Toward an Understanding of
Hadron-Hadron Collisions
From Feynman-Field to the LHC
Rick Field
University of Florida
Outline of Talk
LBNL January 15, 2009
Outgoing Parton
 Before Feynman-Field
PT(hard)
Phenomenology.
Initial-State Radiation
Proton
AntiProton
Underlying Event
Underlying Event
 The early days of Feynman-Field
Phenomenology.
Outgoing Parton
Final-State
Radiation
 Studying “min-bias” collisions and
the “underlying event” at CDF.
 Extrapolations to the LHC.
CDF Run 2
Lawrence Berkeley Laboratory
January 15, 2009
Rick Field – Florida/CDF/CMS
CMS at the LHC
Page 1
Before Feynman-Field
My Ph.D. advisor!
R. D. Field
University of California, Berkeley, 1962-66 (undergraduate)
University of California, Berkeley, 1966-71 (graduate student) me
Rick Field 1964
me
Bob
Cahn
My sister Sally!
Chris
Quigg
J.D.J
The very first “Berkeley
Physics Course”!
Lawrence Berkeley Laboratory
January 15, 2009
Rick Field – Florida/CDF/CMS
Page 2
Before Feynman-Field
Rick & Jimmie
1968
Rick & Jimmie
1970
Rick & Jimmie
1972 (pregnant!)
Rick & Jimmie at CALTECH 1973
Lawrence Berkeley Laboratory
January 15, 2009
Rick Field – Florida/CDF/CMS
Page 3
Toward and Understanding of
Hadron-Hadron Collisions
Feynman-Field Phenomenology1
Feynman
From 7 GeV/c
and
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
Lawrence Berkeley Laboratory
January 15, 2009
st
Rick Field – Florida/CDF/CMS
Underlying Event
Final-State
Radiation
Page 4
The Feynman-Field Days
1973-1983
“Feynman-Field
Jet Model”
 FF1: “Quark Elastic Scattering as a Source of High Transverse Momentum
Mesons”, R. D. Field and R. P. Feynman, Phys. Rev. D15, 2590-2616 (1977).
 FFF1: “Correlations Among Particles and Jets Produced with Large Transverse
Momenta”, R. P. Feynman, R. D. Field and G. C. Fox, Nucl. Phys. B128, 1-65
(1977).
 FF2: “A Parameterization of the properties of Quark Jets”, R. D. Field and R. P.
Feynman, Nucl. Phys. B136, 1-76 (1978).
 F1: “Can Existing High Transverse Momentum Hadron Experiments be
Interpreted by Contemporary Quantum Chromodynamics Ideas?”, R. D. Field,
Phys. Rev. Letters 40, 997-1000 (1978).
 FFF2: “A Quantum Chromodynamic Approach for the Large Transverse
Momentum Production of Particles and Jets”, R. P. Feynman, R. D. Field and G.
C. Fox, Phys. Rev. D18, 3320-3343 (1978).
 FW1: “A QCD Model for e+e- Annihilation”, R. D. Field and S. Wolfram, Nucl.
Phys. B213, 65-84 (1983).
My 1st graduate
student!
Lawrence Berkeley Laboratory
January 15, 2009
Rick Field – Florida/CDF/CMS
Page 5
Hadron-Hadron Collisions
FF1 1977 (preQCD)
 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”
Lawrence Berkeley Laboratory
January 15, 2009
Rick Field – Florida/CDF/CMS
Page 6
Quark-Quark Black-Box Model
No gluons!
Quark Distribution Functions
determined from deep-inelastic
lepton-hadron collisions
FF1 1977 (preQCD)
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.
Lawrence Berkeley Laboratory
January 15, 2009
Rick Field – Florida/CDF/CMS
Quark Fragmentation Functions
determined from e+e- annihilations
Page 7
Quark-Quark Black-Box Model
Predict
particle ratios
FF1 1977 (preQCD)
Predict
increase with increasing
CM energy W
“Beam-Beam
Remnants”
Predict
overall event topology
(FFF1 paper 1977)
7 GeV/c p0’s!
Lawrence Berkeley Laboratory
January 15, 2009
Rick Field – Florida/CDF/CMS
Page 8
Telagram from Feynman
July 1976
SAW CRONIN AM NOW CONVINCED WERE RIGHT TRACK QUICK WRITE
FEYNMAN
Lawrence Berkeley Laboratory
January 15, 2009
Rick Field – Florida/CDF/CMS
Page 9
Letter from Feynman
July 1976
Lawrence Berkeley Laboratory
January 15, 2009
Rick Field – Florida/CDF/CMS
Page 10
Letter from Feynman Page 1
Spelling?
