IMFP2006 - Day 4 April 6, 2006

Rick Field – Florida/CDF/CMS Page 1

XXXIV International Meeting on XXXIV International Meeting on Fundamental PhysicsFundamental Physics

Rick FieldUniversity of Florida

(for the CDF & D0 Collaborations)

CDF Run 2

Real Colegio Maria Cristina, El Escorial, Spain

From HERA and the TEVATRON

to the LHC

Physics at the Tevatron

4th LectureDetailed Study of the “Underlying Event”

at the Tevatron

IMFP2006 - Day 4 April 6, 2006

Rick Field – Florida/CDF/CMS Page 2

The “Underlying Event” in Run 2 (CDF)The “Underlying Event” in Run 2 (CDF)

Two Classes of Events: “Leading Jet” and “Back-to-Back”. Two “Transverse” regions: “transMAX”, “transMIN”, “transDIF”. PTmax and PTmaxT distributions and averages. Distributions: “Density” and “Associated Density”. <pT> versus charged multiplicity: “min-bias” and the “transverse” region.

Correlations between the two “transverse” regions: “trans1” vs “trans2”.

Proton AntiProton

PT(hard)

Outgoing Parton

Outgoing Parton

Underlying Event Underlying Event

Initial-State Radiation

Final-State Radiation

The “underlying event” consists of hard initial & final-state radiation

plus the “beam-beam remnants” and possible multiple parton interactions.

Studying the “Underlying Event”

Studying the “Underlying Event” in Drell-Yan Production.

Extrapolations to the LHC.Extrapolations to the LHC.

Proton AntiProton

Drell-Yan Production Lepton

Underlying Event Underlying Event

Initial-State Radiation

Anti-Lepton CMS at the LHC

UE&MB@CMSUE&MB@CMS

Florida-Perugia

IMFP2006 - Day 4 April 6, 2006

Rick Field – Florida/CDF/CMS Page 3

Jet #1 Direction

“Transverse” “Transverse”

“Toward”

“Away”

“Toward-Side” Jet

“Away-Side” Jet

The “Transverse” RegionsThe “Transverse” Regionsas defined by the Leading Jetas defined by the Leading Jet

Look at charged particle correlations in the azimuthal angle relative to the leading calorimeter jet (JetClu R = 0.7, || < 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).

Charged Particle Correlations pT > 0.5 GeV/c || < 1

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

Jet #1 Direction

“Toward”

“Trans 1” “Trans 2”

“Away”

-1 +1

2

0

Leading Jet

Toward Region

Transverse Region 1

Transverse Region 2

Away Region

Away Region

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

IMFP2006 - Day 4 April 6, 2006

Rick Field – Florida/CDF/CMS Page 4

-1 +1

2

0

1 charged particle

dNchg/dd = 1/4 = 0.08

Particle DensitiesParticle Densities

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”

IMFP2006 - Day 4 April 6, 2006

Rick Field – Florida/CDF/CMS Page 5

-1 +1

2

0

Leading Jet

Toward Region

Transverse Region 1

Transverse Region 2

Away Region

Away Region

““Transverse” Particle DensitiesTransverse” Particle Densities

Study the charged particles (pT > 0.5 GeV/c, || < 1) in the “Transverse 1” and “Transverse 2” 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

1 charged particle in the “transverse 2” region

dNchg/dd = 1/(4 = 0.48

Jet #1 Direction

“Toward”

“Trans 1” “Trans 2”

“Away”

Area = 4/6

The average “transverse” density is the average of “transverse 1” and “transverse 2”.

AVE “transverse”(Trans 1 + Trans 2)/2

IMFP2006 - Day 4 April 6, 2006

Rick Field – Florida/CDF/CMS Page 6

Charged Particle Density Charged Particle Density Dependence Dependence

Shows the dependence of the charged particle density, dNchg/dd, for charged particles in the range pT > 0.5 GeV/c and || < 1 relative to jet#1 (rotated to 270o) for “leading jet” events 30 < ET(jet#1) < 70 GeV.

Also shows charged particle density, dNchg/dd, for charged particles in the range pT > 0.5 GeV/c and || < 1 for “min-bias” collisions.

