University of California, Berkeley January 13, 2009 Rick Field – Florida/CDF/CMSPage 1 Studying the Underlying Event at CDF and the LHC Rick Field University.

University of California, Berkeley January 13, 2009

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

Outline of Talk Review what we learned about

“min-bias” and the “underlying event” in Run 1 at CDF.

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

“CDF-QCD Data for Theory”: Studying the “underlying event” using high pT jet production and Z-boson production.

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

Some things I do not understand about the CDF “underlying event” data.

LBNL January 13, 2009

R. Field, C. Group, & D. Kar



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!



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


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-state radiation.

“Jet”

Proton AntiProton

High PT Z-Boson Production

Z-boson

Outgoing Parton

Initial-State Radiation Final-State Radiation


Z-boson

Outgoing Parton



“Hard Scattering” Component



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



-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



-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.



““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 the soft 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.

Z-Boson Direction



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”

Observables at theObservables at theParticle and Detector LevelParticle and Detector Level



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), 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).



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 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 CTEQ5L 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 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 AW Tune DW Tune D6

PDF CTEQ5L CTEQ5L CTEQ6L

MSTP(81) 1 1 1

MSTP(82) 4 4 4

PARP(82) 2.0 GeV 1.9 GeV 1.8 GeV

PARP(83) 0.5 0.5 0.5

PARP(84) 0.4 0.4 0.4

PARP(85) 0.9 1.0 1.0

PARP(86) 0.95 1.0 1.0

PARP(89) 1.8 TeV 1.8 TeV 1.8 TeV

PARP(90) 0.25 0.25 0.25

PARP(62) 1.25 1.25 1.25

PARP(64) 0.2 0.2 0.2

PARP(67) 4.0 2.5 2.5

MSTP(91) 1 1 1

PARP(91) 2.1 2.1 2.1

PARP(93) 15.0 15.0 15.0

Intrinsic KT

ISR Parameter

UE Parameters

Uses CTEQ6L

All use LO s with = 192 MeV!

Tune A energy dependence!



PYTHIA 6.2 TunesPYTHIA 6.2 TunesParameter Tune DWT Tune D6T ATLAS

PDF CTEQ5L CTEQ6L CTEQ5L

MSTP(81) 1 1 1

MSTP(82) 4 4 4

PARP(82) 1.9409 GeV 1.8387 GeV 1.8 GeV

PARP(83) 0.5 0.5 0.5

PARP(84) 0.4 0.4 0.5

PARP(85) 1.0 1.0 0.33

PARP(86) 1.0 1.0 0.66

PARP(89) 1.96 TeV 1.96 TeV 1.0 TeV

PARP(90) 0.16 0.16 0.16

PARP(62) 1.25 1.25 1.0

PARP(64) 0.2 0.2 1.0

PARP(67) 2.5 2.5 1.0

MSTP(91) 1 1 1

PARP(91) 2.1 2.1 1.0

PARP(93) 15.0 15.0 5.0

Intrinsic KT

ISR Parameter

UE Parameters


ATLAS energy dependence!

Tune A

Tune AW Tune B Tune BW

Tune D

Tune DWTune D6

Tune D6T

These are “old” PYTHIA 6.2 tunes! There are new 6.4 tunes byArthur Moraes (ATLAS)Hendrik Hoeth (MCnet)Peter Skands (Tune S0)



PYTHIA 6.2 TunesPYTHIA 6.2 TunesParameter Tune H(6.418) Tune DWT Tune D6T ATLAS

PDF CTEQ5L CTEQ5L CTEQ6L CTEQ5L

MSTP(81) 1 1 1 1

MSTP(82) 4 4 4 4

PARP(82) 2.1 GeV 1.9409 GeV 1.8387 GeV 1.8 GeV

PARP(83) 0.84 0.5 0.5 0.5

PARP(84) 0.5 0.4 0.4 0.5

PARP(85) 0.82 1.0 1.0 0.33

PARP(86) 0.91 1.0 1.0 0.66

PARP(89) 1.0 1.96 TeV 1.96 TeV 1.0 TeV

PARP(90) 0.17 0.16 0.16 0.16

PARP(62) 2.97 1.25 1.25 1.0

PARP(64) 0.12 0.2 0.2 1.0

PARP(67) 2.74 2.5 2.5 1.0

MSTP(91) 1 1 1 1

PARP(91) 2.0 2.1 2.1 1.0

PARP(93) 5.0 15.0 15.0 5.0

Intrinsic KT

ISR Parameter

UE Parameters


Q2 ordered showers, old MPI!



