XXXVI International Meeting on
Fundamental Physics
Physics at the Tevatron
From IMFP2006 → IMFP2008
Rick Field
University of Florida
(for the CDF & D0 Collaborations)
1st Lecture
FF Phenomenology → Tevatron Jet Physics
Palacio de Jabalquinto, Baeza, Spain
CDF Run 2
IMFP2008 - Day 1
February 4, 2008
Rick Field – Florida/CDF/CMS
Page 1
The Fermilab Tevatron
Proton
CDF
1 mile
AntiProton
Proton
2 TeV
AntiProton
 Fermi National Laboratory (Fermilab) is near
Chicago, Illinois. CDF and DØ are the the two
collider detector experiments at Fermilab.
 Protons collide with antiprotons at a center-ofmass energy of almost 2 TeV (actually 1.96 TeV).
IMFP2008 - Day 1
February 4, 2008
Rick Field – Florida/CDF/CMS
Page 2
Tevatron Performance
The data collected since IMFP 2006 more than doubled
the total data collected in Run 2!
IMFP 2006
~1.5 fb-1 delivered
~1.2 fb-1 recorded
IMFP 2008
~3.3 fb-1 delivered
~2.8 fb-1 recorded
~1.6 fb-1
Integrated Luminosity per Year
23 tt-pairs/month!
 Luminosity Records (IMFP 2006):
 Highest Initial Inst. Lum: ~1.8×1032 cm-2s-1
 Integrated luminosity/week: 25 pb-1
 Integrated luminosity/month: 92 pb-1
IMFP2008 - Day 1
February 4, 2008
 Luminosity records (IMFP 2008):
 Highest Initial Inst. Lum: ~2.92×1032 cm-2s-1
 Integrated luminosity/week: 45 pb-1
 Integrated luminosity/month: 165 pb-1
Rick Field – Florida/CDF/CMS
Page 3
Many New Tevatron Results!
Some of the CDF Results since IMFP2006













IMFP2008 - Day 1
February 4, 2008
Observation of Bs-mixing: Δms = 17.77 ± 0.10 (stat) ± 0.07(sys).
Observation of new baryon states: Sb and Xb.
Observation of new charmless: B→hh states.
Evidence for Do-Dobar mixing .
Precision W mass measurement: Mw = 80.413 GeV (±48 MeV).
cannot
cover
the(±2.2) GeV.
PrecisionI Top
mass possibility
measurement:
Mtop =all
170.5
great physics
results
from
W-width measurement:
2.032
(±0.071)
GeV.the
Tevatron
since
IMFP
WZ discovery
(6-sigma):
s = 5.0
(±1.7)2006!
pb.
I will
show a few of the results!
ZZ evidence
(3-sigma).
Single Top evidence (3-sigma) with 1.5 fb-1: s = 3.0 (±1.2) pb.
|Vtb|= 1.02 ± 0.18 (exp) ± 0.07 (th).
Significant exclusions/reach on many BSM models.
Constant improvement in Higgs Sensitivity.
Rick Field – Florida/CDF/CMS
Page 4
In Search of Rare Processes
PRODUCTION CROSS SECTION (fb)
We might get lucky!
IMFP2008 - Day 1
February 4, 2008
We are beginning to measure
cross-sections ≤ 1 pb!
s(pT(jet) > 525 GeV) ≈ 15 fb!
~9 orders of
magnitude
W’, Z’, T’
Higgs ED
Rick Field – Florida/CDF/CMS
1 pb
15 fb
Page 5
Toward and Understanding of
Hadron-Hadron Collisions
Feynman-Field Phenomenology1
Feynman
 From 7 GeV/c
and
hat!
Field
p0’s
to 600 GeV/c
Jets. The early days of trying to
understand and simulate
hadron-hadron collisions.