Leading Jet

Charged Particle Density: dN/dd

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CDF Preliminarydata uncorrected

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

30 < ET(jet#1) < 70 GeV

"Transverse" Region

Jet#1

Jet #1 Direction

“Transverse” “Transverse”

“Toward”

“Away”

“Toward-Side” Jet

“Away-Side” Jet

Jet #1 Direction

“Transverse” “Transverse”

“Toward”

“Away”

“Toward-Side” Jet

“Away-Side” Jet

Jet #3

Min-Bias0.25 per unit -

Log Scale!

IMFP2006 - Day 4 April 6, 2006

Rick Field – Florida/CDF/CMS Page 7

Charged Particle Density Charged Particle Density Dependence Dependence

Look at the “transverse” region as defined by the leading jet (JetClu R = 0.7, || < 2) or by the leading two jets (JetClu R = 0.7, || < 2). “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 (ET(jet#2)/ET(jet#1) > 0.8) and with ET(jet#3) < 15 GeV.

Charged Particle Density: dN/dd

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CDF Preliminarydata uncorrected

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

30 < ET(jet#1) < 70 GeV

"Transverse" Region

Jet#1

Jet #1 Direction

“Toward”

“Transverse” “Transverse”

“Away”

Jet #1 Direction

“Toward”

“Transverse” “Transverse”

“Away”

Jet #2 Direction

Shows the dependence of the charged particle density, dNchg/dd, for charged particles in the range pT > 0.5 GeV/c and || < 1 relative to jet#1 (rotated to 270o) for 30 < ET(jet#1) < 70 GeV for “Leading Jet” and “Back-to-Back” events.

Charged Particle Density: dN/dd

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(degrees)

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Back-to-Back

Leading Jet

Min-Bias

CDF Preliminarydata uncorrected

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

30 < ET(jet#1) < 70 GeV

"Transverse" Region

Jet#1

Refer to this as a “Leading Jet” event

Refer to this as a “Back-to-Back” event

Su

bset

IMFP2006 - Day 4 April 6, 2006

Rick Field – Florida/CDF/CMS Page 8

Charged Particle Density Charged Particle Density Dependence Dependence

Jet #1 Direction

“Toward”

“Transverse” “Transverse”

“Away”

Jet #1 Direction

“Toward”

“Transverse” “Transverse”

“Away”

Jet #2 Direction

Shows the dependence of the charged particle density, dNchg/dd, for charged particles in the range pT > 0.5 GeV/c and || < 1 relative to jet#1 (rotated to 270o) for 30 < ET(jet#1) < 70 GeV for “Leading Jet” and “Back-to-Back” events.

“Leading Jet”

“Back-to-Back”

Charged Particle Density: dN/dd272

276 280 284288

292296

300304

308

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240244

248252

256260 264 268

CDF Preliminarydata uncorrected

30 < ET(jet#1) < 70 GeV

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

"Transverse" Region

"Transverse" Region

Jet#1

Back-to-BackLeading Jet

0.5

1.0

1.5

2.0

Polar Plot

IMFP2006 - Day 4 April 6, 2006

Rick Field – Florida/CDF/CMS Page 9

““Transverse” PTsum Density versus ETransverse” PTsum Density versus ETT(jet#1)(jet#1)

Jet #1 Direction

“Toward”

“Transverse” “Transverse”

“Away”

Jet #1 Direction

“Toward”

“Transverse” “Transverse”

“Away”

Jet #2 Direction

Shows the average charged PTsum density, dPTsum/dd, in the “transverse” region (pT > 0.5 GeV/c, || < 1) versus ET(jet#1) for “Leading Jet” and “Back-to-Back” events.

“Leading Jet”

“Back-to-Back”

"AVE Transverse" PTsum Density: dPT/dd

0.0

0.2

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0.6

0.8

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1.2

1.4

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ET(jet#1) (GeV)

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GeV

/c)

CDF Run 2 Preliminarydata uncorrected

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

Back-to-Back

Leading Jet

1.96 TeV

Min-Bias0.24 GeV/c per unit -

"AVE Transverse" PTsum Density: dPT/dd

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

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ET(jet#1) (GeV)

"Tra

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GeV

/c)

CDF Preliminarydata uncorrectedtheory + CDFSIM

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

Back-to-Back

Leading Jet

PY Tune A

HW

1.96 TeV

Compares the (uncorrected) data with PYTHIA Tune A and HERWIG after CDFSIM.

Hard Radiation!