Lawrence Berkeley Laboratory
January 15, 2009
Rick Field – Florida/CDF/CMS
Page 11
Letter from Feynman Page 3
It is fun!
Onward!
Lawrence Berkeley Laboratory
January 15, 2009
Rick Field – Florida/CDF/CMS
Page 12
Feynman Talk at Coral Gables
(December 1976)
1st transparency
Last transparency
“Feynman-Field
Jet Model”
Lawrence Berkeley Laboratory
January 15, 2009
Rick Field – Florida/CDF/CMS
Page 13
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
Lawrence Berkeley Laboratory
January 15, 2009
Rick Field – Florida/CDF/CMS
Page 14
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
Lawrence Berkeley Laboratory
January 15, 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 15
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, ....”
Lawrence Berkeley Laboratory
January 15, 2009
Rick Field – Florida/CDF/CMS
Page 16
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
the past
today
FF2 (1978)
Monte-Carlo
simulation of “jets”
ISAJET
HERWIG
(“FF” Fragmentation)
(“FW” Fragmentation)
tomorrow
Lawrence Berkeley Laboratory
January 15, 2009
SHERPA
“FF” or “FW”
Fragmentation
PYTHIA
PYTHIA 6.4
Rick Field – Florida/CDF/CMS
Page 17
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.”
Lawrence Berkeley Laboratory
January 15, 2009
Rick Field – Florida/CDF/CMS
Page 18
CDF DiJet Event: M(jj) ≈ 1.4 TeV
ETjet1 = 666 GeV ETjet2 = 633 GeV
Esum = 1,299 GeV M(jj) = 1,364 GeV
M(jj)/Ecm ≈ 70%!!
Lawrence Berkeley Laboratory
January 15, 2009
Rick Field – Florida/CDF/CMS
Page 19
The Fermilab Tevatron
CDF “SciCo” Shift December 12-19, 2008
My wife Jimmie on shift with me!
Proton
CDF
1 mile
AntiProton
Proton
2 TeV
 I joined CDF in January 1998.
Lawrence Berkeley Laboratory
January 15, 2009
AntiProton
Acquired 4728 nb-1 during
8 hour “owl” shift!
Rick Field – Florida/CDF/CMS
Page 20
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
+ 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
The “hard core” component
contains both “hard” and
“soft” collisions.
“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
Lawrence Berkeley Laboratory
January 15, 2009
Rick Field – Florida/CDF/CMS
Page 21
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!
Lawrence Berkeley Laboratory
January 15, 2009
Rick Field – Florida/CDF/CMS
Page 22
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.
Lawrence Berkeley Laboratory
January 15, 2009
Rick Field – Florida/CDF/CMS
Page 23
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.
Lawrence Berkeley Laboratory
January 15, 2009
Rick Field – Florida/CDF/CMS
Page 24
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!).
Lawrence Berkeley Laboratory
January 15, 2009
Rick Field – Florida/CDF/CMS
Page 25
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.
Lawrence Berkeley Laboratory
January 15, 2009
Rick Field – Florida/CDF/CMS
Page 26
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.
Lawrence Berkeley Laboratory
January 15, 2009
Rick Field – Florida/CDF/CMS
Page 27
ISAJET 7.32
“Transverse” Density
ISAJET uses a naïve leading-log
parton shower-model which does
not agree with the data!
