CDF Collaboration Meeting
Toward an Understanding of
Hadron-Hadron Collisions
Rick Field
University of Florida
La Biodola, Elba Island, Tuscany, Italy
CDF Run 2
From Feynman-Field to the Tevatron
CDF Collaboration Meeting
June 8, 2006
Rick Field – Florida/CDF
Page 1
Toward and Understanding of
Hadron-Hadron Collisions
1 hat!
From Feynman-Field to the Tevatron
st
Feynman
and
Field
 From 7 GeV/c p0’s to 600 GeV/c Jets.
 The “Underlying Event” at the Tevatron
(things we don’t understand).
 New Run 2 Monte-Carlo Tunes
(extrapolations to the LHC).
PT(hard)
Initial-State Radiation
Proton
AntiProton
Underlying Event
 Let’s find the Higgs!
CDF Collaboration Meeting
June 8, 2006
Outgoing Parton
Outgoing Parton
Rick Field – Florida/CDF
Underlying Event
Final-State
Radiation
Page 2
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!
CDF Collaboration Meeting
June 8, 2006
Rick Field – Florida/CDF
Page 3
Before Feynman-Field
Rick Field 1968
CDF Collaboration Meeting
June 8, 2006
Rick Field – Florida/CDF
Page 4
Before Feynman-Field
Rick & Jimmie
1968
Rick & Jimmie
1970
Rick & Jimmie
1972 (pregnant!)
Rick & Jimmie at CALTECH 1973
CDF Collaboration Meeting
June 8, 2006
Rick Field – Florida/CDF
Page 5
The Feynman-Field Days
Rick Field
Chris Quigg
Giorgio Bellettini
Erice 1982
Keith Ellis
Keith Ellis
CDF Collaboration Meeting
June 8, 2006
Rick Field – Florida/CDF
Page 6
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
thatapart
we will
not duplicate too much of the
through each other andsofall
(i.e.
work of others who are similarly analyzing
no hard scattering). The outgoing
various models (e.g. constituent interchange
particles continue in roughly
the same
Parton-Parton
Scattering Outgoing Parton
model, multiperipheral
models,
etc.). We shall
direction as initial proton
and
assume that the high PT particles
arise from
“Soft” Collision
(no large transverse momentum)
antiproton.
direct hard collisions between constituent
in the incoming
particles, which
Hadron
 Occasionally there will bequarks
a large
Hadron
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”
CDF Collaboration Meeting
June 8, 2006
Rick Field – Florida/CDF
Page 7
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.
CDF Collaboration Meeting
June 8, 2006
Rick Field – Florida/CDF
Quark Fragmentation Functions
determined from e+e- annihilations
Page 8
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!
CDF Collaboration Meeting
June 8, 2006
Rick Field – Florida/CDF
Page 9
Telagram from Feynman
July 1976
SAW CRONIN AM NOW CONVINCED WERE RIGHT TRACK QUICK WRITE
FEYNMAN
CDF Collaboration Meeting
June 8, 2006
Rick Field – Florida/CDF
Page 10
Feynman Talk at Coral Gables
(December 1976)
1st transparency
Last transparency
“Feynman-Field
Jet Model”
CDF Collaboration Meeting
June 8, 2006
Rick Field – Florida/CDF
Page 11
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
CDF Collaboration Meeting
June 8, 2006
Rick Field – Florida/CDF
Page 12
High PT Jets
CDF (2006)
Feynman, Field, & Fox (1978)
Predict
large “jet”
cross-section
30 GeV/c!
Feynman quote
from FFF
600 GeV/c
Jets!
“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.”
CDF Collaboration Meeting
June 8, 2006
Rick Field – Florida/CDF
Page 13
A Parameterization of
the Properties of Jets
Secondary Mesons
(after decay)
continue
Field-Feynman 1978
 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
CDF Collaboration Meeting
June 8, 2006
 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
Page 14
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, ....”
CDF Collaboration Meeting
June 8, 2006
Rick Field – Florida/CDF
Page 15
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
CDF Collaboration Meeting
June 8, 2006
SHERPA
Rick Field – Florida/CDF
“FF” or “FW”
Fragmentation
PYTHIA
PYTHIA 6.3
Page 16
Monte-Carlo Simulation
of Quark and Gluon Jets
 ISAJET: Evolve the parton-shower from Q2 (virtual photon invariant mass) to Qmin ~ 5
GeV. Use a complicated fragmentation model to evolve from Qmin to outgoing hadrons.
Q2
 HERWIG: Evolve the parton-shower from Q2 (virtual
photon invariant mass) to Qmin ~ 1 GeV. Form color singlet
clusters which “decay” into hadrons according to 2-particle
phase space.
 MLLA: Evolve the parton-shower from Q2 (virtual
photon invariant mass) to Qmin ~ 230 MeV. Assume that
the charged particles behave the same as the partons
with Nchg/Nparton = 0.56!