JIMMY at CDFJIMMY at CDFThe Energy in the “Underlying

Event” in High PT Jet Production

“Transverse” <Densities> vs PT(jet#1)

Jet #1 Direction

“Toward”


“Away”

"Transverse" PTsum Density: dPT/dd

0.0

0.4

0.8

1.2

1.6

0 50 100 150 200 250 300 350 400 450 500

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

"Tra

nsv

erse

" P

Tsu

m D

ensi

ty (

GeV

/c)

PY Tune A

HW

1.96 TeV


CDF Run 2 Preliminarygenerator level theory

MidPoint R = 0.7 |(jet)| < 2

"Leading Jet"

JIMMY Default

JM325

"Transverse" ETsum Density: dET/dd

0.0

1.0

2.0

3.0

4.0

0 100 200 300 400 500


"Tra

ns

vers

e" E

Tsu

m D

ensi

ty (

GeV

) 1.96 TeV

All Particles (||<1.0)

HW

PY Tune A

MidPoint R = 0.7 |(jet)| < 2CDF Run 2 Preliminarygenerator level theory

"Leading Jet"

JIMMY Default

JM325

JIMMY: MPIJ. M. Butterworth

J. R. ForshawM. H. Seymour

JIMMY was tuned to fit the energy density in the “transverse” region for

“leading jet” events!JIMMY

Runs with HERWIG and adds multiple parton interactions!

PT(JIM)= 2.5 GeV/c.

PT(JIM)= 3.25 GeV/c.

Proton AntiProton

PT(hard)

Outgoing Parton

Outgoing Parton




The Drell-Yan JIMMY TunePTJIM = 3.6 GeV/c,

JMRAD(73) = 1.8JMRAD(91) = 1.8



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)

1

10

100

1000

0 50 100 150 200 250 300 350 400

PT(jet#1) (GeV/c)

Av

era

ge

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

“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

1

2

3

4

5

0 50 100 150 200 250 300 350 400

PT(jet#1) (GeV/c)

Ave

rag

e C

har

ged

Den

sity


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

0.1

1.0

10.0

100.0

0 50 100 150 200 250 300 350 400

PT(jet#1) (GeV/c)

Ch

arg

ed P

Tsu

m D

ensi

ty (

GeV

/c)


pyA generator level



"Toward""Away"

"Transverse"

Factor of ~16

ETsum Density: dET/dd

0.1

1.0

10.0

100.0

0 50 100 150 200 250 300 350 400

PT(jet#1) (GeV/c)

ET

sum

Den

sity

(G

eV)


pyA generator level



"Toward"

"Away"

"Transverse"

Factor of ~13



Z-Boson Direction

“Toward”


“Away”

Charged Particle DensityCharged Particle Density

Data at 1.96 TeV on the density of charged particles, dN/dd, with pT > 0.5 GeV/c and || < 1 for “Z-Boson” and “Leading Jet” events as a function of the leading jet pT or PT(Z) 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 AW and Tune A, respectively, at the particle level (i.e. generator level).

