Toward an Understanding of
the Overall Event Structure
of Hard Collisions
Outline of Talk
 The Past: Feynman-Field
Fenomenology (1973-1980).
7 GeV p0’s
to
400 GeV “jets”
 The Present: Studying the
“Underlying Event” at CDF.
Feynman Festival
August 23, 2002
Rick Field - Florida/CDF
Page 1
CDF Collider
Phenomenology
Proton
In addition to being an exceptional theoretical
CDF
1 mile physicist (and very good at math!), Feynman was
a great phenomenologist and he enjoyed very
much talking with experimenters.
AntiProton
Theorist!
 I am a theorist working in the
CDF experimental collaboration.
 I work on collider phenomenology
related to CDF.
Proton
2 TeV
AntiProton
 Only by working in the experimental collaboration am I able to have
access to data and do the kind of phenomenology I enjoy (i.e. the kind of
phenomenology I did with Feynman many years ago).
Feynman Festival
August 23, 2002
Rick Field - Florida/CDF
Page 2
Feynman-Field
Fenomenology
1973-1980
“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!
Feynman Festival
August 23, 2002
Rick Field - Florida/CDF
Page 3
Feynman-Field
Fenomenology
1973-1980
“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).
Many people have
to our of
understanding
 FF2: “A Parameterizationcontributed
of the properties
Quark Jets”, R. D. Field and R. P.
hadron-hadron
collisions!
Feynman, Nucl. Phys. B136,of
1-76
(1978).
I will sayMomentum
a few words
about Experiments be
 F1: “Can Existing High Transverse
Hadron
Feynman’s
influence
on the field. Ideas?”, R. D. Field,
Interpreted by Contemporary
Quantum
Chromodynamics
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!
Feynman Festival
August 23, 2002
Rick Field - Florida/CDF
Page 4
Hadron-Hadron Collisions
FF1 1977 (preQCD)
 What happens when two hadrons
collide at high energy?
Hadron
 Most of the time the hadrons ooze
through each other and fall apart (i.e.
no hard scattering). The outgoing
particles continue in roughly the same
direction as initial proton and
antiproton.
 Occasionally there will be a large
transverse momentum meson.
Question: Where did it come from?
Hadron
???
Parton-Parton Scattering
Outgoing Parton
Hadron
 We assumed it came from quark-quark
elastic scattering, but we did not know
how to calculate it!
Hadron
Outgoing Parton
high PT meson
“Black-Box Model”
Feynman Festival
August 23, 2002
Rick Field - Florida/CDF
Page 5
Hadron-Hadron Collisions
FF1 1977 (preQCD)
 What happens when two hadrons
collide at high energy?
Hadron
???
Hadron
Feynman quote from FF1:
 Most of the time the hadrons ooze
“The model we shall choose is not a popular one,
through each other and fall apart (i.e.
so that we will not duplicate too much of the
no hard scattering). The
outgoing
work
of others who are similarly analyzing
particles continue in roughly
the same
various models
(e.g. constituent interchange
Parton-Parton
Scattering Outgoing Parton
direction as initial proton
model,and
multiperipheral models,
etc.). We shall
assume that the high PT particles
arise from
antiproton.
“Soft” Collision
(no large transverse momentum)
direct hard collisions between constituent
 Occasionally there will be
a large
quarks
in the incoming
particles, which
Hadron
fragment
or cascade down into several hadrons.”
transverse momentum
meson.
Hadron
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”
Feynman Festival
August 23, 2002
Rick Field - Florida/CDF
Page 6
Quark-Quark
Black-Box Model
Quark Distribution Functions
determined from deep-inelastic
lepton-hadron collisions
FF1 1977 (preQCD)
Quark-Quark Cross-Section
Unknown! Deteremined from
hadron-hadron collisions.
Feynman Festival
August 23, 2002
No gluons!
Rick Field - Florida/CDF
Quark Fragmentation Functions
determined from e+e- annihilations
Page 7
Quark-Quark
Black-Box Model
Quark Distribution Functions
determined from deep-inelastic
lepton-hadron collisions
No gluons!
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.