hadrons
 
CDF Distribution of Particles in Jets
MLLA Curve!
Field-Feynman
5 GeV
1 GeV 200 MeV
CDF Collaboration Meeting
June 8, 2006
Rick Field – Florida/CDF
Page 17
QCD Monte-Carlo Models:
High Transverse Momentum Jets
Hard Scattering
Hard Scattering
Initial-State Radiation
“Jet”
Initial-State Radiation
Outgoing Parton
PT(hard)
Outgoing Parton
“Jet” PT(hard)
Proton
“Hard Scattering” Component
AntiProton
Underlying Event
Final-State Radiation
Underlying Event
Outgoing Parton
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!
CDF Collaboration Meeting
June 8, 2006
Rick Field – Florida/CDF
Page 18
Jet Algorithms
 Clustering algorithms are used to combine calorimeter towers or charged particles into “jets”
in order to study the event topology and to compare with the QCD Monte-Carlo Models.
 We do not detect partons! The outgoing partons fragment into hadrons before they travel a
distance of about the size of the proton. At long distances the partons manifest themselves as
“jets”. The “underlying event” can also form “jets”. Most “jets” are a mixture of particles
arising from the “hard” outgoing partons and the “underlying event”.
 Since we measure hadrons every observable is infrared and collinear safe. There are no
divergences at the hadron level!
 Every “jet” algorithms correspond to a
different observable and different
algorithms give different results.
 Studying the difference between the
algorithms teaches us about the event
structure.
CDF Collaboration Meeting
June 8, 2006
Rick Field – Florida/CDF
Page 19
Jet Corrections & Extrapolations
 Calorimeter Level Jets → Hadron Level Jets:
Hadron ← Parton
 We measure “jets” at the “hadron level” in the calorimeter.
 We certainly want to correct the “jets” for the detector resolution and
efficiency.
 Also, we must correct the “jets” for “pile-up”.
 Must correct what we measure back to the true “hadron level” (i.e.
particle level) observable!
 Particle Level Jets (with the “underlying event” removed):
Useless without a model
of hadronization!
Outgoing Parton
I do
believe
wemodel
shoulddependent
extrapolate
 Do we want
to not
make
further
corrections?
the data to the parton level! We should
 Do we want to try and subtract the “underlying event” from the
publish
what
we measure
(i.e. hadron level
observed
“particle
level”
jets.
with the “underlying event”)!
 This cannot really be done, but if you trust the Monte-Carlo
with event”
theory you
we should
modeling ofTo
thecompare
“underlying
can do it by using the
“extrapolate”
the
parton
level
to the
Monte-Carlo models (use PYTHIA Tune A).
(i.e. add hadronization
and
 This is nohadron
longerlevel
an observable,
it is a model dependent
the “underlying event” to the parton level)!
extrapolation!
HERWIG,
MC@NLO
 Hadron LevelPYTHIA,
Jets → Parton
Level
Jets:
PT(hard)
Initial-State Radiation
Proton
AntiProton
Underlying Event
Outgoing Parton
Underlying Event
Final-State
Radiation
CDF Collaboration Meeting
June 8, 2006
 Do we want to use the data to try and extrapolate back to the
parton level? What parton level, PYTHIA (Leading Log) or fixed
order NLO?
Next-to-leading
order
 This
also cannot
really be done, but again if you trust the Monteparton
level
calculation
Carlo models you can try and do it by using the Monte-Carlo
0, 1, 2, or 3 partons!
models
(use PYTHIA Tune A) including ISR and FSR.
 Cannot extrapolate the data to fixed order NLO!
Rick Field – Florida/CDF
Page 20
Good and Bad Algorithms
Calorimeter Jet
Particle
Jet
 In order to correct what we see in the calorimeter back
to the hadron level we must use an algorithm that can
be defined at both the calorimeter and particle level.
 If you insist on extrapolating the data to the parton
level then it is better to use an algorithm that is well
defined at the parton level (i.e. infrared and collinear
safe at the parton level).
 If you hadronize the parton level and add the
“underlying event” (i.e. PYTHIA, HERWIG,
MC@NLO) then you do not care if the algorithm is
infrared and collinear safe at the parton level. You
can predict any hadron level observable!
CDF Collaboration Meeting
June 8, 2006
Rick Field – Florida/CDF
Infrared Safety (Parton Level)
Soft parton emission changes jet multiplicity
Collinear Safety (Parton Level)
below threshold
(no jets)
above threshold
(1 jet)
Page 21
Four Jet Algorithms
Towers not included in a
jet (i.e. “dark towers”)!
Bad
 JetClu is bad because the algorithm cannot be defined at the particle level.
 The MidPoint and Modified MidPoint (i.e. Search Cone) algorithms are not infrared and
collinear safe at the parton level.
CDF Collaboration Meeting
June 8, 2006
Rick Field – Florida/CDF
Page 22
KT Algorithm
 kT Algorithm:
Begin







For each precluster, calculate
di  pT2,i
For each pair of preculsters, calculate
( y  y j ) 2  (i   j ) 2
dij  min( pT2 ,i , pT2 , j ) i
D2
Find the minimum of all di and dij.
Merge
i and j
yes
Minumum
is dij?
Cluster together calorimeter towers by their kT proximity.
Infrared and collinear safe at all orders of pQCD.
No splitting and merging.
No ad hoc Rsep parameter necessary to compare with parton level.
Every parton, particle, or tower is assigned to a “jet”.
No biases from seed towers.
Favored algorithm in e+e- annihilations!
no
Will the KT algorithm be
effective in the collider
environment where there is
an “underlying event”?
Move i to list of jets
yes
Any
Preclusters
left?
Raw Jet ET = 533 GeV
KT Algorithm
Raw Jet ET = 618 GeV
no
End
Outgoing Parton
PT(hard)
Initial-State Radiation
Proton
AntiProton
Underlying Event
Underlying Event
CDF Run 2
Outgoing Parton
Final-State
Radiation
CDF Collaboration Meeting
June 8, 2006
Only towers with ET > 0.5 GeV are shown
Rick Field – Florida/CDF
Page 23
KT Inclusive Jet Cross Section





KT Algorithm (D = 0.7)
Data corrected to the hadron level
L = 385 pb-1
0.1 < |yjet| < 0.7
Compared with NLO QCD (JetRad)
corrected to the hadron level.
Sensitive to UE + hadronization
effects for PT < 300 GeV/c!
CDF Collaboration Meeting
June 8, 2006
Rick Field – Florida/CDF
Page 24
Search Cone
Inclusive Jet Cross Section
 Modified MidPoint Cone
Algorithm (R = 0.7, fmerge = 0.75)
 Data corrected to the hadron level
and the parton level
 L = 1.04 fb-1
 0.1 < |yjet| < 0.7
 Compared with NLO QCD
(JetRad, Rsep = 1.3)
Sensitive to UE + hadronization
effects for PT < 200 GeV/c!
CDF Collaboration Meeting
June 8, 2006
Rick Field – Florida/CDF
Page 25
Hadronization and
“Underlying Event” Corrections
 Compare the hadronization and “underlying event” corrections for the KT algorithm (D = 0.7)
and the MidPoint algorithm (R = 0.7)!
 We see that the KT algorithm (D = 0.7) is slightly more sensitive to the underlying event than
the cone algorithm (R = 0.7), but with a good model of the “underlying event” both cross
sections can be measured at the Tevatrun!
Note that DØ does not make any
corrections for hadronization
or the “underlying event”!?
MidPoint Cone Algorithm (R = 0.7)
The KT algorithm is slightly more
sensitive to the “underlying event”!
CDF Collaboration Meeting
June 8, 2006
Rick Field – Florida/CDF
Page 26
KT Inclusive Jet Cross Section
 KT Algorithm (D = 0.7).
 Data corrected to the hadron
level.
 L = 385 pb-1.
 Five rapidity regions:
 |yjet| < 0.1