Jet #1 Direction

“Toward”


“Away”


0

1

2

3

4

0 20 40 60 80 100 120 140 160 180 200

PT(jet#1) (GeV/c)

Ave

rag

e C

har

ge

d D

en

sity


pyA generator level



"Away"

"Toward"

"Transverse"


0

1

2

3

0 20 40 60 80 100

PT(Z-Boson) (GeV/c)

Ave

rag

e C

har

ge

d D

ensi

ty


pyAW generator level"Away"

"Transverse"

"Toward"

"Drell-Yan Production"70 < M(pair) < 110 GeV

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

Proton AntiProton


Z-boson

Outgoing Parton


Proton AntiProton

PT(hard)

Outgoing Parton

Outgoing Parton





0.0

0.3

0.6

0.9

1.2

0 20 40 60 80 100 120 140 160 180 200

PT(jet#1) or PT(Z-Boson) (GeV/c)

"Tra

nsv

erse

" C

ha

rged

Den

sit

y


generator level theory


"Leading Jet"

"Z-Boson"

"Away" Charged Particle Density: dN/dd

0

1

2

3

4

0 20 40 60 80 100 120 140 160 180 200


"Aw

ay"

Ch

arg

ed D

ensi

ty




"Leading Jet"

"Z-Boson"

"Away" Charged Particle Density: dN/dd

0

1

2

3

0 20 40 60 80 100

PT(Z-Boson) (GeV/c)

"Aw

ay"

Ch

arg

ed D

en

sity





JIM

HW

pyAW

HERWIG + JIMMYTune (PTJIM = 3.6)

H. Hoeth, MPI@LHC08



Z-Boson Direction

“Toward”


“Away”

Charged PTsum DensityCharged PTsum Density

Data at 1.96 TeV on the charged scalar PTsum density, dPT/dd, with pT > 0.5 GeV/c and || < 1 for “Z-Boson” and “Leading Jet” events as a function of the leading jet pT or PT(Z) 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 AW and Tune A, respectively, at the particle level (i.e. generator level).

Jet #1 Direction

“Toward”


“Away”

Proton AntiProton


Z-boson

Outgoing Parton


Proton AntiProton

PT(hard)

Outgoing Parton

Outgoing Parton





0.1

1.0

10.0

0 20 40 60 80 100

PT(Z-Boson) (GeV/c)

Ch

arg

ed

P

Ts

um

Den

sity

(G

eV

/c)


pyAW generator level


"Away"

"Transverse"

"Toward"



0.1

1.0

10.0

100.0

0 20 40 60 80 100 120 140 160 180 200

PT(jet#1) (GeV/c)

Ch

arg

ed

P

Tsu

m D

en

sity

(G

eV

/c)


pyA generator level



"Toward"

"Away"

"Transverse"

"Transverse" Charged PTsum Density: dPT/dd

0.0

0.5

1.0

1.5

2.0

0 20 40 60 80 100 120 140 160 180 200


"Tra

nsv

erse

" P

Ts

um

Den

sity

(G

eV/c

)




"Leading Jet"

"Z-Boson"

"Away" Charged PTsum Density: dPT/dd

0

5

10

15

20

0 20 40 60 80 100 120 140 160 180 200


"Aw

ay"

PT

sum

Den

sit

y (G

eV

/c) CDF Run 2 Preliminary

data correctedgenerator level theory


"Leading Jet"

"Z-Boson"

"Away" Charged PTsum Density: dPT/dd

0

4

8

12

0 20 40 60 80 100

PT(Z-Boson) (GeV/c)

"Aw

ay"

PT

sum

Den

sit

y (G

eV





pyAW

HW

JIM



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

Data at 1.96 TeV on the charged particle density, dN/dd, with pT > 0.5 GeV/c and || < 1 for “Z-Boson” and “Leading Jet” events as a function of PT(Z) or the leading jet pT for the “transMAX”, and “transMIN” 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 AW and Tune A, respectively, at the particle level (i.e. generator level).