Outgoing Parton
PT(hard)
Initial-State Radiation
Proton
AntiProton
Underlying Event
Outgoing Parton
IMFP2008 - Day 1
February 4, 2008
st
Rick Field – Florida/CDF/CMS
Underlying Event
Final-State
Radiation
Page 6
Hadron-Hadron Collisions
Field-Feynman 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 andsofall
apart (i.e.
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
same
variousthe
models
(e.g. constituent
interchangeScattering
Parton-Parton
Outgoing Parton
direction as initial proton
and
model,
multiperipheral models, etc.). We shall
“Soft” Collision
(no large transverse momentum)
assume that the high PT particles
arise from
antiproton.
direct hard collisions between constituent
Hadron
 Occasionally there will bequarks
a large
in the incoming
particles, which
fragment
transverse momentum
meson.or cascade down into several hadrons.”
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”
IMFP2008 - Day 1
February 4, 2008
Rick Field – Florida/CDF/CMS
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.
IMFP2008 - Day 1
February 4, 2008
Rick Field – Florida/CDF/CMS
Quark Fragmentation Functions
determined from e+e- annihilations
Page 8
Quark-Quark Black-Box Model
Predict
particle ratios
Field-Feynman 1977 (preQCD)
Predict
increase with increasing
CM energy W
“Beam-Beam
Remnants”
Predict
overall event topology
(FFF1 paper 1977)
7 GeV/c p0’s!
IMFP2008 - Day 1
February 4, 2008
Rick Field – Florida/CDF/CMS
Page 9
Feynman Talk at Coral Gables
(December 1976)
1st transparency
Last transparency
“Feynman-Field
Jet Model”
IMFP2008 - Day 1
February 4, 2008
Rick Field – Florida/CDF/CMS
Page 10
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
IMFP2008 - Day 1
February 4, 2008
Rick Field – Florida/CDF/CMS
Page 11
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.”
IMFP2008 - Day 1
February 4, 2008
Rick Field – Florida/CDF/CMS
Page 12
QCD Monte-Carlo Models:
High Transverse Momentum Jets
Hard Scattering
Initial-State Radiation
Hard Scattering
Initial-State Radiation
“Jet”
“Jet”
Outgoing Parton
PT(hard)
Outgoing Parton
PT(hard)
Proton
“Hard Scattering” Component
AntiProton
Underlying Event
Final-State Radiation
Outgoing Parton
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!
IMFP2008 - Day 1
February 4, 2008
Rick Field – Florida/CDF/CMS
Page 13
Collider Coordinates
x-axis
xz-plane
Center-of-Mass
Scattering Angle
x-axis
Beam Axis
P
Proton
Proton
Proton
2 TeV
cm
AntiProton
AntiProton
AntiProton
z-axis
Proton
“Transverse”
xy-plane
 The z-axisLots
is of
defined
be the beam axis with
outgoingtohadrons
AntiProton z-axis
y-axis
y-axis
the xy-plane being the “transverse” plane.
 cm is the center-of-mass scattering angle and  is the
azimuthal angle. The “transverse” momentum of a
particle is given by PT = P cos(cm).
Azimuthal
Scattering Angle
PT

x-axis
h
cm
 Use h and  to determine the direction of an
outgoing particle, where h is the “pseudo-rapidity”
defined by h = -log(tan(cm/2)).
0
90o
1
40o
2
15o
 The “rapidity” is defined by y = log((E+pz)/(E-pz))/2
and is equal to h in the limit E >> mc2.
3
6o
4
2o
IMFP2008 - Day 1
February 4, 2008
Rick Field – Florida/CDF/CMS
Page 14
Quark & Gluon Jets
 The CDF calorimeter measures energy
deposited in a cell of size DhD = 0.11×15o,
whch is converted into transverse energy, ET =
E cos(cm).
 “Jets” are defined to be clusters of transverse
energy with a radius R in h- space. A “jet” is
the representation in the detector of an outgoing
parton (quark or gluon).
 The sum of the ET of the cells within a “jet”
corresponds roughly to the ET of the outgoing
parton and the position of the cluster in the grid
gives the parton’s direction.
