The “Underlying Event” CDF-LHC Comparisons

LHC/CMS Journal Club November 30, 2005

Rick Field - Florida/CMS/CDF Page 1

The “Underlying Event”The “Underlying Event”CDF-LHC ComparisonsCDF-LHC Comparisons

Proton AntiProton

Drell-Yan Production Lepton

Underlying Event Underlying Event

Initial-State Radiation

Anti-Lepton

Outline of Talk

PT(Z-boson): Tuning to fit the PT(Z) distribution in Run 2 at CDF.

Jet Production: The “underlying event” in high pT jet production in Run 2 at CDF.

Extrapolations to the LHC: The “underlying event” in high pT jet production and Drell-Yan at CMS.

Drell-Yan: The “underlying event” in Drell-Yan production in Run 2 at CDF.

Great process to study the “underlying event”!

Proton AntiProton

High PT Jet Production

PT(hard)

Outgoing Parton

Outgoing Parton


Final-State Radiation




Jet #1 Direction

“Transverse” “Transverse”

“Toward”

“Away”

“Toward-Side” Jet

“Away-Side” Jet

The “Transverse” RegionThe “Transverse” Regionas defined by the Leading Jetas defined by the Leading Jet

Look at the “transverse” region as defined by the leading calorimeter jet (MidPoint, R = 0.7, fmerge = 0.75, || < 2).

Define || < 60o as “Toward”, 60o < - < 120o and 60o < < 120o as “Transverse 1” and “Transverse 2”, and || > 120o as “Away”. Each of the two “transverse” regions have area = 2x60o = 4/6. The overall “transverse” region is the sum of the two transverse regions ( = 2x120o = 4/3).

Study the charged particles (pT > 0.5 GeV/c, || < 1) and form the charged particle density, dNchg/dhdf, and the charged scalar pT sum density, dPTsum/dd, by dividing by the area in - space.

Study the calorimeter towers (ET > 0.1 GeV, || < 1) and form the scalar ET sum density, dETsum/dd.

Charged Particles (pT > 0.5 GeV/c, || < 1)Calorimeter Towers (ET > 0.1 GeV, || < 1)

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

Calorimeter Jet #1 Direction

“Toward”


“Away”

-1 +1

2

0

Leading Jet

Toward Region

Transverse Region

Transverse Region

Away Region

Away Region

Look at the charged particle density and the

ETsum density in the “transverse” region!



The “Transverse” RegionThe “Transverse” Regionas defined by the Leading Jetas defined by the Leading Jet

Look at the “transverse” region as defined by the leading calorimeter jet (MidPoint, R = 0.7, fmerge = 0.75, || < 2).

Define || < 60o as “Toward”, 60o < - < 120o and 60o < < 120o as “Transverse 1” and “Transverse 2”, and || > 120o as “Away”. Each of the two “transverse” regions have area = 2x60o = 4/6. The overall “transverse” region is the sum of the two transverse regions ( = 2x120o = 4/3).

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.



Calorimeter Jet #1 Direction

“Toward”


“Away”

-1 +1

2

0

Leading Jet

Toward Region

Transverse Region

Transverse Region

Away Region

Away Region


ETsum density in the “transverse” region!

Jet #1 Direction


“Toward”

“Away”

“Toward-Side” Jet

“Away-Side” Jet

Jet #3

“Transverse” region recieves contributions from initial & final-

state radiation!



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

The “Underlying Event” in High PT Jet Production

“Transverse” <Densities> vs PT(jet#1)

Jet #1 Direction

“Toward”


“Away”

"Transverse" Charged Particle Density: dN/dd

0.0

0.2

0.4

0.6

0.8

1.0

0 50 100 150 200 250 300 350 400 450

PT(jet#1) (GeV/c)

"Tra

ns

vers

e" C

har

ge

d D

ensi

ty

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

PY Tune A

HW

"Leading Jet"

"Transverse" Charged PTsum Density: dPT/dd

0.0

0.4

0.8

1.2

1.6

2.0

0 50 100 150 200 250 300 350 400 450

PT(jet#1) (GeV/c)

"Tra

ns

vers

e" P

Tsu

m D

ens

ity

(G

eV

/c) CDF Run 2 Preliminary

data 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"

PY Tune A

HW

HERWIG (without MPI) lies below the data for PT(jet#1) < 200 GeV/c!