Proton AntiProton


Z-boson

Outgoing Parton


Proton AntiProton

PT(hard)

Outgoing Parton

Outgoing Parton




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

0.0

0.4

0.8

1.2

1.6

0 50 100 150 200 250 300 350 400

PT(jet#1) (GeV/c)

"Tra

ns

vers

e"

Ch

arg

ed D

ensi

ty CDF Run 2 Preliminarydata corrected




PY Tune A

HW

"transMAX"

"transMIN"


0.0

0.4

0.8

1.2

1.6

0 20 40 60 80 100

PT(Z-Boson) (GeV/c)

"Tra

ns

vers

e"

Ch

arg

ed D

ensi

ty





"transMAX"

"transMIN"

pyAW

HW


0.0

0.4

0.8

1.2

1.6

0 20 40 60 80 100

PT(Z-Boson) (GeV/c)

"Tra

ns

vers

e"

Ch

arg

ed D

ensi

ty





"transMAX"

"transMIN"

pyDW

JIM

ATLAS

"TransDIF" Charged Particle Density: dN/dd

0.0

0.3

0.6

0.9

1.2

0 50 100 150 200 250 300 350 400

PT(jet#1) (GeV/c)

Tra

nsM

AX

- T

ran

sMIN

Den

sity





HW

PY Tune A


0.0

0.3

0.6

0.9

1.2

0 20 40 60 80 100

PT(Z-Boson) (GeV/c)

Tra

nsM

AX

- T

ran

sMIN

Den

sity





pyAW

HW


0.0

0.3

0.6

0.9

1.2

0 20 40 60 80 100

PT(Z-Boson) (GeV/c)

Tra

nsM

AX

- T

ran

sMIN

Den

sity





pyDW

JIM

ATLAS


0.0

0.3

0.6

0.9

1.2

0 20 40 60 80 100 120 140 160 180 200


"Tra

ns

DIF

" C

har

ged

De

ns

ity




"Z-Boson"

"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 and for Z-Boson events as a function of PT(Z) for “TransDIF” = “transMAX” minus “transMIN” 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 and HERWIG (without MPI) at the particle level (i.e. generator level).

Jet #1 Direction

“Toward”


“Away”

Z-Boson Direction

“Toward”


“Away”




Data at 1.96 TeV on the charged scalar PTsum density, dPT/dd, with pT > 0.5 GeV/c and || < 1 for “Z-Boson” and “Leading Jet” events as a function of PT(Z) or the leading jet pT for the “transMAX”, and “transMIN” 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 AW and Tune A, respectively, at the particle level (i.e. generator level).

Proton AntiProton


Z-boson

Outgoing Parton


Proton AntiProton

PT(hard)

Outgoing Parton

Outgoing Parton




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 and for Z-Boson events as a function of PT(Z) for “TransDIF” = “transMAX” minus “transMIN” 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 and HERWIG (without MPI) at the particle level (i.e. generator level).

Jet #1 Direction

“Toward”


“Away”

Z-Boson Direction

“Toward”


“Away”

"TransMAX/MIN" Charged PTsum Density

0.0

1.0

2.0

3.0

0 20 40 60 80 100

PT(Z-Boson) (GeV/c)

"Tra

nsv

erse

" P

Ts

um

Den

sity

(G

eV/c

)





"transMAX"

"transMIN"

pyAW

HW

"TransMAX/MIN" Charged PTsum Density

0.0

1.0

2.0

3.0

0 50 100 150 200 250 300 350 400

PT(jet#1) (GeV/c)

"Tra

nsv

erse

" P

Ts

um

Den

sity

(G

eV/c

)





PY Tune A

HW

"transMAX"

"transMIN"

"TransDIF" Charged PTsum Density: dPT/dd

0.0

1.0

2.0

3.0

0 20 40 60 80 100

PT(Z-Boson) (GeV/c)

Tra

ns

MA

X -

Tra

nsM

IN D

ens

ity

(Ge

V/c

)





pyAW

HW


0.0

1.0

2.0

3.0

0 50 100 150 200 250 300 350 400

PT(jet#1) (GeV/c)

Tra

ns

MA

X -

Tra

nsM

IN D

ens

ity

(Ge

V/c

)





PY Tune A

HW


0.0

1.0

2.0

3.0

0 20 40 60 80 100 120 140 160 180 200


"Tra

nsD

IF"

PT

sum

Den

sity

(G

eV




"Leading Jet"

"Z-Boson"



Charged Particle <pCharged Particle <pTT>>

Jet #1 Direction

“Toward”


