1. 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
IMFP Day February 4, 2008
Rick Field – Florida/CDF/CMS

2. Rick Field – Florida/CDF/CMS
The Fermilab Tevatron
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-of-mass energy of almost 2 TeV (actually 1.96 TeV).
IMFP Day February 4, 2008
Rick Field – Florida/CDF/CMS

3. Tevatron Performance
The data collected since IMFP 2006 more than doubled
the total data collected in Run 2!
IMFP 2008
~3.3 fb-1 delivered
~2.8 fb-1 recorded
IMFP 2006
~1.5 fb-1 delivered
~1.2 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
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
IMFP Day February 4, 2008
Rick Field – Florida/CDF/CMS

4. Many New Tevatron Results!
Some of the CDF Results since IMFP2006
I cannot possibility cover all the
great physics results from the
Tevatron since IMFP 2006!
Observation of Bs-mixing: Δms = ± 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 = GeV (±48 MeV).
Precision Top mass measurement: Mtop = (±2.2) GeV.
W-width measurement: (±0.071) GeV.
WZ discovery (6-sigma): s = 5.0 (±1.7) pb.
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.
I will show a few of the results!
IMFP Day February 4, 2008
Rick Field – Florida/CDF/CMS

5. In Search of Rare Processes
We might get lucky!
We are beginning to measure cross-sections ≤ 1 pb!
~9 orders of magnitude
s(pT(jet) > 525 GeV) ≈ 15 fb!
PRODUCTION CROSS SECTION (fb)
1 pb
W’, Z’, T’
Higgs ED
15 fb
IMFP Day February 4, 2008
Rick Field – Florida/CDF/CMS

6. Toward and Understanding of Hadron-Hadron Collisions
Feynman-Field Phenomenology
1st hat!
Feynman
and
Field
From 7 GeV/c p0’s to 600 GeV/c Jets. The early days of trying to understand and simulate hadron-hadron collisions.
IMFP Day February 4, 2008
Rick Field – Florida/CDF/CMS

7. Hadron-Hadron Collisions
Field-Feynman 1977 (preQCD)
What happens when two hadrons collide at high energy?
Feynman quote from FF1
“The model we shall choose is not a popular one,
so that we will not duplicate too much of the
work of others who are similarly analyzing
various models (e.g. constituent interchange
model, multiperipheral models, etc.). We shall
assume that the high PT particles arise from
direct hard collisions between constituent
quarks in the incoming particles, which
fragment or cascade down into several hadrons.”
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?
We assumed it came from quark-quark elastic scattering, but we did not know how to calculate it!
“Black-Box Model”
IMFP Day February 4, 2008
Rick Field – Florida/CDF/CMS

8. Quark-Quark Black-Box Model
No gluons!
FF (preQCD)
Quark Distribution Functions
determined from deep-inelastic
lepton-hadron collisions
Feynman quote from FF1
“Because of the incomplete knowledge of
our functions some things can be predicted
with more certainty than others. Those
experimental results that are not well
predicted can be “used up” to determine
these functions in greater detail to permit
better predictions of further experiments.
Our papers will be a bit long because we
wish to discuss this interplay in detail.”
Quark Fragmentation Functions
determined from e+e- annihilations
Quark-Quark Cross-Section
Unknown! Deteremined from
hadron-hadron collisions.
IMFP Day February 4, 2008
Rick Field – Florida/CDF/CMS

9. Quark-Quark Black-Box Model
Field-Feynman 1977 (preQCD)
Predict
particle ratios
Predict
increase with increasing
CM energy W
“Beam-Beam Remnants”
Predict
overall event topology
(FFF1 paper 1977)
7 GeV/c p0’s!
IMFP Day February 4, 2008
Rick Field – Florida/CDF/CMS

10. Feynman Talk at Coral Gables (December 1976)
1st transparency
Last transparency
“Feynman-Field
Jet Model”
IMFP Day February 4, 2008
Rick Field – Florida/CDF/CMS

