mcnet07 - durham - part 1 april 18-20, 2007 rick field – florida/cdf/cmspage 1 physics and...

MCnet07 - Durham - Part 1 April 18-20, 2007

Rick Field – Florida/CDF/CMS

Physics and Techniques Physics and Techniques of Event Generatorsof Event Generators

Rick FieldUniversity of Florida

(for the CDF & CMS Collaborations)

CDF Run 2

Min-Bias and the Underlying Eventat the TEVATRON and the LHC

CMS at the LHC

UE&MB@CMSUE&MB@CMS1st Lecture

IPPP Durham, April 18-20, 2007

The early days of event generators.

Proton AntiProton

PT(hard)

Outgoing Parton

Outgoing Parton

Underlying Event Underlying Event

Initial-State Radiation

Final-State Radiation

“Min-Bias” at the Tevatron.

Studying the “underlying event” in Run 1 at CDF.

and extrapolations to the LHC.



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!



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.”



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.”



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



No-Bias vs Min-BiasNo-Bias vs Min-BiasCharged Particle Density: dN/d

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PseudoRapidity

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rged

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ticle

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pyDWT HC NoTrigpyDWT DD NoTtrigpyDWT SD NoTrig

No Trigger900 GeV Generated

Charged Particles (all PT)

Charged Particle Density: dN/d

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pyDW HC MbtrigpyDW DD MBtrigpyDW SD MBtrig

CDF Min-Bias Trigger900 GeV Generated



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pyDWT Sum NoTrigpyDWT HC NoTrigpyDWT DD NoTtrigpyDWT SD NoTrig

No Trigger900 GeV Weighted



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PseudoRapidity

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pyDWT Sum MBtrigpyDWT HC MBtrigpyDWT DD MBtrigpyDWT SD MBtrig

CDF Min-Bias Trigger900 GeV Weighted


What you see for “Min-Bias”depends on your triggger!

By comparing different“Min-Bias” triggers one canlearn about the components!



No-Bias vs Min-BiasNo-Bias vs Min-BiasCharged Particle Density: dN/d

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PseudoRapidity

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PYTHIA Tune DWCharged Particles

No-Bias 1.96 TeV(HC+SD+DD+EL)

All PT


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PseudoRapidity

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PYTHIA Tune DWCharged Particles

No-Bias 1.96 TeV(HC+SD+DD+EL)

All PTPT > 0.5 GeV/c


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2.0

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PseudoRapidity

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PYTHIA Tune DWCharged Particles (PT > 0.5 GeV/c) Min-Bias 1.96 TeV

(HC+SD+DD+EL)

CDF Min-Bias Trigger

No Trigger

Charged particle (all pT) pseudo-rapidity distribution, dNchg/dd, at 1.96 TeV with no trigger (i.e. no-bias) from PYTHIA Tune DW.

About 2.5 charged particles per unit at = 0.

About 0.9 charged particles (pT > 0.5 GeV/c) per unit at = 0.

Charged particle (pT > 0.5 GeV/c) pseudo-rapidity distribution, dNchg/dd, at 1.96 TeV with the CDF Min-Bias trigger from PYTHIA Tune DW.

About 1.5 charged particles (pT > 0.5 GeV/c) per unit at = 0 with CDF min-bias trigger.



60 cm


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pyDWT HC+SD+DD NoTrigpyDWT HC+SD+DD NoTrig 10mmCharged Particles (all PT)

Min-Bias 14 TeVPY Tune DWT

Min-Bias Particle TypesMin-Bias Particle Types

Using c = 10 mm reduces the charged particle density by almost 10%! Mostly from Ks→+- (68.6%) and →p-

(64.2%).

With c = 10mm With Stable Particles

charged particle density: 10mm vs Stable

This is a bigger effect than I expected! No-Bias at 14 TeV

Proton AntiProton

Primary

CDF Run 2



-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



Shows CDF “Min-Bias” data on the number of charged particles per unit pseudo-rapidity at 630 and 1,800 GeV. There are about 4.2 charged particles per unit in “Min-Bias” collisions at 1.8 TeV (|| < 1, all pT).