“Away”

Z-BosonDirection

“Toward”


“Away”

Data at 1.96 TeV on the charged particle average pT, with pT > 0.5 GeV/c and || < 1 for the “toward” region for “Z-Boson” and the “transverse” region for “Leading Jet” events as a function of the leading jet pT or PT(Z). 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 AW and Tune A, respectively, at the particle level (i.e. generator level). The Z-Boson data are also compared with PYTHIA Tune DW, the ATLAS tune, and HERWIG (without MPI)

"Transverse" Average PT

0.5

1.0

1.5

2.0

0 50 100 150 200 250 300 350 400

PT(jet#1) (GeV/c)

"Tra

nsv

erse

" A

vera

ge

PT

(G

eV/c

) CDF Run 2 Preliminarydata corrected




PY Tune A

HW

"Toward" Average PT Charged

0.4

0.8

1.2

1.6

0 20 40 60 80 100

PT(Z-Boson) (GeV/c)

"To

war

d"

<P

T>

(G

eV/c

)





HWJIM

ATLAS

pyAWpyDW

H. Hoeth, MPI@LHC08



Z-Boson: “Towards”, Transverse”, Z-Boson: “Towards”, Transverse”, & “TransMIN” Charge Density& “TransMIN” Charge Density

Data at 1.96 TeV on the density of charged particles, dN/dd, with pT > 0.5 GeV/c and || < 1 for “Z-Boson” events as a function of PT(Z) for the “toward” 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 AW and HERWIG (without MPI) at the particle level (i.e. generator level).

Z-BosonDirection

“Toward”


“Away”


0.0

0.3

0.6

0.9

0 20 40 60 80 100

PT(Z-Boson) (GeV/c)

Ch

arg

ed

De

ns

ity


pyAW generator level"Transverse

"Toward"

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

excluding the lepton-pair

Proton AntiProton


Z-boson

Outgoing Parton


Proton AntiProton


Z-boson

Outgoing Parton



0.0

0.3

0.6

0.9

0 20 40 60 80 100

PT(Z-Boson) (GeV/c)

Ch

arg

ed

De

ns

ity





"Toward"

"transMIN"

Z-Boson Direction

“Toward”


“Away”

"Toward" Charged Particle Density: dN/dd

0.0

0.3

0.6

0.9

0 20 40 60 80 100

PT(Z-Boson) (GeV/c)

"To

war

d"

Ch

arg

ed D

ensi

ty





HW

JIM

pyAW

ATLASpyDW

"TransMIN" Charged Particle Density: dN/dd

0.0

0.2

0.4

0.6

0 20 40 60 80 100

PT(Z-Boson) (GeV/c)

"Tra

ns

MIN

" C

har

ged

De

ns

ity CDF Run 2 Preliminary

data corrected generator level theory



ATLAS

HWpyAW

JIM

pyDW

"TransMIN" Charged Particle Density: dN/dd

0.0

0.2

0.4

0.6

0.8

0 20 40 60 80 100 120 140 160 180 200


"Tra

nsM

IN"

Ch

arg

ed D

en

sit

y CDF Run 2 Preliminarydata corrected



"Leading Jet"

"Z-Boson"

H. Hoeth, MPI@LHC08



Z-Boson: “Towards”, Transverse”, Z-Boson: “Towards”, Transverse”, & “TransMIN” Charge Density& “TransMIN” Charge Density

Data at 1.96 TeV on the charged scalar PTsum density, dPT/dd, with pT > 0.5 GeV/c and || < 1 for “Z-Boson” events as a function of PT(Z) for the “toward” 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 AW and HERWIG (without MPI) at the particle level (i.e. generator level).