Charged Jet #1
Direction
1.00
D
“Transverse”
“Transverse”
“Away”
CDF Run 1Data
"Transverse" Charged Density
“Toward”
ISAJET
"Transverse" Charged Particle Density: dN/dhd
Isajet
data uncorrected
theory corrected
0.75
"Hard"
0.50
0.25
“Hard”
Component
"Remnants"
1.8 TeV |h|<1.0 PT>0.5 GeV
Beam-Beam
Remnants
0.00
0
5
10
15
20
25
30
35
40
45
50
PT(charged jet#1) (GeV/c)
 Plot shows average “transverse” charge particle density (|h|<1, pT>0.5 GeV) versus PT(charged jet#1)
compared to the QCD hard scattering predictions of ISAJET 7.32 (default parameters with
PT(hard)>3 GeV/c) .
 The predictions of ISAJET are divided into two categories: charged particles that arise from the
break-up of the beam and target (beam-beam remnants); and charged particles that arise from the
outgoing jet plus initial and final-state radiation (hard scattering component).
Lawrence Berkeley Laboratory
January 15, 2009
Rick Field – Florida/CDF/CMS
Page 28
HERWIG 6.4
“Transverse” Density
D
“Toward”
“Transverse”
“Transverse”
“Away”
1.00
CDF Run 1Data
"Transverse" Charged Density
Charged Jet #1
Direction
HERWIG uses a modified leadinglog parton shower-model which
does agrees better with the data!
"Transverse" Charged Particle Density: dN/dhd
Total
"Hard"
data uncorrected
theory corrected
0.75
0.50
0.25
"Remnants"
Beam-Beam
Remnants
HERWIG
Herwig 6.4 CTEQ5L
PT(hard) > 3 GeV/c
1.8 TeV |h|<1.0 PT>0.5 GeV
0.00
0
5
10
15
20
25
30
PT(charged jet#1) (GeV/c)
35
40
45
50
“Hard”
Component
 Plot shows average “transverse” charge particle density (|h|<1, pT>0.5 GeV) versus PT(charged
jet#1) compared to the QCD hard scattering predictions of HERWIG 5.9 (default parameters with
PT(hard)>3 GeV/c).
 The predictions of HERWIG are divided into two categories: charged particles that arise from the
break-up of the beam and target (beam-beam remnants); and charged particles that arise from the
outgoing jet plus initial and final-state radiation (hard scattering component).
Lawrence Berkeley Laboratory
January 15, 2009
Rick Field – Florida/CDF/CMS
Page 29
MPI: Multiple Parton
Interactions
“Hard”
Collision
Multiple
Parton
Interaction
outgoing parton
“Hard” Component
“Semi-Hard” MPI
“Soft” Component
AntiProton
Proton
initial-state radiation
initial-state radiation
outgoing parton
final-state radiation
or
+
outgoing jet
final-state radiation
 PYTHIA models the “soft” component of the underlying event
with color string fragmentation, but in addition includes a
contribution arising from multiple parton interactions (MPI) in
which one interaction is hard and the other is “semi-hard”.
Beam-Beam Remnants
color string
color string
 The probability that a hard scattering events also contains a semi-hard multiple parton
interaction can be varied but adjusting the cut-off for the MPI.
 One can also adjust whether the probability of a MPI depends on the PT of the hard
scattering, PT(hard) (constant cross section or varying with impact parameter).
 One can adjust the color connections and flavor of the MPI (singlet or nearest neighbor,
q-qbar or glue-glue).
 Also, one can adjust how the probability of a MPI depends on PT(hard) (single or double
Gaussian matter distribution).
Lawrence Berkeley Laboratory
January 15, 2009
Rick Field – Florida/CDF/CMS
Page 30
Tuning PYTHIA:
Multiple Parton Interaction Parameters
Parameter
Default
Description
PARP(83)
0.5
Double-Gaussian: Fraction of total hadronic
matter within PARP(84)
PARP(84)
0.2
Double-Gaussian: Fraction of the overall hadron
radius containing the fraction PARP(83) of the
total hadronic matter.
Multiple Parton Interaction
Color String
Color String
PARP(86)
PARP(89)
PARP(90)
PARP(67)
0.33
0.66
1 TeV
0.16
1.0
Probability that the MPI produces two gluons
with color connections to the “nearest neighbors.
Multiple PartonDetermine
Interactionby comparing
with 630 GeV data!