0.1 < |yjet| < 0.7
0.7 < |yjet| < 1.1
1.1 < |yjet| < 1.6
1.6 < |yjet| < 2.1
 Compared with NLO QCD
(JetRad) with CTEQ6.1
Excellent agreement over
all rapidity ranges!
CDF Collaboration Meeting
June 8, 2006
Rick Field – Florida/CDF
Page 27
The “Transverse” Regions
as defined by the Leading Jet
Jet #1 Direction
“Transverse” region is
very sensitive to the
“underlying event”!
Charged Particle  Correlations
pT > 0.5 GeV/c |h| < 1
2p
Look at the charged
particle density in the
“transverse” region!
Away Region
“Toward-Side” Jet
Jet #1 Direction

“Toward”
“Transverse”
“Transverse”
“Away”
Transverse
Region 1

“Toward”
“Trans 1”

Leading
Jet
“Trans 2”
Toward Region
Transverse
Region 2
“Away”
Away Region
“Away-Side” Jet
0
-1
h
+1
 Look at charged particle correlations in the azimuthal angle relative to the leading

calorimeter jet (JetClu R = 0.7, |h| < 2).
o
o
o
o
o
Define || < 60 as “Toward”, 60 < - < 120 and 60 <  < 120 as “Transverse 1” and
o
“Transverse 2”, and || > 120 as “Away”. Each of the two “transverse” regions have
o
area h = 2x60 = 4p/6. The overall “transverse” region is the sum of the two
o
transverse regions (h = 2x120 = 4p/3).
CDF Collaboration Meeting
June 8, 2006
Rick Field – Florida/CDF
Page 28
Run 1 PYTHIA Tune A
CDF Default!
PYTHIA 6.206 CTEQ5L
"Transverse" Charged Particle Density: dN/dhd
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
PARP(86)
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)
CDF Collaboration Meeting
June 8, 2006
1.00
"Transverse" Charged Density
Parameter
CDF Preliminary
PYTHIA 6.206 (Set A)
PARP(67)=4
data uncorrected
theory corrected
0.75
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
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
Page 29
Charged Particle Density  Dependence
Refer to this as a
“Leading Jet” event
Jet #1 Direction
Charged
Particle Density:
Density: dN/dhd
dN/dhd
Charged Particle

10.0
10.0
Subset
“Transverse”
“Transverse”
“Away”
Refer to this as a
“Back-to-Back” event
Jet #1 Direction

“Toward”
“Transverse”
“Transverse”
Charged Particle
Particle Density
Density
Charged
“Toward”
CDF
CDF Preliminary
Preliminary
30 << ET(jet#1)
ET(jet#1) << 70
70 GeV
GeV
30
Back-to-Back
data
data uncorrected
uncorrected
Leading Jet
Min-Bias
"Transverse"
"Transverse"
Region
Region
1.0
1.0
Jet#1
Jet#1
Charged
Charged Particles
Particles
(|h|<1.0,
(|h|<1.0, PT>0.5
PT>0.5 GeV/c)
GeV/c)
0.1
0.1
00
30
30
60
60
90
“Away”
120
150
180
210
210
240
240
270
270
300
300
330
330
360
360
 (degrees)
Jet #2 Direction
 Look at the “transverse” region as defined by the leading jet (JetClu R = 0.7, |h| < 2) or by the
leading two jets (JetClu R = 0.7, |h| < 2). “Back-to-Back” events are selected to have at least
two jets with Jet#1 and Jet#2 nearly “back-to-back” (12 > 150o) with almost equal
transverse energies (ET(jet#2)/ET(jet#1) > 0.8) and with ET(jet#3) < 15 GeV.
 Shows the  dependence of the charged particle density, dNchg/dhd, for charged
particles in the range pT > 0.5 GeV/c and |h| < 1 relative to jet#1 (rotated to 270o) for 30
< ET(jet#1) < 70 GeV for “Leading Jet” and “Back-to-Back” events.
CDF Collaboration Meeting
June 8, 2006
Rick Field – Florida/CDF
Page 30
“Transverse” PTsum Density vs ET(jet#1)
Jet #1 Direction

“Toward”
“Transverse”
“Transverse”
“Away”
“Back-to-Back”
Jet #1 Direction

“Toward”
“Transverse”
"AVE Transverse" PTsum Density: dPT/dhd
1.4
“Transverse”
"Transverse" PTsum Density (GeV/c)
“Leading Jet”
uncorrected
datadata
uncorrected
theory + CDFSIM
PY Tune A
1.0
Hard Radiation!
0.8
0.6
0.4
Back-to-Back
HW
0.2
1.96 TeV
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
0.0
0
50
“Away”
Jet #2 Direction
Leading Jet
CDF Run
2 Preliminary
Preliminary
1.2
100
150
200
250
ET(jet#1) (GeV)
Min-Bias
0.24 GeV/c per unit h-
 Shows the average charged PTsum density, dPTsum/dhd, in the “transverse” region (pT
> 0.5 GeV/c, |h| < 1) versus ET(jet#1) for “Leading Jet” and “Back-to-Back” events.
 Compares the (uncorrected) data with PYTHIA Tune A and HERWIG (without MPI)
after CDFSIM.
CDF Collaboration Meeting
June 8, 2006
Rick Field – Florida/CDF
Page 31
“TransMAX/MIN” PTsum Density
PYTHIA Tune A vs HERWIG
Jet #1 Direction
“TransMAX”
“TransMIN”
“Away”
3.0


