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Toward an Understanding of Hadron-Hadron Collisions. From Feynman-Field to the LHC. Rick Field University of Florida. Outline of Talk. LBNL January 15, 2009. Before Feynman-Field Phenomenology. The early days of Feynman-Field Phenomenology. - PowerPoint PPT Presentation
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Lawrence Berkeley Laboratory January 15, 2009
Rick Field – Florida/CDF/CMS Page 1
Toward an Understanding ofToward an Understanding ofHadron-Hadron CollisionsHadron-Hadron Collisions
Rick FieldUniversity of Florida
Outline of Talk LBNL January 15, 2009
Proton AntiProton
PT(hard)
Outgoing Parton
Outgoing Parton
Underlying Event Underlying Event
Initial-State Radiation
Final-State Radiation
CMS at the LHCCDF Run 2
The early days of Feynman-Field Phenomenology.
Studying “min-bias” collisions and the “underlying event” at CDF.
Extrapolations to the LHC.
From Feynman-Field to the LHC
Before Feynman-Field Phenomenology.
Lawrence Berkeley Laboratory January 15, 2009
Rick Field – Florida/CDF/CMS Page 2
Before Feynman-FieldBefore Feynman-FieldRick Field 1964 R. D. Field
University of California, Berkeley, 1962-66 (undergraduate)University of California, Berkeley, 1966-71 (graduate student) me
My sister Sally!
The very first “Berkeley Physics Course”!
My Ph.D. advisor!
J.D.JBob
Cahn
Chris Quiggme
Lawrence Berkeley Laboratory January 15, 2009
Rick Field – Florida/CDF/CMS Page 3
Before Feynman-FieldBefore Feynman-Field
Rick & Jimmie1968
Rick & Jimmie1970 Rick & Jimmie
1972 (pregnant!)
Rick & Jimmie at CALTECH 1973
Lawrence Berkeley Laboratory January 15, 2009
Rick Field – Florida/CDF/CMS Page 4
Toward and Understanding of Toward and Understanding of Hadron-Hadron CollisionsHadron-Hadron Collisions
From 7 GeV/c 0’s to 600 GeV/c Jets. The early days of trying to understand and simulate hadron-hadron collisions.
Feynman-Field Phenomenology
Feynman and Field
Proton AntiProton
PT(hard)
Outgoing Parton
Outgoing Parton
Underlying Event Underlying Event
Initial-State Radiation
Final-State Radiation
1st hat!
Lawrence Berkeley Laboratory January 15, 2009
Rick Field – Florida/CDF/CMS Page 5
“Feynman-Field Jet Model”
The FeynmanThe Feynman-Field -Field DaysDays
FF1: “Quark Elastic Scattering as a Source of High Transverse Momentum Mesons”, R. D. Field and R. P. Feynman, Phys. Rev. D15, 2590-2616 (1977).
FFF1: “Correlations Among Particles and Jets Produced with Large Transverse Momenta”, R. P. Feynman, R. D. Field and G. C. Fox, Nucl. Phys. B128, 1-65 (1977).
FF2: “A Parameterization of the properties of Quark Jets”, R. D. Field and R. P. Feynman, Nucl. Phys. B136, 1-76 (1978).
F1: “Can Existing High Transverse Momentum Hadron Experiments be Interpreted by Contemporary Quantum Chromodynamics Ideas?”, R. D. Field, Phys. Rev. Letters 40, 997-1000 (1978).
FFF2: “A Quantum Chromodynamic Approach for the Large Transverse Momentum Production of Particles and Jets”, R. P. Feynman, R. D. Field and G. C. Fox, Phys. Rev. D18, 3320-3343 (1978).
1973-1983
FW1: “A QCD Model for e+e- Annihilation”, R. D. Field and S. Wolfram, Nucl. Phys. B213, 65-84 (1983).
My 1st graduate student!
Lawrence Berkeley Laboratory January 15, 2009
Rick Field – Florida/CDF/CMS Page 6
Hadron-Hadron CollisionsHadron-Hadron Collisions
What happens when two hadrons collide at high energy?
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!
Hadron Hadron ???
Hadron Hadron
“Soft” Collision (no large transverse momentum)
Hadron Hadron
high PT meson
Parton-Parton Scattering Outgoing Parton
Outgoing Parton
FF1 1977 (preQCD)
Feynman quote from FF1“The model we shall choose is not a popular one,
so that we will not duplicate too much of thework 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.”
“Black-Box Model”
Lawrence Berkeley Laboratory January 15, 2009
Rick Field – Florida/CDF/CMS Page 7
QuarkQuark--Quark BlackQuark Black--Box ModelBox ModelFF1 1977 (preQCD)Quark Distribution Functions
determined from deep-inelasticlepton-hadron collisions
Quark Fragmentation Functionsdetermined from e+e- annihilationsQuark-Quark Cross-Section
Unknown! Deteremined fromhadron-hadron collisions.
No gluons!
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.”
Lawrence Berkeley Laboratory January 15, 2009
Rick Field – Florida/CDF/CMS Page 8
Quark-Quark Black-Box ModelQuark-Quark Black-Box Model
FF1 1977 (preQCD)Predictparticle ratios
Predictincrease with increasing
CM energy W
Predictoverall event topology
(FFF1 paper 1977)
“Beam-Beam Remnants”
7 GeV/c 0’s!
Lawrence Berkeley Laboratory January 15, 2009
Rick Field – Florida/CDF/CMS Page 9
Telagram from FeynmanTelagram from FeynmanJuly 1976
SAW CRONIN AM NOW CONVINCED WERE RIGHT TRACK QUICK WRITEFEYNMAN
Lawrence Berkeley Laboratory January 15, 2009
Rick Field – Florida/CDF/CMS Page 10
Letter from FeynmanLetter from FeynmanJuly 1976
Lawrence Berkeley Laboratory January 15, 2009
Rick Field – Florida/CDF/CMS Page 11
Letter from Feynman Page 1Letter from Feynman Page 1
Spelling?