Proton AntiProton


PT(hard)

Outgoing Parton

Outgoing Parton






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




Anti-Lepton


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


ETsum 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

s = 1.0

s = 2.5

s = 5.0

Parameter Tune ATune 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



Parameter Tune A Tune AW

MSTP(81) 1 1

MSTP(82) 4 4

PARP(82) 2.0 GeV 2.0 GeV

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(89) 1.8 TeV 1.8 TeV

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.

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 AW (<pT(Z)> = 11.7 GeV/c).

UE Parameters

ISR Parameters

Intrensic KT

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 AWCDF Run 1

published

1.8 TeV

Normalized to 1

s = 2.1

PYTHIA 6.2 CTEQ5L



Drell-Yan ProductionDrell-Yan Productionat CDFat CDF

Shows the lepton-pair average PT versus the lepton-pair invariant mass at 1.96 TeV for PYTHIA Tune AW and PYTHIA Tune A.

Lepton-Pair Transverse Momentum

0

5

10

15

20

0 50 100 150 200 250

Lepton-Pair Invariant Mass (GeV)

Av

era

ge

Pai

r P

T

Drell-Yan1.96 TeV

RDF Preliminarygenerator level

PY Tune A

PY Tune AW

Shows the lepton-pair average PT versus the lepton-pair invariant mass at 1.96 TeV for PYTHIA Tune AW and HERWIG.

<PT(pair)> versus M(pair)Lepton-Pair Transverse Momentum

Proton AntiProton

Drell-Yan Production

PT(pair)

Lepton-Pair

Outgoing Parton





0

5

10

15

20

0 50 100 150 200 250


Av

era

ge

Pai

r P

T

Drell-Yan1.96 TeV


PY Tune AW

HERWIG

Z Z



Drell-Yan ProductionDrell-Yan Productionat CMSat CMS

Shows the lepton-pair average PT versus the lepton-pair invariant mass at 1.96 TeV for PYTHIA Tune AW and HERWIG.

Shows the lepton-pair average PT versus the lepton-pair invariant mass at 14 TeV for PYTHIA Tune AW and HERWIG.

<PT(pair)> versus M(pair)Lepton-Pair Transverse Momentum

Proton AntiProton


PT(pair)

Lepton-Pair

Outgoing Parton





0

5

10

15

20

0 50 100 150 200 250


Av

era

ge

Pai

r P

T

Drell-Yan1.96 TeV


PY Tune AW

HERWIG


0

10

20

30

40

0 50 100 150 200 250


Av

era

ge

Pai

r P

T

Drell-Yan


PY Tune AW

HERWIGCDF

LHC

The lepton-pair <PT> much larger at the LHC!

Z Z



The “Underlying Event” inThe “Underlying Event” inDrell-Yan Production (CDF)Drell-Yan Production (CDF)

Shows the charged particle density versus the lepton-pair invariant mass at 1.96 TeV for PYTHIA Tune AW and PYTHIA Tune A.

Shows the charged particle density versus the lepton-pair invariant mass at 1.96 TeV for PYTHIA Tune AW and HERWIG (with no MPI).

Charged particle density versus M(pair)

Charged Particle Density: dN/dd

0.0

0.2

0.4

0.6

0.8

1.0

0 50 100 150 200 250


Ch

arg

ed

Pa

rtic

le D

en

sity


Drell-Yan1.96 TeV


PY Tune A

PY Tune AW

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 )

HERWIG (without MPI) is much less active than

PY Tune AW (with MPI)!

Z Z



The “Underlying Event” inThe “Underlying Event” inDrell-Yan Production (CMS)Drell-Yan Production (CMS)

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


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



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!