Charged Particle Pseudo-Rapidity Distribution: dN/d

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-4 -3 -2 -1 0 1 2 3 4

Pseudo-Rapidity

dN/d

CDF Min-Bias 1.8 TeVCDF Min-Bias 630 GeV all PT

CDF Published

<dNchg/d> = 4.2

Charged Particle Density: dN/dd

0.0

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-4 -3 -2 -1 0 1 2 3 4

Pseudo-Rapidity

dN/d

d

CDF Min-Bias 630 GeVCDF Min-Bias 1.8 TeV all PT

CDF Published

<dNchg/dd> = 0.67

Convert to charged particle density, dNchg/dd by dividing by 2. There are about 0.67 charged particles per unit - in “Min-Bias” collisions at 1.8 TeV (|| < 1, all pT).

= 1

= 1

x = 1

0.67

There are about 0.25 charged particles per unit - in “Min-Bias” collisions at 1.96 TeV (|| < 1, pT > 0.5 GeV/c).

0.25

CDF Run 1 “Min-Bias” DataCDF Run 1 “Min-Bias” DataCharged Particle DensityCharged Particle Density




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-4 -3 -2 -1 0 1 2 3 4

Pseudo-Rapidity

dN/d

d

CDF Min-Bias 630 GeVCDF Min-Bias 1.8 TeV all PT

CDF Published

Shows the center-of-mass energy dependence of the charged particle density, dNchg/dd for “Min-Bias” collisions at = 0. Also show a log fit (Fit 1) and a (log)2 fit (Fit 2) to the CDF plus UA5 data.


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1.2

1.4

10 100 1,000 10,000 100,000CM Energy W (GeV)

Cha

rged

den

sity

dN

/d

d

CDF DataUA5 DataFit 2Fit 1

= 0

<dNchg/dd> = 0.51 = 0 630 GeV

What should we expect for the LHC?

<dNchg/dd> = 0.63 = 0 1.8 TeV

LHC?

24% increase

CDF Run 1 “MinCDF Run 1 “Min--Bias” DataBias” DataEnergy DependenceEnergy Dependence




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Pseudo-Rapidity

dN/d

d

630 GeV1.8 TeV

Herwig "Soft" Min-Bias 14 TeV

all PT

Shows the center-of-mass energy dependence of the charged particle density, dNchg/dd for “Min-Bias” collisions compared with the HERWIG “Soft” Min-Bias Monte-Carlo model. Note: there is no “hard” scattering in HERWIG “Soft” Min-Bias.

HERWIG “Soft” Min-Bias contains no hard parton-parton interactions and describes fairly well the charged particle density, dNchg/dd, in “Min-Bias” collisions.


0.0

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10 100 1,000 10,000 100,000

CM Energy W (GeV)

Cha

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sity

dN

/d d

CDF DataUA5 DataFit 2Fit 1HW Min-Bias

= 0

HERWIG “Soft” Min-Bias predicts a 45% rise in dNchg/dd at = 0 in going from the Tevatron (1.8 TeV) to the LHC (14 TeV). 4 charged particles per unit becomes 6.

Can we believe HERWIG “soft” Min-Bias?

Can we believe HERWIG “soft” Min-Bias? No!

LHC?

Herwig “Soft” Min-BiasHerwig “Soft” Min-Bias



Charged Particle Density

1.0E-06

1.0E-05

1.0E-04

1.0E-03

1.0E-02

1.0E-01

1.0E+00

1.0E+01

0 2 4 6 8 10 12 14

PT (GeV/c)C

harg

ed D

ensi

ty d

N/d

d

dPT

(1/G

eV/c

)

||<1CDF Preliminary

CDF Min-Bias Data at 1.8 TeV

HW "Soft" Min-Biasat 630 GeV, 1.8 TeV, and 14 TeV


0.0

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Pseudo-Rapidity

dN/d

d

630 GeV1.8 TeV

Herwig "Soft" Min-Bias 14 TeV

all PT

Shows the pT dependence of the charged particle density, dNchg/dddPT, for “Min-Bias” collisions at 1.8 TeV collisions compared with HERWIG “Soft” Min-Bias.

