University of Toronto March 18, 2008 Rick Field – Florida/CDF/CMSPage 1 Studying the Underlying Event at CDF and the LHC Rick Field University of Florida.

University of Toronto March 18, 2008

Rick Field – Florida/CDF/CMS Page 1

Studying the Underlying Event atStudying the Underlying Event atCDF and the LHCCDF and the LHC

Proton AntiProton

PT(hard)

Outgoing Parton

Outgoing Parton

Underlying Event Underlying Event

Initial-State Radiation

Final-State Radiation

Rick FieldUniversity of Florida

CMS at the LHCCDF Run 2

University of Toronto PhysicsMarch 18, 2008

Outline of Talk Review what we learned about “min-bias” and

the “underlying event” in Run 1 at CDF.

Discuss using Drell-Yan lepton-pair production to study the “underlying event”.

Explain the various PYTHIA “underlying event” tunes and extrapolations to the LHC.

UE&MB@CMS: Plans to measure “min-bias” and the “underlying event” at CMS.

“CDF-QCD Data for Theory”: My latest CDF Run 2 project.



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




“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

AverageAverage 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

0

1

2

3

4

5

6

7

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

Pseudo-Rapidity

dN

/d

CDF Min-Bias 1.8 TeV

CDF Min-Bias 630 GeV all PT

CDF Published

<dNchg/d> = 4.2

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

CDF Min-Bias 630 GeV

CDF 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



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


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)

Ch

arg

ed

Pa

rtic

le D

en

sit

y

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

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)

As

so

cia

ted

Pa

rtic

le D

en

sit

y

PTmax > 2.0 GeV/c

PTmax > 1.0 GeV/c

PTmax > 0.5 GeV/c

CDF Preliminarydata uncorrected

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!



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

nsv

erse

" C

har

ged

Den

sity

CDF Min-Bias

CDF JET20CDF 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

har

ged

Den

sity

dN

/d

d d

PT

(1/

GeV

/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


0.00

0.25

0.50

0.75

1.00

0 5 10 15 20 25 30 35 40 45 50


"Tra

ns

ve

rse

" C

ha

rge

d D

en

sit

y

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

ns

ve

rse

" C

ha

rge

d D

en

sit

y 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



"Transverse" 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

har

ged

Den

sity

dN

/d

d d

PT

(1/

GeV

/c)

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


0.00

0.25

0.50

0.75

1.00

0 5 10 15 20 25 30 35 40 45 50


"Tra

nsv

erse

" C

har

ged

Den

sity


1.8 TeV ||<1.0 PT>0.5 GeV

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-off

PT0 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 10,000 100,000

CM Energy W (GeV)P

T0

(G

eV

/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

ran

sver

se"

Ch

arg

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


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)).


0.00

0.25

0.50

0.75

1.00

0 5 10 15 20 25 30 35 40 45 50


"Tra

nsv

erse

" C

har

ged

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!



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


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 A

CDF 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

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)

Ch

arg

ed D

ensi

ty d

N/d

d d

PT

(1/

GeV

/c)

Pythia 6.206 Set A

CDF 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




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)

Ch

arg

ed D

ensi

ty d

N/d

d d

PT

(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 10,000 100,000

CM Energy W (GeV)

% o

f E

ven

ts

PT(hard) > 5 GeV/c

PT(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



QCD Monte-Carlo Models:QCD Monte-Carlo Models:Lepton-Pair ProductionLepton-Pair Production

Start with the perturbative Drell-Yan muon pair production and add initial-state gluon radiation (in the leading log approximation or modified leading log approximation).

Proton AntiProton


Proton AntiProton


“Hard Scattering” Component

Lepton-Pair Production

Lepton

Anti-Lepton


Lepton-Pair Production

Lepton

Anti-Lepton


“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 “Central” RegionThe “Central” Regionin Drell-Yan Productionin Drell-Yan Production

Look at the “central” region after removing the lepton-pair.

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, by dividing by the area in - space.

Proton AntiProton

Drell-Yan Production Lepton



Anti-Lepton

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

After removing the lepton-pair everything else is the

“underlying event”!

Proton AntiProton

Multiple Parton Interactions

Anti-Lepton

Lepton


-1 +1

2

0

Central Region

Look at the charged particle density and the

PTsum density in the “central” region!



CDF Run 1 PCDF Run 1 PTT(Z)(Z)

Shows the Run 1 Z-boson pT distribution (<pT(Z)> ≈ 11.5 GeV/c) compared with PYTHIA Tune A (<pT(Z)> = 9.7 GeV/c), Tune A25 (<pT(Z)> = 10.1 GeV/c), and Tune A50 (<pT(Z)> = 11.2 GeV/c).

Z-Boson Transverse Momentum

0.00

0.04

0.08

0.12

0 2 4 6 8 10 12 14 16 18 20

Z-Boson PT (GeV/c)

PT

Dis

trib

uti

on

1/N

dN

/dP

T

CDF Run 1 Data

PYTHIA Tune A

PYTHIA Tune A25

PYTHIA Tune A50

CDF Run 1published

1.8 TeV

Normalized to 1

= 1.0

= 2.5

= 5.0

Parameter Tune A Tune A25 Tune A50

MSTP(81) 1 1 1

MSTP(82) 4 4 4

PARP(82) 2.0 GeV 2.0 GeV 2.0 GeV

PARP(83) 0.5 0.5 0.5

PARP(84) 0.4 0.4 0.4

PARP(85) 0.9 0.9 0.9

PARP(86) 0.95 0.95 0.95

PARP(89) 1.8 TeV 1.8 TeV 1.8 TeV

PARP(90) 0.25 0.25 0.25

PARP(67) 4.0 4.0 4.0

MSTP(91) 1 1 1

PARP(91) 1.0 2.5 5.0

PARP(93) 5.0 15.0 25.0

UE Parameters

ISR Parameter

Intrensic KT

PYTHIA 6.2 CTEQ5L

Vary the intrensic KT!




Shows the Run 1 Z-boson pT distribution (<pT(Z)> ≈ 11.5 GeV/c) compared with PYTHIA Tune A (<pT(Z)> = 9.7 GeV/c), and PYTHIA Tune AW (<pT(Z)> = 11.7 GeV/c).