Z



The “Underlying Event” inThe “Underlying Event” inDrell-Yan Production (CDF)Drell-Yan Production (CDF)

Shows the charged PTsum density versus the lepton-pair invariant mass at 1.96 TeV for PYTHIA Tune AW and PYTHIA Tune A.

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

Charged PTsum density versus M(pair)

Charged PTsum Density: dPT/dd

0.0

0.4

0.8

1.2

1.6

0 50 100 150 200 250


Ch

arg

ed

PT

sum

De

nsi

ty (

GeV

/c) RDF Preliminary

generator level

Drell-Yan1.96 TeV Charged Particles (||<1.0, PT>0.5 GeV/c)

PY Tune A

PY Tune AW



0.0

0.4

0.8

1.2

1.6

0 50 100 150 200 250


Ch

arg

ed P

Tsu

m D

ensi

ty (

GeV

/c) RDF Preliminary

generator level

Drell-Yan1.96 TeV

PY Tune AW

HERWIGCharged Particles (||<1.0, PT>0.5 GeV/c)


Proton AntiProton




Anti-Lepton



Z




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

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


Proton AntiProton




Anti-Lepton


0.0

0.4

0.8

1.2

1.6

0 50 100 150 200 250


Ch

arg

ed P

Tsu

m D

en

sity

(G

eV/c

) RDF Preliminarygenerator level

Drell-Yan1.96 TeV

PY Tune AW




0.0

0.5

1.0

1.5

2.0

2.5

0 50 100 150 200 250


Ch

arg

ed P

Tsu

m D

en

sity

(G

eV/c


Drell-Yan

PY Tune AW

HERWIG

LHC

CDF


Charged PTsum density versus M(pair)




Z




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

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

ETsum density versus M(pair)The “Underlying Event”

Proton AntiProton




Anti-Lepton

Transverse Energy Density: dET/dd

0.0

0.5

1.0

1.5

2.0

0 50 100 150 200 250


ET

sum

Den

sity

(G

eV)


All Particles (||<1.0, all PT)(excluding lepton-pair )

Drell-Yan1.96 TeV

PY Tune AW

HERWIG

Transverse Energy Density: dET/dd

0.0

1.0

2.0

3.0

4.0

5.0

0 50 100 150 200 250


ET

sum

Den

sity

(G

eV)


Drell-Yan

PY Tune AW

HERWIG

All Particles (||<1.0, all PT)(excluding lepton-pair )

LHC

CDF

ZZ



The “Underlying Event”The “Underlying Event”Drell-Yan vs Jets at CDFDrell-Yan vs Jets at CDF

-1 +1

2

0

Central Region

The “Underlying Event” in High PT Lepton-Pair and Jet Production

Jet #1 Direction

“Toward”


“Away”


0.0

0.2

0.4

0.6

0.8

1.0

0 50 100 150 200 250 300 350 400 450 500

PT(jet#1) or Lepton-Pair Mass

Ch

arg

ed P

arti

cle

Den

sity


1.96 TeV

PY Tune AW

HERWIG


"Leading Jet"

Drell-Yan


0.0

0.4

0.8

1.2

1.6

0 50 100 150 200 250 300 350 400 450 500


Ch

arg

ed P

Tsu

m D

ensi

ty (

GeV

/c)

"Leading Jet"RDF Preliminarygenerator level

1.96 TeVPY Tune AW



Drell-Yan

Lepton

Anti-Lepton

“Central Region”

-1 +1

2

0

Leading Jet

Toward Region

Transverse Region

Transverse Region

Away Region

Away Region

Drell-Yan “Leading Jet”



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

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).