“Toward”
"TransMAX" Charged PTsum Density: dPT/dhd
Jet #1 Direction
"Transverse" PTsum Density (GeV/c)
“Leading Jet”
PYTHIA Tune A does a fairly
good job fitting the PTsum
density in the “transverse”
region!
“Back-to-Back”
HERWIG does a poor job!
“Toward”
“TransMAX”
“TransMIN”
“Away”
Jet #2 Direction
CDF Run 2 Preliminary
data corrected to particle level
2.5
"Leading Jet"
1.96 TeV
2.0
PY Tune A
1.5
"Back-to-Back"
1.0
MidPoint R = 0.7 |h(jet#1) < 2
0.5
HW
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
0.0
0
50
100
150
CDF Collaboration Meeting
June 8, 2006
300
350
400
450
"TransMIN" Charged PTsum Density: dPT/dhd
0.6
"Transverse" PTsum Density (GeV/c)

250
PT(jet#1) (GeV/c)
 Shows the charged particle PTsum
density, dPTsum/dhd, in the
“transMAX” and “transMIN”
region (pT > 0.5 GeV/c, |h| < 1)
versus PT(jet#1) for “Leading Jet”
and “Back-to-Back” events.
Compares the (corrected) data with
PYTHIA Tune A (with MPI) and
HERWIG (without MPI) at the
particle level.
200
CDF Run 2 Preliminary
MidPoint R = 0.7 |h(jet#1) < 2
data corrected to particle level
0.5
1.96 TeV
"Leading Jet"
0.4
0.3
"Back-to-Back"
0.2
0.1
PY Tune A
HW
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
0.0
0
50
Rick Field – Florida/CDF
100
150
200
250
300
350
400
450
PT(jet#1) (GeV/c)
Page 32
“TransMAX/MIN” ETsum Density
PYTHIA Tune A vs HERWIG
“Back-to-Back”
Jet #1 Direction
Jet #1 Direction


“Toward”
“TransMAX”
“TransMIN”
“Away”
"TransMAX" ETsum Density: dET/dhd
7.0
“Toward”
Neither PY Tune A or
“TransMIN”
HERWIG
fits the
ETsum density in the
“Away”
“transferse” region!
HERWIG does slightly
than Tune A!
Jet better
#2 Direction
“TransMAX”
"Transverse" ETsum Density (GeV)
“Leading Jet”
CDF Run 2 Preliminary
6.0
"Leading Jet"
1.96 TeV
5.0
4.0
3.0
HW
"Back-to-Back"
2.0
1.0
PY Tune A
MidPoint R = 0.7 |h(jet#1) < 2
Particles (|h|<1.0, all PT)
0.0
 Shows the data on the tower ETsum
0
50
100
150
200
250
300
350
400
450
PT(jet#1) (GeV/c)
density, dETsum/dhd, in the
“transMAX” and “transMIN” region (ET
> 100 MeV, |h| < 1) versus PT(jet#1) for
“Leading Jet” and “Back-to-Back”
events.
Compares the (corrected) data with
PYTHIA Tune A (with MPI) and
HERWIG (without MPI) at the particle
level (all particles, |h| < 1).
"TransMIN" ETsum Density: dET/dhd
3.0
"Transverse" ETsum Density (GeV)

data corrected to particle level
CDF Run 2 Preliminary
MidPoint R = 0.7 |h(jet#1) < 2
data corrected to particle level
2.5
Particles (|h|<1.0, all PT)
1.96 TeV
2.0
HW
"Leading Jet"
1.5
1.0
0.5
"Back-to-Back"
PY Tune A
0.0
0
50
100
150
200
250
300
350
400
450
PT(jet#1) (GeV/c)
CDF Collaboration Meeting
June 8, 2006
Rick Field – Florida/CDF
Page 33
“TransDIF” ETsum Density
PYTHIA Tune A vs HERWIG
“Leading Jet”
Jet #1 Direction

"TransDIF" ETsum Density: dET/dhd
“Toward”
Jet #1 Direction

“TransMIN”
“Away”
“Toward”
“TransMAX”
“TransMIN”
“Away”
Jet #2 Direction
“Back-to-Back”
"Transverse" ETsum Density (GeV)
“TransMAX”
5.0
CDF Run 2 Preliminary
data corrected to particle level
4.0
"Leading Jet"
1.96 TeV
3.0
PY Tune A
2.0
HW
"Back-to-Back"
1.0
MidPoint R = 0.7 |h(jet#1) < 2
Particles (|h|<1.0, all PT)
0.0
“transDIF” is more sensitive to
the “hard scattering” component
of the “underlying event”!
0
50
100
150
200
250
300
350
400
450
PT(jet#1) (GeV/c)
 Use the leading jet to define the MAX and MIN “transverse” regions on an event-byevent basis with MAX (MIN) having the largest (smallest) charged PTsum density.
 Shows the “transDIF” = MAX-MIN ETsum density, dETsum/dhd, for all particles (|h| <
1) versus PT(jet#1) for “Leading Jet” and “Back-to-Back” events.
CDF Collaboration Meeting
June 8, 2006
Rick Field – Florida/CDF
Page 34
Possible Scenario??
 PYTHIA Tune A fits the charged particle
"Transverse" pT Distribution: dN/dpT
1.0E+01
"Transverse" PT Distribution
Sharp Rise at
Low PT?
PTsum density for pT > 0.5 GeV/c, but it
does not produce enough ETsum for
towers with ET > 0.1 GeV.
Possible Scenario??
But I cannot get any
of the Monte-Carlo to
do this perfectly!
1.0E+00
1.0E-01
 It is possible that there is a sharp rise in
Multiple
Parton
Interactions
the number of particles in the “underlying
event” at low pT (i.e. pT < 0.5 GeV/c).
1.0E-02
Beam-Beam
Remnants
1.0E-03
 Perhaps there are two components, a vary
1.0E-04
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
pT All Particles (GeV/c)
CDF Collaboration Meeting
June 8, 2006
4.0
4.5
5.0
“soft” beam-beam remnant component
(gaussian or exponential) and a “hard”
multiple interaction component.
Rick Field – Florida/CDF
Page 35
QCD Monte-Carlo Models:
Lepton-Pair Production
Lepton-Pair Production
Anti-Lepton
Initial-State Radiation
Lepton-Pair Production
Initial-State Radiation
Anti-Lepton
“Hard Scattering” Component
“Jet”
Proton
AntiProton
Lepton
Underlying Event
Underlying Event
Proton
Lepton
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 and final-state radiation.
CDF Collaboration Meeting
June 8, 2006
Rick Field – Florida/CDF
Page 39
The “Central” Region
in Drell-Yan Production
Look at the charged
particle density and the
PTsum density in the
“central” region!
Charged Particles (pT > 0.5 GeV/c, |h| < 1)
Drell-Yan Production
Lepton
2p
Proton
AntiProton
Underlying Event
Underlying Event
Initial-State
Radiation