HERWIG “Soft” Min-Bias does not describe the “Min-Bias” data! The “Min-Bias” data contains a lot of “hard” parton-parton collisions which results in many more particles at large PT than are produces by any “soft” model.

Shows the energy dependence of the charged particle density, dNchg/dd for “Min-Bias” collisions compared with HERWIG “Soft” Min-Bias.

Lots of “hard” scattering in “Min-Bias”!

HERWIG “Soft” Min-Bias

CDF Run 1 “Min-Bias” DataCDF Run 1 “Min-Bias” DatappTT Distribution Distribution




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Pseudo-Rapidity

dN/d

d

CDF Min-Bias Data Herwig Jet3 Herwig Min-Bias

1.8 TeV all PTHW "Soft" Min-Bias

HW PT(hard) > 3 GeV/c


1.0E-06

1.0E-05

1.0E-04

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1.0E+00

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0 2 4 6 8 10 12 14

PT (GeV/c)C

harg

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ensi

ty d

N/d

d

dPT

(1/G

eV/c

)

Herwig Jet3Herwig Min-BiasCDF Min-Bias Data

1.8 TeV ||<1

CDF Preliminary

HW PT(hard) > 3 GeV/c

HW "Soft" Min-Bias

HERWIG “hard” QCD with PT(hard) > 3 GeV/c describes well the high pT tail but produces too many charged particles overall. Not all of the “Min-Bias” collisions have a hard scattering with PT(hard) > 3 GeV/c!

One cannot run the HERWIG “hard” QCD Monte-Carlo with PT(hard) < 3 GeV/c because the perturbative 2-to-2 cross-sections diverge like 1/PT(hard)4?

HERWIG “soft” Min-Bias does not fit the “Min-Bias” data!

Hard-Scattering Cross-Section

0.01

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1.00

10.00

100.00

0 2 4 6 8 10 12 14 16 18 20Hard-Scattering Cut-Off PTmin

Cro

ss-S

ectio

n (m

illib

arns

)

PYTHIAHERWIG

CTEQ5L1.8 TeV

HC

PYTHIA cuts off the divergence.

Can run PT(hard)>0!

CDF Run 1 “Min-Bias” DataCDF Run 1 “Min-Bias” DataCombining “Soft” + “Hard”Combining “Soft” + “Hard” HERWIG diverges!

No easy way to“mix” HERWIG “hard” with HERWIG “soft”.



PYTHIA Tune A Min-BiasPYTHIA Tune A Min-Bias“Soft” + ”Hard”“Soft” + ”Hard”


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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.


1.0E-06

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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!


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



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


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Cha

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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 2 Min-Bias “Associated”CDF Run 2 Min-Bias “Associated”Charged Particle DensityCharged Particle Density



Associated Particle Density: dN/dd

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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 2 Min-Bias “Associated”CDF Run 2 Min-Bias “Associated”Charged Particle DensityCharged Particle Density Rapid rise in the particle

density in the “transverse” region as PTmax increases!



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 GeV/c and PTmax > 2.0 GeV/c compared with PYTHIA Tune A (after CDFSIM).

PTmax Direction

Correlations in

Associated Particle Density: dN/dd

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Ass

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icle

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PTmax > 2.0 GeV/cPY Tune APTmax > 0.5 GeV/cPY Tune A

CDF Preliminarydata uncorrectedtheory + CDFSIM

PTmaxPTmax not included (||<1.0, PT>0.5 GeV/c)

PY Tune A 1.96 TeV

PYTHIA Tune A predicts a larger correlation than is seen in the “min-bias” data (i.e. Tune A “min-bias” is a bit too “jetty”).