Feynman Festival
August 23, 2002
Rick Field - Florida/CDF
Quark Fragmentation Functions
determined from e+e- annihilations
Page 8
Predict
particle ratios
Quark-Quark
Black-Box Model
FF1 1977 (preQCD)
Predict
increase with increasing
CM energy W
Predict
overall event topology
(FFF1 paper 1977)
Feynman Festival
August 23, 2002
Rick Field - Florida/CDF
Page 9
Telagram from Feynman
July 1976
SAW CRONIN AM NOW CONVINCED WERE RIGHT TRACK QUICK WRITE
FEYNMAN
Feynman Festival
August 23, 2002
Rick Field - Florida/CDF
Page 10
Letter from Feynman
July 1976
Feynman Festival
August 23, 2002
Rick Field - Florida/CDF
Page 11
Letter from Feynman:
page 1
Spelling?
Feynman Festival
August 23, 2002
Rick Field - Florida/CDF
Page 12
Letter from Feynman:
page 3
It is fun!
Onward!
Feynman Festival
August 23, 2002
Rick Field - Florida/CDF
Page 13
Napkin from Feynman
Feynman Festival
August 23, 2002
Rick Field - Florida/CDF
Page 14
QCD Approach
Quarks & Gluons
Quark & Gluon Fragmentation
Functions
2
Q dependence predicted from QCD
FFF2 1978
Parton Distribution Functions
Q2 dependence predicted from
QCD
Quark & Gluon Cross-Sections
Calculated from QCD
Feynman Festival
August 23, 2002
Rick Field - Florida/CDF
Page 15
QCD Approach
Quarks & Gluons
Quark & Gluon Fragmentation
Functions
2
Q 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
Feynman Festival
August 23, 2002
Rick Field - Florida/CDF
Page 16
QCD Approach
Quarks & Gluons
FFF2 1978
Predict
large “jet”
cross-section
Feynman quote from FFF2:
“At the time of this writing,
there is still no sharp
quantitative test of QCD.
An important test will come
in connection with the phenomena
of high PT discussed here.”
30 GeV!
Feynman Festival
August 23, 2002
Rick Field - Florida/CDF
Page 17
CDF Run II DiJet Event
July 2002
ETjet1 = 403 GeV
ETjet2 = 322 GeV
Feynman Festival
August 23, 2002
Raw ET values!!
Rick Field - Florida/CDF
Page 18
Monte-Carlo Simulation
of Hadron-Hadron Collisions
 Color singlet proton collides
with a color singlet antiproton.
 A red quark gets knocked out
of the proton and a blue
antiquark gets knocked out of
the antiproton.
 At short times (small distances) the color forces
are weak and the outgoing partons move away
from the beam-beam remnants.
Jet
quark-antiquark
pairs
color string
Proton
Beam
Beam Beam
Remnants
Remnants
Remnants
AntiProton
Beam
Beam
Beam
Remnants
Remnants
Remnants
color string
quark-antiquark
pairs
Jet
 At long times (large distances) the
color forces become strong and quarkantiquark pairs are pulled out of the
vacuum and hadrons are formed.
Feynman Festival
August 23, 2002
Rick Field - Florida/CDF
 The resulting event consists of
hadrons and leptons in the
form of two large transverse
momentum outgoing jets plus
the beam-beam remnants.
Page 19
Monte-Carlo Simulation
of Hadron-Hadron Collisions
FF1-FFF1 (1977)
“Black-Box” Model
F1-FFF2 (1978)
QCD Approach
FF2 (1978)
Monte-Carlo
simulation of “jets”
FFFW “FieldJet” (1980)
QCD “leading-log order” simulation
of hadron-hadron collisions
today
ISAJET
HERWIG
(“FF” Fragmentation)
(“FW” Fragmentation)
Feynman Festival
August 23, 2002
Rick Field - Florida/CDF
“FF” or “FW”
Fragmentation
PYTHIA
Page 20
Monte-Carlo Simulation
of Hadron-Hadron Collisions
FF1-FFF1 (1977)
“Black-Box” Model
F1-FFF2 (1978)
QCD Approach
FF2 (1978)
Monte-Carlo
simulation of “jets”
Feynman quote from FF2:
“The predictions
the model are
reasonable
FFFW of
“FieldJet”
(1980)
enough
physically thatorder”
we expect
it may
QCD
“leading-log
simulation
be close enough to reality to be useful in
of hadron-hadron
designing
future experimentscollisions
and to serve
as a reasonable approximation to compare
to data. We do not think of the model
as a sound physical theory, ....”
