1. 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

2. Toward and Understanding of Hadron-Hadron Collisions
From Feynman-Field to the Tevatron
1st hat!
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).
Let’s find the Higgs!
CDF Collaboration Meeting June 8, 2006
Rick Field – Florida/CDF

3. The Feynman-Field Days
“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, (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, (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, (1978).
FW1: “A QCD Model for e+e- Annihilation”, R. D. Field and S. Wolfram, Nucl. Phys. B213, (1983).
My 1st graduate student!
CDF Collaboration Meeting June 8, 2006
Rick Field – Florida/CDF

4. Rick Field – Florida/CDF
Before Feynman-Field
Rick Field 1968
CDF Collaboration Meeting June 8, 2006
Rick Field – Florida/CDF

5. Rick Field – Florida/CDF
Before Feynman-Field
Rick & Jimmie
1970
Rick & Jimmie
1968
Rick & Jimmie
1972 (pregnant!)
Rick & Jimmie at CALTECH 1973
CDF Collaboration Meeting June 8, 2006
Rick Field – Florida/CDF

6. 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

7. Hadron-Hadron Collisions
FF (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”
CDF Collaboration Meeting June 8, 2006
Rick Field – Florida/CDF

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.
CDF Collaboration Meeting June 8, 2006
Rick Field – Florida/CDF

9. Quark-Quark Black-Box Model
Predict
particle ratios
FF (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

10. SAW CRONIN AM NOW CONVINCED WERE RIGHT TRACK QUICK WRITE
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

11. 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

12. 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
CDF Collaboration Meeting June 8, 2006
Rick Field – Florida/CDF

13. 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!
CDF Collaboration Meeting June 8, 2006
Rick Field – Florida/CDF

14. A Parameterization of the Properties of Jets
Field-Feynman 1978
Secondary Mesons
(after decay)
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 quark “b” with momentum P1 = h1P0.
Rank 2
Rank 1
Assume that the mesons originating from quark “b” are distributed in presisely the same way as the mesons which came from quark a (i.e. same function f(h)), leaving quark “c” with momentum P2 = h2P1 = h2h1P0.
Primary Mesons
(cb)
(ba)
cc pair
bb pair
continue
Add in flavor dependence by letting bu = probabliity of producing u-ubar pair, bd = probability of producing d-dbar pair, etc.
Calculate F(z) from f(h) and bi!
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.
Original quark with flavor “a” and momentum P0
CDF Collaboration Meeting June 8, 2006
Rick Field – Florida/CDF

15. Feynman-Field Jet Model
R. P. Feynman
ISMD, Kaysersberg, France, June 12, 1977
Feynman quote from FF2
“The predictions of the model are reasonable
enough physically that we expect it may
be close enough to reality to be useful in
designing future experiments and to serve
as a reasonable approximation to compare
to data. We do not think of the model
as a sound physical theory, ....”
CDF Collaboration Meeting June 8, 2006
Rick Field – Florida/CDF

16. Monte-Carlo Simulation of Hadron-Hadron Collisions
FF1-FFF1 (1977) “Black-Box” Model
FF2 (1978)
Monte-Carlo simulation of “jets”
F1-FFF2 (1978) QCD Approach
FFFW “FieldJet” (1980)
QCD “leading-log order” simulation
of hadron-hadron collisions
“FF” or “FW” Fragmentation
the past
today
ISAJET
(“FF” Fragmentation)
HERWIG
(“FW” Fragmentation)
PYTHIA
tomorrow
SHERPA
PYTHIA 6.3
CDF Collaboration Meeting June 8, 2006
Rick Field – Florida/CDF

17. 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.
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.
hadrons
Field-Feynman
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! Q2
CDF Distribution of Particles in Jets
MLLA Curve!
5 GeV
1 GeV
200 MeV
CDF Collaboration Meeting June 8, 2006
Rick Field – Florida/CDF