Parameter Tune A Tune AW

MSTP(81) 1 1

MSTP(82) 4 4


PARP(83) 0.5 0.5

PARP(84) 0.4 0.4

PARP(85) 0.9 0.9

PARP(86) 0.95 0.95


PARP(90) 0.25 0.25

PARP(62) 1.0 1.25

PARP(64) 1.0 0.2

PARP(67) 4.0 4.0

MSTP(91) 1 1

PARP(91) 1.0 2.1

PARP(93) 5.0 15.0

The Q2 = kT2 in s for space-like showers is scaled by PARP(64)!

Effective Q cut-off, below which space-like showers are not evolved.

UE Parameters

ISR Parameters

Intrensic KT

PYTHIA 6.2 CTEQ5LZ-Boson Transverse Momentum

0.00

0.04

0.08

0.12

0 2 4 6 8 10 12 14 16 18 20

Z-Boson PT (GeV/c)

PT

Dis

trib

uti

on

1/N

dN

/dP

T

CDF Run 1 Data

PYTHIA Tune A

PYTHIA Tune AW

CDF Run 1published

1.8 TeV

Normalized to 1

Tune used by the CDF-EWK group!



JetJet--Jet Correlations (DJet Correlations (DØ)Ø)

Jet#1-Jet#2 Distribution Jet#1-Jet#2

MidPoint Cone Algorithm (R = 0.7, fmerge = 0.5)

L = 150 pb-1 (Phys. Rev. Lett. 94 221801 (2005))Data/NLO agreement good. Data/HERWIG agreement

good.Data/PYTHIA agreement good provided PARP(67) =

1.0→4.0 (i.e. like Tune A, best fit 2.5).




Shows the Run 1 Z-boson pT distribution (<pT(Z)> ≈ 11.5 GeV/c) compared with PYTHIA Tune DW, and HERWIG.

Parameter Tune DW Tune AW

MSTP(81) 1 1

MSTP(82) 4 4


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(90) 0.25 0.25

PARP(62) 1.25 1.25

PARP(64) 0.2 0.2

PARP(67) 2.5 4.0

MSTP(91) 1 1

PARP(91) 2.1 2.1

PARP(93) 15.0 15.0

UE Parameters

ISR Parameters

Intrensic KT

PYTHIA 6.2 CTEQ5LZ-Boson Transverse Momentum

0.00

0.04

0.08

0.12

0 2 4 6 8 10 12 14 16 18 20

Z-Boson PT (GeV/c)

PT

Dis

trib

uti

on

1/N

dN

/dP

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CDF Run 1 Data

PYTHIA Tune DW

HERWIG

CDF Run 1published

1.8 TeV

Normalized to 1

Tune DW has a lower value of PARP(67) and slightly more MPI!

Tune DW uses D0’s perfered value of PARP(67)!



PYTHIA 6.2 TunesPYTHIA 6.2 TunesParameter Tune DW Tune DWT ATLAS Tune D6 Tune D6T

PDF CTEQ5L CTEQ5L CTEQ5L CTEQ6L CTEQ6L

MSTP(2) 1 1 1 1 1

MSTP(33) 0 0 0 0 1

PARP(31) 1.0 1.0 1.0 1.0 1.0

MSTP(81) 1 1 1 1 1

MSTP(82) 4 4 4 4 4

PARP(82) 1.9 GeV 1.9409 GeV 1.8 GeV 1.8 GeV 1.8387 GeV

PARP(83) 0.5 0.5 0.5 0.5 0.5

PARP(84) 0.4 0.4 0.5 0.4 0.4

PARP(85) 1.0 1.0 0.33 1.0 1.0

PARP(86) 1.0 1.0 0.66 1.0 1.0

PARP(89) 1.8 TeV 1.96 TeV 1.0 TeV 1.8 TeV 1.96 TeV

PARP(90) 0.25 0.16 0.16 0.25 0.16

PARP(62) 1.25 1.25 1.0 1.25 1.25

PARP(64) 0.2 0.2 1.0 0.2 0.2

PARP(67) 2.5 2.5 1.0 2.5 2.5

MSTP(91) 1 1 1 1 1

PARP(91) 2.1 2.1 1.0 2.1 2.1

PARP(93) 15.0 15.0 5.0 15.0 15.0

Intrinsic KT

ISR Parameter

UE Parameters

Use LO s with = 192 MeV!

CMS uses Tune DWT and Tune D6T!

CTEQ6L Tune



PYTHIA 6.2 TunesPYTHIA 6.2 Tunes


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Leading Jet (||<2.0)Charged Particles (||<1.0, PT>0.5 GeV/c)

1.96 TeVHERWIG

PY Tune DW

PY-ATLAS

PY Tune A

"Transverse" PTsum Density: dPT/dd

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PY-ATLAS

PY Tune DW

PY Tune A

"Transverse" Charged Particle Average pT

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HERWIG


1.96 TeV


PY Tune DWPY Tune A

Parameter Tune A Tune DW Tune DWT ATLAS

MSTP(81) 1 1 1 1

MSTP(82) 4 4 4 4

PARP(82) 2.0 GeV 1.9 GeV 1.9409 GeV 1.8 GeV

PARP(83) 0.5 0.5 0.5 0.5

PARP(84) 0.4 0.4 0.4 0.5

PARP(85) 0.9 1.0 1.0 0.33

PARP(86) 0.95 1.0 1.0 0.66

PARP(89) 1.8 TeV 1.8 TeV 1.96 TeV 1.0 TeV

PARP(90) 0.25 0.25 0.16 0.16

PARP(62) 1.0 1.25 1.25 1.0

PARP(64) 1.0 0.2 0.2 1.0

PARP(67) 4.0 2.5 2.5 1.0

MSTP(91) 1 1 1 1

PARP(91) 1.0 2.1 2.1 1.0

PARP(93) 5.0 15.0 15.0 5.0

PYTHIA 6.2 CTEQ5L

Shows the “transverse” charged particle density, dN/dd, versus PT(jet#1) for “leading jet” events at 1.96 TeV for Tune A, DW, ATLAS, and HERWIG (without MPI).

(MPI) at 1.96 TeV (MPI) at 14 TeV

Tune A 309.7 mb 484.0 mb

Tune DW 351.7 mb 549.2 mb

Tune DWT 351.7 mb 829.1 mb

ATLAS 324.5 mb 768.0 mb

Shows the “transverse” charged PTsum density, dPT/dd, versus PT(jet#1) for “leading jet” events at 1.96 TeV for Tune A, DW, ATLAS, and HERWIG (without MPI).