0.0

0.2

0.4

0.6

0.8

1.0

0 50 100 150 200 250 300 350 400 450 500

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

"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

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)


Proton AntiProton


PT(hard)

Outgoing Parton

Outgoing Parton







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

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


"Transverse" PTsum Density: dPT/dd

0.0

0.5

1.0

1.5

2.0

0 50 100 150 200 250 300 350 400 450 500


"Tra

ns

vers

e" P

Ts

um

Den

sit

y (

Ge

V/c

)



"Leading Jet"

PY Tune AW

HERWIG

1.96 TeV

"Transverse" PTsum Density: dPT/dd

0.0

2.0

4.0

6.0

8.0

0 250 500 750 1000 1250 1500 1750 2000 2250 2500


"Tra

ns

vers

e" P

Ts

um

Den

sit

y (

Ge

V/c

)



"Leading Jet"

PY Tune AW

HERWIG

CDF

LHC

Charged PTsum density versus PT(jet#1)


Proton AntiProton


PT(hard)

Outgoing Parton

Outgoing Parton







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

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


"Transverse" ETsum Density: dET/dd

0.0

1.0

2.0

3.0

4.0

0 50 100 150 200 250 300 350 400 450 500


"Tra

ns

ve

rse

" E

Ts

um

De

ns

ity

(G

eV

)

All Particles (||<1.0, all PT)


"Leading Jet"

PY Tune AW

HERWIG

1.96 TeV

"Transverse" ETsum Density: dET/dd

0.0

2.0

4.0

6.0

8.0

10.0

12.0

14.0

0 250 500 750 1000 1250 1500 1750 2000 2250 2500


"Tra

ns

vers

e" E

Ts

um

Den

sit

y (

Ge

V)

All Particles (||<1.0, all PT)


"Leading Jet"

PY Tune AW

HERWIG

LHC

CDF

ETsum density versus PT(jet#1)


Proton AntiProton


PT(hard)

Outgoing Parton

Outgoing Parton






The “Underlying Event”The “Underlying Event”Drell-Yan vs Jets at CMSDrell-Yan vs Jets at CMS

-1 +1

2

0

Central Region

The “Underlying Event” in High PT Lepton-Pair and Jet Production

Jet #1 Direction

“Toward”


“Away”

Lepton

Anti-Lepton

“Central Region”

-1 +1

2

0

Leading Jet

Toward Region

Transverse Region

Transverse Region

Away Region

Away Region

Drell-Yan “Leading Jet”


0.0

0.5

1.0

1.5

2.0

0 250 500 750 1000 1250 1500 1750 2000 2250 2500

PT(jet#1) orLepton-Pair Mass

Ch

arg

ed P

arti

cle

Den

sity

"Leading Jet"

PY Tune AW

HERWIG


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


14 TeV


0.0

2.0

4.0

6.0

8.0

0 250 500 750 1000 1250 1500 1750 2000 2250 2500


Ch

arg

ed P

Tsu

m D

en

sity

(G

eV/c


"Leading Jet"PY Tune AW

HERWIG

Drell-Yan

14 TeV




Proton Proton


PT(hard)

Outgoing Parton

Outgoing Parton




UE&MB@CMSUE&MB@CMS

“Underlying Event” Studies: The “transverse region” in “leading Jet” and “back-to-back” jet production. The “central region” in Drell-Yan production. (requires charged tracks and calorimeter 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)>, ds/dpT(pair) (only requires muons). Event structure for large lepton-pair pT (i.e. +jets, requires muons and calorimeter).

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


PT(pair)

Lepton-Pair

Outgoing Parton






Proton Proton


PT(hard)

Outgoing Parton

Outgoing Parton




UE&MB@CMSUE&MB@CMS

“Underlying Event” Studies: The “transverse region” in “leading Jet” and “back-to-back” jet production. The “central region” in Drell-Yan production. (requires charged tracks and calorimeter 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)>, ds/dpT(pair) (only requires muons). Event structure for large lepton-pair pT (i.e. +jets, requires muons and calorimeter).

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


PT(pair)

Lepton-Pair

Outgoing Parton




UE&MB@CMSRick Field (Florida)

Darin Acosta (Florida)Albert De Roeck (CERN)

Paolo Bartalini (UF Postdoc at CERN)Livio Fano' (INFN/Perugia at CERN)

Filippo Ambroglini (INFN/Perugia at CERN)

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The “Underlying Event” CDF-LHC Comparisons

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