IMFP2006 - Day 4 April 6, 2006

Rick Field – Florida/CDF/CMS Page 10

““Transverse” PTsum Density versus ETransverse” PTsum Density versus ETT(jet#1)(jet#1)

Jet #1 Direction

“Toward”

“Transverse” “Transverse”

“Away”

Jet #1 Direction

“Toward”

“Transverse” “Transverse”

“Away”

Jet #2 Direction

30-70 GeV 95-130 GeV

"AVE Transverse" PTsum Density: dPT/dd

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

0 50 100 150 200 250

ET(jet#1) (GeV)

"Tra

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GeV

/c)

CDF Run 2 Preliminarydata uncorrected

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

Back-to-Back

Leading Jet

1.96 TeV

Charged PTsum Density: dPT/dd

0.1

1.0

10.0

100.0

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(degrees)

Ch

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PT

su

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Ge

V/c

) 95 < ET(jet#1) < 130 GeV

30 < ET(jet#1) < 70 GeV

Min-Bias

Leading Jet

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

CDF Preliminarydata uncorrected

Jet#1

"Transverse" Region

Charged PTsum Density: dPT/dd

0.1

1.0

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100.0

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(degrees)

Ch

arg

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PT

su

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Ge

V/c

) 95 < ET(jet#1) < 130 GeV

30 < ET(jet#1) < 70 GeV

Min-Bias

Back-to-Back

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

CDF Preliminarydata uncorrected

Jet#1

"Transverse" Region

Very little dependence on ET(jet#1) in the “transverse”

region for “back-to-back” events!

IMFP2006 - Day 4 April 6, 2006

Rick Field – Florida/CDF/CMS Page 11

““TransDIF” PTsum Density versus ETransDIF” PTsum Density versus ETT(jet#1)(jet#1)

Use the leading jet to define the MAX and MIN “transverse” regions on an event-by-event basis with MAX (MIN) having the largest (smallest) charged PTsum density.

Jet #1 Direction

“Toward”

“TransMAX” “TransMIN”

“Away”

Jet #1 Direction

“Toward”

“TransMAX” “TransMIN”

Jet #2 Direction

“Away”

Shows the “transDIF” = MAX-MIN charge PTsum density, dPTsum/dd, for pT > 0.5 GeV/c, || < 1 versus ET(jet#1) for “Leading Jet” and “Back-to-Back” events.

Jet #1 Direction

“Toward”

“TransMAX” “TransMIN”

“Away”

“Leading Jet”

“Back-to-Back”

"MAX-MIN Transverse" PTsum Density: dPT/dd

0.0

0.5

1.0

1.5

2.0

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ET(jet#1) (GeV)

"Tra

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GeV

/c)

CDF Run 2 Preliminarydata uncorrectedtheory + CDFSIM

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

Back-to-Back

LeadingJet

"MAX-MIN Transverse" PTsum Density: dPT/dd

0.0

0.5

1.0

1.5

2.0

0 50 100 150 200 250

ET(jet#1) (GeV)

"Tra

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erse

" P

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GeV

/c) CDF Run 2 Preliminary

data uncorrectedtheory + CDFSIM

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

PY Tune A

HW

Back-to-Back

LeadingJet

“MAX-MIN” is very sensitive to the “hard scattering” component

of the “underlying event”!

Hard Radiation!

IMFP2006 - Day 4 April 6, 2006

Rick Field – Florida/CDF/CMS Page 12

““TransMIN” PTsum Density versus ETransMIN” PTsum Density versus ETT(jet#1)(jet#1)

Use the leading jet to define the MAX and MIN “transverse” regions on an event-by-event basis with MAX (MIN) having the largest (smallest) charged particle density.

Jet #1 Direction

“Toward”

“TransMAX” “TransMIN”

“Away”

Jet #1 Direction

“Toward”

“TransMAX” “TransMIN”

Jet #2 Direction

“Away”

Shows the “transMIN” charge particle density, dNchg/dd, for pT > 0.5 GeV/c, || < 1 versus ET(jet#1) for “Leading Jet” and “Back-to-Back” events.