PTmax > 2.0 GeV/c

PTmax > 0.5 GeV/c

PTmax Direction

“Toward”


“Away”

Transverse Region Transverse

Region

PY Tune A

CDF Run 2 Min-Bias “Associated”CDF Run 2 Min-Bias “Associated”Charged Particle DensityCharged Particle Density




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Pseudo-Rapidity

dN/d

d

all PT

CDF Data Pythia 6.206 Set A

630 GeV

1.8 TeV

14 TeV

PYTHIA was tuned to fit the “underlying event” in hard-scattering processes at 1.8 TeV and 630 GeV.


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Cha

rged

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sity

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/d

d

Pythia 6.206 Set ACDF DataUA5 DataFit 2Fit 1

= 0

Shows the center-of-mass energy dependence of the charged particle density, dNchg/dd for “Min-Bias” collisions compared with PYTHIA Tune A with PT(hard) > 0.

PYTHIA Tune A predicts a 42% rise in dNchg/dd at = 0 in going from the Tevatron (1.8 TeV) to the LHC (14 TeV). Similar to HERWIG “soft” min-bias, 4 charged particles per unit becomes 6.

LHC?

PYTHIA Tune APYTHIA Tune ALHC Min-Bias PredictionsLHC Min-Bias Predictions




1.0E-06

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PT(charged) (GeV/c)

Cha

rged

Den

sity

dN

/d

ddP

T (1

/GeV

/c)

CDF Data

||<1

630 GeV

Pythia 6.206 Set A

1.8 TeV

14 TeV

Hard-Scattering in Min-Bias Events

0%

10%

20%

30%

40%

50%

100 1,000 10,000 100,000CM Energy W (GeV)

% o

f Eve

nts

PT(hard) > 5 GeV/cPT(hard) > 10 GeV/c

Pythia 6.206 Set A

Shows the center-of-mass energy dependence of the charged particle density, dNchg/dddPT, for “Min-Bias” collisions compared with PYTHIA Tune A with PT(hard) > 0.

PYTHIA Tune A predicts that 1% of all “Min-Bias” events at 1.8 TeV are a result of a hard 2-to-2 parton-parton scattering with PT(hard) > 10 GeV/c which increases to 12% at 14 TeV!



LHC?

PYTHIA Tune APYTHIA Tune ALHC Min-Bias PredictionsLHC Min-Bias Predictions



PYTHIA Tune A and Tune DW predict about 6 charged particles per unit at = 0, while the ATLAS tune predicts around 9.

Shows the predictions of PYTHIA Tune A, Tune DW, Tune DWT, and the ATLAS tune for the charged particle density dN/d and dN/dY at 14 TeV (all pT).

PYTHIA Tune DWT is identical to Tune DW at 1.96 TeV, but extrapolates to the LHC using the ATLAS energy dependence.


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Charged Particles (all pT)

Generator Level14 TeV

Charged Particle Density: dN/dY

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Generator Level14 TeV

Charged Particles (all pT)

PYTHIA 6.2 TunesPYTHIA 6.2 TunesLHC Min-Bias PredictionsLHC Min-Bias Predictions



The ATLAS tune has many more “soft” particles than does any of the CDF Tunes. The ATLAS tune has <pT> = 548 MeV/c while Tune A has <pT> = 641 MeV/c (100 MeV/c more per particle)!

Shows the predictions of PYTHIA Tune A, Tune DW, Tune DWT, and the ATLAS tune for the charged particle pT distribution at 14 TeV (|| < 1) and the average number of charged particles with pT > pT

min (|| < 1).