Lawrence Berkeley Laboratory January 15, 2009
Rick Field – Florida/CDF/CMS Page 12
Letter from Feynman Page 3Letter from Feynman Page 3It is fun!
Onward!
Lawrence Berkeley Laboratory January 15, 2009
Rick Field – Florida/CDF/CMS Page 13
Feynman Talk at Coral GablesFeynman Talk at Coral Gables (December 1976)(December 1976)
“Feynman-Field Jet Model”
1st transparency Last transparency
Lawrence Berkeley Laboratory January 15, 2009
Rick Field – Florida/CDF/CMS Page 14
QCD Approach: Quarks & GluonsQCD Approach: Quarks & Gluons
FFF2 1978
Parton Distribution FunctionsQ2 dependence predicted from
QCD
Quark & Gluon Fragmentation Functions
Q2 dependence predicted from QCD
Quark & Gluon Cross-SectionsCalculated from QCD
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.”
Lawrence Berkeley Laboratory January 15, 2009
Rick Field – Florida/CDF/CMS Page 15
A Parameterization of A Parameterization of the Properties of Jetsthe Properties of Jets
Assumed that jets could be analyzed on a “recursive” principle.
Field-Feynman 1978
Original quark with flavor “a” and momentum P0
bb pair
(ba)
Let f()d be the probability that the rank 1 meson leaves fractional momentum to the remaining cascade, leaving quark “b” with momentum P1 = 1P0.
cc pair
(cb) Primary Mesons
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()), leaving quark “c” with momentum P2 = 2P1 = 21P0.
Add in flavor dependence by letting u = probabliity of producing u-ubar pair, d = probability of producing d-dbar pair, etc.
Let F(z)dz be the probability of finding a meson (independent of rank) with fractional mementum z of the original quark “a” within the jet.
Rank 2
continue
Calculate F(z) from f() and i!
(bk) (ka)
Rank 1
Secondary Mesons(after decay)
Lawrence Berkeley Laboratory January 15, 2009
Rick Field – Florida/CDF/CMS Page 16
Feynman-Field Jet ModelFeynman-Field Jet ModelR. 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, ....”
Lawrence Berkeley Laboratory January 15, 2009
Rick Field – Florida/CDF/CMS Page 17
Monte-Carlo SimulationMonte-Carlo Simulationof Hadron-Hadron Collisionsof Hadron-Hadron Collisions
FF1-FFF1 (1977) “Black-Box” Model
F1-FFF2 (1978) QCD Approach
FF2 (1978) Monte-Carlo
simulation of “jets”
FFFW “FieldJet” (1980) QCD “leading-log order” simulation
of hadron-hadron collisions
ISAJET(“FF” Fragmentation)
HERWIG(“FW” Fragmentation)
PYTHIAtoday
“FF” or “FW” Fragmentationthe past
tomorrow SHERPA PYTHIA 6.4
Lawrence Berkeley Laboratory January 15, 2009
Rick Field – Florida/CDF/CMS Page 18
High PHigh PTT Jets Jets
30 GeV/c!
Predictlarge “jet”
cross-section
Feynman, Field, & Fox (1978) CDF (2006)
600 GeV/c Jets!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.”
Lawrence Berkeley Laboratory January 15, 2009
Rick Field – Florida/CDF/CMS Page 19
CDF DiJet Event: M(jj) CDF DiJet Event: M(jj) ≈ 1.4 TeV≈ 1.4 TeV ET
jet1 = 666 GeV ETjet2 = 633 GeV
Esum = 1,299 GeV M(jj) = 1,364 GeV
M(jj)/Ecm ≈ 70%!!
Lawrence Berkeley Laboratory January 15, 2009
Rick Field – Florida/CDF/CMS Page 20
The Fermilab TevatronThe Fermilab Tevatron
I joined CDF in January 1998.
Proton AntiProton 2 TeV
Proton
AntiProton
1 mile CDF
CDF “SciCo” Shift December 12-19, 2008
Acquired 4728 nb-1 during 8 hour “owl” shift!
My wife Jimmie on shift with me!
Lawrence Berkeley Laboratory January 15, 2009
Rick Field – Florida/CDF/CMS Page 21
Proton-AntiProton CollisionsProton-AntiProton Collisionsat the Tevatronat the Tevatron
Elastic Scattering Single Diffraction
M
tot = ELSD DD HC
Double Diffraction
M1 M2
Proton AntiProton
“Soft” Hard Core (no hard scattering)
Proton AntiProton
PT(hard)
Outgoing Parton
Outgoing Parton
Underlying Event Underlying Event Initial-State Radiation
Final-State Radiation
“Hard” Hard Core (hard scattering)
Hard Core
1.8 TeV: 78mb = 18mb + 9mb + (4-7)mb + (47-44)mb
The CDF “Min-Bias” trigger picks up most of the “hard
core” cross-section plus a small amount of single & double
diffraction.
The “hard core” component contains both “hard” and
“soft” collisions.
Beam-Beam Counters
3.2 < || < 5.9
CDF “Min-Bias” trigger1 charged particle in forward BBC
AND1 charged particle in backward BBC
tot = ELIN
Lawrence Berkeley Laboratory January 15, 2009
Rick Field – Florida/CDF/CMS Page 22
QCD Monte-Carlo Models:QCD Monte-Carlo Models:High Transverse Momentum JetsHigh Transverse Momentum Jets
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).
Hard Scattering
PT(hard)
Outgoing Parton
Outgoing Parton
Initial-State Radiation
Final-State Radiation
Hard Scattering
PT(hard)
Outgoing Parton
Outgoing Parton
Initial-State Radiation
Final-State Radiation
Proton AntiProton
Underlying Event Underlying Event
Proton AntiProton
Underlying Event Underlying Event
“Hard Scattering” Component
“Jet”
“Jet”
“Underlying Event”
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.
“Jet”
The “underlying event” is an unavoidable background to most collider observables and having good understand of it leads to
more precise collider measurements!