18. 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!
CDF Collaboration Meeting June 8, 2006
Rick Field – Florida/CDF

19. Rick Field – Florida/CDF
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

20. Jet Corrections & Extrapolations
Calorimeter Level Jets → Hadron Level Jets:
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!
Hadron ← Parton
I do not believe we should extrapolate
the data to the parton level! We should
publish what we measure (i.e. hadron level
with the “underlying event”)!
To compare with theory we should
“extrapolate” the parton level to the
hadron level (i.e. add hadronization and
the “underlying event” to the parton level)!
PYTHIA, HERWIG,
Particle Level Jets (with the “underlying event” removed):
Do we want to make further model dependent corrections?
Do we want to try and subtract the “underlying event” from the observed “particle level” jets.
This cannot really be done, but if you trust the Monte-Carlo modeling of the “underlying event” you can do it by using the Monte-Carlo models (use PYTHIA Tune A).
This is no longer an observable, it is a model dependent extrapolation!
Useless without a model of hadronization!
Hadron Level Jets → Parton Level Jets:
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?
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 (use PYTHIA Tune A) including ISR and FSR.
Cannot extrapolate the data to fixed order NLO!
Next-to-leading order parton level calculation
0, 1, 2, or 3 partons!
CDF Collaboration Meeting June 8, 2006
Rick Field – Florida/CDF

21. Good and Bad Algorithms
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).
Infrared Safety (Parton Level) Soft parton emission changes jet multiplicity
below threshold
(no jets)
above threshold
(1 jet)
Collinear Safety (Parton Level)
If you hadronize the parton level and add the “underlying event” (i.e. PYTHIA, HERWIG, 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

22. Towers not included in a jet (i.e. “dark towers”)!
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

23. Rick Field – Florida/CDF
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
CDF Collaboration Meeting June 8, 2006
Rick Field – Florida/CDF

24. 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

25. 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

26. Hadronization and “Underlying Event” Corrections
Note that DØ does not make any
corrections for hadronization
or the “underlying event”!?
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!
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

27. 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

28. The “Transverse” Regions as defined by the Leading Jet
Charged Particle Df Correlations pT > 0.5 GeV/c |h| < 1
Look at the charged particle density in the “transverse” region!
“Transverse” region is very sensitive to the “underlying event”!
Look at charged particle correlations in the azimuthal angle Df relative to the leading calorimeter jet (JetClu R = 0.7, |h| < 2).
Define |Df| < 60o as “Toward”, 60o < -Df < 120o and 60o < Df < 120o as “Transverse 1” and “Transverse 2”, and |Df| > 120o as “Away”. Each of the two “transverse” regions have area DhDf = 2x60o = 4p/6. The overall “transverse” region is the sum of the two transverse regions (DhDf = 2x120o = 4p/3).
CDF Collaboration Meeting June 8, 2006
Rick Field – Florida/CDF

29. Run 1 PYTHIA Tune A PYTHIA 6.206 CTEQ5L
CDF Default!
PYTHIA CTEQ5L
Parameter
Tune B
Tune A
MSTP(81) 1
MSTP(82) 4
PARP(82)
1.9 GeV
2.0 GeV
PARP(83)
0.5
PARP(84)
0.4
PARP(85)
1.0
0.9
PARP(86)
0.95
PARP(89)
1.8 TeV
PARP(90)
0.25
PARP(67)
4.0
Run 1 Analysis
Plot shows the “transverse” charged particle density versus PT(chgjet#1) compared to the QCD hard scattering predictions of two tuned versions of PYTHIA (CTEQ5L, Set B (PARP(67)=1) and Set A (PARP(67)=4)).
Old PYTHIA default
(more initial-state radiation)
Old PYTHIA default
(more initial-state radiation)
New PYTHIA default
(less initial-state radiation)
New PYTHIA default
(less initial-state radiation)
CDF Collaboration Meeting June 8, 2006
Rick Field – Florida/CDF

