Florida/CDF/CMS
Page 34
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!
Rutgers High Energy Physics Seminar
October 13, 2009
Rick Field – Florida/CDF/CMS
Page 35
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
Rutgers High Energy Physics Seminar
October 13, 2009
Rick Field – Florida/CDF/CMS
Page 36
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
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)
PARP(93)
Tune 2.1
DW
15.0
2.1
15.0
5.0
Tune D6T
Intrinsic KT
Rutgers High Energy Physics Seminar
October 13, 2009
1.0
Tune D6
Rick Field – Florida/CDF/CMS
Page 37
Peter’s Pythia Tunes WEBsite
 http://home.fnal.gov/~skands/leshouches-plots/
Rutgers High Energy Physics Seminar
October 13, 2009
Rick Field – Florida/CDF/CMS
Page 38
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!
Rutgers High Energy Physics Seminar
October 13, 2009
Rick Field – Florida/CDF/CMS
Page 39
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).
Rutgers High Energy Physics Seminar
October 13, 2009
Rick Field – Florida/CDF/CMS
Page 40
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.
Rutgers High Energy Physics Seminar
October 13, 2009
Rick Field – Florida/CDF/CMS
Page 41
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)
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 (|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
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, |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.
Rutgers High Energy Physics Seminar
October 13, 2009
Rick Field – Florida/CDF/CMS
Page 42
“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.
Rutgers High Energy Physics Seminar
October 13, 2009
Rick Field – Florida/CDF/CMS
Page 43
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).
Rutgers High Energy Physics Seminar
October 13, 2009
Rick Field – Florida/CDF/CMS
Page 44
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).
Rutgers High Energy Physics Seminar
October 13, 2009
Rick Field – Florida/CDF/CMS
Page 45
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!
Rutgers High Energy Physics Seminar
October 13, 2009
Rick Field – Florida/CDF/CMS
Page 46
“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.
Rutgers High Energy Physics Seminar
October 13, 2009
Rick Field – Florida/CDF/CMS
Page 47
50
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!
Rutgers High Energy Physics Seminar
October 13, 2009
Rick Field – Florida/CDF/CMS
Page 48
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!
Rutgers High Energy Physics Seminar
October 13, 2009
Rick Field – Florida/CDF/CMS
Page 49
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.
Rutgers High Energy Physics Seminar
October 13, 2009
Rick Field – Florida/CDF/CMS
Page 50
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.
Rutgers High Energy Physics Seminar
October 13, 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 51
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.
Rutgers High Energy Physics Seminar
October 13, 2009
Rick Field – Florida/CDF/CMS
Page 52
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.
Rutgers High Energy Physics Seminar
October 13, 2009
Rick Field – Florida/CDF/CMS
Page 53
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.
Underlying Event
Final-State
Radiation
PY Tune DW
PY Tune A
PY64 Tune S320
2.0
-8
-6
-4
-2
“Away”
scattering events.
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
Outgoing Parton
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)
Rutgers High Energy Physics Seminar
October 13, 2009
Rick Field – Florida/CDF/CMS
Page 54
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”!
AntiProton
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!
Rutgers High Energy Physics Seminar
October 13, 2009
Rick Field – Florida/CDF/CMS
100
1,000
10,000
100,000
CM Energy W (GeV)
UE&MB@CMS
Page 55