11. QCD Approach: Quarks & Gluons
Quark & Gluon Fragmentation 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.”
Parton Distribution Functions
Q2 dependence predicted from QCD
Quark & Gluon Cross-Sections
Calculated from QCD
IMFP Day February 4, 2008
Rick Field – Florida/CDF/CMS

12. High PT Jets CDF (2006) Feynman, Field, & Fox (1978) 30 GeV/c! Predict
large “jet” cross-section
30 GeV/c!
Feynman quote from FFF
“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.”
600 GeV/c Jets!
IMFP Day February 4, 2008
Rick Field – Florida/CDF/CMS

13. QCD Monte-Carlo Models: High Transverse Momentum Jets
“Hard Scattering” Component
“Underlying Event”
Start with the perturbative 2-to-2 (or sometimes 2-to-3) parton-parton scattering and add initial and final-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.
The “underlying event” is an unavoidable background to most collider observables and having good understand of it leads to more precise collider measurements!
IMFP Day February 4, 2008
Rick Field – Florida/CDF/CMS

14. Rick Field – Florida/CDF/CMS
Collider Coordinates
The z-axis is defined to be the beam axis with the xy-plane being the “transverse” plane.
qcm is the center-of-mass scattering angle and f is the azimuthal angle. The “transverse” momentum of a particle is given by PT = P cos(qcm). h
qcm
90o 1
40o 2
15o 3 6o 4 2o
Use h and f to determine the direction of an outgoing particle, where h is the “pseudo-rapidity” defined by h = -log(tan(qcm/2)).
The “rapidity” is defined by y = log((E+pz)/(E-pz))/2 and is equal to h in the limit E >> mc2.
IMFP Day February 4, 2008
Rick Field – Florida/CDF/CMS

15. Can also construct jets from the charged particles!
Quark & Gluon Jets
The CDF calorimeter measures energy deposited in a cell of size DhDf = 0.11×15o, whch is converted into transverse energy, ET = E cos(qcm).
“Jets” are defined to be clusters of transverse energy with a radius R in h-f 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.
Can also construct jets from the charged particles!
Calorimeter Jets
IMFP Day February 4, 2008
Rick Field – Florida/CDF/CMS

16. Next-to-leading order parton level calculation
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”!
IMFP Day February 4, 2008
Rick Field – Florida/CDF/CMS

17. Rick Field – Florida/CDF/CMS
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?
This also cannot really be done, but again if you trust the Monte-Carlo models you can try and do it by using the Monte-Carlo models.
The “underlying event” consists of hard initial & final-state radiation plus the “beam-beam remnants” and possible multiple parton interactions.
IMFP Day February 4, 2008
Rick Field – Florida/CDF/CMS

18. 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
Run I CDF Inclusive Jet Data (Statistical Errors Only) JetClu RCONE= <||<0.7 R=F=ET /2 RSEP=1.3
CTEQ4M PDFs CTEQ4HJ PDFs
CTEQ4HJ
CTEQ4M
IMFP Day February 4, 2008
Rick Field – Florida/CDF/CMS

19. 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
0.1 < |yjet| < 0.7
Compared with NLO QCD
IMFP2006
today
1.13 fb-1
s(pT > 525 GeV) ≈ 15 fb!
Sensitive to UE + hadronization effects for PT < 200 GeV/c!
IMFP Day February 4, 2008
Rick Field – Florida/CDF/CMS

20. Rick Field – Florida/CDF/CMS
KT Algorithm
kT Algorithm:
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!
KT Algorithm
Will the KT algorithm be effective in the collider environment where there is an “underlying event”?
Raw Jet ET = 533 GeV
Raw Jet ET = 618 GeV
CDF Run 2
Only towers with ET > 0.5 GeV are shown
IMFP Day February 4, 2008
Rick Field – Florida/CDF/CMS