Probability that the MPI produces two gluons
either as described by PARP(85) or as a closed
gluon
loop.
remaining
fraction consists of
Affects
the The
amount
of
quark-antiquark
pairs.
initial-state radiation!
Color String
Hard-Scattering Cut-Off PT0
5
Determines the reference energy E0.
Determines the energy dependence of the cut-off
PT0 as follows PT0(Ecm) = PT0(Ecm/E0)e with
e = PARP(90)
A scale factor that determines the maximum
parton virtuality for space-like showers. The
larger the value of PARP(67) the more initialstate radiation.
PYTHIA 6.206
e = 0.25 (Set A))
4
PT0 (GeV/c)
PARP(85)
Take E0 = 1.8 TeV
3
2
e = 0.16 (default)
1
100
1,000
10,000
100,000
CM Energy W (GeV)
Reference point
at 1.8 TeV
Lawrence Berkeley Laboratory
January 15, 2009
Rick Field – Florida/CDF/CMS
Page 31
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)
Lawrence Berkeley Laboratory
January 15, 2009
Default parameters give
very poor description of
the “underlying event”!
Rick Field – Florida/CDF/CMS
Page 32
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)
Lawrence Berkeley Laboratory
January 15, 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 33
Run 1 vs Run 2: “Transverse”
Charged Particle Density
“Transverse” region as
defined by the leading
“charged particle jet”
"Transverse"
"Transverse" Charged
Charged Particle
Particle Density:
Density: dN/dhd
dN/dhd
"Transverse"
Charged
Particle
Density:
dN/dhd
"Transverse"
Charged
Particle
Density:
dN/dhd
Charged Particle Jet #1
Direction
D
“Toward”
“Transverse”
“Transverse”
“Away”
"Transverse"
ChargedDensity
Density
"Transverse"Charged
Charged
Density
"Transverse"
"Transverse"
Charged
Density
1.25
1.25
1.25
CDF Run 1 Min-Bias
CDF Run 1 Min-Bias
CDF
Run
11Published
CDF
Run
JET20
CDF
Run
1 Published
CDF
Run
1 JET20
CDF Run 2 Preliminary
CDF Run 2 Preliminary
PYTHIA Tune A
CDF Run 2
CDFPreliminary
Run 1 Data
CDF
CDF
Preliminary
CDF
Preliminary
data
uncorrected
1.00
1.00
1.00
data
uncorrected
data
uncorrected
data
uncorrected
theory corrected
0.75
0.75
0.75
0.50
0.50
0.50
0.25
0.25
0.25
|h|<1.0
PT>0.5
GeV/c
|h|<1.0
PT>0.5
GeV/c
1.8
TeV
|h|<1.0
|h|<1.0
PT>0.5PT>0.5
GeV GeV
0.00
0.00
0.00
0.00
000
0
10
20
10
10 5 20
20
30
30
10
30
40
50
40
4015 50
50
60
70 2580
60
20
60 70
70 80
80
PT(charged
jet#1)
PT(charged jet#1)
90
10035110
120
140 150
90
130
30
40 130
50
90 100
100 110
110 120
120
13045140
140 150
150
(GeV/c)
PT(charged jet#1) (GeV/c)
(GeV/c)
 Shows the
Excellent agreement
between
Run
1 and 2!
data
on the
average
“transverse” charge particle density (|h|<1, pT>0.5 GeV) as
a function of the transverse momentum of the leading charged particle jet from Run 1.
 Compares the Run 2 data (Min-Bias, JET20, JET50, JET70, JET100) with Run 1. The
errors on the (uncorrected) Run 2 data include both statistical andPYTHIA
correlated
Tune A was tuned to fit
the “underlying event” in Run I!
systematic uncertainties.
 Shows the prediction of PYTHIA Tune A at 1.96 TeV after detector simulation (i.e. after
CDFSIM).
Lawrence Berkeley Laboratory
January 15, 2009
Rick Field – Florida/CDF/CMS
Page 34
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
Charged Density dN/dhddPT (1/GeV/c)
dN/dhd
Pythia 6.206 Set A
Tune B
These
6.2 tunes!
