toward an understanding of hadron-hadron collisions

Lawrence Berkeley Laboratory January 15, 2009

Rick Field – Florida/CDF/CMS

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.



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



Before Feynman-FieldBefore Feynman-Field

Rick & Jimmie1968

Rick & Jimmie1970 Rick & Jimmie

1972 (pregnant!)

Rick & Jimmie at CALTECH 1973



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




1st hat!



“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!



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”



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.”



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!



Telagram from FeynmanTelagram from FeynmanJuly 1976

SAW CRONIN AM NOW CONVINCED WERE RIGHT TRACK QUICK WRITEFEYNMAN



Letter from FeynmanLetter from FeynmanJuly 1976



Letter from Feynman Page 1Letter from Feynman Page 1

Spelling?



Letter from Feynman Page 3Letter from Feynman Page 3It is fun!

Onward!



Feynman Talk at Coral GablesFeynman Talk at Coral Gables (December 1976)(December 1976)

“Feynman-Field Jet Model”

1st transparency Last transparency



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.”



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)



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, ....”



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



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.”



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%!!



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!



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


“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



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



Hard Scattering

PT(hard)

Outgoing Parton

Outgoing Parton



Proton AntiProton


Proton AntiProton


“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!



-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



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



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


PTmaxPTmax not included


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!



Charged Jet #1Direction


“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.


“Toward”


“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”



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

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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”


“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



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”


“Away”

“Hard”Component


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0.25

0.50

0.75

1.00

0 5 10 15 20 25 30 35 40 45 50


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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!



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


“Toward”


“Away”


0.00

0.25

0.50

0.75

1.00

0 5 10 15 20 25 30 35 40 45 50


"Tra

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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



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


final-state radiation outgoing jet Beam-Beam Remnants

or

“Soft” Component

Proton AntiProton

“Hard” Collision


final-state radiation outgoing parton

outgoing parton



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


Color String

Color String


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




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



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)).


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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!



Charged Particle Jet #1 Direction

“Toward”


“Away”


0.00

0.25

0.50

0.75

1.00

1.25

0 5 10 15 20 25 30 35 40 45 50


rans

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CDF Run 1 Min-BiasCDF Run 1 JET20

CDF Run 1 Datadata uncorrected

1.8 TeV ||<1.0 PT>0.5 GeV


0.00

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rans

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CDF Run 1 Min-BiasCDF Run 1 JET20

||<1.0 PT>0.5 GeV


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.


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CDF Run 2


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CDF Run 2 Preliminary

||<1.0 PT>0.5 GeV/c


Excellent agreement between Run 1 and 2!


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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”



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)



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


Min-Bias1.96 TeV

ATLAS

pyA

pyDW



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



“Hard” Hard Core (hard scattering)

CDF “Min-Bias”

= +


0.6

0.8

1.0

1.2

1.4

0 5 10 15 20 25 30 35 40


Ave

rage

PT

(GeV

/c)




Min-Bias1.96 TeV

pyAnoMPI

ATLAS

pyA

Proton AntiProton

Multiple-Parton Interactions

PT(hard)

Outgoing Parton

Outgoing Parton




+

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!



Average PT versus NchgAverage PT versus Nchg

Proton AntiProton

“Minumum Bias” Collisions

Proton AntiProton

Drell-Yan Production

Anti-Lepton

Lepton


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.


0.5

1.0

1.5

2.0

2.5

0 5 10 15 20 25 30 35


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


0.5

1.0

1.5

2.0

2.5

0 5 10 15 20 25 30 35


Ave

rage

PT

(GeV

/c)





HW

JIM

pyAW

ATLAS


0.6

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1.0

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0 5 10 15 20 25 30 35 40


Ave

rage

PT

(GeV

/c)




Min-Bias1.96 TeV

pyAnoMPI

ATLAS

pyA




Proton AntiProton

Drell-Yan Production (no MPI)

Anti-Lepton

Lepton



0.5

1.0

1.5

2.0

2.5

0 5 10 15 20 25 30 35


Ave

rage

PT

(GeV

/c)





HW

JIM

pyAW

ATLAS

Proton AntiProton

Drell-Yan Production (with MPI)

Anti-Lepton

Lepton


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!



Average PT(Z) versus NchgAverage PT(Z) versus Nchg

Proton AntiProton


Anti-Lepton

Lepton


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).


0.5

1.0

1.5

2.0

2.5

0 5 10 15 20 25 30 35


Ave

rage

PT

(GeV

/c)





HW

JIM

pyAW

ATLAS

PT(Z-Boson) versus Nchg

0

20

40

60

80

0 5 10 15 20 25 30 35 40


Ave

rage

PT(

Z) (G

eV/c

)




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


Ave

rage

PT(

Z) (G

eV/c

)





pyAW

HW

JIM

ATLAS

Proton AntiProton

High PT Z-Boson Production

Z-boson

Outgoing Parton





Proton AntiProton


Anti-Lepton

Lepton


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


Ave

rage

PT

(GeV

/c)



PT(Z) < 10 GeV/cCharged Particles (||<1.0, PT>0.5 GeV/c)

excluding the lepton-pair

HW

pyAW


0.6

0.8

1.0

1.2

1.4

0 5 10 15 20 25 30 35


Ave

rage

PT

(GeV

/c)





HW

JIM

ATLAS

pyAW


0.6

0.8

1.0

1.2

1.4

0 5 10 15 20 25 30 35


Ave

rage

PT

(GeV

/c)






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!


0.6

0.8

1.0

1.2

1.4

0 10 20 30 40


Ave

rage

PT

(GeV

/c)



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.



Proton Proton

High PT Jet Production

PT(hard)

Outgoing Parton

Outgoing Parton




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


Anti-Lepton

Proton Proton

“Minimum-Bias” Collisions

Proton Proton

Drell-Yan Production PT(pair)

Lepton-Pair

Outgoing Parton



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



"Drell-Yan Production"70 < M(pair) < 110 GeV Charged Particles (||<1.0, PT>0.5 GeV/c)


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




HW LHC14

pyDWT LHC14

pyDWT TevatronHW Tevatron

Z-BosonDirection

“Toward”


“Away”

DWT

toward an understanding of hadron-hadron collisions

Documents

hadronhadron collisionsfrom

hadronhadron collisionswhat

early days of feynman

quarkquark elastic scattering

large transverse momenta

high pt particles

properties of quark

gevc jets