today
ISAJET
HERWIG
(“FF” Fragmentation)
(“FW” Fragmentation)
Feynman Festival
August 23, 2002
Rick Field - Florida/CDF
“FF” or “FW”
Fragmentation
PYTHIA
Page 21
The “Underlying Event” in
Hard Scattering Processes
 What happens when a proton and an
antiproton collide with a center-ofmass energy of 2 TeV?
 Most of the time the proton and
antiproton ooze through each other
and fall apart (i.e. no hard scattering).
The outgoing particles continue in
roughly the same direction as initial
proton and antiproton.
“Soft” Collision (no hard scattering)
ProtonProton
“Hard” Scattering
Feynman Festival
August 23, 2002
Outgoing Parton
PT(hard)
Proton
AntiProton
Underlying Event
 Occasionally there will be a “hard”
parton-parton collision resulting in large
transverse momentum outgoing partons.
 The “underlying event” is everything
except the two outgoing hard scattered
“jets”. It is an unavoidable background
to many collider observables.
AntiProton
AntiProton
2 TeV
Underlying Event
Initial-State
Radiation
Final-State
Radiation
Outgoing Parton
“Underlying Event”
Proton
Beam-Beam Remnants
Rick Field - Florida/CDF
AntiProton
Beam-Beam Remnants
Initial-State
Radiation
Page 22
Beam-Beam Remnants
“Hard” Collision
outgoing parton
“Hard” Component
“Soft” Component
AntiProton
Proton
initial-state radiation
initial-state radiation
+
Beam-Beam Remnants
outgoing jet
outgoing parton
final-state radiation
final-state radiation
 The underlying event in a hard scattering process has a “hard” component (particles
that arise from initial & final-state radiation and from the outgoing hard scattered
partons) and a “soft” component (beam-beam remnants).
 However the “soft” component is color connected to the “hard” component so this
separation is (at best) an approximation.
Min-Bias?
color string
color string
Feynman Festival
August 23, 2002
 For ISAJET (no color flow) the “soft” and “hard” components
are completely independent and the model for the beam-beam
remnant component is the same as for min-bias (“cut
pomeron”) but with a larger <PT>.
 HERWIG breaks the color connection with a soft q-qbar pair
and then models the beam-beam remnant component the same
as HERWIG min-bias (cluster decay).
Rick Field - Florida/CDF
Page 23
Studying the “Underlying Event”
at CDF
Outgoing Parton
The Underlying Event:
beam-beam remnants
initial-state radiation
multiple-parton interactions
PT(hard)
Initial-State Radiation
Proton
AntiProton
Underlying Event
 The underlying event in a hard scattering
process is a complicated and not very well
understood object. It is an interesting
region since it probes the interface between
perturbative and non-perturbative physics.
 There are two CDF analyses which
quantitatively study the underlying event
and compare with the QCD Monte-Carlo
models.
 It is important to model this region well
since it is an unavoidable background to all
collider observables. Also, we need a good
model of min-bias (zero-bias) collisions.
Underlying Event
Outgoing Parton
CDF
CDF
Evolution of Charged Jets
Cone Analysis
Valeria Tano
Eve Kovacs
Joey Huston
Anwar Bhatti
Ph.D. Thesis
Feynman Festival
August 23, 2002
Final-State
Radiation
Rick Field - Florida/CDF
Rick Field
David Stuart
Rich Haas
PRD65:092002, 2002
Page 24
Evolution of Charged Jets
“Underlying Event”
Charged Particle  Correlations
PT > 0.5 GeV/c |h| < 1
Charged Jet #1
Direction
“Toward-Side” Jet

“Toward”
“Transverse”
2p
Away Region
Charged Jet #1
Direction

“Toward”
Transverse
Region

Leading
Jet
Toward Region
“Transverse”
“Away”
“Transverse”
“Transverse”
Transverse
Region
“Away”
Away Region
0
-1
“Away-Side” Jet
h
+1
 Look at charged particle correlations in the azimuthal angle  relative to the leading charged
particle jet.