Tune
AWare “old” PYTHIA
0.2
There are new 6.4 tunes by
Pythia 6.206 Set A
1.8 TeV all PT
CDF Min-Bias 1.8 TeV
Tune
A
Arthur Moraes (ATLAS)
0.0
-4
-3
-2
-1
0
1
2
3
4
Hendrik
Hoeth (MCnet)
Pseudo-Rapidity h
Peter Skands (Tune S0)
 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
Tune DW
PT“Min-Bias”
(hard) > 0.
One
can simulate both “hard”
at the
Tevatron!
and “soft”
collisions
in one program.
Tune
D
1.0E-02
1.8 TeV |h|<1
Tune
BW events
12%
of “Min-Bias”
PT(hard) > 0 GeV/c
have PT(hard) > 5 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
Tune
D6
6
8
10
12
14
PT(charged) (GeV/c)
Tune D6T
 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)!
Lawrence Berkeley Laboratory
January 15, 2009
Rick Field – Florida/CDF/CMS
Page 35
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).
Lawrence Berkeley Laboratory
January 15, 2009
Rick Field – Florida/CDF/CMS
Page 36
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
Lawrence Berkeley Laboratory
January 15, 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 37
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.
Lawrence Berkeley Laboratory
January 15, 2009
Rick Field – Florida/CDF/CMS
Page 38
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
Lawrence Berkeley Laboratory
January 15, 2009
Rick Field – Florida/CDF/CMS
Page 39
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).
Lawrence Berkeley Laboratory
January 15, 2009
Rick Field – Florida/CDF/CMS
Page 40
Average PT versus Nchg
PT(Z) < 10 GeV/c
Average
Charged
PT
versus
Nchg
Average
Average Charged
Charged PT
PT versus
versus Nchg
Nchg
CDF
Run
Preliminary
CDF
CDF Run
Run 22
2 Preliminary
Preliminary
data corrected
generator
level
generator
level theory
theory
generator level theory
1.2
1.2
1.2
pyAW
pyAW
pyAW
1.0
1.0
1.0
HW
HW
HW
0.8
0.8
0.8
"Drell-Yan
Production"
"Drell-Yan
"Drell-Yan Production"
Production"
70
M(pair)
110
GeV
70
70 <<
< M(pair)
M(pair) <<
< 110
110 GeV
GeV
PT(Z)
10
GeV/c
PT(Z)
PT(Z) <<
< 10
10 GeV/c
GeV/c
CDF Run 2 Preliminary
JIM
JIM
Average PT (GeV/c)
Average
PT
(GeV/c)
AveragePT
PT(GeV/c)
(GeV/c)
Average
1.4
1.4
1.4
Average PT versus Nchg
1.4
ATLAS
ATLAS
Drell-Yan PT > 0.5 GeV PT(Z) < 10 GeV/c
data corrected
generator level theory
1.2
pyAW
No MPI!
1.0
Min-Bias PT > 0.4 GeV/c
0.8
Charged
Particles
(|h|<1.0,
PT>0.5
GeV/c)
Charged
Charged Particles
Particles (|h|<1.0,
(|h|<1.0, PT>0.5
PT>0.5 GeV/c)
GeV/c)
excluding
the
lepton-pair
excluding
excluding the
the lepton-pair
lepton-pair
Charged Particles (|h|<1.0)
pyA
0.6
0.6
0.6
0.6
00
0
55
5
10
10
10
15
15
15
20
20
20
25
25
25
30
30
30
35
35
35
0
Number
of
Charged
Particles
Number
Number of
of Charged
Charged Particles
Particles
Drell-Yan Production
Proton
20
30
40
Number of Charged Particles
Lepton
AntiProton
Underlying Event
10
Underlying Event
Remarkably similar behavior!
Perhaps indicating that MPIProton
playing an important role in
both processes.
“Minumum Bias” Collisions
AntiProton
Anti-Lepton
 Predictions
for thepTaverage
pT ofparticles
chargedversus
particles
theofnumber
charged(p
particles
(pT > 0.5
Data the average
of charged
theversus
number
chargedofparticles
|h|GeV/c,
< 1, |h|
T > 0.5 GeV/c,
<
1, excluding
the lepton-pair)
forDrell-Yan
for Drell-Yan
production
< M(pair)
110 GeV,
PT(pair)
10 GeV/c)
at
excluding
the lepton-pair)
for for
production
(70 <(70
M(pair)
< 110< GeV,
PT(pair)
< 10<GeV/c)
at CDF
CDF
Run
Run 2.