Lawrence Berkeley Laboratory January 15, 2009
Rick Field – Florida/CDF/CMS Page 23
-1 +1
2
0
1 charged particle
dNchg/dd = 1/4 = 0.08
Study the charged particles (pT > 0.5 GeV/c, || < 1) and form the charged particle density, dNchg/dd, and the charged scalar pT sum density, dPTsum/dd.
Charged Particles pT > 0.5 GeV/c || < 1
= 4 = 12.6
1 GeV/c PTsum
dPTsum/dd = 1/4 GeV/c = 0.08 GeV/c
dNchg/dd = 3/4 = 0.24
3 charged particles
dPTsum/dd = 3/4 GeV/c = 0.24 GeV/c
3 GeV/c PTsum
CDF Run 2 “Min-Bias”Observable Average Average Density
per unit -
NchgNumber of Charged Particles
(pT > 0.5 GeV/c, || < 1) 3.17 +/- 0.31 0.252 +/- 0.025
PTsum (GeV/c)
Scalar pT sum of Charged Particles(pT > 0.5 GeV/c, || < 1) 2.97 +/- 0.23 0.236 +/- 0.018
Divide by 4
CDF Run 2 “Min-Bias”
Particle DensitiesParticle Densities
Lawrence Berkeley Laboratory January 15, 2009
Rick Field – Florida/CDF/CMS Page 24
Use the maximum pT charged particle in the event, PTmax, to define a direction and look at the the “associated” density, dNchg/dd, in “min-bias” collisions (pT > 0.5 GeV/c, || < 1).
PTmax Direction
Correlations in
Charged Particle Density: dN/dd
0.0
0.1
0.2
0.3
0.4
0.5
0 30 60 90 120 150 180 210 240 270 300 330 360 (degrees)
Cha
rged
Par
ticle
Den
sity
PTmax
Associated DensityPTmax not included
CDF Preliminarydata uncorrected
Charged Particles (||<1.0, PT>0.5 GeV/c)
Charge Density
Min-Bias
“Associated” densities do not include PTmax!
Highest pT charged particle!
PTmax Direction
Correlations in
Shows the data on the dependence of the “associated” charged particle density, dNchg/dd, for charged particles (pT > 0.5 GeV/c, || < 1, not including PTmax) relative to PTmax (rotated to 180o) for “min-bias” events. Also shown is the average charged particle density, dNchg/dd, for “min-bias” events.
It is more probable to find a particle accompanying PTmax than it is to
find a particle in the central region!
CDF Run 1 Min-Bias “Associated”CDF Run 1 Min-Bias “Associated”Charged Particle DensityCharged Particle Density
Lawrence Berkeley Laboratory January 15, 2009
Rick Field – Florida/CDF/CMS Page 25
Associated Particle Density: dN/dd
0.0
0.2
0.4
0.6
0.8
1.0
0 30 60 90 120 150 180 210 240 270 300 330 360 (degrees)
Ass
ocia
ted
Part
icle
Den
sity
PTmax > 2.0 GeV/cPTmax > 1.0 GeV/cPTmax > 0.5 GeV/c
CDF Preliminarydata uncorrected
PTmaxPTmax not included
Charged Particles (||<1.0, PT>0.5 GeV/c)
Min-Bias
PTmax Direction
Correlations in
Shows the data on the dependence of the “associated” charged particle density, dNchg/dd, for charged particles (pT > 0.5 GeV/c, || < 1, not including PTmax) relative to PTmax (rotated to 180o) for “min-bias” events with PTmax > 0.5, 1.0, and 2.0 GeV/c.
Transverse Region
Transverse Region
Jet #1
Shows “jet structure” in “min-bias” collisions (i.e. the “birth” of the leading two jets!).
Jet #2
Ave Min-Bias0.25 per unit -
PTmax Direction
“Toward”
“Transverse” “Transverse”
“Away”
PTmax > 0.5 GeV/c
PTmax > 2.0 GeV/c
CDF Run 1 Min-Bias “Associated”CDF Run 1 Min-Bias “Associated”Charged Particle DensityCharged Particle Density Rapid rise in the particle
density in the “transverse” region as PTmax increases!
Lawrence Berkeley Laboratory January 15, 2009
Rick Field – Florida/CDF/CMS Page 26
Charged Jet #1Direction
“Transverse” “Transverse”
“Toward”
“Away”
“Toward-Side” Jet
“Away-Side” Jet
Look at charged particle correlations in the azimuthal angle relative to the leading charged particle jet.
Define || < 60o as “Toward”, 60o < || < 120o as “Transverse”, and || > 120o as “Away”.All three regions have the same size in - space, x = 2x120o = 4/3.
Charged Jet #1Direction
“Toward”
“Transverse” “Transverse”
“Away”
-1 +1
2
0
Leading Jet
Toward Region
Transverse Region
Transverse Region
Away Region
Away Region
Charged Particle Correlations PT > 0.5 GeV/c || < 1
Look at the charged particle density in the “transverse” region!“Transverse” region
very sensitive to the “underlying event”!
CDF Run 1 Analysis
CDF Run 1: Evolution of Charged JetsCDF Run 1: Evolution of Charged Jets“Underlying Event”“Underlying Event”
Lawrence Berkeley Laboratory January 15, 2009
Rick Field – Florida/CDF/CMS Page 27
Compares the average “transverse” charge particle density with the average “Min-Bias” charge particle density (||<1, pT>0.5 GeV). Shows how the “transverse” charge particle density and the Min-Bias charge particle density is distributed in pT.
CDF Run 1 Min-Bias data<dNchg/dd> = 0.25
PT(charged jet#1) > 30 GeV/c“Transverse” <dNchg/dd> = 0.56
Factor of 2!