Shows the “transverse” charged average pT, versus PT(jet#1) for “leading jet” events at 1.96 TeV for Tune A, DW, ATLAS, and HERWIG (without MPI).

Identical to DW at 1.96 TeV but usesATLAS extrapolation to the LHC!

"Transverse" Charged Average PT

0.7

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1.1

1.3

1.5

1.7

0 50 100 150 200 250 300 350 400 450

PT(jet#1) (GeV/c)

"Tra

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" <

PT

> (

GeV

/c)

CDF Run 2 Preliminarydata corrected to particle level

MidPoint R = 0.7 |(jet#1) < 2

Charged Particles (||<1.0, PT>0.5 GeV/c) 1.96 TeV

"Leading Jet"

HERWIG

PY-ATLAS

PY Tune A, DW

CDF Run 2 Data!



The “Underlying Event” inThe “Underlying Event” inHigh PHigh PTT Jet Production (LHC) Jet Production (LHC)

Charged particle density in the “Transverse” region versus PT(jet#1) at 1.96 TeV for PY Tune AW and HERWIG (without MPI).

Charged particle density in the “Transverse” region versus PT(jet#1) at 14 TeV for PY Tune AW and HERWIG (without MPI).

The “Underlying Event”


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RDF Preliminarygenerator level

Charged Particles (||<1.0, PT>0.5 GeV/c) "Leading Jet"

PY Tune AW

1.96 TeV

HERWIG


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Charged Particles (||<1.0, PT>0.5 GeV/c) "Leading Jet"

PY Tune AW

CDF

LHC

HERWIG

Charged particle density versus PT(jet#1)

“Underlying event” much more active at the LHC!

Proton AntiProton

High PT Jet Production

PT(hard)

Outgoing Parton

Outgoing Parton






PYTHIA 6.2 TunesPYTHIA 6.2 Tunes

Parameter Tune A Tune DW Tune DWT ATLAS

MSTP(81) 1 1 1 1

MSTP(82) 4 4 4 4

PARP(82) 2.0 GeV 1.9 GeV 1.9409 GeV 1.8 GeV

PARP(83) 0.5 0.5 0.5 0.5

PARP(84) 0.4 0.4 0.4 0.5

PARP(85) 0.9 1.0 1.0 0.33

PARP(86) 0.95 1.0 1.0 0.66

PARP(89) 1.8 TeV 1.8 TeV 1.96 TeV 1.0 TeV

PARP(90) 0.25 0.25 0.16 0.16

PARP(62) 1.0 1.25 1.25 1.0

PARP(64) 1.0 0.2 0.2 1.0

PARP(67) 4.0 2.5 2.5 1.0

MSTP(91) 1 1 1 1

PARP(91) 1.0 2.1 2.1 1.0

PARP(93) 5.0 15.0 15.0 5.0

PYTHIA 6.2 CTEQ5L

Shows the “transverse” charged particle density, dN/dd, versus PT(jet#1) for “leading jet” events at 14 TeV for Tune A, DW, ATLAS, and HERWIG (without MPI).

(MPI) at 1.96 TeV (MPI) at 14 TeV

Tune A 309.7 mb 484.0 mb

Tune DW 351.7 mb 549.2 mb

Tune DWT 351.7 mb 829.1 mb

ATLAS 324.5 mb 768.0 mb

Shows the “transverse” charged PTsum density, dPT/dd, versus PT(jet#1) for “leading jet” events at 14 TeV for Tune A, DW, ATLAS, and HERWIG (without MPI).

Shows the “transverse” charged average pT, versus PT(jet#1) for “leading jet” events at 14 TeV for Tune A, DW, ATLAS, and HERWIG (without MPI).

Identical to DW at 1.96 TeV but usesATLAS extrapolation to the LHC!


0.0

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2.5

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"Tra

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PY Tune DWT


14 TeV

PY Tune DW

HERWIG

PY-ATLAS

"Transverse" PTsum Density: dPT/dd

0.0

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4.0

6.0

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"Tra

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generator level


14 TeV

HERWIG

PY-ATLAS

PY Tune DW

PY Tune DWT

"Transverse" Charged Particle Average pT

1.0

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2.0

2.5

0 250 500 750 1000 1250 1500 1750 2000


"Tra

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PT

(G

eV/c

) RDF Preliminary generator level


14 TeV

PY-ATLAS

HERWIG

PY Tune DWT

PY Tune DW



Proton AntiProton

PT(hard)

Outgoing Parton

Outgoing Parton




Proton AntiProton

“Minumum Bias” Collisions

PYTHIA Tune DW is very similar to Tune A except that it fits the CDF PT(Z) distribution and it uses the DØ prefered value of PARP(67) = 2.5 (determined from the dijet distribution).

PYTHIA Tune DWT is identical to Tune DW at 1.96 TeV but uses the ATLAS energy extrapolation to the LHC (i.e. PARP(90) = 0.16).

SummarySummaryTevatron LHC

PYTHIA Tune D6 and D6T are similar to Tune DW and DWT, respectively, but use CTEQ6L (i.e. LHAPDF = 10042).



DrellDrell--Yan Production (Run 2 vs LHC)Yan Production (Run 2 vs LHC)

Average Lepton-Pair transverse momentum at the Tevatron and the LHC for PYTHIA Tune DW and HERWIG (without MPI).

Shape of the Lepton-Pair pT distribution at the Z-boson mass at the Tevatron and the LHC for PYTHIA Tune DW and HERWIG (without MPI).

Proton AntiProton




Anti-Lepton

Lepton-Pair Transverse Momentum

Shapes of the pT(+-) distribution at the Z-boson mass.

<pT(+-)> is much larger at the LHC!

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

rag

e P

air

PT

Drell-Yangenerator level LHC

Tevatron Run 2

PY Tune DW (solid)HERWIG (dashed)

Drell-Yan PT(+-) Distribution

0.00

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0.04

0.06

0.08

0.10

0 5 10 15 20 25 30 35 40

PT(+-) (GeV/c)

1/N

dN

/dP

T (

1/G

eV

)

Drell-Yangenerator level

PY Tune DW (solid)HERWIG (dashed)

70 < M(-pair) < 110 GeV|(-pair)| < 6

Normalized to 1LHC

Tevatron Run2

Z



The “Underlying Event” inThe “Underlying Event” inDrellDrell--Yan ProductionYan Production

Charged particle density versus the lepton-pair invariant mass at 1.96 TeV for PYTHIA Tune AW and HERWIG (without MPI).