Charged PT Distribution

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Charged Particle PT (GeV/c)

1/N

ev d

N/d

PT (1

/GeV

/c)

pyA <PT> = 641 MeV/c

pyDW <PT> = 665 MeV/c

pyDWT <PT> = 693 MeV/c

ATLAS <PT> = 548 MeV/c

Charged Particles (||<1.0)

Generator LevelMin-Bias 14 TeV

Average Number of Charged Particles vs PTmin

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<Nch

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pyA pyDW pyDWTATLAS

Charged Particles (||<1.0, PT>PTmin)

Generator LevelMin-Bias 14 TeV

PYTHIA 6.2 TunesPYTHIA 6.2 TunesLHC Min-Bias PredictionsLHC Min-Bias Predictions



Shows the average transverse momentum of charged particles (||<1, pT>0.5 GeV) versus the number of charged particles, Nchg, for the CDF Run 2 Min-Bias events.

The charged <PT> rises with Nchg!

Average PT versus Nchg

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Number of Charged Particles

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/c)

CDF Preliminarydata uncorrectedtheory + CDFSIM

PYTHIA Tune A 1.96 TeV


Min-Bias

Charged <PCharged <PTT> versus N> versus Nchgchg



Using Pile-Up to Study Min-BiasUsing Pile-Up to Study Min-Bias

The primary vertex is the highest PTsum of charged particles pointing towards it.

Proton AntiProton

60 cm

Primary

Normally one only includes those charged particles which point back to the primary vertex.

Pile-Up

However, the primary vertex is presumably the collision that satisfied the trigger and is hence biased.

Perhaps the pile-up is not biases and can serve as a new type of “Min-Bias” trigger.

This assumes that the pile-up is not affected by the trigger (i.e. it is the same for all primary processes).

High PT Jet

Primary

MB

CDF Run 2



Using Pile-Up to Study Min-BiasUsing Pile-Up to Study Min-BiasCharged Particle Density: dN/d

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Charged Particles (PT > 0.5 GeV/c)

CDF Pre-PreliminaryMin-Bias at 1.96 TeVPrimary


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Charged Particles (PT > 0.5 GeV/c)

CDF Pre-PreliminaryMin-Bias at 1.96 TeV

Pile-Up

Primary

Shows the the charged particle density, dNchg/dfor charged particles (pT > 0.5 GeV/c) pointing to theprimary vertex for “Min-Bias” collisions at 1.96 TeV.

About 2.6 charged particles per unit at = 0.

About 1.6 charged particles per unit at = 0 per pile-up

interaction.

Shows the the charged particle density, dNchg/d(per interaction) for charged particles (pT > 0.5 GeV/c) pointing to thepile-up vertices for “Min-Bias” collisions at 1.96 TeV.

Clearly the pile-up “min-bias” is biased because there must to be some particles in the central region to form a vertex (e.g. elestic scattering does not contribute), but it is less biased than CDF “min-bias”.



Is the Pile-Up Biased?Is the Pile-Up Biased?Pile-Up: Charged Particle Multiplicity

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CDF Pre-Preliminary1.96 TeV

Charged Particles (PT > 0.5 GeV/c, || < 1)

Pile-Up: Charged Particle Multiplicity

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CDF Pre-Preliminary1.96 TeV

PT(jet#1) > 150 GeV/c<Nchg> = 4.2

Charged Particles (PT > 0.5 GeV/c, || < 1)

Shows the the charged particle multiplicity distribution(per interaction)for charged particles (pT > 0.5 GeV/c, || <1) pointing to thepile-up vertices for “Min-Bias” collisions at 1.96 TeV.

Shows the the charged particle multiplicity distribution (per interaction) for charged particles (pT > 0.5 GeV/c, || <1) pointing to thepile-up vertices for high p jet production (PT(jet#1) > 150 GeV/c) at 1.96 TeV.

The pile-up is different for Min-bias collisions and high pT jet production! Amasing!

Warning! This data is verypreliminary and

not “blessed” by CDF.So do not believe it yet!