The2.data are corrected to the particle level and are compared with various Monte-Carlo tunes at the
particle level (i.e. generator level).
Lawrence Berkeley Laboratory
January 15, 2009
Rick Field – Florida/CDF/CMS
Page 41
Z-BosonDirection
D
UE&MB@CMS
UE&MB@CMS
“Minimum-Bias” Collisions
“Toward”
“Transverse”
Proton
“Transverse”
Proton
 Min-Bias Studies: Charged particle distributions and
correlations. Construct
“charged particle jets” and look
CDF Run 2 Preliminary
"Drell-Yan Production"
CDF Run 2 Preliminary
pyDWT LHC14
70 < M(pair) <pyDW
110 GeV
at “mini-jet”
structure
and the onset of the “underlying
ATLAS
JIM
event”. (requires only charged tracks)
"Toward"
"Toward" Charged
Charged Particle
Particle Density:
Density: dN/dhd
dN/dhd
“Away”
"Toward" Charged Density
High PT Jet Production
0.9
2.0
Outgoing Parton
PT(hard)
Initial-State
Radiation
Proton
Proton
1.0
Underlying Event
HW Tevatron
pyDWT Tevatron
Final-State
Radiation
Drell-Yan Production
0.3
0.5
0.0
Lepton
0
Proton
Shapes of the pT(m+m-)
“transverse
region”
distribution
at the
Z-boson in
mass.
HW LHC14

Event” Studies: The
pyAW
“leading
Jet” and “back-to-back”
charged particle jet
Study
the “underlying
event” by
"Drell-Yan
Production"
HW
Charged Particles
Particles (|h|<1.0,
(|h|<1.0, PT>0.5
PT>0.5 GeV/c)
GeV/c)
Charged
70 < M(pair) < 110 GeV
and the
“central
excluding
themuons!
lepton-pair region” in Drell-Yan
using production
charged particles
and
excluding
the
lepton-pair
production.
charged
tracks
and muons for Drellas 40soon75(requires
as 60possible)
20
80125
100
25 (start
50
100
150
Yan) PT(Z-Boson)
PT(Z-Boson) (GeV/c)
(GeV/c)
DWT
“Underlying
Underlying Event
<pT(m+m-)> is much
Outgoing Parton
larger
at the LHC!
Proton
Lepton-Pair
Transverse
Momentum
Underlying
Event
80
Initial-State
Radiation
Drell-Yan
Average Pair PT
generator level
60
40
Lepton-Pair
PT(pair)
Proton
20
Underlying Event
Drell-Yan
 Drell-Yan Studies: Transverse
momentum distribution
of
generator leve
Tevatron Run2
0.08
the lepton-pair versus the mass of the lepton-pair,
PY Tune DW (solid)
(dashed)
2(pair)>, ds/dp (pair) (only HERWIG
<pT(pair)>, <pT0.06
requires
T
70 < M(m-pair) < 110 GeV
<6
Event 0.04
structure for large lepton-pair|h(m-pair)|
pT (i.e.
mm
Tevatron Runmuons).
2
+jets, requires muons).
l
LHC
Anti-Lepton
Drell-Yan Production
Drell-Yan PT(m+m-) Distribution
0.10
Underlying Event
Initial-State
Radiation
1/N dN/dPT (1/GeV)
Underlying Event
Proton
1.5
0.6
generator level theory
data corrected
generator level theory
0.02
PY Tune DW (solid)
HERWIG (dashed)
Final-State
Radiation
0
Outgoing Parton
0
100
200
LHC
Normalized to 1
0.00
300
400
500
600
700
800
900
1000
0
5
Lawrence Berkeley Laboratory
January 15, 2009
10
15
20
25
30
35
40
PT(m+m-) (GeV/c)
Lepton-Pair Invariant Mass (GeV)
Rick Field – Florida/CDF/CMS
Page 42