“Min-Bias”
"Transverse" Charged Particle Density: dN/dd
0.00
0.25
0.50
0.75
1.00
0 5 10 15 20 25 30 35 40 45 50
PT(charged jet#1) (GeV/c)
"Tra
nsve
rse"
Cha
rged
Den
sity
CDF Min-BiasCDF JET20
CDF Run 1data uncorrected
1.8 TeV ||<1.0 PT>0.5 GeV/c
Charged Particle Jet #1 Direction
“Toward”
“Transverse” “Transverse”
“Away”
Charged Particle Density
1.0E-06
1.0E-05
1.0E-04
1.0E-03
1.0E-02
1.0E-01
1.0E+00
0 2 4 6 8 10 12 14
PT(charged) (GeV/c)C
harg
ed D
ensi
ty d
N/d
d
dPT
(1/G
eV/c
)
CDF Run 1data uncorrected
1.8 TeV ||<1 PT>0.5 GeV/c
Min-Bias
"Transverse"PT(chgjet#1) > 5 GeV/c
"Transverse"PT(chgjet#1) > 30 GeV/c
Run 1 Charged Particle DensityRun 1 Charged Particle Density “Transverse” p“Transverse” pTT Distribution Distribution
Lawrence Berkeley Laboratory January 15, 2009
Rick Field – Florida/CDF/CMS Page 28
Plot shows average “transverse” charge particle density (||<1, pT>0.5 GeV) versus PT(charged jet#1) compared to the QCD hard scattering predictions of ISAJET 7.32 (default parameters with PT(hard)>3 GeV/c) .
The predictions of ISAJET are divided into two categories: charged particles that arise from the break-up of the beam and target (beam-beam remnants); and charged particles that arise from the outgoing jet plus initial and final-state radiation (hard scattering component).
Beam-BeamRemnants
ISAJETCharged Jet #1Direction
“Toward”
“Transverse” “Transverse”
“Away”
“Hard”Component
"Transverse" Charged Particle Density: dN/dd
0.00
0.25
0.50
0.75
1.00
0 5 10 15 20 25 30 35 40 45 50
PT(charged jet#1) (GeV/c)
"Tra
nsve
rse"
Cha
rged
Den
sity
CDF Run 1Datadata uncorrectedtheory corrected
1.8 TeV ||<1.0 PT>0.5 GeV
Isajet
"Remnants"
"Hard"
ISAJET 7.32ISAJET 7.32“Transverse” Density“Transverse” Density
ISAJET uses a naïve leading-log parton shower-model which does
not agree with the data!
Lawrence Berkeley Laboratory January 15, 2009
Rick Field – Florida/CDF/CMS Page 29
Plot shows average “transverse” charge particle density (||<1, pT>0.5 GeV) versus PT(charged jet#1) compared to the QCD hard scattering predictions of HERWIG 5.9 (default parameters with PT(hard)>3 GeV/c).
The predictions of HERWIG are divided into two categories: charged particles that arise from the break-up of the beam and target (beam-beam remnants); and charged particles that arise from the outgoing jet plus initial and final-state radiation (hard scattering component).
Beam-BeamRemnants
HERWIG
Charged Jet #1Direction
“Toward”
“Transverse” “Transverse”
“Away”
"Transverse" Charged Particle Density: dN/dd
0.00
0.25
0.50
0.75
1.00
0 5 10 15 20 25 30 35 40 45 50
PT(charged jet#1) (GeV/c)
"Tra
nsve
rse"
Cha
rged
Den
sity
CDF Run 1Datadata uncorrectedtheory corrected
1.8 TeV ||<1.0 PT>0.5 GeV
Herwig 6.4 CTEQ5LPT(hard) > 3 GeV/c
Total "Hard"
"Remnants"
“Hard”Component
HERWIG uses a modified leading-log parton shower-model which
does agrees better with the data!
HERWIG 6.4HERWIG 6.4“Transverse” Density“Transverse” Density
Lawrence Berkeley Laboratory January 15, 2009
Rick Field – Florida/CDF/CMS Page 30
MPI: Multiple PartonMPI: Multiple PartonInteractionsInteractions
PYTHIA models the “soft” component of the underlying event with color string fragmentation, but in addition includes a contribution arising from multiple parton interactions (MPI) in which one interaction is hard and the other is “semi-hard”.
Proton AntiProton
Multiple Parton Interaction
initial-state radiation
final-state radiation outgoing parton
outgoing parton
color string
color string
The probability that a hard scattering events also contains a semi-hard multiple parton interaction can be varied but adjusting the cut-off for the MPI.
One can also adjust whether the probability of a MPI depends on the PT of the hard scattering, PT(hard) (constant cross section or varying with impact parameter).
One can adjust the color connections and flavor of the MPI (singlet or nearest neighbor, q-qbar or glue-glue).
Also, one can adjust how the probability of a MPI depends on PT(hard) (single or double Gaussian matter distribution).
+
“Semi-Hard” MPI “Hard” Component
initial-state radiation
final-state radiation outgoing jet Beam-Beam Remnants
or
“Soft” Component
Proton AntiProton
“Hard” Collision
initial-state radiation
final-state radiation outgoing parton
outgoing parton
Lawrence Berkeley Laboratory January 15, 2009
Rick Field – Florida/CDF/CMS Page 31
Parameter Default
Description
PARP(83) 0.5 Double-Gaussian: Fraction of total hadronic matter within PARP(84)
PARP(84) 0.2 Double-Gaussian: Fraction of the overall hadron radius containing the fraction PARP(83) of the total hadronic matter.
PARP(85) 0.33 Probability that the MPI produces two gluons with color connections to the “nearest neighbors.
PARP(86) 0.66 Probability that the MPI produces two gluons either as described by PARP(85) or as a closed gluon loop. The remaining fraction consists of quark-antiquark pairs.
PARP(89) 1 TeV Determines the reference energy E0.
PARP(90) 0.16 Determines the energy dependence of the cut-offPT0 as follows PT0(Ecm) = PT0(Ecm/E0) with = PARP(90)
PARP(67) 1.0 A scale factor that determines the maximum parton virtuality for space-like showers. The larger the value of PARP(67) the more initial-state radiation.