Transverse Energy Grid
“Jet” is a cluster of
transverse energy
within rasius R.

h
Charged Particle Jet Can also construct jets from
the charged particles!
Calorimeter Jets
IMFP2008 - Day 1
February 4, 2008
Rick Field – Florida/CDF/CMS
Page 15
Jets at Tevatron
“Theory Jets”
“Tevatron Jets”
Next-to-leading order
parton level calculation
0, 1, 2, or 3 partons!
 Experimental Jets: The study of “real” jets requires a “jet algorithm” and the different
algorithms correspond to different observables and give different results!
 Experimental Jets: The study of “real” jets requires a good understanding of the calorimeter
response!
 Experimental Jets: To compare with NLO parton level (and measure structure functions)
requires a good understanding of the “underlying event”!
IMFP2008 - Day 1
February 4, 2008
Rick Field – Florida/CDF/CMS
Page 16
Jet Corrections
 Calorimeter Jets:
 We measure “jets” at the “hadron level” in the calorimeter.
 We certainly want to correct the “jets” for the detector resolution and
effieciency.
 Also, we must correct the “jets” for “pile-up”.
 Must correct what we measure back to the true “particle level” jets!
 Particle Level Jets:
 Do we want to make further model dependent corrections?
 Do we want to try and subtract the “underlying event” from the
“particle level” jets.
 This cannot really be done, but if you trust the Monte-Carlo
models modeling of the “underlying event” you can try and do it
by using the Monte-Carlo models (use PYTHIA Tune A).
 Parton Level Jets:
 Do we want to use our data to try and extrapolate back to the
parton level?
PT(hard)
 This also cannot really be done, but again if you trust the MonteInitial-State Radiation
AntiProton Carlo models you can try and do it by using the Monte-Carlo
models.
Underlying Event
Outgoing Parton
Proton
Underlying Event
Outgoing Parton
IMFP2008 - Day 1
February 4, 2008
Final-State
Radiation
The “underlying event” consists of
hard initial & final-state radiation
plus the “beam-beam remnants” and
possible multiple parton interactions.
Rick Field – Florida/CDF/CMS
Page 17
Inclusive Jet Cross Section (CDF)
 Run 1 showed a possible excess at
large jet ET (see below).
 This resulted in new PDF’s with
more gluons at large x.
 The Run 2 data are consistent with
the new structure functions
(CTEQ6.1M).
IMFP2006
CTEQ4M PDFs
CTEQ4HJ PDFs
CTEQ4HJ
CTEQ4M
Run I CDF Inclusive Jet Data
(Statistical Errors Only)
JetClu RCONE=0.7
0.1<|h|<0.7
R=F=ET /2 RSEP=1.3
IMFP2008 - Day 1
February 4, 2008
Rick Field – Florida/CDF/CMS
Page 18
Inclusive Jet Cross Section (CDF)
 MidPoint Cone Algorithm
(R
= 0.7, fmerge = 0.75)
 Data corrected to the hadron level
 L = 1.04 fb-1 today 1.13 fb-1
 0.1 < |yjet| < 0.7
 Compared with NLO QCD
IMFP2006
s(pT > 525 GeV) ≈ 15 fb!
Sensitive to UE + hadronization
effects for PT < 200 GeV/c!
IMFP2008 - Day 1
February 4, 2008
Rick Field – Florida/CDF/CMS
Page 19
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
Move i to list of jets
yes
Will the KT algorithm be
effective in the collider
environment where there is
an “underlying event”?
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
IMFP2008 - Day 1
February 4, 2008
Final-State
Radiation
Only towers with ET > 0.5 GeV are shown
Rick Field – Florida/CDF/CMS
Page 20
KT Inclusive Jet Cross Section (CDF)





KT Algorithm (D = 0.7)
Data corrected to the hadron level
L = 385 pb-1 today 1.0 fb-1
0.1 < |yjet| < 0.7
Compared with NLO QCD.
IMFP2006
Sensitive to UE + hadronization
effects for PT < 200 GeV/c!