Central Region
Anti-Lepton
Multiple Parton Interactions
Proton
Lepton
AntiProton
Underlying Event
0
Underlying Event
Anti-Lepton
-1
After removing the leptonpair everything else is the
“underlying event”!
h
+1
 Look at the “central” region after removing the lepton-pair.
 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, by
dividing by the area in h- space.
CDF Collaboration Meeting
June 8, 2006
Rick Field – Florida/CDF
Page 40
CDF Run 1 PT(Z)
PYTHIA 6.2 CTEQ5L
Parameter
Tune A
Tune A25
s = 1.0
Tune A50
MSTP(81)
1
1
1
MSTP(82)
4
4
4
PARP(82)
2.0 GeV
2.0 GeV
2.0 GeV
PARP(83)
0.5
0.5
0.5
PARP(84)
0.4
0.4
0.4
PARP(85)
0.9
0.9
0.9
PARP(86)
0.95
0.95
0.95
1.8 TeV
1.8 TeV
1.8 TeV
PARP(90)
0.25
0.25
0.25
PARP(67)
4.0
4.0
4.0
MSTP(91)
1
1
1
PARP(91)
1.0
2.5
5.0
PARP(93)
5.0
15.0
25.0
CDF Run 1 Data
PYTHIA Tune A
PYTHIA Tune A25
PYTHIA Tune A50
s = 2.5
0.08
CDF Run 1
published
1.8 TeV
s = 5.0
Normalized to 1
0.04
0.00
0
ISR Parameter PARP(89)
Z-Boson Transverse Momentum
0.12
PT Distribution 1/N dN/dPT
UE Parameters
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), Tune A25
(<pT(Z)> = 10.1 GeV/c), and
Tune A50
(<pT(Z)> = 11.2 GeV/c).
Vary the intrensic KT!
Intrensic KT
CDF Collaboration Meeting
June 8, 2006
20
Rick Field – Florida/CDF
Page 41
CDF Run 1 PT(Z)
PYTHIA 6.2 CTEQ5L
Tune used by the
CDF-EWK group!
Z-Boson Transverse Momentum
UE Parameters
ISR Parameters
Parameter
Tune A
Tune AW
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
PT Distribution 1/N dN/dPT
0.12
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)!
CDF Collaboration Meeting
June 8, 2006
20
Rick Field – Florida/CDF
Page 42
Jet-Jet Correlations (DØ)
Jet#1-Jet#2  Distribution
 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).
CDF Collaboration Meeting
June 8, 2006
Rick Field – Florida/CDF
Page 43
CDF Run 1 PT(Z)
PYTHIA 6.2 CTEQ5L
Z-Boson Transverse Momentum
UE Parameters
ISR Parameters
Parameter
Tune DW
Tune AW
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
PT Distribution 1/N dN/dPT
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!
CDF Collaboration Meeting
June 8, 2006
Rick Field – Florida/CDF
Page 44
“Transverse” Nchg Density
Parameter
Intrensic KT
Tune AW
Tune DW
"Transverse" Charged
Charged Particle
Particle Density:
Density: dN/dhd
dN/dhd
"Transverse"
Tune BW
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)
ISR Parameter
Three different amounts of MPI!
PYTHIA 6.2 CTEQ5L
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
1.0
MSTP(91)
1
1
1
PARP(91)
2.5
2.5
2/5
PARP(93)
15.0
15.0
15.0
Three different amounts of ISR!
CDF Collaboration Meeting
June 8, 2006
1.0
1.0
"Transverse"
"Transverse"Charged
ChargedDensity
Density
UE Parameters
RDF Preliminary
Preliminary
RDF
PY Tune BW
generator level
level
generator
0.8
0.8
PYPY
Tune
DW
Tune
DW
PY-ATLAS
PY Tune A
0.6
0.6
0.4
0.4
PY Tune AW
HERWIG
HERWIG
1.96 TeV
TeV
1.96
0.2
0.2
Leading Jet
Jet (|h|<2.0)
(|h|<2.0)
Leading
Charged Particles
Particles (|h|<1.0,
(|h|<1.0, PT>0.5
PT>0.5 GeV/c)
GeV/c)
Charged
0.0
0.0
00
50
50
100
100
150
150
200
200
250
250
300
300
350
350
400
400
450
450
500
500
PT(particle jet#1)
jet#1) (GeV/c)
(GeV/c)
PT(particle
 Shows the “transverse” charged particle
density, dN/dhd, versus PT(jet#1) for “leading
jet” events at 1.96 TeV for PYTHIA Tune A,
Tune AW, Tune DW, Tune BW, and HERWIG
(without MPI).
 Shows the “transverse” charged particle
density, dN/dhd, versus PT(jet#1) for “leading
jet” events at 1.96 TeV for Tune DW, ATLAS,
and HERWIG (without MPI).
Rick Field – Florida/CDF
Page 45
“Transverse” PTsum Density
ISR Parameter
Intrensic KT
Three different amounts of MPI!
PYTHIA 6.2 CTEQ5L
"Transverse" PTsum Density: dPT/dhd
Parameter
Tune AW
Tune DW
Tune BW
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
1.0
MSTP(91)
1
1
1
PARP(91)
2.5
2.5
2/5
PARP(93)
15.0
15.0
15.0
Three different amounts of ISR!
CDF Collaboration Meeting
June 8, 2006
"Transverse" PTsum
PTsum Density
Density (GeV/c)
(GeV/c)
"Transverse"
UE Parameters
1.6
RDF Preliminary
generator level
1.2
PY Tune BW
PY Tune A
PY-ATLAS
0.8
PY Tune AW
PY Tune DW
1.96 TeV
0.4
HERWIG
Leading Jet (|h|<2.0)
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
HERWIG
0.0
0
50
100
150
200
250
300
350
400
450
PT(particle jet#1) (GeV/c)
 Shows the “transverse” charged PTsum
density, dPT/dhd, versus PT(jet#1) for
“leading jet” events at 1.96 TeV for PYTHIA
Tune A, Tune AW, Tune DW, Tune BW, and
HERWIG (without MPI).
 Shows the “transverse” charged PTsum
density, dPT/dhd, versus PT(jet#1) for
“leading jet” events at 1.96 TeV for Tune DW,
ATLAS, and HERWIG (without MPI).
Rick Field – Florida/CDF
Page 46
500
MIT Search Scheme 12
Exclusive 3 Jet Final State Challenge
At least 1 Jet (“trigger” jet)
(PT > 40 GeV/c, |h| < 1.0)
CDF Data
Normalized to 1
PYTHIA
Tune A
Exactly 3 jets
(PT > 20 GeV/c, |h| < 2.5)
R(j2,j3)
Order Jets by PT
Jet1 highest PT, etc.
Bruce Knuteson
Khaldoun
Makhoul
Georgios
Choudalakis
CDF Collaboration Meeting
June 8, 2006
Markus
Klute
Conor
Henderson
Rick Field – Florida/CDF
Ray
Culbertson
Gene
Flanagan
Page 47
3Jexc R(j2,j3) Normalized
The data have more
3 jet events with
small R(j2,j3)!?