Hard Core
Multiple Parton Interaction
Color String
Color String
Multiple Parton Interaction
Color String
Hard-Scattering Cut-Off PT0
1
2
3
4
5
100 1,000 10,000 100,000CM Energy W (GeV)
PT0
(GeV
/c)
PYTHIA 6.206
= 0.16 (default)
= 0.25 (Set A))
Take E0 = 1.8 TeV
Reference pointat 1.8 TeV
Determine by comparingwith 630 GeV data!
Affects the amount ofinitial-state radiation!
Tuning PYTHIA:Tuning PYTHIA:Multiple Parton Interaction ParametersMultiple Parton Interaction Parameters
Lawrence Berkeley Laboratory January 15, 2009
Rick Field – Florida/CDF/CMS Page 32
"Transverse" Charged Particle Density: dN/dd
0.00
0.25
0.50
0.75
1.00
0 5 10 15 20 25 30 35 40 45 50
PT(charged jet#1) (GeV/c)"T
rans
vers
e" C
harg
ed D
ensi
ty
CTEQ3L CTEQ4L CTEQ5L CDF Min-Bias CDF JET20
1.8 TeV ||<1.0 PT>0.5 GeV
Pythia 6.206 (default)MSTP(82)=1
PARP(81) = 1.9 GeV/c
CDF Datadata uncorrectedtheory corrected
Default parameters give very poor description of the “underlying event”!
Note ChangePARP(67) = 4.0 (< 6.138)PARP(67) = 1.0 (> 6.138)
Parameter 6.115 6.125 6.158 6.206
MSTP(81) 1 1 1 1
MSTP(82) 1 1 1 1
PARP(81) 1.4 1.9 1.9 1.9
PARP(82) 1.55 2.1 2.1 1.9
PARP(89) 1,000 1,000 1,000
PARP(90) 0.16 0.16 0.16
PARP(67) 4.0 4.0 1.0 1.0
Plot shows the “Transverse” charged particle density versus PT(chgjet#1) compared to the QCD hard scattering predictions of PYTHIA 6.206 (PT(hard) > 0) using the default parameters for multiple parton interactions and CTEQ3L, CTEQ4L, and CTEQ5L.
PYTHIA default parameters
PYTHIA 6.206 DefaultsPYTHIA 6.206 DefaultsMPI constant
probabilityscattering
Lawrence Berkeley Laboratory January 15, 2009
Rick Field – Florida/CDF/CMS Page 33
Old PYTHIA default(more initial-state radiation)New PYTHIA default
(less initial-state radiation)
Parameter Tune B Tune A
MSTP(81) 1 1
MSTP(82) 4 4
PARP(82) 1.9 GeV 2.0 GeV
PARP(83) 0.5 0.5
PARP(84) 0.4 0.4
PARP(85) 1.0 0.9
PARP(86) 1.0 0.95
PARP(89) 1.8 TeV 1.8 TeV
PARP(90) 0.25 0.25
PARP(67) 1.0 4.0
Old PYTHIA default(more initial-state radiation)New PYTHIA default
(less initial-state radiation)
Plot shows the “transverse” charged particle density versus PT(chgjet#1) compared to the QCD hard scattering predictions of two tuned versions of PYTHIA 6.206 (CTEQ5L, Set B (PARP(67)=1) and Set A (PARP(67)=4)).
"Transverse" Charged Particle Density: dN/dd
0.00
0.25
0.50
0.75
1.00
0 5 10 15 20 25 30 35 40 45 50
PT(charged jet#1) (GeV/c)
"Tra
nsve
rse"
Cha
rged
Den
sity
1.8 TeV ||<1.0 PT>0.5 GeV
CDF Preliminarydata uncorrectedtheory corrected
CTEQ5L
PYTHIA 6.206 (Set A)PARP(67)=4
PYTHIA 6.206 (Set B)PARP(67)=1
Run 1 Analysis
Run 1 PYTHIA Tune ARun 1 PYTHIA Tune APYTHIA 6.206 CTEQ5L
CDF Default!
Lawrence Berkeley Laboratory January 15, 2009
Rick Field – Florida/CDF/CMS Page 34
Charged Particle Jet #1 Direction
“Toward”
“Transverse” “Transverse”
“Away”
"Transverse" Charged Particle Density: dN/dd
0.00
0.25
0.50
0.75
1.00
1.25
0 5 10 15 20 25 30 35 40 45 50
PT(charged jet#1) (GeV/c)"T
rans
vers
e" C
harg
ed D
ensi
ty
CDF Run 1 Min-BiasCDF Run 1 JET20
CDF Run 1 Datadata uncorrected
1.8 TeV ||<1.0 PT>0.5 GeV
"Transverse" Charged Particle Density: dN/dd
0.00
0.25
0.50
0.75
1.00
1.25
0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150
PT(charged jet#1) (GeV/c)"T
rans
vers
e" C
harg
ed D
ensi
ty
CDF Run 1 Min-BiasCDF Run 1 JET20
||<1.0 PT>0.5 GeV
CDF Preliminarydata uncorrected
Shows the data on the average “transverse” charge particle density (||<1, pT>0.5 GeV) as a function of the transverse momentum of the leading charged particle jet from Run 1.
Compares the Run 2 data (Min-Bias, JET20, JET50, JET70, JET100) with Run 1. The errors on the (uncorrected) Run 2 data include both statistical and correlated systematic uncertainties.
"Transverse" Charged Particle Density: dN/dd
0.00
0.25
0.50
0.75
1.00
1.25
0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150
PT(charged jet#1) (GeV/c)
"Tra
nsve
rse"
Cha
rged
Den
sity
CDF Run 2
"Transverse" Charged Particle Density: dN/dd
0.00
0.25
0.50
0.75
1.00
1.25
0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150
PT(charged jet#1) (GeV/c)
"Tra
nsve
rse"
Cha
rged
Den
sity CDF Run 1 Published
CDF Run 2 Preliminary
||<1.0 PT>0.5 GeV/c
CDF Preliminarydata uncorrected
Excellent agreement between Run 1 and 2!