Jet #1 Direction

“Toward”

“TransMAX” “TransMIN”

“Away”

“Leading Jet”

“Back-to-Back”

"MIN Transverse" PTsum Density: dPT/dd

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ET(jet#1) (GeV)

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GeV

/c)

CDF Run 2 Preliminarydata uncorrectedtheory + CDFSIM

1.96 TeV

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

Min-BiasBack-to-Back

Leading Jet

"MIN Transverse" PTsum Density: dPT/dd

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ET(jet#1) (GeV)

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/c)

CDF Run 2 Preliminarydata uncorrectedtheory + CDFSIM

1.96 TeV

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

PY Tune A

HW Back-to-Back

Leading Jet

“transMIN” is very sensitive to the “beam-beam remnant” component

of the “underlying event”!

IMFP2006 - Day 4 April 6, 2006

Rick Field – Florida/CDF/CMS Page 13

““Transverse” PTsum DensityTransverse” PTsum Density PYTHIA Tune A vs HERWIG PYTHIA Tune A vs HERWIG

Jet #1 Direction

“Toward”

“Transverse” “Transverse”

“Away”

Jet #1 Direction

“Toward”

“Transverse” “Transverse”

“Away”

Jet #2 Direction

Shows the average charged PTsum density, dPTsum/dd, in the “transverse” region (pT > 0.5 GeV/c, || < 1) versus ET(jet#1) for “Leading Jet” and “Back-to-Back” events.

Compares the (uncorrected) data with PYTHIA Tune A and HERWIG after CDFSIM.

“Leading Jet”

“Back-to-Back”

"AVE Transverse" PTsum Density: dPT/dd

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CDF Preliminarydata uncorrectedtheory + CDFSIM

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

Back-to-Back

Leading Jet

PY Tune A

HW

1.96 TeV

Now look in detail at “back-to-back” events in the region 30 < ET(jet#1) < 70 GeV!

IMFP2006 - Day 4 April 6, 2006

Rick Field – Florida/CDF/CMS Page 14

Charged PTsum DensityCharged PTsum DensityPYTHIA Tune A vs HERWIGPYTHIA Tune A vs HERWIG

Charged PTsum Density: dPT/dd

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(degrees)

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su

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) Back-to-Back

PY Tune A30 < ET(jet#1) < 70 GeVCharged Particles

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

CDF Preliminarydata uncorrectedtheory + CDFSIM

Jet#1"Transverse" Region

Charged PTsum Density: dPT/dd

0.1

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su

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) Back-to-Back

HERWIG30 < ET(jet#1) < 70 GeVCharged Particles

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

CDF Preliminarydata uncorrectedtheory + CDFSIM

Jet#1

"Transverse" Region

Data - Theory: Charged PTsum Density dPT/dd

-2

-1

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1

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0 30 60 90 120 150 180 210 240 270 300 330 360

(degrees)

Da

ta -

Th

eo

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(Ge

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)

CDF Preliminarydata uncorrectedtheory + CDFSIM

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

Back-to-Back30 < ET(jet#1) < 70 GeV

PYTHIA Tune A

Jet#1

"Transverse" Region

Data - Theory: Charged PTsum Density dPT/dd

-2

-1

0

1

2

0 30 60 90 120 150 180 210 240 270 300 330 360

(degrees)

Da

ta -

Th

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(Ge

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)

CDF Preliminarydata uncorrectedtheory + CDFSIM

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

30 < ET(jet#1) < 70 GeVBack-to-Back

HERWIG

Jet#1

"Transverse" Region

HERWIG (without multiple parton interactions) does not produces

enough PTsum in the “transverse” region for 30 < ET(jet#1) < 70 GeV!

IMFP2006 - Day 4 April 6, 2006

Rick Field – Florida/CDF/CMS Page 18

Min-Bias “Associated”Min-Bias “Associated”Charged 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

Charged Particle Density: dN/dd

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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!

IMFP2006 - Day 4 April 6, 2006

Rick Field – Florida/CDF/CMS Page 19

Min-Bias “Associated”Min-Bias “Associated”Charged Particle DensityCharged Particle Density

Associated Particle Density: dN/dd

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PTmax > 1.0 GeV/c

PTmax > 0.5 GeV/c

CDF Preliminarydata uncorrected

PTmaxPTmax not included

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

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

Rapid rise in the particle density in the “transverse” region as PTmax increases!