21. KT Inclusive Jet Cross Section (CDF)
KT Algorithm (D = 0.7)
Data corrected to the hadron level
L = 385 pb-1
0.1 < |yjet| < 0.7
Compared with NLO QCD.
IMFP2006
today
1.0 fb-1
Sensitive to UE + hadronization effects for PT < 200 GeV/c!
IMFP Day February 4, 2008
Rick Field – Florida/CDF/CMS

22. Big uncertainty for 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
low x
IMFP Day February 4, 2008
Rick Field – Florida/CDF/CMS

23. KT Forward Jet Cross Section (CDF)
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
today
1.0 fb-1
IMFP2006
IMFP Day February 4, 2008
Rick Field – Florida/CDF/CMS

24. Forward Jet Cross Section (CDF)
since IMFP2006
New
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
1.0 fb-1
IMFP Day February 4, 2008
Rick Field – Florida/CDF/CMS

25. Inclusive Jet Cross Section (DØ )
MidPoint Cone Algorithm (R = 0.7, fmerge = 0.5)
L = 378 pb-1
Two rapidity bins
Highest PT jet is 630 GeV/c
Compared with NLO QCD (JetRad, No Rsep)
today
0.9 fb-1
IMFP2006
Log-Log Scale!
IMFP Day February 4, 2008
Rick Field – Florida/CDF/CMS

26. Without threshold corrections!
CDF versus DØ
Without threshold corrections!
Inclusive Jet (CDF)
Inclusive Jet (DØ)
MidPoint Cone Algorithm (R = 0.7, fmerge = 0.75)
CTEQ6.1M m = PT/2
MidPoint Cone Algorithm (R = 0.7, fmerge = 0.5)
CTEQ6.1M m = PT
Threshold corrections (2 loops)
IMFP Day February 4, 2008
Rick Field – Florida/CDF/CMS

27. DiJet Cross Section (CDF)
since IMFP2006
New
CDF Run II Preliminary
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
Sensitive to UE + hadronization effects!
IMFP Day February 4, 2008
Rick Field – Florida/CDF/CMS

28. Inclusive Jet versus DiJet (CDF)
Inclusive Jet (CDF)
DiJet (CDF)
MidPoint Cone Algorithm (R = 0.7, fmerge = 0.75)
CTEQ6.1M m = PT/2
MidPoint Cone Algorithm (R = 0.7, fmerge = 0.75)
CTEQ6.1M m = mean(PT1,PT2)
IMFP Day February 4, 2008
Rick Field – Florida/CDF/CMS

29. 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
since IMFP2006
New
M(jj)/Ecm ≈ 70%!!
CDF Run II
IMFP Day February 4, 2008
Rick Field – Florida/CDF/CMS

30. “Towards”, “Away”, “Transverse”
Look at the charged particle density, the charged PTsum density and the ETsum density in all 3 regions!
Df Correlations relative to the leading jet
Charged particles pT > 0.5 GeV/c |h| < 1
Calorimeter towers ET > 0.1 GeV |h| < 1
“Transverse” region is very sensitive to the “underlying event”!
Look at correlations in the azimuthal angle Df relative to the leading charged particle jet (|h| < 1) or the leading calorimeter jet (|h| < 2).
Define |Df| < 60o as “Toward”, 60o < |Df| < 120o as “Transverse ”, and |Df| > 120o as “Away”. Each of the three regions have area DhDf = 2×120o = 4p/3.
IMFP Day February 4, 2008
Rick Field – Florida/CDF/CMS