30. Charged Particle Density Df Dependence
Refer to this as a “Leading Jet” event
Subset
Refer to this as a
“Back-to-Back” event
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” (Df12 > 150o) with almost equal transverse energies (ET(jet#2)/ET(jet#1) > 0.8) and with ET(jet#3) < 15 GeV.
Shows the Df dependence of the charged particle density, dNchg/dhdf, 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

31. “Transverse” PTsum Density vs ET(jet#1)
“Leading Jet”
Hard Radiation!
“Back-to-Back”
Min-Bias
0.24 GeV/c per unit h-f
Shows the average charged PTsum density, dPTsum/dhdf, 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

32. “TransMAX/MIN” PTsum Density PYTHIA Tune A vs HERWIG
PYTHIA Tune A does a fairly good job fitting the PTsum density in the “transverse” region!
HERWIG does a poor job!
“Leading Jet”
“Back-to-Back”
Shows the charged particle PTsum density, dPTsum/dhdf, 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.
CDF Collaboration Meeting June 8, 2006
Rick Field – Florida/CDF

33. “TransMAX/MIN” ETsum Density PYTHIA Tune A vs HERWIG
“Leading Jet”
“Back-to-Back”
Neither PY Tune A or HERWIG fits the ETsum density in the “transferse” region!
HERWIG does slightly better than Tune A!
Shows the data on the tower ETsum density, dETsum/dhdf, 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).
CDF Collaboration Meeting June 8, 2006
Rick Field – Florida/CDF

34. “TransDIF” ETsum Density PYTHIA Tune A vs HERWIG
“Leading Jet”
“Back-to-Back”
“transDIF” is more sensitive to the “hard scattering” component of the “underlying event”!
Use the leading jet to define the MAX and MIN “transverse” regions on an event-by-event basis with MAX (MIN) having the largest (smallest) charged PTsum density.
Shows the “transDIF” = MAX-MIN ETsum density, dETsum/dhdf, 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

35. Rick Field – Florida/CDF
Possible Scenario??
PYTHIA Tune A fits the charged particle PTsum density for pT > 0.5 GeV/c, but it does not produce enough ETsum for towers with ET > 0.1 GeV.
It is possible that there is a sharp rise in the number of particles in the “underlying event” at low pT (i.e. pT < 0.5 GeV/c).
Perhaps there are two components, a vary “soft” beam-beam remnant component (gaussian or exponential) and a “hard” multiple interaction component.
CDF Collaboration Meeting June 8, 2006
Rick Field – Florida/CDF

36. QCD Monte-Carlo Models: Lepton-Pair Production
“Hard Scattering” Component
“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

37. 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)
After removing the lepton-pair everything else is the “underlying event”!
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/dhdf, and the charged scalar pT sum density, dPTsum/dhdf, by dividing by the area in h-f space.
CDF Collaboration Meeting June 8, 2006
Rick Field – Florida/CDF

38. Rick Field – Florida/CDF
CDF Run 1 PT(Z)
PYTHIA 6.2 CTEQ5L
UE Parameters
Parameter
Tune A
Tune A25
Tune A50
MSTP(81) 1
MSTP(82) 4
PARP(82)
2.0 GeV
PARP(83)
0.5
PARP(84)
0.4
PARP(85)
0.9
PARP(86)
0.95
PARP(89)
1.8 TeV
PARP(90)
0.25
PARP(67)
4.0
MSTP(91)
PARP(91)
1.0
2.5
5.0
PARP(93)
15.0
25.0
ISR Parameter
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
Rick Field – Florida/CDF