IMFP2006 - Day 4 April 6, 2006

Rick Field – Florida/CDF/CMS Page 20

““Transverse” PTmax versus ETransverse” PTmax versus ETT(jet#1)(jet#1)

Shows the average PTmaxT, in the “transverse” region (pT > 0.5 GeV/c, || < 1) versus ET(jet#1) for “Leading Jet” and “Back-to-Back” events compared with the average maximum pT particle, PTmax, in “min-bias” collisions (pT > 0.5 GeV/c, || < 1).

“Leading Jet”

“Back-to-Back”

"Transverse" Charged PTmax

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ET(jet#1) (GeV)

"Tra

ns

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Tm

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(G

eV

/c) CDF Run 2 Preliminary

data uncorrected1.96 TeV

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

Min-Bias

Leading Jet

Back-to-Back

Use the leading jet to define the “transverse” region and look at the maximum pT charged particle in the “transverse” region, PTmaxT.

Jet #1 Direction

“Toward”

“TransMIN”

“Away”

“TransMAX”

PTmaxT

Jet #1 Direction

“Toward”

“TransMIN” “TransMAX”

PTmaxT

Jet #2 Direction

“Away”

Jet #1 Direction

“Toward”

“TransMIN”

“Away”

“TransMAX”

PTmaxT

Highest pT particle in the “transverse” region!

Min-Bias

IMFP2006 - Day 4 April 6, 2006

Rick Field – Florida/CDF/CMS Page 21

Back-to-Back “Associated”Back-to-Back “Associated”Charged Particle DensitiesCharged Particle Densities

Use the leading jet in “back-to-back” events to define the “transverse” region and look at the maximum pT charged particle in the “transverse” region, PTmaxT.

“Associated” densities do not include PTmaxT!

Jet #1 Direction

“Toward”

“TransMIN” “TransMAX”

PTmaxT

Jet #2 Direction

“Away”

Jet#1 Region

PTmaxT Direction

Jet#2 Region

PTmaxT Direction

Jet#1 Region

Jet#2 Region

Look at the dependence of the “associated” charged particle and PTsum densities, dNchg/dd and dPTsum/dd for charged particles (pT > 0.5 GeV/c, || < 1, not including PTmaxT) relative to PTmaxT.

Rotate so that PTmaxT is at the center of the plot (i.e. 180o).

Maximum pT particle in the “transverse” region!

IMFP2006 - Day 4 April 6, 2006

Rick Field – Florida/CDF/CMS Page 22

Back-to-Back “Associated”Back-to-Back “Associated”Charged Particle DensitiesCharged Particle Densities

PTmaxT Direction

Jet#1 Region

Jet#2 Region

Look at the dependence of the “associated” charged particle density, dNchg/dd for charged particles (pT > 0.5 GeV/c, || < 1, not including PTmaxT) relative to PTmaxT (rotated to 180o) for PTmaxT > 0.5 GeV/c, PTmaxT > 1.0 GeV/c and PTmaxT > 2.0 GeV/c, for “back-to-back” events with 30 < ET(jet#1) < 70 GeV.

Shows “jet structure” in the “transverse” region (i.e. the “birth” of the 3rd & 4th jet).

Associated Particle Density: dN/dd

0.1

1.0

10.0

0 30 60 90 120 150 180 210 240 270 300 330 360

(degrees)A

ss

oc

iate

d P

art

icle

De

ns

ity

PTmaxT > 2.0 GeV/c

PTmaxT > 1.0 GeV/c

PTmaxT > 0.5 GeV/c

CDF Preliminarydata uncorrected

PTmaxT

Back-to-Back30 < ET(jet#1) < 70 GeV

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

PTmaxT not included

"Jet#1" Region

Jet#2 Region

Jet #1

Jet #2

Jet #4

“Associated” densities do not include PTmaxT!

Jet #3

Log Scale!

??

IMFP2006 - Day 4 April 6, 2006

Rick Field – Florida/CDF/CMS Page 24

Back-to-Back “Associated”Back-to-Back “Associated”Charged Particle DensitiesCharged Particle Densities

Jet#1 Region

PTmaxT Direction

Jet#2 Region

Charged Particle Density: dN/dd

0.1

1.0

10.0

0 30 60 90 120 150 180 210 240 270 300 330 360

(degrees)

Ch

arg

ed P

arti

cle

Den

sity

Back-to-Back

PTmaxT > 0.5 GeV/c

CDF Preliminarydata uncorrected

30 < ET(jet#1) < 70 GeVCharged Particles (||<1.0, PT>0.5 GeV/c)

"Transverse" Region

PTmaxT Jet#1

Associated DensityPTmaxT not included

Shows the dependence of the “associated” charged particle density, dNchg/dd for charged particles (pT > 0.5 GeV/c, || < 1, not including PTmaxT) relative to PTmaxT (rotated to 180o) for PTmaxT > 0.5 GeV/c, PTmaxT > 1.0 GeV/c and PTmaxT > 2.0 GeV/c, for “back-to-back” events with 30 < ET(jet#1) < 70 GeV.