Is the Pile-Up Biased?Is the Pile-Up Biased? Jet#1 Direction

Correlations in


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Charged Particles (PT > 0.5 GeV/c, || <1)

PrimaryCDF Preliminary1.96 TeV

150 < PT(jet#1) < 250 GeV/c

Shows the data on the dependence of the charged particle density, dNchg/dd, for charged particles (pT > 0.5 GeV/c, || < 1) pointing to theprimary vertex relative to the leading calorimeter jet (rotated to 270o) for 150 < PT(jet#1) < 250 GeV/c |(jet#1)| < 2.

Shows the data on the dependence of the charged particle density, dNchg/dd, for charged particles (pT > 0.5 GeV/c, || < 1) (per interaction) pointing to thepile-up vertices relative to the leading calorimeter jet (rotated to 270o) for 150 < PT(jet#1) < 250 GeV/c |(jet#1)| < 2.

Transverse Region


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CDF Preliminary1.96 TeV

150 < PT(jet#1) < 250 GeV/c

Charged PTsum Density: dPT/dd

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150 < PT(jet#1) < 250 GeV/cPrimary

Pile-Up/Interaction

The pile-up knows the direction of the leading high pT jet! Amasing!

The pile-up conspires to help give you what you ask for

(i.e. satisfy your “trigger” or your event selection)!

Warning! This data is verypreliminary and

not “blessed” by CDF.So do not believe it yet!



Min-Bias SummaryMin-Bias Summary “Min-Bias” is not well defined. What you

see depends on what you trigger on! Every trigger produces some biases. We learn about “min-bias” by comparing different “low bias” triggers.

Proton AntiProton

“Minumum Bias” Collisions

Preliminary results seem to show that pile-up is biased! and that it conspires to help give you what you ask for (i.e. satisfy your “trigger” or your event selection)!

If true this means the pile-up is not the same for all processes. It is process (i.e. trigger) dependent! This would have big implications for the LHC!

Pile-Up Charged PTsum Density: dPT/dd

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CDF Preliminary1.96 TeV

I must double check my analysis and get it “blessed”!

Leading Jet



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!



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

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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”


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Min-Bias

"Transverse"PT(chgjet#1) > 5 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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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”


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Herwig 6.4 CTEQ5LPT(hard) > 3 GeV/c

Total "Hard"

"Remnants"

“Hard”Component


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Isajet

"Remnants"

"Hard"

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



"Transverse" Charged Particle Density

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CDF Datadata uncorrectedtheory corrected

1.8 TeV ||<1 PT>0.5 GeV/c

PT(chgjet#1) > 5 GeV/c

PT(chgjet#1) > 30 GeV/c

Herwig 6.4 CTEQ5L

Herwig PT(chgjet#1) > 5 GeV/c<dNchg/dd> = 0.40

Herwig PT(chgjet#1) > 30 GeV/c“Transverse” <dNchg/dd> = 0.51


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Herwig 6.4 CTEQ5LPT(hard) > 3 GeV/c

Total "Hard"

"Remnants"

Compares the average “transverse” charge particle density (||<1, pT>0.5 GeV) versus PT(charged jet#1) and the pT distribution of the “transverse” density, dNchg/dddPT with the QCD hard scattering predictions of HERWIG 6.4 (default parameters with PT(hard)>3 GeV/c. Shows how the “transverse” charge particle density is distributed in pT.

HERWIG has the too steep of a pT dependence of the “beam-beam remnant”

component of the “underlying event”! Charged Jet #1Direction

“Toward”


“Away”

HERWIG 6.4HERWIG 6.4“Transverse” P“Transverse” PTT Distribution Distribution



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




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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


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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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!




“Toward”


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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


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||<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


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”



Shows the data on the average “transverse” charged PTsum density (||<1, pT>0.5 GeV) as a function of the transverse momentum of the leading charged particle jet from Run 1.