Z-BosonDirection

“Toward”


“Away”

Proton AntiProton


Z-boson

Outgoing Parton


Proton AntiProton


Z-boson

Outgoing Parton


Z-Boson Direction

“Toward”


“Away”


0.0

0.6

1.2

1.8

0 20 40 60 80 100

PT(Z-Boson) (GeV/c)

Ch

arg

ed

PT

su

m D

en

sit

y (

GeV

/c)





"Transverse

"Toward"


0.0

0.4

0.8

1.2

0 20 40 60 80 100

PT(Z-Boson) (GeV/c)

Ch

arg

ed

PT

su

m D

en

sit

y (

GeV

/c)





"transMIN"

"Toward"

"Toward" Charged PTsum Density: dPT/dd

0.0

0.4

0.8

1.2

0 20 40 60 80 100

PT(Z-Boson) (GeV/c)

"To

war

d"

PT

sum

Den

sity

(G

eV/c

)




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

JIM

ATLAS

pyAW

pyDW

"TransMIN" Charged PTsum Density: dPT/dd

0.0

0.2

0.4

0.6

0.8

0 20 40 60 80 100

PT(Z-Boson) (GeV/c)

"Tra

nsM

IN"

PT

sum

Den

sity

(G

eV




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

ATLAS

pyAW

JIM

pyDW

"TransMIN" Charged PTsum Density: dPT/dd

0.0

0.2

0.4

0.6

0.8

0 20 40 60 80 100 120 140 160 180 200


"Tra

nsM

IN"

PT

sum

Den

sity

(G

eV




"Leading Jet"

"Z-Boson"

H. Hoeth, MPI@LHC08



Z-Boson: “Towards” RegionZ-Boson: “Towards” Region

Data at 1.96 TeV on the density of charged particles, dN/dd, with pT > 0.5 GeV/c and || < 1 for “Z-Boson” events as a function of PT(Z) 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 AW and HERWIG (without MPI) at the particle level (i.e. generator level).

Z-BosonDirection

“Toward”


“Away”

Z-BosonDirection

“Toward”


“Away”


0.0

0.3

0.6

0.9

0 20 40 60 80 100

PT(Z-Boson) (GeV/c)

"To

war

d"

Ch

arg

ed D

ensi

ty





HW

JIM

pyAW

ATLASpyDW


0.0

0.5

1.0

1.5

2.0

0 25 50 75 100 125 150

PT(Z-Boson) (GeV/c)

"To

war

d"

Ch

arg

ed D

ensi

ty


pyDWT generator level



TevatronLHC10

LHC14


0.0

0.5

1.0

1.5

2.0

0 25 50 75 100 125 150

PT(Z-Boson) (GeV/c)

"To

war

d"

Ch

arg

ed D

ensi

ty

CDF Run 2 Preliminarygenerator level theory



HW LHC14

pyDWT LHC14

pyDWT TevatronHW Tevatron


0.0

0.3

0.6

0.9

0 20 40 60 80 100

PT(Z-Boson) (GeV/c)

"To

war

d"

Ch

arg

ed D

ensi

ty


HW generator level



Tevatron

LHC10

LHC14

HW without MPI

DWT



Z-Boson: “Towards” RegionZ-Boson: “Towards” Region

Data at 1.96 TeV on the average pT of charged particles with pT > 0.5 GeV/c and || < 1 for “Z-Boson” events as a function of PT(Z) 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 AW and HERWIG (without MPI) at the particle level (i.e. generator level).

Z-BosonDirection

“Toward”


“Away”

Z-BosonDirection

“Toward”


“Away”


0.4

0.8

1.2

1.6

0 20 40 60 80 100

PT(Z-Boson) (GeV/c)

"To

war

d"

<P

T>

(G

eV/c

)


pyDWT LHC14


pyDWT TevatronHW Tevatron HW LHC14



DWT

HW (without MPI)almost no change!


0.4

0.8

1.2

1.6

0 20 40 60 80 100

PT(Z-Boson) (GeV/c)

"To

war

d"

<P

T>

(G

eV/c

)





HWJIM

ATLAS

pyAWpyDW



“Leading Jet”

The “Transverse” RegionThe “Transverse” Region

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

1.0

2.0

3.0

4.0

5.0

0 50 100 150 200 250 300 350 400

PT(jet#1) (GeV/c)

"Tra

nsv

erse

" E

Ts

um

Den

sity

(G

eV) CDF Run 2 Preliminary




PY Tune A

HW


-0.4

0.0

0.4

0.8

1.2

1.6

0 50 100 150 200 250 300 350 400

PT(jet#1) (GeV/c)

Dat

a -

Th

eory

(G

eV)





HWPY Tune A

0.4 density corresponds to 1.67 GeV in the

“transverse” region!