 Let Ntrig40 equal the number of events
Exclusive 3-Jet Production: R(j2,j3)
with at least one jet with PT > 40 geV and
|h| < 1.0 (this is the “offline” trigger).
0.16
 Let N3Jexc20 equal the number of events
0.12
with exactly three jets with PT > 20 GeV/c
and |h| < 2.5 which also have at least one
jet with PT > 40 GeV/c and |h| < 1.0.
 Let N3JexcFr = N3Jexc20/Ntrig40. The is
the fraction of the “offline” trigger events
that are exclusive 3-jet events.
Initial-State Radiation
0.08
Normalized to
N3JexcFr
0.04
0.00
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
Underlying Event
 PARP(67) affects the initial-state radiation which
contributes primarily to the region R(j2,j3) > 1.0.
“Jet 3”
Outgoing Parton
Initial-State Radiation
“Jet 2”
R > 1.0
CDF Collaboration Meeting
June 8, 2006
5.0
R(j2,j3)
with PYTHIA Tune AW (PARP(67)=4), Tune DW
(PARP(67)=2.5), Tune BW (PARP(67)=1).
AntiProton
Underlying Event
Data R(j2,j3)
pyAW
pyDW
pyBW
data uncorrected
generator level theory
 The CDF data on dN/dR(j2,j3) at 1.96 TeV compared
Outgoing Parton
“Jet 1”
Proton
dN/dR(j2,j3)
CDF Run 2 Preliminary
Rick Field – Florida/CDF
Page 48
3Jexc R(j2,j3) Normalized
 Let Ntrig40 equal the number of events
Exclusive
Exclusive 3-Jet
3-Jet Production:
Production: R(j2,j3)
R(j2,j3)
0.16
0.80
0.16
with at least one jet with PT > 40 geV and
|h| < 1.0 (this is the “offline” trigger).
0.12
0.60
0.12
dN/dR(j2,j3)
dN/dR(j2,j3)
dN/dR(j2,j3)
 Let N3Jexc20 equal the number of events
CDF Run
Run 22 Preliminary
Preliminary
CDF
with exactly three jets with PT > 20 GeV/c
0.08
0.40
0.08
I do not understand
the
and |h| < 2.5 which also have at least one
excess number
of events
0.04
jet with PT > 40 GeV/c and |h| < 1.0.
0.20
0.04
data
uncorrected
datauncorrected
uncorrected
data
generator
level
theory
generatorlevel
leveltheory
theory
generator
CDF Data
Data
Data R(j2,j3)
R(j2,j3)
hw05
pyDW
pyDW
pyDW
pyDWnoFSR
hw05
pyBW
Normalized to
N3JexcFr
with R(j2,j3) < 1.0.
Normalized to 1
 Let N3JexcFr = N3Jexc20/Ntrig40.
The is this0.00
Perhaps
is
related
to the
0.00
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
the fraction of the “offline” trigger“soft
eventsenergy”
0.0 problem??
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
R(j2,j3)
R(j2,j3)
that are exclusive 3-jet events.
For now the best tune is
 The Tune
CDF data
PYTHIA
DW.on dN/dR(j2,j3) at 1.96 TeV compared
Final-State Radiation
Outgoing Parton
“Jet 1”
with PYTHIA Tune DW (PARP(67)=2.5) and
HERWIG (without MPI).
Proton
AntiProton
Underlying Event
Underlying Event
Outgoing Parton
Final-State Radiation
“Jet “Jet
2” 3”
R < 1.0
CDF Collaboration Meeting
June 8, 2006
 Final-State radiation contributes to the region R(j2,j3)
< 1.0.
 If you ignore the normalization and normalize all the
distributions to one then the data prefer Tune BW, but
I believe this is misleading.
Rick Field – Florida/CDF
Page 49
Drell-Yan Production (Run 2 vs LHC)
Drell-Yan Production
Proton
<pT(m+m-)> is much
larger at the LHC!
Lepton-Pair Transverse
Momentum
Lepton
AntiProton
Underlying Event
Underlying Event
Shapes of the pT(m+m-)
distribution at the Z-boson mass.
Initial-State
Radiation
Anti-Lepton
Lepton-Pair Transverse Momentum
Drell-Yan PT(m+m-) Distribution
80
0.10
Drell-Yan
Drell-Yan
LHC
60
1/N dN/dPT (1/GeV)
Average Pair PT
generator level
40
Tevatron Run 2
20
0
0.08
PY Tune DW (solid)
HERWIG (dashed)
0.06
70 < M(m-pair) < 110 GeV
|h(m-pair)| < 6
0.04
0.02
PY Tune DW (solid)
HERWIG (dashed)
Z
generator level
Tevatron Run2
LHC
Normalized to 1
0.00
0
100
200
300
400
500
600
700
800
900
1000
0
5
Lepton-Pair Invariant Mass (GeV)
10
15
20
25
30
35
40
PT(m+m-) (GeV/c)
 Average Lepton-Pair transverse momentum  Shape of the Lepton-Pair pT distribution at the
Z-boson mass at the Tevatron and the LHC for
at the Tevatron and the LHC for PYTHIA
PYTHIA Tune DW and HERWIG (without MPI).
Tune DW and HERWIG (without MPI).
CDF Collaboration Meeting
June 8, 2006
Rick Field – Florida/CDF
Page 50
The “Underlying Event” in
Drell-Yan Production
Drell-Yan Production
The “Underlying Event”
Lepton
Proton
HERWIG (without MPI)
is much less active than
PY Tune AW (with MPI)!
Underlying Event
Charged particle density
versus M(pair)
AntiProton
Underlying Event
“Underlying event” much
more active at the LHC!
Initial-State
Radiation
Anti-Lepton
Charged Particle Density: dN/dhd
Charged Particle Density: dN/dhd
1.5
1.0
RDF Preliminary
generator level
PY Tune AW
0.8
0.6
0.4
HERWIG
0.2
Drell-Yan
1.96 TeV
Z
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
(excluding lepton-pair )
Charged Particle Density
Charged Particle Density
RDF Preliminary
generator level
Z
LHC
1.0
PY Tune AW
CDF
0.5
Drell-Yan
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
(excluding lepton-pair )
HERWIG
0.0
0.0
0
50
100
150
200
250
0
50
100
150
200
250
Lepton-Pair Invariant Mass (GeV)
Lepton-Pair Invariant Mass (GeV)
 Charged particle density versus the lepton-  Charged particle density versus the lepton-pair
invariant mass at 14 TeV for PYTHIA Tune AW
pair invariant mass at 1.96 TeV for PYTHIA
and HERWIG (without MPI).
Tune AW and HERWIG (without MPI).
CDF Collaboration Meeting
June 8, 2006