"Transverse" Charged Particle Density: dN/dd
0.00
0.25
0.50
0.75
1.00
1.25
0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150
PT(charged jet#1) (GeV/c)
"Tra
nsve
rse"
Cha
rged
Den
sity
CDF Run 1 PublishedCDF Run 2 PreliminaryPYTHIA Tune A
||<1.0 PT>0.5 GeV/c
CDF Preliminarydata uncorrectedtheory corrected
PYTHIA Tune A was tuned to fit the “underlying event” in Run I!
Shows the prediction of PYTHIA Tune A at 1.96 TeV after detector simulation (i.e. after CDFSIM).
Run 1 vs Run 2: “Transverse” Run 1 vs Run 2: “Transverse” Charged Particle DensityCharged Particle Density“Transverse” region as defined by the leading “charged particle jet”
Lawrence Berkeley Laboratory January 15, 2009
Rick Field – Florida/CDF/CMS Page 35
PYTHIA Tune A Min-BiasPYTHIA Tune A Min-Bias“Soft” + ”Hard”“Soft” + ”Hard”
Charged Particle Density: dN/dd
0.0
0.2
0.4
0.6
0.8
1.0
-4 -3 -2 -1 0 1 2 3 4
Pseudo-Rapidity
dN/d
d
Pythia 6.206 Set ACDF Min-Bias 1.8 TeV 1.8 TeV all PT
CDF Published
PYTHIA regulates the perturbative 2-to-2 parton-parton cross sections with cut-off parameters which allows one to run with PT(hard) > 0. One can simulate both “hard” and “soft” collisions in one program.
The relative amount of “hard” versus “soft” depends on the cut-off and can be tuned.
Charged Particle Density
1.0E-06
1.0E-05
1.0E-04
1.0E-03
1.0E-02
1.0E-01
1.0E+00
0 2 4 6 8 10 12 14
PT(charged) (GeV/c)C
harg
ed D
ensi
ty d
N/d
d
dPT
(1/G
eV/c
)
Pythia 6.206 Set ACDF Min-Bias Data
CDF Preliminary
1.8 TeV ||<1
PT(hard) > 0 GeV/c
Tuned to fit the CDF Run 1 “underlying event”!
12% of “Min-Bias” events have PT(hard) > 5 GeV/c!
1% of “Min-Bias” events have PT(hard) > 10 GeV/c!
This PYTHIA fit predicts that 12% of all “Min-Bias” events are a result of a hard 2-to-2 parton-parton scattering with PT(hard) > 5 GeV/c (1% with PT(hard) > 10 GeV/c)!
Lots of “hard” scattering in “Min-Bias” at the Tevatron!
PYTHIA Tune ACDF Run 2 Default
Tune A
Tune AW Tune B Tune BW
Tune D
Tune DW Tune D6Tune D6T
These are “old” PYTHIA 6.2 tunes! There are new 6.4 tunes byArthur Moraes (ATLAS)Hendrik Hoeth (MCnet)Peter Skands (Tune S0)
Lawrence Berkeley Laboratory January 15, 2009
Rick Field – Florida/CDF/CMS Page 36
Min-Bias CorrelationsMin-Bias Correlations
Data at 1.96 TeV on the average pT of charged particles versus the number of charged particles (pT > 0.4 GeV/c, || < 1) for “min-bias” collisions at CDF Run 2. The data are corrected to the particle level and are compared with PYTHIA Tune A at the particle level (i.e. generator level).
Proton AntiProton
“Minumum Bias” Collisions
Average PT versus Nchg
0.6
0.8
1.0
1.2
1.4
0 10 20 30 40 50
Number of Charged Particles
Ave
rage
PT
(GeV
/c)
CDF Run 2 Preliminarydata corrected
generator level theory
Charged Particles (||<1.0, PT>0.4 GeV/c)
Min-Bias1.96 TeV
ATLAS
pyA
pyDW
Lawrence Berkeley Laboratory January 15, 2009
Rick Field – Florida/CDF/CMS Page 37
Min-Bias: Average PT versus NchgMin-Bias: Average PT versus Nchg
Proton AntiProton
“Soft” Hard Core (no hard scattering)
Proton AntiProton
PT(hard)
Outgoing Parton
Outgoing Parton
Underlying Event Underlying Event Initial-State Radiation
Final-State Radiation
“Hard” Hard Core (hard scattering)
CDF “Min-Bias”
= +
Average PT versus Nchg
0.6
0.8
1.0
1.2
1.4
0 5 10 15 20 25 30 35 40
Number of Charged Particles
Ave
rage
PT
(GeV
/c)
CDF Run 2 Preliminarydata corrected
generator level theory
Charged Particles (||<1.0, PT>0.4 GeV/c)
Min-Bias1.96 TeV
pyAnoMPI
ATLAS
pyA
Proton AntiProton
Multiple-Parton Interactions
PT(hard)
Outgoing Parton
Outgoing Parton
Underlying Event Underlying Event
Final-State Radiation
Initial-State Radiation
+
Beam-beam remnants (i.e. soft hard core) produces low multiplicity and small <pT> with <pT> independent of the multiplicity.
Hard scattering (with no MPI) produces large multiplicity and large <pT>.
Hard scattering (with MPI) produces large multiplicity and medium <pT>.
The CDF “min-bias” trigger picks up most of the “hard
core” component!
This observable is sensitive to the MPI tuning!
Lawrence Berkeley Laboratory January 15, 2009
Rick Field – Florida/CDF/CMS Page 38
Average PT versus NchgAverage PT versus Nchg
Proton AntiProton
“Minumum Bias” Collisions
Proton AntiProton
Drell-Yan Production
Anti-Lepton
Lepton
Underlying Event Underlying Event
Data at 1.96 TeV on the average pT of charged particles versus the number of charged particles (pT > 0.4 GeV/c, || < 1) for “min-bias” collisions at CDF Run 2. The data are corrected to the particle leveland are compared with PYTHIA Tune A, Tune DW, and the ATLAS tune at the particle level (i.e. generator level).