"Transverse" Charged PTsum Density: dPTsum/dd

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) CDF JET20CDF Min-Bias

CDF Run 1 Datadata uncorrected

1.8 TeV ||<1.0 PT>0.5 GeV

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 1 PublishedCDF Run 2 Preliminary


||<1.0 PT>0.5 GeV/c



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1.25

0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150


rans

vers

e" P

Tsum

Den

sity

(GeV

/c)

CDF Run 1 PublishedCDF Run 2 PreliminaryPYTHIA Tune A


||<1.0 PT>0.5 GeV/c

Shows the prediction of PYTHIA Tune A at 1.96 TeV after detector simulation (i.e. after CDFSIM).

PYTHIA Tune A was tuned to fit the “underlying event” in Run I!

Run 1 vs Run 2: “Transverse” Run 1 vs Run 2: “Transverse” Charged PTsum DensityCharged PTsum Density

“Transverse” region as defined by the leading “charged particle jet”



Compares the average “transverse” charge particle density (||<1, pT>0.5 GeV) versus PT(charged jet#1) with the pT distribution of the “transverse” density, dNchg/dddPT. Shows how the “transverse” charge particle density is distributed in pT.

Compares the Run 2 data (Min-Bias, JET20, JET50, JET70, JET100) with Run 1.


1.0E-07

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 16 18 20

PT(charged) (GeV/c)

Cha

rged

Den

sity

dN

/d

ddP

T (1

/GeV

/c)


Charged Particles || < 1.0

Min-Bias



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"Tra

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Cha

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||<1.0 PT>0.5 GeV



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CDF Run 2


1.0E-07

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0 2 4 6 8 10 12 14 16 18 20

PT(charged) (GeV/c)

Cha

rged

Den

sity

dN

/d

ddP

T (1

/GeV

/c)




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"Tra

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Den

sity CDF Run 1 Published

CDF Run 2 Preliminary

||<1.0 PT>0.5 GeV/c



1.0E-07

1.0E-06

1.0E-05

1.0E-04

1.0E-03

1.0E-02

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1.0E+00

0 2 4 6 8 10 12 14 16 18 20

PT(charged) (GeV/c)

Cha

rged

Den

sity

dN

/d

ddP

T (1

/GeV

/c) Run 2 Min-Bias Preliminary

Run 1 Min-Bias PreliminaryRun 2 PreliminaryRun 1 Published



Min-Bias



Charged Particle DensityCharged Particle Density “Transverse” p “Transverse” pTT Distribution Distribution



JetClu Jet #1 Direction


“Toward”

“Away”

“Toward-Side” Jet

“Away-Side” Jet

Look at charged particle correlations in the azimuthal angle relative to the leading JetClu 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 Particle Correlations pT > 0.5 GeV/c || < 1

Away-side “jet”(sometimes)

Perpendicular to the plane of the 2-to-2 hard scattering

“Transverse” region is very sensitive to the “underlying event”!


“Toward”


“Away”

-1 +1

2

0

Leading Jet

Toward Region

Transverse Region

Transverse Region

Away Region

Away Region

Look at the charged particle density in the “transverse” region!

““Underlying Event”Underlying Event”as defined by “Calorimeter Jets”as defined by “Calorimeter Jets”



Shows the data on the average “transverse” charge particle density (||<1, PT>0.5 GeV) as a function of the transverse energy of the leading JetClu jet (R = 0.7, |(jet)| < 2) from Run 2.


“Toward”


“Away”

Compares the “transverse” region of the leading “charged particle jet”, chgjet#1, with the “transverse” region of the leading “calorimeter jet” (JetClu R = 0.7), jet#1.

JetClu Jet #1 or ChgJet#1

Direction

“Toward”


“Away”

, compared with PYTHIA Tune A after CDFSIM.