Charged particle density versus the lepton-pair invariant mass at 14 TeV for PYTHIA Tune AW and HERWIG (without MPI).


Proton AntiProton




Anti-Lepton


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Drell-Yan1.96 TeV

PY Tune AW

HERWIG

Charged Particles (||<1.0, PT>0.5 GeV/c)(excluding lepton-pair )


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Drell-YanCharged Particles (||<1.0, PT>0.5 GeV/c)

(excluding lepton-pair )

PY Tune AW

HERWIG

LHC

CDF

Charged particle density versus M(pair)

“Underlying event” much more active at the LHC!

HERWIG (without MPI) is much less active than

PY Tune AW (with MPI)!

Z

Z



Extrapolations to the LHC:Extrapolations to the LHC:DrellDrell--Yan ProductionYan Production

Average charged particle density versus the lepton-pair invariant mass at 1.96 TeV for PYTHIA Tune A, Tune AW, Tune BW, Tune DW and HERWIG (without MPI).

Proton AntiProton




Anti-Lepton

Average charged particle density versus the lepton-pair invariant mass at 14 TeV for PYTHIA Tune DW, Tune DWT, ATLAS and HERWIG (without MPI).

The “Underlying Event”Charged particle density

versus M(pair)

Tune DW and DWT are identical at 1.96 TeV, but have different MPI energy

dependence!


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14 TeV

HERWIG

PY-ATLAS

PY Tune DW

PY Tune DWT

Z


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HERWIG

PY Tune BWPY Tune DW

PY Tune A PY Tune AW

1.96 TeV

Z



Extrapolations to the LHC:Extrapolations to the LHC:DrellDrell--Yan ProductionYan Production

Average charged particle density (pT > 0.5 GeV/c) versus the lepton-pair invariant mass at 14 TeV for PYTHIA Tune DW, Tune DWT, ATLAS and HERWIG (without MPI).

Average charged particle density (pT > 0.9 GeV/c) versus the lepton-pair invariant mass at 14 TeV for PYTHIA Tune DW, Tune DWT, ATLAS and HERWIG (without MPI).


Proton AntiProton




Anti-Lepton

Charged particle density versus M(pair)

Charged Particles (||<1.0, pT > 0.5 GeV/c)


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14 TeV

HERWIG

PY-ATLAS

PY Tune DW

PY Tune DWT

Z Z


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Generator Level14 TeV

HERWIG

PY-ATLASPY Tune DW

PY Tune DWT

Charged Particles (||<1.0, pT > 0.9 GeV/c)


0.0

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Minimum pT (GeV/c)

Ch

arg

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Charged Particles (pT > min, ||<1.0)

(excluding lepton-pair )

Drell-YanGenerator Level

14 TeV

70 < M(+-) < 110 GeV

HERWIG

PY Tune DW

PY-ATLAS

The ATLAS tune has a much “softer” distribution of charged particles than

the CDF Run 2 Tunes!



Most Recent CDF Most Recent CDF “Underlying Event” Studies“Underlying Event” Studies

Proton AntiProton

PT(hard)

Outgoing Parton

Outgoing Parton




Proton AntiProton

Drell-Yan Production

Anti-Lepton

Lepton


Fermilab 2008

The goal is to produce data (corrected to the particle level) that can be used by the theorists to tune and improve the QCD Monte-Carlo models that are used to simulate hadron-hadron collisions.

CDF-QCD Data for Theory

Rick FieldCraig GroupDeepak Kar

Outline of the Project The “Towards”, “Away”, and

“Transverse” regions of - space.

Four Jet Topologies.

The “transMAX”, “transMIN”, and “transDIF” regions.

Also, study the “underlying event” in Drell-Yan production.

Jet #1 Direction

“Toward”


“Away”

Over 128 plots to get “blessed” and then to published. So far we have only looked at average quantities. We plan to also produce distributions and flow plots.

We plan to construct a “CDF-QCD Data for Theory” WEBsite with the “blessed” plots together with tables of the data points and errors so that people can have access to the results.



-1 +1

2

0

Leading Jet

Toward Region

Transverse Region

Transverse Region

Away Region

Away Region

Jet #1 Direction


“Toward”

“Away”


“Away-Side” Jet

““Towards”, “Away”, “Transverse”Towards”, “Away”, “Transverse”

Look at correlations in the azimuthal angle relative to the leading charged particle jet (|| < 1) or the leading calorimeter jet (|| < 2).

Define || < 60o as “Toward”, 60o < | < 120o as “Transverse ”, and || > 120o as “Away”. Each of the three regions have area = 2×120o = 4/3.

Jet #1 Direction

“Toward”


“Away”

Correlations relative to the leading jetCharged particles pT > 0.5 GeV/c || < 1Calorimeter towers ET > 0.1 GeV || < 1“Transverse” region is

very sensitive to the “underlying event”!

Look at the charged particle density, the

charged PTsum density and the ETsum density in

all 3 regions!

Z-Boson Direction



Event TopologiesEvent Topologies“Leading Jet” events correspond to the leading

calorimeter jet (MidPoint R = 0.7) in the region || < 2 with no other conditions.

Jet #1 Direction

“Toward”


“Away”

“Leading Jet”

“Leading ChgJet” events correspond to the leading charged particle jet (R = 0.7) in the region || < 1 with no other conditions.

ChgJet #1 Direction

“Toward”


“Away”

Jet #1 Direction

“Toward”


“Away”

Jet #2 Direction

“Charged Jet”

“Inc2J Back-to-Back”

“Exc2J Back-to-Back”

“Inclusive 2-Jet Back-to-Back” events are selected to have at least two jets with Jet#1 and Jet#2 nearly “back-to-back” (12 > 150o) with almost equal transverse energies (PT(jet#2)/PT(jet#1) > 0.8) with no other conditions .

“Exclusive 2-Jet Back-to-Back” events are selected to have at least two jets with Jet#1 and Jet#2 nearly “back-to-back” (12 > 150o) with almost equal transverse energies (PT(jet#2)/PT(jet#1) > 0.8) and PT(jet#3) < 15 GeV/c.

subset

subset

Z-Boson Direction

“Toward”


“Away”

Z-Boson“Z-Boson” events are Drell-Yan events with 70 < M(lepton-pair) < 110 GeV with no other conditions.