31. Event Topologies Rick Field & Craig Group CDF-QCD Data for Theory
The goal is to produce data
(corrected to the particle level)
that can be used by the theorists
to tune and improve the QCD
Monte-Carlo models that are used
to simulate hadron-hadron collisions.
Rick Field & Craig Group
“Leading Jet” events correspond to the leading calorimeter jet (MidPoint R = 0.7) in the region |h| < 2 with no other conditions.
“Leading Jet”
subset
“Back-to-Back Inclusive 2-Jet” events are selected to have at least two jets with Jet#1 and Jet#2 nearly “back-to-back” (Df12 > 150o) with almost equal transverse energies (PT(jet#2)/PT(jet#1) > 0.8) with no other conditions .
“Back-to-Back Inc2J”
“Back-to-Back Exclusive 2-Jet” events are selected to have at least two jets with Jet#1 and Jet#2 nearly “back-to-back” (Df12 > 150o) with almost equal transverse energies (PT(jet#2)/PT(jet#1) > 0.8) and PT(jet#3) < 15 GeV/c.
subset
“Back-to-Back Exc2J”
“Charged Jet”
“Leading ChgJet” events correspond to the leading charged particle jet (R = 0.7) in the region |h| < 1 with no other conditions.
IMFP Day February 4, 2008
Rick Field – Florida/CDF/CMS

32. Overall Totals (|h| < 1)
ETsum = 775 GeV!
“Leading Jet”
ETsum = 330 GeV
PTsum = 190 GeV/c
Nchg = 30
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)..
IMFP Day February 4, 2008
Rick Field – Florida/CDF/CMS

33. “Towards”, “Away”, “Transverse”
“Leading Jet”
Factor of ~13
Factor of ~16
Factor of ~4.5
Data at 1.96 TeV on the charged particle scalar pT sum density, dPT/dhdf, with pT > 0.5 GeV/c and |h| < 1 for “leading jet” events as a function of the leading jet pT for the “toward”, “away”, and “transverse” regions. 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).
Data at 1.96 TeV on the density of charged particles, dN/dhdf, with pT > 0.5 GeV/c and |h| < 1 for “leading jet” events as a function of the leading jet pT for the “toward”, “away”, and “transverse” regions. 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).
Data at 1.96 TeV on the particle scalar ET sum density, dET/dhdf, for |h| < 1 for “leading jet” events as a function of the leading jet pT for the “toward”, “away”, and “transverse” regions. 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).
IMFP Day February 4, 2008
Rick Field – Florida/CDF/CMS

34. Rick Field – Florida/CDF/CMS
The “Toward” Region
“Leading Jet”
Data at 1.96 TeV on the charged scalar pT sum density, dPT/dhdf, with pT > 0.5 GeV/c and |h| < 1 for “leading jet” events as a function of the leading jet pT for the “toward” region. 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 and HERWIG (without MPI) at the particle level (i.e. generator level).
Data at 1.96 TeV on the density of charged particles, dN/dhdf, with pT > 0.5 GeV/c and |h| < 1 for “leading jet” events as a function of the leading jet pT for the “toward” region. 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 and HERWIG (without MPI) at the particle level (i.e. generator level).
Data at 1.96 TeV on the scalar ET sum density, dET/dhdf, with |h| < 1 for “leading jet” events as a function of the leading jet pT for the “toward” region. 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 and HERWIG (without MPI) at the particle level (i.e. generator level).
IMFP Day February 4, 2008
Rick Field – Florida/CDF/CMS

35. Rick Field – Florida/CDF/CMS
The “Away” Region
“Leading Jet”
Data at 1.96 TeV on the charged scalar pT sum density, dPT/dhdf, with pT > 0.5 GeV/c and |h| < 1 for “leading jet” events as a function of the leading jet pT for the “away” region. 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 and HERWIG (without MPI) at the particle level (i.e. generator level).
Data at 1.96 TeV on the density of charged particles, dN/dhdf, with pT > 0.5 GeV/c and |h| < 1 for “leading jet” events as a function of the leading jet pT for the “away” region. 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 and HERWIG (without MPI) at the particle level (i.e. generator level).
Data at 1.96 TeV on the scalar ET sum density, dET/dhdf, with |h| < 1 for “leading jet” events as a function of the leading jet pT for the “away” region. 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 and HERWIG (without MPI) at the particle level (i.e. generator level).
IMFP Day February 4, 2008
Rick Field – Florida/CDF/CMS