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ET(jet#1) (GeV)

"Tra

nsve

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Cha

rged

Den

sity



JetClu (R = 0.7, |(jet#1)| < 2)

“Transverse” region as defined by the leading

“calorimeter jet” "Transverse" Charged Particle Density: dN/dd

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ET(jet#1) (GeV)

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sity

PYTHIA Tune ACDF Run 2 Preliminary



JetClu (R = 0.7, |(jet#1)| < 2)


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PT(chgjet#1) or ET(jet#1) (GeV)

"Tra

nsve

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Cha

rged

Den

sity CDF Preliminary

data uncorrected


ChgJet#1 R = 0.7

JetClu Jet#1 (R = 0.7,|(jet)|<2)


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"Tra

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ChgJet#1 R = 0.7

JetClu Jet#1 (R = 0.7, |(jet)|<2)


““Transverse” Transverse” Charged Particle DensityCharged Particle Density



Shows the data on the average “transverse” charged PTsum density (||<1, PT>0.5 GeV) as a function of the transverse energy of the leading JetClu jet (R = 0.7, |(jet)| < 2) from Run 2.


“Toward”


“Away”

Compares the “transverse” region of the leading “charged particle jet”, chgjet#1, with the “transverse” region of the leading “calorimeter jet” (JetClu R = 0.7), jet#1.

JetClu Jet #1 or ChgJet#1

Direction

“Toward”


“Away”

, compared with PYTHIA Tune A after CDFSIM.


0.0

0.5

1.0

1.5

0 25 50 75 100 125 150 175 200 225 250

ET(jet#1) (GeV)

"Tra

nsve

rse"

PTs

um D

ensi

ty (G

eV/c

)



JetClu (R = 0.7, |(jet#1)| < 2)

“Transverse” region as defined by the leading

“calorimeter jet” "Transverse" Charged PTsum Density: dPTsum/dd

0.0

0.5

1.0

1.5

0 25 50 75 100 125 150 175 200 225 250

ET(jet#1) (GeV)

"Tra

nsve

rse"

PTs

um D

ensi

ty (G

eV/c

)




JetClu (R = 0.7, |(jet#1)| < 2)


0.0

0.5

1.0

1.5

0 25 50 75 100 125 150 175 200 225 250


"Tra

nsve

rse"

PTs

um D

ensi

ty (G

eV/c

)


Charged Particles (||<1.0, PT>0.5 GeV/c) ChgJet#1 R = 0.7



0.0

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1.0

1.5

0 25 50 75 100 125 150 175 200 225 250


"Tra

nsve

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PTs

um D

ensi

ty (G

eV/c

) CDF Preliminarydata uncorrectedtheory corrected

Charged Particles (||<1.0, PT>0.5 GeV/c) ChgJet#1 R = 0.7



““Transverse” Transverse” Charged PTsum DensityCharged PTsum Density



Shows the ratio of PT(chgjet#1) to the “matched” JetClu jet ET versus PT(chgjet#1).

Shows the “matched” JetClu jet ET versus the transverse momentum of the leading “charged particle jet” (closest jet within R = 0.7 of the leading chgjet).

ET(matched jet) vs PT(charged jet#1)

0

20

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160

180

0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150


Mat

ched

Jet

ET

(GeV

)




JetClu (R = 0.7, |(jet#1)| < 2)

PT(chgjet#1)/ET(matched jet) vs PT(chgjet#1)

0.2

0.4

0.6

0.8

1.0

1.2

0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150


PT(c

hgje

t#1)

/ET(

mat

ched

jet)


CDF Preliminarydata uncorrectedtheory corrected Charged Particles (||<1.0, PT>0.5 GeV/c)

JetClu (R = 0.7, |(jet#1)| < 2)

The leading chgjet comes from a JetClu jet that is, on the average,

about 90% charged!

In lecture 2 I will show youA more detailed study of the

“underlying event” inRun 2 at CDF!

Relationship BetweenRelationship Between“Calorimeter” and “Charged Particle” Jets“Calorimeter” and “Charged Particle” Jets

mcnet07 - durham - part 1 april 18-20, 2007 rick field – florida/cdf/cmspage 1 physics and...

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