Jet #1 Direction

“Toward”


“Away”

Jet #1 Direction

“Toward”


“Away”

Jet #2 Direction

“Back-to-Back”

Observable Particle Level Detector Level

dNchg/ddNumber of charged particles

per unit -(pT > 0.5 GeV/c, || < 1)

Number of “good” charged tracksper unit -

(pT > 0.5 GeV/c, || < 1)

dPTsum/ddScalar pT sum of charged particles

per unit -(pT > 0.5 GeV/c, || < 1)

Scalar pT sum of “good” charged tracks per

unit -(pT > 0.5 GeV/c, || < 1)

<pT>Average pT of charged particles

(pT > 0.5 GeV/c, || < 1)

Average pT of “good” charged tracks

(pT > 0.5 GeV/c, || < 1)

PTmax

Maximum pT charged particle

(pT > 0.5 GeV/c, || < 1)

Require Nchg ≥ 1

Maximum pT “good” charged tracks

(pT > 0.5 GeV/c, || < 1)

Require Nchg ≥ 1

dETsum/ddScalar ET sum of all particles

per unit -(all pT, || < 1)

Scalar ET sum of all calorimeter towers

per unit -(ET > 0.1 GeV, || < 1)

PTsum/ETsum

Scalar pT sum of charged particles

(pT > 0.5 GeV/c, || < 1)

divided by the scalar ET sum of

all particles (all pT, || < 1)

Scalar pT sum of “good” charged tracks

(pT > 0.5 GeV/c, || < 1)

divided by the scalar ET sum of

calorimeter towers (ET > 0.1 GeV, || < 1)

“Leading Jet”

““Leading Jet” Observables at theLeading Jet” Observables at theParticle and Detector LevelParticle and Detector Level

Also include the leading jet mass (new)!



Jet #1 Direction

“Overall”

“Leading Jet”

Overall Totals (|Overall Totals (|| < 1)| < 1)

Data at 1.96 TeV on the overall number of charged particles (pT > 0.5 GeV/c, || < 1) and the overall scalar pT sum of charged particles (pT > 0.5 GeV/c, || < 1) and the overall scalar ET sum of all particles (|| < 1) for “leading jet” events as a function of the leading jet pT. The data are corrected to the particle level (with errors that include both the statistical error and the systematic uncertainty) and are compared with PYTHIA Tune A at the particle level (i.e. generator level)..

Overall Totals versus PT(jet#1)

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PT(jet#1) (GeV/c)

Av

era

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CDF Run 2 Preliminarydata corrected

pyA generator level

"Leading Jet"MidPoint R=0.7 |(jet#1)|<2


Stable Particles (||<1.0, all PT)

ETsum (GeV)

PTsum (GeV/c)

Nchg

Nchg = 30

PTsum = 190 GeV/c

ETsum = 330 GeV

ETsum = 775 GeV!



Jet #1 Direction

“Overall”

“Leading Jet”

Overall Totals (|Overall Totals (|| < 1)| < 1)

Data at 1.96 TeV on the overall number of charged particles (pT > 0.5 GeV/c, || < 1) for “leading jet” events as a function of the leading jet pT. The data are corrected to the particle level (with errors that include both the statistical error and the systematic uncertainty) and are compared with PYTHIA Tune A and HERWIG (without MPI) at the particle level (i.e. generator level).

Overall Number of Charged Particles

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PY Tune A

HW

Overall Charged PTsum

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PY Tune A

HW

Data at 1.96 TeV on the overall scalar pT sum of charged particles (pT > 0.5 GeV/c, || < 1) for “leading jet” events as a function of the leading jet pT. The data are corrected to the particle level (with errors that include both the statistical error and the systematic uncertainty) and are compared with PYTHIA Tune A and HERWIG (without MPI) at the particle level (i.e. generator level).

Overall ETsum versus PT(jet#1)

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PY Tune A

HW

Data at 1.96 TeV on the overall scalar ET sum of all particles (|| < 1) for “leading jet” events as a function of the leading jet pT. The data are corrected to the particle level (with errors that include both the statistical error and the systematic uncertainty) and are compared with PYTHIA Tune A and HERWIG (without MPI) at the particle level (i.e. generator level).



CDF DiJet Event: M(jj) CDF DiJet Event: M(jj) ≈ 1.4 TeV≈ 1.4 TeV

ETjet1 = 666 GeV ET

jet2 = 633 GeV Esum = 1,299 GeV M(jj) = 1,364 GeV

M(jj)/Ecm ≈ 70%!!



Jet #1 Direction

“Toward”


“Away”

“Leading Jet”

““Towards”, “Away”, “Transverse”Towards”, “Away”, “Transverse”

Data at 1.96 TeV on the density of charged particles, dN/dd, with pT > 0.5 GeV/c and || < 1 for “leading jet” events as a function of the leading jet pT for the “toward”, “away”, and “transverse” regions. The data are corrected to the particle level (with errors that include both the statistical error and the systematic uncertainty) and are compared with PYTHIA Tune A at the particle level (i.e. generator level).


0

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PT(jet#1) (GeV/c)

Ave

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Den

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pyA generator level



"Away"

"Toward"

"Transverse"

Data at 1.96 TeV on the charged particle scalar pT sum density, dPT/dd, with pT > 0.5 GeV/c and || < 1 for “leading jet” events as a function of the leading jet pT for the “toward”, “away”, and “transverse” regions. The data are corrected to the particle level (with errors that include both the statistical error and the systematic uncertainty) and are compared with PYTHIA Tune A at the particle level (i.e. generator level).

Data at 1.96 TeV on the particle scalar ET sum density, dET/dd, for || < 1 for “leading jet” events as a function of the leading jet pT for the “toward”, “away”, and “transverse” regions. The data are corrected to the particle level (with errors that include both the statistical error and the systematic uncertainty) and are compared with PYTHIA Tune A at the particle level (i.e. generator level).

Factor of ~4.5

Charged PTsum Density: dPT/dd

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Ch

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/c)


pyA generator level



"Toward""Away"

"Transverse"

Factor of ~16

ETsum Density: dET/dd

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ET

sum

Den

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(G

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pyA generator level



"Toward"

"Away"

"Transverse"

Factor of ~13



Jet #1 Direction

“Toward”


“Away”

“Leading Jet”

The “Toward” RegionThe “Toward” Region

Data at 1.96 TeV on the density of charged particles, dN/dd, with pT > 0.5 GeV/c and || < 1 for “leading jet” events as a function of the leading jet pT for the “toward” region. The data are corrected to the particle level (with errors that include both the statistical error and the systematic uncertainty) and are compared with PYTHIA Tune A and HERWIG (without MPI) at the particle level (i.e. generator level).