“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

0.0

2.0

4.0

6.0

0 50 100 150 200 250 300 350 400

PT(jet#1) (GeV/c)

"Tra

nsM

AX

" E

Tsu

m D

ensi

ty (

GeV





PY Tune A

HW

"TransMIN" ETsum Density: dET/dd

0.0

1.0

2.0

3.0

0 50 100 150 200 250 300 350 400

PT(jet#1) (GeV/c)

"Tra

nsv

eMIN

" E

Tsu

m D

ensi

ty (

GeV

)





PY Tune A

HW

"TransMAX/MIN" ETsum Density: dET/dd

0.0

2.0

4.0

6.0

0 50 100 150 200 250 300 350 400

PT(jet#1) (GeV/c)

"Tra

nsv

erse

" E

Tsu

m D

ensi

ty (

GeV





PY Tune A

HW

"transMAX"

"transMIN"

"TransDIF" ETsum Density: dET/dd

0.0

1.0

2.0

3.0

4.0

5.0

0 50 100 150 200 250 300 350 400

PT(jet#1) (GeV/c)

Tra

ns

MA

X -

Tra

nsM

IN (

GeV

)




PY Tune A

HWStable Particles (||<1.0, all PT)



“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

“Toward”


“Away”

Leading Jet Invariant Mass

0

10

20

30

40

50

60

70

0 50 100 150 200 250 300 350 400

PT(jet#1) (GeV/c)

Jet

Mas

s (G

eV)




PY Tune A

HW

Leading Jet Invariant Mass

-4.0

0.0

4.0

8.0

12.0

0 50 100 150 200 250 300 350 400

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

Dat

a -

Th

eory

(G

eV)




HW PY Tune A

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

0

2

4

6

8

10

-10 -8 -6 -4 -2 0 2 4 6 8 10

PseudoRapidity

Ch

arg

ed P

arti

cle

Den

sity

pyA

pyDW

pyDWT

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!



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”


0.0

0.2

0.4

0.6

0.8

1.0

0 50 100 150 200 250 300 350 400 450 500


"Tra

ns

ve

rse

" C

ha

rge

d D

en

sit

y

RDF Preliminarygenerator level

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

PY Tune AW

1.96 TeV

HERWIG


0.0

0.5

1.0

1.5

2.0

0 250 500 750 1000 1250 1500 1750 2000 2250 2500


"Tra

ns

vers

e" C

ha

rge

d D

en

sity


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






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

Drell-Yan Production Lepton



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

0.02

0.04

0.06

0.08

0.10

0 5 10 15 20 25 30 35 40

PT(+-) (GeV/c)

1/N

dN

/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).

The “Underlying Event”

Proton AntiProton




Anti-Lepton


0.0

0.2

0.4

0.6

0.8

1.0

0 50 100 150 200 250


Ch

arg

ed P

arti

cle

De

nsi

ty


Drell-Yan1.96 TeV

PY Tune AW

HERWIG

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


0.0

0.5

1.0

1.5

0 50 100 150 200 250


Ch

arg

ed P

arti

cle

De

nsi

ty


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



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

CDF Run 2 publication. Should be out soon!

In my RPM talk on ThursdayI will show new results on

<pT> versus Nchgfor min-bias and Z-boson production!

University of California, Berkeley January 13, 2009 Rick Field – Florida/CDF/CMSPage 1 Studying the Underlying Event at CDF and the LHC Rick Field University.

Documents

underlying event observables

underlying event atcdf

cdf underlying event

initialstate gluon radiation

finalstate gluon radiation

beambeam remnants

beambeam counters3

leading log approximation