36. The “Transverse” Region
“Leading Jet”
Data at 1.96 TeV on the charged scalar pT sum density, dPT/dhdf, with pT > 0.5 GeV/c and |h| < 1 for “leading jet” events as a function of the leading jet pT for the “transverse” region. 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 and HERWIG (without MPI) at the particle level (i.e. generator level).
Data at 1.96 TeV on the density of charged particles, dN/dhdf, with pT > 0.5 GeV/c and |h| < 1 for “leading jet” events as a function of the leading jet pT for the “transverse” region. 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 and HERWIG (without MPI) at the particle level (i.e. generator level).
Data at 1.96 TeV on the scalar ET sum density, dET/dhdf, with |h| < 1 for “leading jet” events as a function of the leading jet pT for the “transverse” region. 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 and HERWIG (without MPI) at the particle level (i.e. generator level).
Data at 1.96 TeV on the charged particle maximum pT, with pT > 0.5 GeV/c and |h| < 1 for “leading jet” events as a function of the leading jet pT for the “transverse” region. 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 and HERWIG (without MPI) at the particle level (i.e. generator level).
Data at 1.96 TeV on the charged particle average pT, with pT > 0.5 GeV/c and |h| < 1 for “leading jet” events as a function of the leading jet pT for the “transverse” region. 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 and HERWIG (without MPI) at the particle level (i.e. generator level).
IMFP Day February 4, 2008
Rick Field – Florida/CDF/CMS

37. The “Transverse” Region
“Leading Jet”
0.1 density corresponds to 0.42 charged particles in the “transverse” region!
Data at 1.96 TeV on the density of charged particles, dN/dhdf, with pT > 0.5 GeV/c and |h| < 1 for “leading jet” events as a function of the leading jet pT for the “transverse” region. 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 and HERWIG (without MPI) at the particle level (i.e. generator level).
Shows the Data - Theory for the density of charged particles, dN/dhdf, with pT > 0.5 GeV/c and |h| < 1 for “leading jet” events as a function of the leading jet pT for the “transverse” region for PYTHIA Tune A and HERWIG (without MPI).
IMFP Day February 4, 2008
Rick Field – Florida/CDF/CMS

38. The “Transverse” Region
“Leading Jet”
0.1 density corresponds to 420 MeV/c in the “transverse” region!
Data at 1.96 TeV on the charged scalar pT sum density, dPT/dhdf, with pT > 0.5 GeV/c and |h| < 1 for “leading jet” events as a function of the leading jet pT for the “transverse” region. 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 and HERWIG (without MPI) at the particle level (i.e. generator level).
Shows the Data - Theory for the charged scalar pT sum density, dPT/dhdf, with pT > 0.5 GeV/c and |h| < 1 for “leading jet” events as a function of the leading jet pT for the “transverse” region for PYTHIA Tune A and HERWIG (without MPI).
IMFP Day February 4, 2008
Rick Field – Florida/CDF/CMS

39. The “Transverse” Region
“Leading Jet”
0.4 density corresponds to 1.67 GeV in the “transverse” region!
Data at 1.96 TeV on the scalar ET sum density, dET/dhdf, with |h| < 1 for “leading jet” events as a function of the leading jet pT for the “transverse” region. 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 and HERWIG (without MPI) at the particle level (i.e. generator level).
Shows the Data - Theory for the scalar ET sum density, dET/dhdf, with |h| < 1 for “leading jet” events as a function of the leading jet pT for the “transverse” region for PYTHIA Tune A and HERWIG (without MPI).
IMFP Day February 4, 2008
Rick Field – Florida/CDF/CMS