IMFP2008 - Day 1
February 4, 2008
Rick Field – Florida/CDF/CMS
Page 21
High x Gluon PDF
from Run I
 Forward jets measurements put
constraints on the high x gluon
distribution!
Big uncertainty for
high-x gluon PDF!
Uncertainty on gluon
PDF (from CTEQ6)
x
Forward Jets
high x
IMFP2008 - Day 1
February 4, 2008
Rick Field – Florida/CDF/CMS
low x
Page 22
KT Forward Jet Cross Section (CDF)
 KT Algorithm (D = 0.7).
 Data corrected to the hadron
level.
-1
 L = 385 pb-1. today 1.0 fb
 Five rapidity regions:
 |yjet| < 0.1




IMFP2006
0.1 < |yjet| < 0.7
0.7 < |yjet| < 1.1
1.1 < |yjet| < 1.6
1.6 < |yjet| < 2.1
 Compared with NLO QCD
IMFP2008 - Day 1
February 4, 2008
Rick Field – Florida/CDF/CMS
Page 23
Forward Jet Cross Section (CDF)
 MidPoint Cone Algorithm
(R = 0.7, fmerge = 0.75)
 Data corrected to the
hadron level
 L = 1.13 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
since IMFP2006
1.0 fb-1
IMFP2008 - Day 1
February 4, 2008
Rick Field – Florida/CDF/CMS
Page 24
Inclusive Jet Cross Section (DØ )
 MidPoint Cone Algorithm
(R = 0.7, fmerge = 0.5)
 L = 378 pb-1 today
0.9 fb-1
 Two rapidity bins
 Highest PT jet is 630 GeV/c
 Compared with NLO QCD
(JetRad, No Rsep)
IMFP2006
Log-Log Scale!
IMFP2008 - Day 1
February 4, 2008
Rick Field – Florida/CDF/CMS
Page 25
CDF versus DØ
Without threshold
corrections!
Inclusive Jet (CDF)
Inclusive Jet (DØ)
 MidPoint Cone Algorithm
(R = 0.7, fmerge = 0.75)
 CTEQ6.1M  = PT/2
IMFP2008 - Day 1
February 4, 2008
 MidPoint Cone Algorithm
(R = 0.7, fmerge = 0.5)
 CTEQ6.1M  = PT
 Threshold corrections (2 loops)
Rick Field – Florida/CDF/CMS
Page 26
DiJet Cross Section (CDF)
since IMFP2006
 MidPoint Cone Algorithm
(R
= 0.7, fmerge = 0.75)
 Data corrected to the hadron level
 L = 1.13 fb-1
 |yjet1,2| < 1.0
 Compared with NLO QCD
CDF Run II Preliminary
Sensitive to UE + hadronization effects!
IMFP2008 - Day 1
February 4, 2008
Rick Field – Florida/CDF/CMS
Page 27
Inclusive Jet versus DiJet (CDF)
Inclusive Jet (CDF)
DiJet (CDF)
 MidPoint Cone Algorithm
(R = 0.7, fmerge = 0.75)
 CTEQ6.1M  = PT/2
IMFP2008 - Day 1
February 4, 2008
 MidPoint Cone Algorithm
(R = 0.7, fmerge = 0.75)
 CTEQ6.1M  = mean(PT1,PT2)
Rick Field – Florida/CDF/CMS
Page 28
CDF DiJet Event: M(jj) ≈ 1.4 TeV
ETjet1 = 666 GeV ETjet2 = 633 GeV
Esum = 1,299 GeV M(jj) = 1,364 GeV
Exclusive p+p → p+p+e++e- (16 events)
s = 1.6 ± 0.3 pb
CDF Run II
IMFP2008 - Day 1
February 4, 2008
since IMFP2006
M(jj)/Ecm ≈ 70%!!
Rick Field – Florida/CDF/CMS
Page 29
“Towards”, “Away”, “Transverse”
Look at the charged
particle density, the
charged PTsum density
and the ETsum density in
all 3 regions!