"Toward" Charged Particle Density: dN/dd

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HW

"Toward" Charged PTsum Density: dPT/dd

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/c) CDF Run 2 Preliminary

data correctedgenerator level theory



PY Tune A

HW

"Toward" ETsum Density: dET/dd

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PT(jet#1) (GeV/c)

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PY Tune A

HW

Data at 1.96 TeV on the charged scalar pT sum density, dPT/dd, with pT > 0.5 GeV/c and || < 1 for “leading jet” events as a function of the leading jet pT for the “toward” region. The data are corrected to the particle level (with errors that include both the statistical error and the systematic uncertainty) and are compared with PYTHIA Tune A and HERWIG (without MPI) at the particle level (i.e. generator level).

Data at 1.96 TeV on the scalar ET sum density, dET/dd, with || < 1 for “leading jet” events as a function of the leading jet pT for the “toward” region. The data are corrected to the particle level (with errors that include both the statistical error and the systematic uncertainty) and are compared with PYTHIA Tune A and HERWIG (without MPI) at the particle level (i.e. generator level).



Jet #1 Direction

“Toward”


“Away”

“Leading Jet”

The “Away” RegionThe “Away” Region

Data at 1.96 TeV on the density of charged particles, dN/dd, with pT > 0.5 GeV/c and || < 1 for “leading jet” events as a function of the leading jet pT for the “away” region. The data are corrected to the particle level (with errors that include both the statistical error and the systematic uncertainty) and are compared with PYTHIA Tune A and HERWIG (without MPI) at the particle level (i.e. generator level).

Data at 1.96 TeV on the charged scalar pT sum density, dPT/dd, with pT > 0.5 GeV/c and || < 1 for “leading jet” events as a function of the leading jet pT for the “away” region. The data are corrected to the particle level (with errors that include both the statistical error and the systematic uncertainty) and are compared with PYTHIA Tune A and HERWIG (without MPI) at the particle level (i.e. generator level).

Data at 1.96 TeV on the scalar ET sum density, dET/dd, with || < 1 for “leading jet” events as a function of the leading jet pT for the “away” region. The data are corrected to the particle level (with errors that include both the statistical error and the systematic uncertainty) and are compared with PYTHIA Tune A and HERWIG (without MPI) at the particle level (i.e. generator level).

"Away" Charged Particle Density: dN/dd

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"Away" Charged PTsum Density: dPT/dd

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) CDF Run 2 Preliminarydata corrected




PY Tune A

HW

"Away" ETsum Density: dET/dd

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PY Tune A

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“Leading Jet”

The “Transverse” RegionThe “Transverse” Region

Data at 1.96 TeV on the density of charged particles, dN/dd, with pT > 0.5 GeV/c and || < 1 for “leading jet” events as a function of the leading jet pT for the “transverse” region. The data are corrected to the particle level (with errors that include both the statistical error and the systematic uncertainty) and are compared with PYTHIA Tune A and HERWIG (without MPI) at the particle level (i.e. generator level).

Data at 1.96 TeV on the charged scalar pT sum density, dPT/dd, with pT > 0.5 GeV/c and || < 1 for “leading jet” events as a function of the leading jet pT for the “transverse” region. The data are corrected to the particle level (with errors that include both the statistical error and the systematic uncertainty) and are compared with PYTHIA Tune A and HERWIG (without MPI) at the particle level (i.e. generator level).

Data at 1.96 TeV on the scalar ET sum density, dET/dd, with || < 1 for “leading jet” events as a function of the leading jet pT for the “transverse” region. The data are corrected to the particle level (with errors that include both the statistical error and the systematic uncertainty) and are compared with PYTHIA Tune A and HERWIG (without MPI) at the particle level (i.e. generator level).

Jet #1 Direction

“Toward”


“Away”


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PY Tune A

"Transverse" Charged PTsum Density: dPT/dd

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"Transverse" ETsum Density: dET/dd

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(G

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PY Tune A

HW

"Transverse" Average PT

0.5

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PT(jet#1) (GeV/c)"T

ran

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T (

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PY Tune A

HW

Data at 1.96 TeV on the charged particle average pT, with pT > 0.5 GeV/c and || < 1 for “leading jet” events as a function of the leading jet pT for the “transverse” region. The data are corrected to the particle level (with errors that include both the statistical error and the systematic uncertainty) and are compared with PYTHIA Tune A and HERWIG (without MPI) at the particle level (i.e. generator level).

"Transverse" Average PTmax

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(Ge

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Excludes events with no "Transverse" Charged Particles

PY Tune A

HW

Data at 1.96 TeV on the charged particle maximum pT, with pT > 0.5 GeV/c and || < 1 for “leading jet” events as a function of the leading jet pT for the “transverse” region. The data are corrected to the particle level (with errors that include both the statistical error and the systematic uncertainty) and are compared with PYTHIA Tune A and HERWIG (without MPI) at the particle level (i.e. generator level).



“Leading Jet”


Data at 1.96 TeV on the density of charged particles, dN/dd, with pT > 0.5 GeV/c and || < 1 for “leading jet” events as a function of the leading jet pT for the “transverse” region. The data are corrected to the particle level (with errors that include both the statistical error and the systematic uncertainty) and are compared with PYTHIA Tune A and HERWIG (without MPI) at the particle level (i.e. generator level).

Shows the Data - Theory for the density of charged particles, dN/dd, with pT > 0.5 GeV/c and || < 1 for “leading jet” events as a function of the leading jet pT for the “transverse” region for PYTHIA Tune A and HERWIG (without MPI).

Jet #1 Direction

“Toward”


“Away”


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PY Tune A


-0.2

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PT(jet#1) (GeV/c)D

ata

- T

heo

ry





HW

PY Tune A

0.1 density corresponds to 0.42 charged particles in the

“transverse” region!



“Leading Jet”


Data at 1.96 TeV on the charged scalar pT sum density, dPT/dd, with pT > 0.5 GeV/c and || < 1 for “leading jet” events as a function of the leading jet pT for the “transverse” region. The data are corrected to the particle level (with errors that include both the statistical error and the systematic uncertainty) and are compared with PYTHIA Tune A and HERWIG (without MPI) at the particle level (i.e. generator level).