 Define || < 60o as “Toward”, 60o < || < 120o as “Transverse”, and || > 120o as “Away”.
 All three regions have the same size in h- space, hx = 2x120o = 4p/3.
Feynman Festival
August 23, 2002
Rick Field - Florida/CDF
Page 25
Charged Multiplicity
versus PT(chgjet#1)
Charged Jet #1
Direction

“Transverse”
“Transverse”
“Away”
12
CDF Preliminary
<Nchg> in 1 GeV/c bin
“Toward”
Nchg versus PT(charged jet#1)
"Toward"
data uncorrected
10
8
"Away"
6
4
"Transverse"
2
1.8 TeV |h|<1.0 PT>0.5 GeV
0
0
Underlying Event
“plateau”
5
10
15
20
25
30
35
40
45
50
PT(charged jet#1) (GeV/c)
Factor of 2 more active than
an average Min-Bias event!
 Data on the average number of “toward” (||<60o), “transverse” (60<||<120o), and
“away” (||>120o) charged particles (PT > 0.5 GeV, |h| < 1, including jet#1) as a
function of the transverse momentum of the leading charged particle jet. Each point
corresponds to the <Nchg> in a 1 GeV bin. The solid (open) points are the Min-Bias
(JET20) data. The errors on the (uncorrected) data include both statistical and
correlated systematic uncertainties.
Feynman Festival
August 23, 2002
Rick Field - Florida/CDF
Page 26
ISAJET: “Transverse” Nchg
versus PT(chgjet#1)
Charged Jet #1
Direction
“Toward”
“Transverse”
“Transverse”
“Away”
Beam-Beam
Remnants
"Transverse" <Nchg> in 1 GeV/c bin

ISAJET
"Transverse" Nchg versus PT(charged jet#1)
4
Isajet Total
CDF Preliminary
data uncorrected
theory corrected
3
Hard Component
Outgoing Jets
plus
Initial &
Final-State
Radiation
2
1
Beam-Beam Remnants
1.8 TeV |h|<1.0 PT>0.5 GeV
0
0
5
10
15
20
25
30
35
40
45
50
PT(charged jet#1) (GeV/c)
 Plot shows the “transverse” <Nchg> vs PT(chgjet#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).
Feynman Festival
August 23, 2002
Rick Field - Florida/CDF
Page 27
HERWIG: “Transverse” Nchg
versus PT(chgjet#1)
Charged Jet #1
Direction
“Toward”
“Transverse”
“Transverse”
“Away”
Beam-Beam
Remnants
"Transverse" <Nchg> in 1 GeV/c bin

"Transverse" Nchg versus PT(charged jet#1)
4
HERWIG
CDF Preliminary
Herwig Total
data uncorrected
theory corrected
3
2
Hard Component
1
Beam-Beam Remnants
1.8 TeV |h|<1.0 PT>0.5 GeV
0
0
5
10
15
20
25
30
35
PT (charged jet#1) (GeV/c)
40
45
50
Outgoing Jets
plus
Initial &
Final-State
Radiation
 Plot shows the “transverse” <Nchg> vs PT(chgjet#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).
Feynman Festival
August 23, 2002
Rick Field - Florida/CDF
Page 28
MPI: Multiple Parton
Interactions
“Hard”
Collision
Multiple
Parton
Interaction
outgoing parton
“Hard” Component
“Semi-Hard” MPI
“Soft” Component
AntiProton
Proton
initial-state radiation
outgoing parton
final-state radiation
or
+
initial-state radiation
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).
Feynman Festival
August 23, 2002
Rick Field - Florida/CDF
Page 29
PYTHIA: Multiple Parton
Interactions
Multiple Parton Interactions
Outgoing Parton
PT(hard)
Proton
AntiProton
Underlying Event
Parameter
Underlying Event
Value
Outgoing Parton
MSTP(81)
MSTP(82)
Feynman Festival
August 23, 2002
Pythia uses multiple parton
interactions to enhace
the underlying event.