D Correlations relative to the leading jet
Jet #1 Direction
“Transverse” region is
very sensitive to the
“underlying event”!
Charged particles pT > 0.5 GeV/c |h| < 1
Calorimeter towers ET > 0.1 GeV |h| < 1
2p
“Toward-Side” Jet
D
Away Region
Jet #1 Direction
D
Transverse
Region
“Toward”
“Toward”
“Transverse”
“Transverse”
“Away”
“Transverse”
“Transverse”

Leading
Jet
Toward Region
“Away”
Transverse
Region
“Away-Side” Jet
Away Region
0
-1
h
+1
 Look at correlations in the azimuthal angle D relative to the leading charged particle jet (|h| <

1) or the leading calorimeter jet (|h| < 2).
o
o
o
o
Define |D| < 60 as “Toward”, 60 < |D| < 120 as “Transverse ”, and |D| > 120 as “Away”.
o
Each of the three regions have area DhD = 2×120 = 4p/3.
IMFP2008 - Day 1
February 4, 2008
Rick Field – Florida/CDF/CMS
Page 30
Event Topologies
 “Leading Jet” events correspond
the leading
Rick to
Field
& Craig
calorimeter jet (MidPoint R = 0.7) in the region |h| < 2
with no other conditions.
Jet #1 Direction
Group
D
“Leading Jet”
“Toward”
 “Back-to-Back Inclusive 2-Jet” events are selected to
have at least two jets with Jet#1
and Jet#2Data
nearlyfor Theory
CDF-QCD
“Transverse”
“Transverse”
subset
“Away”
“back-to-back” (D12 >
withgoal
almost
equal
The
is to
produce data
transverse energies (PT(jet#2)/P
(jet#1)
>
0.8)
with no level) Jet #1 Direction
T
(corrected
to the particle
D
other conditions .
150o)
that can be used by the theorists “Toward”
to tune
andareimprove
 “Back-to-Back Exclusive 2-Jet”
events
selected the
to QCD
models
have at least two jets withMonte-Carlo
Jet#1 and Jet#2
nearly that are used
o
“back-to-back” (D12 > 150
) with almost
equal
to simulate
hadron-hadron
collisions.
“Away”
“Transverse”
transverse energies (PT(jet#2)/PT(jet#1) > 0.8) and
PT(jet#3) < 15 GeV/c.
 “Leading ChgJet” events correspond to the leading
charged particle jet (R = 0.7) in the region |h| < 1
with no other conditions.
“Back-to-Back Inc2J”
subset
“Transverse”
“Back-to-Back Exc2J”
Jet #2 Direction
ChgJet #1
Direction D
“Charged Jet”
“Toward”
“Transverse”
“Transverse”
“Away”
IMFP2008 - Day 1
February 4, 2008
Rick Field – Florida/CDF/CMS
Page 31
Overall Totals (|h| < 1)
ETsum = 775 GeV!
“Leading Jet”
Overall Totals versus PT(jet#1)
ETsum = 330 GeV
1000
CDF Run 2 Preliminary
ETsum (GeV)
data corrected
pyA generator level
Jet #1 Direction
D
PTsum (GeV/c)
Average
100
“Overall”
Nchg
"Leading Jet"
MidPoint R=0.7 |h(jet#1)|<2
10
PTsum = 190 GeV/c
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
Stable Particles (|h|<1.0, all PT)
1
0
50
Nchg = 30
100
150
200
250
300
350
400
PT(jet#1) (GeV/c)
 Data at 1.96 TeV on the overall number of charged particles (pT > 0.5 GeV/c, |h| < 1) and the overall
scalar pT sum of charged particles (pT > 0.5 GeV/c, |h| < 1) and the overall scalar ET sum of all
particles (|h| < 1) for “leading jet” events as a function of the leading jet pT. The data are corrected
to the particle level (with errors that include both the statistical error and the systematic uncertainty)
and are compared with PYTHIA Tune A at the particle level (i.e. generator level)..