Shows the Data - Theory for the charged scalar pT sum density, dPT/dd, with pT > 0.5 GeV/c and || < 1 for “leading jet” events as a function of the leading jet pT for the “transverse” region for PYTHIA Tune A and HERWIG (without MPI).

Jet #1 Direction

“Toward”


“Away”


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PY Tune A

HW


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PT(jet#1) (GeV/c)

Dat

a -

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eory

(G

eV/c

)




Charged Particles (||<1.0, PT>0.5 GeV/c) PY Tune A

HW

0.1 density corresponds to 420 MeV/c in the




“Leading Jet”


Data at 1.96 TeV on the scalar ET sum density, dET/dd, with || < 1 for “leading jet” events as a function of the leading jet pT for the “transverse” region. The data are corrected to the particle level (with errors that include both the statistical error and the systematic uncertainty) and are compared with PYTHIA Tune A and HERWIG (without MPI) at the particle level (i.e. generator level).

Shows the Data - Theory for the scalar ET sum density, dET/dd, with || < 1 for “leading jet” events as a function of the leading jet pT for the “transverse” region for PYTHIA Tune A and HERWIG (without MPI).

Jet #1 Direction

“Toward”


“Away”


0.0

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PT(jet#1) (GeV/c)

"Tra

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" E

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Den

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(G

eV) CDF Run 2 Preliminary




PY Tune A

HW


-0.4

0.0

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0.8

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PT(jet#1) (GeV/c)

Dat

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(G

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HWPY Tune A

0.4 density corresponds to 1.67 GeV in the




““transMAX” & “transMIN”transMAX” & “transMIN”

Define the MAX and MIN “transverse” regions (“transMAX” and “transMIN”) on an event-by-event basis with MAX (MIN) having the largest (smallest) density. Each of the two “transverse” regions have an area in - space of 4/6.

The “transMIN” region is very sensitive to the “beam-beam remnant” and multiple parton interaction components of the “underlying event”.

Jet #1 Direction

“Toward”

“TransMAX” “TransMIN”

“Away”

Jet #1 Direction


“Toward”

“Away”


“Away-Side” Jet

Jet #3

The difference, “transDIF” (“transMAX” minus “transMIN”), is very sensitive to the “hard scattering” component of the “underlying event” (i.e. hard initial and final-state radiation).

Area = 4/6

“transMIN” very sensitive to the “beam-beam remnants”!

The overall “transverse” density is the average of the “transMAX” and “transMIN” densities.



“Leading Jet”

The “TransMAX/MIN” RegionsThe “TransMAX/MIN” Regions

Data at 1.96 TeV on the density of charged particles, dN/dd, with pT > 0.5 GeV/c and || < 1 for “leading jet” events as a function of the leading jet pT for the “transMAX” region. The data are corrected to the particle level (with errors that include both the statistical error and the systematic uncertainty) and are compared with PYTHIA Tune A and HERWIG (without MPI) at the particle level (i.e. generator level).

Data at 1.96 TeV on the density of charged particles, dN/dd, with pT > 0.5 GeV/c and || < 1 for “leading jet” events as a function of the leading jet pT for the “transMIN” region. The data are corrected to the particle level (with errors that include both the statistical error and the systematic uncertainty) and are compared with PYTHIA Tune A and HERWIG (without MPI) at the particle level (i.e. generator level).

Data at 1.96 TeV on the density of charged particles, dN/dd, with pT > 0.5 GeV/c and || < 1 for “leading jet” events as a function of the leading jet pT for “transDIF” = “transMAX”-”transMIN. The data are corrected to the particle level (with errors that include both the statistical error and the systematic uncertainty) and are compared with PYTHIA Tune A and HERWIG (without MPI) at the particle level (i.e. generator level).

Jet #1 Direction

“Toward”


“Away”

"TransMAX" Charged Particle Density: dN/dd

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PY Tune A

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"TransMIN" Charged Particle Density: dN/dd

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Charged Particles (||<1.0, PT>0.5 GeV/c) PY Tune A

HW

"TransMAX/MIN" Charged Particle Density: dN/dd

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"transMAX"

"transMIN"

"TransDIF" Charged Particle Density: dN/dd

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PY Tune A



“Leading Jet”


Data at 1.96 TeV on the charged scalar pT sum density, dPT/dd, with pT > 0.5 GeV/c and || < 1 for “leading jet” events as a function of the leading jet pT for the “transMAX” region. The data are corrected to the particle level (with errors that include both the statistical error and the systematic uncertainty) and are compared with PYTHIA Tune A and HERWIG (without MPI) at the particle level (i.e. generator level).

Data at 1.96 TeV on the charged scalar pT sum density, dPT/dd, with pT > 0.5 GeV/c and || < 1 for “leading jet” events as a function of the leading jet pT for the “transMIN” region. The data are corrected to the particle level (with errors that include both the statistical error and the systematic uncertainty) and are compared with PYTHIA Tune A and HERWIG (without MPI) at the particle level (i.e. generator level).

Data at 1.96 TeV on the charged scalar pT sum density, dPT/dd, with pT > 0.5 GeV/c and || < 1 for “leading jet” events as a function of the leading jet pT for “transDIF” = “transMAX”-”transMIN. The data are corrected to the particle level (with errors that include both the statistical error and the systematic uncertainty) and are compared with PYTHIA Tune A and HERWIG (without MPI) at the particle level (i.e. generator level).

Jet #1 Direction

“Toward”


“Away”

"TransMAX" Charged PTsum Density: dPT/dd

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PY Tune A

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"TransMIN" Charged PTsum Density: dPT/dd

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PY Tune A

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"TransMAX/MIN" Charged PTsum Density

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"transMAX"

"transMIN"

"TransDIF" Charged PTsum Density: dPT/dd

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(GeV

/c)





PY Tune A

HW



“Leading Jet”


Data at 1.96 TeV on the scalar ET sum density, dET/dd, with || < 1 for “leading jet” events as a function of the leading jet pT for the “transMAX” region. The data are corrected to the particle level (with errors that include both the statistical error and the systematic uncertainty) and are compared with PYTHIA Tune A and HERWIG (without MPI) at the particle level (i.e. generator level).