39. CDF Run 1 PT(Z) PYTHIA 6.2 CTEQ5L
Tune used by the
CDF-EWK group!
PYTHIA 6.2 CTEQ5L
Parameter
Tune A
Tune AW
MSTP(81) 1
MSTP(82) 4
PARP(82)
2.0 GeV
PARP(83)
0.5
PARP(84)
0.4
PARP(85)
0.9
PARP(86)
0.95
PARP(89)
1.8 TeV
PARP(90)
0.25
PARP(62)
1.0
1.25
PARP(64)
0.2
PARP(67)
4.0
MSTP(91)
PARP(91)
2.1
PARP(93)
5.0
15.0
UE Parameters
ISR Parameters
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
Rick Field – Florida/CDF

40. Jet-Jet Correlations (DØ)
Df Jet#1-Jet#2
Jet#1-Jet#2 Df Distribution
MidPoint Cone Algorithm (R = 0.7, fmerge = 0.5)
L = 150 pb-1 (Phys. Rev. Lett (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

41. CDF Run 1 PT(Z) PYTHIA 6.2 CTEQ5L
Parameter
Tune DW
Tune AW
MSTP(81) 1
MSTP(82) 4
PARP(82)
1.9 GeV
2.0 GeV
PARP(83)
0.5
PARP(84)
0.4
PARP(85)
1.0
0.9
PARP(86)
0.95
PARP(89)
1.8 TeV
PARP(90)
0.25
PARP(62)
1.25
PARP(64)
0.2
PARP(67)
2.5
4.0
MSTP(91)
PARP(91)
2.1
PARP(93)
15.0
UE Parameters
ISR Parameters
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

42. “Transverse” Nchg Density
PYTHIA 6.2 CTEQ5L
Three different amounts of MPI!
UE Parameters
Parameter
Tune AW
Tune DW
Tune BW
MSTP(81) 1
MSTP(82) 4
PARP(82)
2.0 GeV
1.9 GeV
1.8 GeV
PARP(83)
0.5
PARP(84)
0.4
PARP(85)
0.9
1.0
PARP(86)
0.95
PARP(89)
1.8 TeV
PARP(90)
0.25
PARP(62)
1.25
PARP(64)
0.2
PARP(67)
4.0
2.5
MSTP(91)
PARP(91)
2/5
PARP(93)
15.0
ISR Parameter
Shows the “transverse” charged particle density, dN/dhdf, 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/dhdf, versus PT(jet#1) for “leading jet” events at 1.96 TeV for Tune DW, ATLAS, and HERWIG (without MPI).
Intrensic KT
Three different amounts of ISR!
CDF Collaboration Meeting June 8, 2006
Rick Field – Florida/CDF

43. “Transverse” PTsum Density
PYTHIA 6.2 CTEQ5L
Three different amounts of MPI!
UE Parameters
Parameter
Tune AW
Tune DW
Tune BW
MSTP(81) 1
MSTP(82) 4
PARP(82)
2.0 GeV
1.9 GeV
1.8 GeV
PARP(83)
0.5
PARP(84)
0.4
PARP(85)
0.9
1.0
PARP(86)
0.95
PARP(89)
1.8 TeV
PARP(90)
0.25
PARP(62)
1.25
PARP(64)
0.2
PARP(67)
4.0
2.5
MSTP(91)
PARP(91)
2/5
PARP(93)
15.0
ISR Parameter
Shows the “transverse” charged PTsum density, dPT/dhdf, 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/dhdf, versus PT(jet#1) for “leading jet” events at 1.96 TeV for Tune DW, ATLAS, and HERWIG (without MPI).
Intrensic KT
Three different amounts of ISR!
CDF Collaboration Meeting June 8, 2006
Rick Field – Florida/CDF

44. MIT Search Scheme 12 Exclusive 3 Jet Final State Challenge
CDF Data
At least 1 Jet (“trigger” jet)
(PT > 40 GeV/c, |h| < 1.0)
Bruce Knuteson
Normalized to 1
PYTHIA Tune A
Exactly 3 jets
(PT > 20 GeV/c, |h| < 2.5)
Order Jets by PT
Jet1 highest PT, etc.
R(j2,j3)
Khaldoun Makhoul
Georgios Choudalakis
Markus Klute
Conor Henderson
Ray Culbertson
Gene Flanagan
CDF Collaboration Meeting June 8, 2006
Rick Field – Florida/CDF