Rick Field – Florida/CDF
Page 51
Extrapolations to the LHC:
Drell-Yan Production
Drell-Yan Production
Charged particle density
versus M(pair)
Lepton
The “Underlying Event”
Proton
AntiProton
Underlying Event
Tune DW and DWT are
identical at 1.96 TeV, but
have different MPI energy
dependence!
Underlying Event
Initial-State
Radiation
Anti-Lepton
Charged Particle Density: dN/dhd
Charged Particle Density: dN/dhd
2.5
1.0
Charged Particle Density
PY Tune BW
generator level
PY Tune DW
0.8
0.6
0.4
PY Tune A
PY Tune AW
1.96 TeV
0.2
HERWIG
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
(excluding lepton-pair )
Z
50
100
generator level
PY-ATLAS
PY Tune DWT
2.0
1.5
PY Tune DW
1.0
14 TeV
0.5
Z
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
(excluding lepton-pair )
HERWIG
0.0
0.0
0
Charged Particle Density
RDF Preliminary
RDF Preliminary
150
200
250
300
350
400
450
500
0
100
200
300
400
500
600
700
800
900
1000
Lepton-Pair Invariant Mass (GeV)
Lepton-Pair Invariant Mass (GeV)
 Average charged particle density versus the  Average charged particle density versus the
lepton-pair invariant mass at 1.96 TeV for
lepton-pair invariant mass at 14 TeV for
PYTHIA Tune A, Tune AW, Tune BW, Tune
PYTHIA Tune DW, Tune DWT, ATLAS and
DW and HERWIG (without MPI).
HERWIG (without MPI).
CDF Collaboration Meeting
June 8, 2006
Rick Field – Florida/CDF
Page 52
Extrapolations to the LHC:
Drell-Yan Production
Drell-Yan Production
The “Underlying Event”
Charged particle charged
PTsum density versus M(pair)
Lepton
Proton
AntiProton
Underlying Event
The ATLAS tune has a much “softer”
distribution of charged particles than
the CDF Run 2 Tunes!
Underlying Event
Initial-State
Radiation
Anti-Lepton
Charged PTsum Density: dPT/dhd
Charged PTsum Density: dPT/dhd
RDF Preliminary
5.0
PY Tune BW
generator level
0.9
PY Tune A
0.6
PY Tune AW
PY Tune DW
1.96 TeV
0.3
Charged Particles (|h|<1.0, PT>0.9 GeV/c)
(excluding lepton-pair )
HERWIG
Z
0.0
0
50
100
Charged PTsum Density (GeV/c)
Charged PTsum Density (GeV/c)
1.2
RDF Preliminary
PY Tune DWT
generator level
PY Tune DW
4.0
PY-ATLAS
3.0
2.0
14 TeV
1.0
Leading Jet (|h|<2.0)
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
HERWIG
Z
0.0
150
200
250
300
350
400
450
500
0
100
200
300
400
500
600
700
800
900
1000
Lepton-Pair Invariant Mass (GeV)
Lepton-Pair Invariant Mass (GeV)
 Average charged PTsum density versus the  Average charged PTsum density versus the
lepton-pair invariant mass at 14 TeV for PYTHIA
lepton-pair invariant mass at 1.96 TeV for
Tune DW, Tune DWT, ATLAS and HERWIG
PYTHIA Tune A, Tune AW, Tune BW, Tune
(without MPI).
DW and HERWIG (without MPI).
CDF Collaboration Meeting
June 8, 2006
Rick Field – Florida/CDF
Page 53
Extrapolations to the LHC:
Drell-Yan Production
The “Underlying Event”
Charged Particles
(|h|<1.0, pT > 0.5 GeV/c)
Drell-Yan Production
Charged particle density
versus M(pair)
Lepton
The ATLAS tune has a much “softer”
distribution of charged particles than
the CDF Run 2 AntiProton
Tunes!
Proton
Underlying Event
Underlying Event
Charged Particles
(|h|<1.0, pT > 0.9 GeV/c)
Initial-State
Radiation
Anti-Lepton
Charged Particle Density: dN/dhd
Charged Particle Density: dN/dhd
Drell-Yan
PY Tune DWT
Generator Level
14 TeV
Charged Particle
4.0 Density: dN/dhd
PY-ATLAS
generator level
2.0
1.5
1.0
0.5
Z
HERWIG
100
200
0.0
0
Charged Particle Density
Charged Particle Density
RDF Preliminary
300
1.2
PY-ATLAS
PY Tune DWT
3.0
PY Tune DW
PY Tune DW
2.0
14 TeV
1.0
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
(excluding lepton-pair )
Charged Particle Density
2.5
0.8
Charged Particles (pT > min, |h|<1.0)
(excluding lepton-pair
PY Tune DW )
0.4
PY-ATLAS
70 < M(m+m-) < 110 GeV
Z
Generator Level
14 TeV
HERWIG
Charged Particles (|h|<1.0, PT>0.9 GeV/c)
(excluding lepton-pair )
0.0
400
500
600
HERWIG
700
800
900
1000
0
100
200
300
400
500
600
700
800
900
1000
Lepton-Pair Invariant Mass (GeV)
Lepton-Pair Invariant Mass (GeV)
0.0
particle
0.0
0.2
0.4(pT >0.60.5 0.8  Average
1.0
1.2charged
1.4
1.6
1.8density (pT > 0.9 GeV/c)
 Average charged particle
density
the lepton-pair invariant mass at 14 TeV
GeV/c) versus the lepton-pair invariantMinimum
mass pversus
T (GeV/c)
at 14 TeV for PYTHIA Tune DW, Tune DWT, for PYTHIA Tune DW, Tune DWT, ATLAS and
HERWIG (without MPI).
ATLAS and HERWIG (without MPI).
CDF Collaboration Meeting
June 8, 2006
Rick Field – Florida/CDF
Page 54
Constraining the Higgs Mass
 Top quark mass is a fundamental
parameter of SM.
 Radiative corrections to SM
predictions dominated by top
mass.
 Top mass together with W mass
places a constraint on Higgs
mass!
Tevatron Run I + LEP2
Summer 05
Spring 2006
Light Higgs very interesting for the
Tevatron!
CDF Collaboration Meeting
June 8, 2006
Rick Field – Florida/CDF
Page 55
20 Years of Measuring W & Z
CDF Collaboration Meeting
June 8, 2006
Rick Field – Florida/CDF
Page 56
The W+W Cross Section
Campbell & Ellis 1999
pb-1
CDF (pb)
NLO (pb)
s(WW) CDF
184
14.6+5.8(stat)-5.1(stat)1.8(sys)0.9(lum)
12.40.8
s(WW) DØ
240
13.8+4.3(stat)-3.8(stat)1.2(sys)0.9(lum)
12.40.8
CDF Collaboration Meeting
June 8, 2006
Rick Field – Florida/CDF
Page 57
The W+W Cross Section