Data at 1.96 TeV on the scalar ET sum density, dET/dd, with || < 1 for “leading jet” events as a function of the leading jet pT for the “transMIN” region. The data are corrected to the particle level (with errors that include both the statistical error and the systematic uncertainty) and are compared with PYTHIA Tune A and HERWIG (without MPI) at the particle level (i.e. generator level).

Data at 1.96 TeV on the scalar ET sum density, dET/dd, with || < 1 for “leading jet” events as a function of the leading jet pT for “transDIF” = “transMAX”-”transMIN. The data are corrected to the particle level (with errors that include both the statistical error and the systematic uncertainty) and are compared with PYTHIA Tune A and HERWIG (without MPI) at the particle level (i.e. generator level).

Jet #1 Direction

“Toward”


“Away”

"TransMAX" ETsum Density: dET/dd

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PT(jet#1) (GeV/c)

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PY Tune A

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"TransMIN" ETsum Density: dET/dd

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PY Tune A

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"TransMAX/MIN" ETsum Density: dET/dd

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PY Tune A

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"transMAX"

"transMIN"

"TransDIF" ETsum Density: dET/dd

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Tra

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MA

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IN (

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)




PY Tune A

HWStable Particles (||<1.0, all PT)



““TransMIN” Nchg DensityTransMIN” Nchg Density

Data at 1.96 TeV on the density of charged particles, dN/dd, with pT > 0.5 GeV/c and || < 1 for “leading jet” events as a function of the leading jet pT for the “transMIN” region. The data are corrected to the particle level (with errors that include both the statistical error and the systematic uncertainty) and are compared with PYTHIA Tune A and HERWIG (without MPI) at the particle level (i.e. generator level).

"TransMIN" Charged Particle Density: dN/dd

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PT(jet#1) (GeV/c)

"Tra

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PY Tune A

HW

Jet #1 Direction

“Toward”


“Away”

These are the key plots!Tune A does not produce

enough activity in the “transMIN” region!



““TransMIN” PTsum DensityTransMIN” PTsum Density

Data at 1.96 TeV on the charged scalar PTsum density, dPT/dd, with pT > 0.5 GeV/c and || < 1 for “leading jet” events as a function of the leading jet pT for the “transMIN” region. The data are corrected to the particle level (with errors that include both the statistical error and the systematic uncertainty) and are compared with PYTHIA Tune A and HERWIG (without MPI) at the particle level (i.e. generator level).

Jet #1 Direction

“Toward”


“Away”

"TransMIN" Charged PTsum Density: dPT/dd

0.0

0.2

0.4

0.6

0 50 100 150 200 250 300 350 400

PT(jet#1) (GeV/c)

"Tra

nsM

IN"

PT

sum

Den

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(G

eV





PY Tune A

HW





““TransMIN” ETsum DensityTransMIN” ETsum Density

Data at 1.96 TeV on the scalar ETsum density, dET/dd, with || < 1 for “leading jet” events as a function of the leading jet pT for the “transMIN” region. The data are corrected to the particle level (with errors that include both the statistical error and the systematic uncertainty) and are compared with PYTHIA Tune A and HERWIG (without MPI) at the particle level (i.e. generator level).

Jet #1 Direction

“Toward”


“Away”

"TransMIN" ETsum Density: dET/dd

0.0

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3.0

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PT(jet#1) (GeV/c)

"Tra

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" E

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PY Tune A

HW





“Leading Jet”

The Leading Jet MassThe Leading Jet Mass

Data at 1.96 TeV on the leading jet invariant mass for “leading jet” events as a function of the leading jet pT for the “transverse” region. The data are corrected to the particle level (with errors that include both the statistical error and the systematic uncertainty) and are compared with PYTHIA Tune A and HERWIG (without MPI) at the particle level (i.e. generator level).

Shows the Data - Theory for the leading jet invariant mass for “leading jet” events as a function of the leading jet pT for the “transverse” region for PYTHIA Tune A and HERWIG (without MPI).

Jet #1 Direction

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Leading Jet Invariant Mass

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Leading Jet Invariant Mass

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Off by ~2 GeV



Min-Bias at the LHCMin-Bias at the LHC “Min-Bias” is not well defined. What you

see depends on what you trigger on! Every trigger produces some biases.

Proton AntiProton

“Minumum Bias” Collisions

We have learned a lot about “Min-Bias” at the Tevatron, but we do not know what to expect at the LHC.

Charged Particle Density: dN/d

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pyA

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ATLAS

Charged Particles (all pT)

Generator Level14 TeVThis will depend on the Min-Bias Trigger!

We are making good progress in understanding and modeling the “underlying event”. However, we do not yet have a perfect fit to all the features of the CDF “underlying event” data!

Proton AntiProton

PT(hard)

Outgoing Parton

Outgoing Parton




Need to measure “Min-Bias” and the “underlying event” at the LHC as soon as possible and tune the Monte-Carlo modles and compare with CDF!



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




Anti-Lepton

Proton Proton

“Minimum-Bias” Collisions

Proton Proton

Drell-Yan Production

PT(pair)

Lepton-Pair

Outgoing Parton




UE&MB@CMSUE&MB@CMS

Study charged particles and muons using the CMS detector

at the LHC (as soon as possible)!



SummarySummary It is important to produce a lot of plots (corrected to the particle level) so that the theorists

can tune and improve the QCD Monte-Carlo models. If they improve the “transverse” region they might miss-up the “toward” region etc.. We need to show the whole story!

There are over 128 plots to get “blessed” and then published. So far we have only looked at average quantities. We plan to also produce distributions and flow plots

We are making good progress in understanding and modeling the “underlying event”. However, we do not yet have a perfect fit to all the features of the CDF “underlying event” data!

Proton AntiProton

PT(hard)

Outgoing Parton

Outgoing Parton




Need to measure “Min-Bias” and the “underlying event” at the LHC as soon as possible and tune the Monte-Carlo modles and compare with CDF!

I will construct a “CDF-QCD Data for Theory” WEBsite with the “blessed” plots together with tables of the data points and errors so that people can have access to the results .

UE&MB@CMSUE&MB@CMS

CDF-QCD Data for Theory

CMS analysis approval in December 2007!

University of Toronto March 18, 2008 Rick Field – Florida/CDF/CMSPage 1 Studying the Underlying Event at CDF and the LHC Rick Field University of Florida.

Documents

charged particles pt

underlying event observables

number of charged particles

underlying event atcdf

gevc h

charged scalar pt sum

bias collisions

hard core component