45. The data have more 3 jet events with small R(j2,j3)!?
3Jexc R(j2,j3) Normalized
The data have more 3 jet events with small R(j2,j3)!?
Let Ntrig40 equal the number of events with at least one jet with PT > 40 geV and |h| < 1.0 (this is the “offline” trigger).
Let N3Jexc20 equal the number of events 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.
Normalized to N3JexcFr
Let N3JexcFr = N3Jexc20/Ntrig40. The is the fraction of the “offline” trigger events that are exclusive 3-jet events.
The CDF data on dN/dR(j2,j3) at 1.96 TeV compared with PYTHIA Tune AW (PARP(67)=4), Tune DW (PARP(67)=2.5), Tune BW (PARP(67)=1).
PARP(67) affects the initial-state radiation which contributes primarily to the region R(j2,j3) > 1.0.
R > 1.0
CDF Collaboration Meeting June 8, 2006
Rick Field – Florida/CDF

46. excess number of events Perhaps this is related to the
3Jexc R(j2,j3) Normalized
I do not understand the
excess number of events
with R(j2,j3) < 1.0.
Perhaps this is related to the
“soft energy” problem??
For now the best tune is
PYTHIA Tune DW.
Let Ntrig40 equal the number of events with at least one jet with PT > 40 geV and |h| < 1.0 (this is the “offline” trigger).
Let N3Jexc20 equal the number of events 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.
Normalized to N3JexcFr
Let N3JexcFr = N3Jexc20/Ntrig40. The is the fraction of the “offline” trigger events that are exclusive 3-jet events.
The CDF data on dN/dR(j2,j3) at 1.96 TeV compared with PYTHIA Tune DW (PARP(67)=2.5) and HERWIG (without MPI).
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.
R < 1.0
CDF Collaboration Meeting June 8, 2006
Rick Field – Florida/CDF

47. Drell-Yan Production (Run 2 vs LHC)
Lepton-Pair Transverse Momentum
<pT(m+m-)> is much larger at the LHC!
Shapes of the pT(m+m-) distribution at the Z-boson mass. Z
Average Lepton-Pair transverse momentum at the Tevatron and the LHC for PYTHIA Tune DW and HERWIG (without MPI).
Shape of the Lepton-Pair pT distribution at the Z-boson mass at the Tevatron and the LHC for PYTHIA Tune DW and HERWIG (without MPI).
CDF Collaboration Meeting June 8, 2006
Rick Field – Florida/CDF

48. The “Underlying Event” in Drell-Yan Production
Charged particle density versus M(pair)
HERWIG (without MPI) is much less active than PY Tune AW (with MPI)!
“Underlying event” much more active at the LHC! Z Z
Charged particle density versus the lepton-pair invariant mass at 1.96 TeV for PYTHIA Tune AW and HERWIG (without MPI).
Charged particle density versus the lepton-pair invariant mass at 14 TeV for PYTHIA Tune AW and HERWIG (without MPI).
CDF Collaboration Meeting June 8, 2006
Rick Field – Florida/CDF

49. Extrapolations to the LHC: Drell-Yan Production
Charged particle density versus M(pair)
The “Underlying Event”
Tune DW and DWT are identical at 1.96 TeV, but have different MPI energy dependence! Z Z
Average charged particle density versus the lepton-pair invariant mass at 1.96 TeV for PYTHIA Tune A, Tune AW, Tune BW, Tune DW and HERWIG (without MPI).
Average charged particle density versus the lepton-pair invariant mass at 14 TeV for PYTHIA Tune DW, Tune DWT, ATLAS and HERWIG (without MPI).
CDF Collaboration Meeting June 8, 2006
Rick Field – Florida/CDF