WW→dileptons + MET
Two leptons pT > 20 GeV/c.
Z veto.
MET > 20 GeV.
Zero jets with ET>15 GeV
and |h|<2.5.
Observe 95 events with
We are beginning to study the details of37.2 background!
Di-Boson production at the Tevatron!
s(WW)
L
CDF (pb)
NLO (pb)
825 pb-1
13.72.3(stat)1.6(sys)1.2(lum)
12.40.8
Missing ET!
CDF Collaboration Meeting
June 8, 2006
Lepton-Pair Mass!
Rick Field – Florida/CDF
ET Sum!
Page 58
Di-Bosons at the Tevatron
W
We are getting closer to
the Higgs!
Z
W+
Z+
W+W
W+Z
CDF Collaboration Meeting
June 8, 2006
Rick Field – Florida/CDF
Page 59
The Z→tt Cross Section
 Taus are difficult to reconstruct at hadron colliders
• Exploit event topology to suppress backgrounds (QCD & W+jet).
• Measurement of cross section important for Higgs and SUSY analyses.
Signal
cone
 CDF strategy of hadronic τ reconstruction:
• Study charged tracks define signal and isolation cone (isolation = require no
tracks in isolation cone).
• Use hadronic calorimeter clusters (to suppress electron background).
• π0 detected by the CES detector and required to be in the signal cone.
 CES: resolution 2-3mm, proportional strip/wire drift chamber at 6X0 of
EM calorimeter.
Isolation
cone
 Channel for Z→ττ: electron + isolated track
• One t decays to an electron: τ→e+X (ET(e) > 10 GeV) .
• One t decays to hadrons: τ → h+X (pT > 15GeV/c).
 Remove Drell-Yan e+e- and apply event topology cuts for non-Z
background.
CDF Collaboration Meeting
June 8, 2006
Rick Field – Florida/CDF
Page 60
The Z→tt Cross Section
 CDF Z→ττ (350 pb-1): 316 Z→ττ candidates.
 Novel method for background estimation: main contribution QCD.
 τ identification efficiency ~60% with uncertainty about 3%!
1 and 3 tracks,
opposite sign
same sign,
opposite sign
s(Z→t+t-)
CDF Collaboration Meeting
June 8, 2006
CDF (pb)
NNLO (pb)
26520(stat)21(sys)15(lum)
252.35.0
Rick Field – Florida/CDF
Page 61
Higgs → tt Search
140 GeV
Higgs Signal!
Let’s find the Higgs!
“Higgs Discovery Group”
 Data mass distribution agrees with SM expectation:
• MH > 120 GeV: 8.4±0.9 expected, 11 observed.
 Fit mass distribution for Higgs Signal (MSSM scenario):
• Exclude 140 GeV Higgs at 95% C.L.
• Upper limit on cross section times branching ratio.
CDF Collaboration Meeting
June 8, 2006
Rick Field – Florida/CDF
Page 62
Job Searching – Craig Group
 Craig Group will graduate in December 2006 and is
looking for a postdoctoral position.
 He is a student of myself and K. Matchev
(phenomenology).
 His CDF thesis is the 1 fb-1 jet cross section (central
and forward).
 He was one of the authors on LHAPDF.
 He set a CDF-CAF at Florida.
 He is good at both theory and analysis.
 He would like to continue to work on CDF for
several years and then move to the LHC.
 He is an excellent physicist! One of the best students
I have had!
CDF Collaboration Meeting
June 8, 2006
Rick Field – Florida/CDF
Page 63