IMFP2008 - Day 1
February 4, 2008
Rick Field – Florida/CDF/CMS
Page 32
“Towards”, “Away”, “Transverse”
“Leading Jet”
Jet #1 Direction
D
“Toward”
“Transverse”
“Transverse”
“Away”
ETsum
Density
(GeV)
Charged
PTsum
Density
(GeV/c)
Average
Charged
Density
Charged
Particle
Density:
dN/dhd
Charged
PTsum
Density:
dPT/dhd
ETsum
Density:
dET/dhd
5
100.0
100.0
CDFCDF
RunRun
2 Preliminary
2 Preliminary
4
data corrected
data"Toward"
corrected
pyA generator level
pyA generator level
10.0
3
"Toward"
"Away"
"Away"
Factor of ~13
"Toward"
"Transverse"
Factor of ~16
"Away"
"Transverse" "Leading Jet"
Factor of MidPoint
~4.5 R=0.7 |h(jet#1)|<2
2
1.0
1.0
1
0 0.1
0.1
0 0
0
"Transverse"
CDF Run 2 Preliminary
data corrected
pyA generator level
50 50
50
100100
100
150
150
150
"Leading Jet"
"Leading Jet"
MidPoint R=0.7 |h(jet#1)|<2
MidPoint R=0.7 |h(jet#1)|<2
ChargedStable
Particles
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IMFP2008 - Day 1
February 4, 2008
Rick Field – Florida/CDF/CMS
Page 33
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IMFP2008 - Day 1
February 4, 2008
Rick Field – Florida/CDF/CMS
Page 34
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IMFP2008 - Day 1
February 4, 2008
Rick Field – Florida/CDF/CMS
Page 35
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IMFP2008 - Day 1
February 4, 2008
Rick Field – Florida/CDF/CMS
Page 36
The “Transverse” Region
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IMFP2008 - Day 1
February 4, 2008
Rick Field – Florida/CDF/CMS
Page 37
The “Transverse” Region
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IMFP2008 - Day 1
February 4, 2008
Rick Field – Florida/CDF/CMS
Page 38
The “Transverse” Region
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IMFP2008 - Day 1
February 4, 2008
Rick Field – Florida/CDF/CMS
Page 39
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IMFP2008 - Day 1
February 4, 2008
Rick Field – Florida/CDF/CMS
Page 40
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Fraction: PTsum/ETsum
PTsum/ETsum
Jet #1 Direction
D
“Toward”
“Transverse”
“Transverse”
“Away”
"Transverse"
"Transverse" Charged
Charged Fraction
Fraction
0.8
0.5
CDF Run
Run 2
CDF
2 Preliminary
Preliminary
"Leading Jet"
MidPoint R=0.7 |h(jet#1)|<2
PY Tune A
HW
ETsum Stable Particles
(|h|<1.0, all PT)
data corrected
generator level theory
generator level theory
0.4
0.6
PY Tune A
PTsum Charged Particles (|h|<1.0, all PT)
0.3
PT(min) = 0 → 0.5 GeV/c
"Leading Jet"
MidPoint R=0.7 |h(jet#1)|<2
0.4
0.2
HW
PTsum Charged Particles (|h|<1.0, PT>0.5 GeV/c)
PTsum Charged Particles (|h|<1.0, PT>0.5 GeV/c)
ETsum Stable Particles (|h|<1.0, all PT)
0.1
0.2
00
50
50
100
100
150
150
200
200
250
250
300
300
350
350
400
400
PT(jet#1)
(GeV/c)
PT(particle
jet#1)
(GeV/c)

generator
level
predictions
for the
charged fraction,
PTsum/ETsum,
for PTsum
pT, |h|
< 1) (all
 Shows
Data atthe
1.96
TeV on the
charged
fraction,
PTsum/ETsum,
for PTsum
(pT > 0.5 GeV/c,
|h| <(all
1) and
ETsum
and
ETsum
(all“leading
pT, |h| <jet”
1) and
for PTsum
(pT > 0.5
GeV/c,
|h| <jet
1)pand
ETsum (all pT, |h| <region.