Description
0
Multiple-Parton Scattering off
1
Multiple-Parton Scattering on
1
Multiple interactions assuming the same probability, with
an abrupt cut-off PTmin=PARP(81)
3
Multiple interactions assuming a varying impact
parameter and a hadronic matter overlap consistent with
a single Gaussian matter distribution, with a smooth turnoff PT0=PARP(82)
4
Multiple interactions assuming a varying impact
parameter and a hadronic matter overlap consistent with
a double Gaussian matter distribution (governed by
PARP(83) and PARP(84)), with a smooth turn-off
PT0=PARP(82)
Rick Field - Florida/CDF
and now
HERWIG
!
Herwig MPI
J. M. Butterworth
J. R. Forshaw
M. H. Seymour
Multiple parton
interaction more
likely in a hard
(central) collision!
Hard Core
Page 30
PYTHIA 6.206 Defaults
PYTHIA default parameters
6.115
6.125
6.158
5
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
CDF
"Transverse" <Nchg>
Parameter
"Transverse" Nchg versus PT(charged jet#1)
4
3
2
1
1.8 TeV |h|<1.0 PT>0.5 GeV/c
0
0
PARP(67)
4.0
Pythia 6.206 (default)
MSTP(82)=1
PARP(81) = 1.9 GeV/c
data uncorrected
theory corrected
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 “Transverse” <Nchg> 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.
Constant
Default parameters give
very poor description of
the “underlying event”!
Feynman Festival
August 23, 2002
Rick Field - Florida/CDF
Probability
Scattering
Page 31
Tuned PYTHIA 6.206
PYTHIA 6.206 CTEQ5L
Tune 1
Tune 2
MSTP(81)
1
1
MSTP(82)
3
3
PARP(82)
1.6 GeV
1.7 GeV
PARP(85)
1.0
1.0
PARP(86)
1.0
1.0
PARP(89)
1.8 TeV
1.8 TeV
PARP(90)
0.16
0.16
PARP(67)
1.0
4.0
"Transverse" <Nchg> in 1 GeV/c bin
Parameter
"Transverse" Nchg versus PT(charged jet#1)
4
Tuned PYTHIA 6.206
PARP(67)=4
CDF
data uncorrected
theory corrected
3
2
Tuned PYTHIA 6.206
PARP(67)=1
1
CTEQ5L
1.8 TeV |h|<1.0 PT>0.5 GeV
0
0
5
10
15
20
25
30
35
40
45
50
PT(charged jet#1) (GeV/c)
 Plot shows “Transverse” <Nchg> versus PT(chgjet#1) compared to the QCD hard
scattering predictions of two tuned versions of PYTHIA 6.206 (CTEQ5L, PARP(67)=1
and PARP(67)=4).
New
New PYTHIA
PYTHIA default
default
(less
(less initial-state
initial-state radiation)
radiation)
Feynman Festival
August 23, 2002
Old PYTHIA
PYTHIA default
default
Old
(less
initial-state
radiation)
(less initial-state radiation)
Rick Field - Florida/CDF
Can we distinguish between
PARP(67)=1 and PARP(67)=4?
Page 32
Collider Phenomenology
From 7 GeV/c po’s to 400 GeV “Jets”
NLO QCD (2002)
400 GeV “jets”
FF1 (1977)
7 GeV/c p0’s
Feynman Festival
August 23, 2002
Rick Field - Florida/CDF
Page 33
Collider Phenomenology
From 7 GeV/c po’s to 400 GeV “Jets”
Rick Field (Feynman Festival):
“At the time of this writing,
there is still no sharp
quantitative test of QCD.
We believe it is the correct
theory of strong interactions
QCD (2002)
becauseNLO
it qualitatively
describes
400
GeV
“jets”
an enormous variety and amount
of data over many decades of Q2.”
Feynman played an enormous role in our
understanding of hadron-hadron collisions
and his influence is still being felt!
FF1 (1977)
7 GeV/c p0’s
Feynman Festival
August 23, 2002
Rick Field - Florida/CDF
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