40. Rick Field – Florida/CDF/CMS
The Leading Jet Mass
“Leading Jet”
Off by ~2 GeV
Data at 1.96 TeV on the leading jet invariant mass 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 and HERWIG (without MPI) at the particle level (i.e. generator level).
Shows the Data - Theory for the leading jet invariant mass for “leading jet” events as a function of the leading jet pT for PYTHIA Tune A and HERWIG (without MPI).
IMFP Day February 4, 2008
Rick Field – Florida/CDF/CMS

41. The “Transverse” Region
“Leading Jet”
PT(min) = 0 → 0.5 GeV/c
Shows the generator level predictions for the charged fraction, PTsum/ETsum, for PTsum (all pT, |h| < 1) and ETsum (all pT, |h| < 1) and for PTsum (pT > 0.5 GeV/c, |h| < 1) and ETsum (all pT, |h| < 1) for “leading jet” events as a function of the leading jet pT for the “transverse” region from PYTHIA Tune A and HERWIG (without MPI).
Data at 1.96 TeV on the charged fraction, PTsum/ETsum, for PTsum (pT > 0.5 GeV/c, |h| < 1) and ETsum (all pT, |h| < 1) for “leading jet” events as a function of the leading jet pT for the “transverse” region. 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 and HERWIG (without MPI) at the particle level (i.e. generator level).
IMFP Day February 4, 2008
Rick Field – Florida/CDF/CMS

42. 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, Dfjj, etc.).
IMFP Day February 4, 2008
Rick Field – Florida/CDF/CMS

43. The Sources of Heavy Quarks
Leading-Log Order
QCD Monte-Carlo Model (LLMC)
Leading Order Matrix Elements
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).
(structure functions)
× (matrix elements)
× (Fragmentation)
+ (initial and final-state radiation: LLA)
IMFP Day February 4, 2008
Rick Field – Florida/CDF/CMS

44. Other Sources of Heavy Quarks
“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 2-to-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 2
s(gg→QQg) =
Amp(gg→QQg) = + +
IMFP Day February 4, 2008
Rick Field – Florida/CDF/CMS

45. bb DiJet Cross Section (CDF)
IMFP2006
ET(b-jet#1) > 35 GeV, ET(b-jet#2) > 32 GeV, |h(b-jets)| < 1.2.
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
28.5 ± 0.6 nb
+ 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!
Proton
AntiProton
“Flavor Creation”
b-quark
Underlying Event
Initial -
State Radiation
Final
State
Radiation
JIMMY: MPI
J. M. Butterworth
J. R. Forshaw
M. H. Seymour
Adding multiple parton interactions (i.e. JIMMY) to enhance the “underlying event” increases the b-bbar jet cross section!
IMFP Day February 4, 2008
Rick Field – Florida/CDF/CMS

46. bb DiJet Cross Section (CDF)
since IMFP2006
New
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
5421 ± 105 nb
Predominately Flavor creation!
Sensitive to the “underlying event”!
IMFP Day February 4, 2008
Rick Field – Florida/CDF/CMS

47. bb DiJet Df Distribution (CDF)
since IMFP2006
New
Large Df (i.e. b-jets are “back-to-back”) is predominately “flavor creation”.
Small Df (i.e. b-jets are near each other) is predominately “flavor excitation” and “gluon splitting”.
It takes NLO + “underlying event” to get it right!
IMFP Day February 4, 2008
Rick Field – Florida/CDF/CMS

48. Z + b-Jet Production (CDF)
since IMFP2006
New
IMFP2006
Important background for new physics!
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.
L = 335 pb-1
today
1.5 fb-1
Extract fraction of b-tagged jets from secondary vertex mass distribution: NO assumption on the charm content.
Observable
CDF Data
PYTHIA Tune A
MCFM NLO (+UE)
s(Z+b-jet)
0.94±0.15±0.15 pb --
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”!
IMFP Day February 4, 2008
Rick Field – Florida/CDF/CMS

49. 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
IMFP Day February 4, 2008
Rick Field – Florida/CDF/CMS