1) for The
“leading
pT, |h|
< 1) for
events
as a function
of the
leading
data
T for the “transverse”
jet”
events
as
a
function
of
the
leading
jet
p
for
the
“transverse”
region
from
PYTHIA
Tune
A
and
T
are corrected to the particle level (with errors that include both the statistical error and the systematic
HERWIG
(without
uncertainty)
and areMPI).
compared with PYTHIA Tune A and HERWIG (without MPI) at the particle level (i.e.
generator level).
IMFP2008 - Day 1
February 4, 2008
Rick Field – Florida/CDF/CMS
Page 41
bb DiJet Cross Section (CDF)
≈ 85% purity!
Collision point
 b-quark tag based on displaced vertices. Secondary vertex mass
discriminates flavor.
 Require two secondary vertex tagged b-jets within |y|< 1.2 and study
the two b-jets (Mjj, Djj, etc.).
IMFP2008 - Day 1
February 4, 2008
Rick Field – Florida/CDF/CMS
Page 42
The Sources of Heavy Quarks
Leading-Log Order
QCD Monte-Carlo Model (LLMC)
“Flavor Creation”
Proton
Leading Order Matrix Elements
Q-quark
AntiProton
Underlying Event
Underlying Event
Initial-State
Radiation
Q-quark
 We do not observe c or b quarks directly. We measure D-mesons (which contain a c-quark)
or we measure B-mesons (which contain a b-quark) or we measure c-jets (jets containing a
D-meson) or we measure b-jets (jets containing a B-meson).
ds ( B)  G pi  G p  j  ds (ij  bk )  Fb D
(structure functions) × (matrix elements) × (Fragmentation)
+ (initial and final-state radiation: LLA)
IMFP2008 - Day 1
February 4, 2008
Rick Field – Florida/CDF/CMS
Page 43
Other Sources of Heavy Quarks
“Flavor Excitation”
“Gluon Splitting”
Q-quark
Proton
Proton
AntiProton
Underlying Event
AntiProton
Underlying Event
Underlying Event
Q-quark
Underlying Event
Initial-State
Radiation
Initial-State
Radiation
gluon, quark,
or antiquark
Q-quark
Q-quark
“Flavor Excitation” (LLMC) corresponds to
the scattering of a b-quark (or bbar-quark)
out of the initial-state into the final-state by a
gluon or by a light quark or antiquark.
“Gluon-Splitting” (LLMC) is where a b-bbar pair is created
within a parton shower or during the the fragmentation process
of a gluon or a light quark or antiquark. Here the QCD hard 2to-2 subprocess involves only gluons and light quarks and
antiquarks.
 In the leading-log order Monte-Carlo models (LLMC) the separation into “flavor creation”,
“flavor excitation”, and “gluon splitting” is unambiguous, however at next to leading order the
same amplitudes contribute to all three processes! and there are interference terms!
Next to Leading Order Matrix Elements
Q
g
Amp(gg→QQg)
s(gg→QQg)
= =
g
+
Amp (FC)
Q
g
IMFP2008 - Day 1
February 4, 2008
Q
g
g
Q
g
Q
+
g
Q
Amp (FE)
Rick Field – Florida/CDF/CMS
g
Amp (GS)
g
Page 44
2
bb DiJet Cross Section (CDF)
 ET(b-jet#1) > 35 GeV, ET(b-jet#2) > 32
GeV, |h(b-jets)| < 1.2.
IMFP2006
Preliminary CDF Results:
sbb = 34.5  1.8  10.5 nb
QCD Monte-Carlo Predictions:
PYTHIA Tune A
CTEQ5L
38.7 ± 0.6 nb
HERWIG CTEQ5L
21.5 ± 0.7 nb
MC@NLO
28.5 ± 0.6 nb
MC@NLO + Jimmy
35.7 ± 2.0 nb
Differential Cross Section as a function of
the b-bbar DiJet invariant mass!