Particle level predictions for the average pT of charged particles versus the number of charged particles (pT > 0.5 GeV/c, || < 1, excluding the lepton-pair) for for Drell-Yan production (70 < M(pair) < 110 GeV) at CDF Run 2.
Average PT versus Nchg
0.5
1.0
1.5
2.0
2.5
0 5 10 15 20 25 30 35
Number of Charged Particles
Ave
rage
PT
(GeV
/c)
CDF Run 2 Preliminarygenerator level theory
"Drell-Yan Production"70 < M(pair) < 110 GeV
Charged Particles (||<1.0, PT>0.5 GeV/c)excluding the lepton-pair
HW
JIM
pyAW
ATLAS
Average PT versus Nchg
0.5
1.0
1.5
2.0
2.5
0 5 10 15 20 25 30 35
Number of Charged Particles
Ave
rage
PT
(GeV
/c)
CDF Run 2 Preliminarydata corrected
generator level theory
"Drell-Yan Production"70 < M(pair) < 110 GeV
Charged Particles (||<1.0, PT>0.5 GeV/c)excluding the lepton-pair
HW
JIM
pyAW
ATLAS
Average PT versus Nchg
0.6
0.8
1.0
1.2
1.4
0 5 10 15 20 25 30 35 40
Number of Charged Particles
Ave
rage
PT
(GeV
/c)
CDF Run 2 Preliminarydata corrected
generator level theory
Charged Particles (||<1.0, PT>0.4 GeV/c)
Min-Bias1.96 TeV
pyAnoMPI
ATLAS
pyA
Lawrence Berkeley Laboratory January 15, 2009
Rick Field – Florida/CDF/CMS Page 39
Average PT versus NchgAverage PT versus Nchg
Proton AntiProton
Drell-Yan Production (no MPI)
Anti-Lepton
Lepton
Underlying Event Underlying Event
Average PT versus Nchg
0.5
1.0
1.5
2.0
2.5
0 5 10 15 20 25 30 35
Number of Charged Particles
Ave
rage
PT
(GeV
/c)
CDF Run 2 Preliminarydata corrected
generator level theory
"Drell-Yan Production"70 < M(pair) < 110 GeV
Charged Particles (||<1.0, PT>0.5 GeV/c)excluding the lepton-pair
HW
JIM
pyAW
ATLAS
Proton AntiProton
Drell-Yan Production (with MPI)
Anti-Lepton
Lepton
Underlying Event Underlying Event
Drell-Yan
Proton AntiProton
High PT Z-Boson Production
Z-boson
Outgoing Parton
Initial-State Radiation Final-State Radiation
= +
Z-boson production (with low pT(Z) and no MPI) produces low multiplicity and small <pT>.
+
High pT Z-boson production produces large multiplicity and high <pT>.
Z-boson production (with MPI) produces large multiplicity and medium <pT>.
No MPI!
Lawrence Berkeley Laboratory January 15, 2009
Rick Field – Florida/CDF/CMS Page 40
Average PT(Z) versus NchgAverage PT(Z) versus Nchg
Proton AntiProton
Drell-Yan Production
Anti-Lepton
Lepton
Underlying Event Underlying Event
Data on the average pT of charged particles versus the number of charged particles (pT > 0.5 GeV/c, || < 1, excluding the lepton-pair) for for Drell-Yan production (70 < M(pair) < 110 GeV) at CDF Run 2. The data are corrected to the particle level and are compared with various Monte-Carlo tunes at the particle level (i.e. generator level).
Average PT versus Nchg
0.5
1.0
1.5
2.0
2.5
0 5 10 15 20 25 30 35
Number of Charged Particles
Ave
rage
PT
(GeV
/c)
CDF Run 2 Preliminarydata corrected
generator level theory
"Drell-Yan Production"70 < M(pair) < 110 GeV
Charged Particles (||<1.0, PT>0.5 GeV/c)excluding the lepton-pair
HW
JIM
pyAW
ATLAS
PT(Z-Boson) versus Nchg
0
20
40
60
80
0 5 10 15 20 25 30 35 40
Number of Charged Particles
Ave
rage
PT(
Z) (G
eV/c
)
CDF Run 2 Preliminarygenerator level theory
"Drell-Yan Production"70 < M(pair) < 110 GeV
Charged Particles (||<1.0, PT>0.5 GeV/c)excluding the lepton-pair
pyAW
HW
JIM
ATLAS
No MPI!
Predictions for the average PT(Z-Boson) versus the number of charged particles (pT > 0.5 GeV/c, || < 1, excluding the lepton-pair) for for Drell-Yan production (70 < M(pair) < 110 GeV) at CDF Run 2.
PT(Z-Boson) versus Nchg
0
20
40
60
80
0 5 10 15 20 25 30 35 40
Number of Charged Particles
Ave
rage
PT(
Z) (G
eV/c
)
CDF Run 2 Preliminarydata corrected
generator level theory
"Drell-Yan Production"70 < M(pair) < 110 GeV
Charged Particles (||<1.0, PT>0.5 GeV/c)excluding the lepton-pair
pyAW
HW
JIM
ATLAS
Proton AntiProton
High PT Z-Boson Production
Z-boson
Outgoing Parton
Initial-State Radiation
Lawrence Berkeley Laboratory January 15, 2009
Rick Field – Florida/CDF/CMS Page 41
Average PT versus NchgAverage PT versus Nchg
Proton AntiProton
Drell-Yan Production
Anti-Lepton
Lepton
Underlying Event Underlying Event
Predictions for the average pT of charged particles versus the number of charged particles (pT > 0.5 GeV/c, || < 1, excluding the lepton-pair) for for Drell-Yan production (70 < M(pair) < 110 GeV, PT(pair) < 10 GeV/c) at CDF Run 2.