50. Extrapolations to the LHC: Drell-Yan Production
Charged particle charged PTsum density versus M(pair)
The “Underlying Event”
The ATLAS tune has a much “softer” distribution of charged particles than the CDF Run 2 Tunes! Z Z
Average charged PTsum density versus the lepton-pair invariant mass at 1.96 TeV for PYTHIA Tune A, Tune AW, Tune BW, Tune DW and HERWIG (without MPI).
Average charged PTsum density versus the lepton-pair invariant mass at 14 TeV for PYTHIA Tune DW, Tune DWT, ATLAS and HERWIG (without MPI).
CDF Collaboration Meeting June 8, 2006
Rick Field – Florida/CDF

51. Extrapolations to the LHC: Drell-Yan Production
Charged particle density versus M(pair)
The “Underlying Event”
The ATLAS tune has a much “softer” distribution of charged particles than the CDF Run 2 Tunes!
Charged Particles (|h|<1.0, pT > 0.5 GeV/c)
Charged Particles (|h|<1.0, pT > 0.9 GeV/c) Z Z
Average charged particle density (pT > 0.5 GeV/c) versus the lepton-pair invariant mass at 14 TeV for PYTHIA Tune DW, Tune DWT, ATLAS and HERWIG (without MPI).
Average charged particle density (pT > 0.9 GeV/c) versus the lepton-pair invariant mass at 14 TeV for PYTHIA Tune DW, Tune DWT, ATLAS and HERWIG (without MPI).
CDF Collaboration Meeting June 8, 2006
Rick Field – Florida/CDF

52. Constraining the Higgs Mass
Tevatron Run I + LEP2
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!
Summer 05
Spring 2006
Light Higgs very interesting for the Tevatron!
CDF Collaboration Meeting June 8, 2006
Rick Field – Florida/CDF

53. Rick Field – Florida/CDF
20 Years of Measuring W & Z
CDF Collaboration Meeting June 8, 2006
Rick Field – Florida/CDF

54. Rick Field – Florida/CDF
The W+W Cross Section
Campbell & Ellis 1999
pb-1
CDF (pb)
NLO (pb)
s(WW) CDF
184
(stat)-5.1(stat)1.8(sys)0.9(lum)
12.40.8
s(WW) DØ
240
(stat)-3.8(stat)1.2(sys)0.9(lum)
CDF Collaboration Meeting June 8, 2006
Rick Field – Florida/CDF

55. The W+W Cross Section WW→dileptons + MET Two leptons pT > 20 GeV/c.
L = 825 pb-1
WW→dileptons + MET
Two leptons pT > 20 GeV/c.
Z veto.
MET > 20 GeV.
Zero jets with ET>15 GeV and |h|<2.5.
We are beginning to study the details of
Di-Boson production at the Tevatron!
Observe 95 events with 37.2 background! L
CDF (pb)
NLO (pb)
s(WW)
825 pb-1
13.72.3(stat)1.6(sys)1.2(lum)
12.40.8
Missing ET!
Lepton-Pair Mass!
ET Sum!
CDF Collaboration Meeting June 8, 2006
Rick Field – Florida/CDF

56. Di-Bosons at the TevatronW
We are getting closer to the Higgs! Z
W+g
Z+g
W+W
W+Z
CDF Collaboration Meeting June 8, 2006
Rick Field – Florida/CDF

57. Rick Field – Florida/CDF
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.
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.
Signal
cone
Isolation
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

58. Rick Field – Florida/CDF
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
CDF (pb)
NNLO (pb)
s(Z→t+t-)
26520(stat)21(sys)15(lum)
252.35.0
CDF Collaboration Meeting June 8, 2006
Rick Field – Florida/CDF

59. “Higgs Discovery Group”
Higgs → tt Search
Let’s find the Higgs!
“Higgs Discovery Group”
events
140 GeV Higgs Signal!
1 event
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

60. 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