JIMMY
Runs with HERWIG and adds
multiple parton interactions!
“Flavor Creation”
b-quark
Initial-State Radiation
JIMMY: MPI
J. M. Butterworth
J. R. Forshaw
M. H. Seymour
IMFP2008 - Day 1
February 4, 2008
Adding multiple parton interactions (i.e.
JIMMY) to enhance the “underlying
event” increases the b-bbar jet cross
section!
Rick Field – Florida/CDF/CMS
Proton
AntiProton
Underlying Event
Underlying Event
b-quark
Final-State
Radiation
Page 45
bb DiJet Cross Section (CDF)
since IMFP2006
 ET(b-jet#1) > 35 GeV,
ET(b-jet#2) > 32 GeV, |h(b-jets)| < 1.2.
Systematic
Uncertainty
Preliminary CDF Results:
sbb = 5664  168  1270 pb
QCD Monte-Carlo Predictions:
PYTHIA Tune A
CTEQ5L
5136 ± 52 pb
HERWIG
CTEQ5L+Jimmy
5296 ± 98 pb
MC@NLO+Jimmy
5421 ± 105 nb
Predominately
Flavor creation!
“Flavor Creation”
Proton
b-quark
AntiProton
Underlying Event
Underlying Event
Sensitive to the “underlying event”!
Initial-State
Radiation
b-quark
IMFP2008 - Day 1
February 4, 2008
Rick Field – Florida/CDF/CMS
Page 46
bb DiJet D Distribution (CDF)
since IMFP2006
b-jet direction
D
“Toward”
“Away”
bbar-jet
 Large D (i.e. b-jets are “back-to-back”) is
predominately “flavor creation”.
 Small D (i.e. b-jets are near each other) is
predominately “flavor excitation” and
“gluon splitting”.
 It takes NLO + “underlying event” to get it
right!
“Flavor Creation”
“Gluon Splitting”
Proton
AntiProton
Underlying Event
Underlying Event
Proton
b-quark
AntiProton
Underlying Event
Underlying Event
Initial-State
Radiation
Initial-State
Radiation
b-quark
Q-quark
Q-quark
IMFP2008 - Day 1
February 4, 2008
Rick Field – Florida/CDF/CMS
Page 47
Z + b-Jet Production (CDF)
since IMFP2006
 Important background for new physics!





IMFP2006
Leptonic decays for the Z.
Z associated with jets.
CDF: JETCLU, D0:
R = 0.7, |hjet| < 1.5, ET >20 GeV
Look for tagged jets in Z events.
today
1.5 fb-1
Extract fraction of b-tagged jets from
secondary vertex mass distribution: NO
assumption on the charm content.
s ( ZObservable
 bjet )  0.96  0.32 CDF
0.14Data
pb
PYTHIA Tune A
s [ Z  bjet]
0.94±0.15±0.15
pb)  0.0033( syst
-- )
R  s(Z+b-jet)  0.0237
 0.0078( stat
s [ Z  jet]
MCFM NLO (+UE)
0.51 (0.56) pb
s(Z+b-jet)/s(Z)
0.369±0.057±0.055 %
0.35%
0.21 (0.23) %
s(Z+b-jet)/s(Z+jet)
2.35±0.36±0.45 %
2.18%
1.88 (1.77) %
Sensitive to the “underlying event”!
IMFP2008 - Day 1
February 4, 2008
Rick Field – Florida/CDF/CMS
Page 48
XXXVI International Meeting on
Fundamental Physics
Physics at the Tevatron
From IMFP2006 → IMFP2008
Rick Field
University of Florida
(for the CDF & D0 Collaborations)
2nd Lecture (Tomorrow)
Bosons, Top, and Higgs
Palacio de Jabalquinto, Baeza, Spain
CDF Run 2
IMFP2008 - Day 1
February 4, 2008
Rick Field – Florida/CDF/CMS
Page 49