Average Charged PT versus Nchg
0.6
0.8
1.0
1.2
1.4
0 5 10 15 20 25 30 35
Number of Charged Particles
Ave
rage
PT
(GeV
/c)
CDF Run 2 Preliminarygenerator level theory
"Drell-Yan Production"70 < M(pair) < 110 GeV
PT(Z) < 10 GeV/cCharged Particles (||<1.0, PT>0.5 GeV/c)
excluding the lepton-pair
HW
pyAW
Average Charged PT versus Nchg
0.6
0.8
1.0
1.2
1.4
0 5 10 15 20 25 30 35
Number of Charged Particles
Ave
rage
PT
(GeV
/c)
CDF Run 2 Preliminarygenerator level theory
"Drell-Yan Production"70 < M(pair) < 110 GeV
PT(Z) < 10 GeV/cCharged Particles (||<1.0, PT>0.5 GeV/c)
excluding the lepton-pair
HW
JIM
ATLAS
pyAW
Average Charged PT versus Nchg
0.6
0.8
1.0
1.2
1.4
0 5 10 15 20 25 30 35
Number of Charged Particles
Ave
rage
PT
(GeV
/c)
CDF Run 2 Preliminarydata corrected
generator level theory
"Drell-Yan Production"70 < M(pair) < 110 GeV
PT(Z) < 10 GeV/cCharged Particles (||<1.0, PT>0.5 GeV/c)
excluding the lepton-pair
HW
JIM
ATLAS
pyAW
Data the average pT of charged particles versus the number of charged particles (pT > 0.5 GeV/c, || < 1, excluding the lepton-pair) for for Drell-Yan production (70 < M(pair) < 110 GeV, PT(pair) < 10 GeV/c) at CDF Run 2. The data are corrected to the particle level and are compared with various Monte-Carlo tunes at the particle level (i.e. generator level).
PT(Z) < 10 GeV/c
No MPI!
Average PT versus Nchg
0.6
0.8
1.0
1.2
1.4
0 10 20 30 40
Number of Charged Particles
Ave
rage
PT
(GeV
/c)
CDF Run 2 Preliminarydata corrected
generator level theory
Charged Particles (||<1.0)pyA
Min-Bias PT > 0.4 GeV/c
Drell-Yan PT > 0.5 GeV PT(Z) < 10 GeV/c
pyAW
Proton AntiProton
“Minumum Bias” Collisions Remarkably similar behavior! Perhaps indicating that MPI playing an important role in
both processes.
Lawrence Berkeley Laboratory January 15, 2009
Rick Field – Florida/CDF/CMS Page 42
Proton Proton
High PT Jet Production
PT(hard)
Outgoing Parton
Outgoing Parton
Underlying Event Underlying Event
Final-State Radiation
Initial-State Radiation
UE&MB@CMSUE&MB@CMS
“Underlying Event” Studies: The “transverse region” in “leading Jet” and “back-to-back” charged particle jet production and the “central region” in Drell-Yan production. (requires charged tracks and muons for Drell-Yan)
Drell-Yan Studies: Transverse momentum distribution of the lepton-pair versus the mass of the lepton-pair, <pT(pair)>, <pT
2(pair)>, d/dpT(pair) (only requires muons). Event structure for large lepton-pair pT (i.e. +jets, requires muons).
Min-Bias Studies: Charged particle distributions and correlations. Construct “charged particle jets” and look at “mini-jet” structure and the onset of the “underlying event”. (requires only charged tracks)
Proton Proton
Drell-Yan Production Lepton
Underlying Event Underlying Event Initial-State Radiation
Anti-Lepton
Proton Proton
“Minimum-Bias” Collisions
Proton Proton
Drell-Yan Production PT(pair)
Lepton-Pair
Outgoing Parton
Underlying Event Underlying Event Initial-State Radiation
Final-State Radiation
UE&MB@CMSUE&MB@CMS
Study the “underlying event” by using charged particles and muons!
(start as soon as possible)
Lepton-Pair Transverse Momentum
0
20
40
60
80
0 100 200 300 400 500 600 700 800 900 1000
Lepton-Pair Invariant Mass (GeV)
Ave
rage
Pai
r PT
Drell-Yangenerator level LHC
Tevatron Run 2
PY Tune DW (solid)HERWIG (dashed)
Drell-Yan PT(+-) Distribution
0.00
0.02
0.04
0.06
0.08
0.10
0 5 10 15 20 25 30 35 40
PT(+-) (GeV/c)
1/N
dN
/dPT
(1/G
eV)
Drell-Yangenerator level
PY Tune DW (solid)HERWIG (dashed)
70 < M(-pair) < 110 GeV|(-pair)| < 6
Normalized to 1LHC
Tevatron Run2
<pT(+-)> is much larger at the LHC!
Shapes of the pT(+-) distribution at the Z-boson mass.
"Toward" Charged Particle Density: dN/dd
0.0
0.3
0.6
0.9
0 20 40 60 80 100
PT(Z-Boson) (GeV/c)
"Tow
ard"
Cha
rged
Den
sity
CDF Run 2 Preliminarydata corrected
generator level theory
"Drell-Yan Production"70 < M(pair) < 110 GeV Charged Particles (||<1.0, PT>0.5 GeV/c)
excluding the lepton-pair
HW
JIM
pyAW
ATLASpyDW
"Toward" Charged Particle Density: dN/dd
0.0
0.5
1.0
1.5
2.0
0 25 50 75 100 125 150
PT(Z-Boson) (GeV/c)
"Tow
ard"
Cha
rged
Den
sity
CDF Run 2 Preliminarygenerator level theory
"Drell-Yan Production"70 < M(pair) < 110 GeV
Charged Particles (||<1.0, PT>0.5 GeV/c)excluding the lepton-pair
HW LHC14
pyDWT LHC14
pyDWT TevatronHW Tevatron
Z-BosonDirection
“Toward”
“Transverse” “Transverse”
“Away”
DWT