Shows dependence of the charged particle density, dNchg/dd for charged particles (pT > 0.5 GeV/c, || < 1) relative to jet#1 (rotated to 270o) for “back-to-back events” with 30 < ET(jet#1) < 70 GeV.

Jet #1 Direction

“Toward”

“Transverse” “Transverse”

“Away”

Jet #2 Direction

It is more probable to find a particle accompanying PTmaxT than it is to find a particle in the

“transverse” region!

“Back-to-Back”“associated” density

“Back-to-Back”charge density

IMFP2006 - Day 4 April 6, 2006

Rick Field – Florida/CDF/CMS Page 25

Back-to-Back “Associated”Back-to-Back “Associated”Charged Particle DensitiesCharged Particle Densities

Jet#1 Region

PTmaxT Direction

Jet#2 Region

Shows the dependence of the “associated” charged particle density, dNchg/dd, pT > 0.5 GeV/c, || < 1 (not including PTmaxT) relative to PTmaxT (rotated to 180o) and the charged particle density, dNchg/dd, pT > 0.5 GeV/c, || < 1 relative to jet#1 (rotated to 270o) for “back-to-back events” with 30 < ET(jet#1) < 70 GeV.

Jet #1 Direction

“Toward”

“Transverse” “Transverse”

“Away”

Jet #2 Direction

Charged Particle Density: dN/dd2

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30 < ET(jet#1) < 70 GeVBack-to-Back

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

"Transverse" Region "Transverse"

Region

Jet#1

Associated DensityPTmaxT not included

PTmaxT

Polar Plot

0.5

1.0

1.5

2.0

“Back-to-Back”charge density

“Back-to-Back”“associated” density

IMFP2006 - Day 4 April 6, 2006

Rick Field – Florida/CDF/CMS Page 26

Back-to-Back “Associated”Back-to-Back “Associated”Charged Particle DensitiesCharged Particle Densities

Jet#1 Region

PTmaxT Direction

Jet#2 Region

Shows the dependence of the “associated” charged particle density, dNchg/dd, pT > 0.5 GeV/c, || < 1, PTmaxT > 2.0 GeV/c (not including PTmaxT) relative to PTmaxT (rotated to 180o) and the charged particle density, dNchg/dd, pT > 0.5 GeV/c, || < 1, relative to jet#1 (rotated to 270o) for “back-to-back events” with 30 < ET(jet#1) < 70 GeV.

Jet #1 Direction

“Toward”

“Transverse” “Transverse”

“Away”

Jet #2 Direction

Charged Particle Density: dN/dd2

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CDF Preliminarydata uncorrected

30 < ET(jet#1) < 70 GeVBack-to-Back

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

"Transverse" Region "Transverse"

Region

Jet#1

Associated DensityPTmaxT > 2 GeV/c

(not included)

PTmaxT

Polar Plot

“Back-to-Back”“associated” density

“Back-to-Back”charge density

0.5

1.0

1.5

2.0

IMFP2006 - Day 4 April 6, 2006

Rick Field – Florida/CDF/CMS Page 27

Jet TopologiesJet Topologies

Jet#1 Region

PTmaxT Direction

Jet#2 Region

Shows the dependence of the “associated” charged particle density, dNchg/dd, pT > 0.5 GeV/c, || < 1, PTmaxT > 2.0 GeV/c (not including PTmaxT) relative to PTmaxT (rotated to 180o) and the charged particle density, dNchg/dd, pT > 0.5 GeV/c, || < 1, relative to jet#1 (rotated to 270o) for “back-to-back events” with 30 < ET(jet#1) < 70 GeV.

Charged Particle Density: dN/dd2

6 1014

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30 < ET(jet#1) < 70 GeVBack-to-Back

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

"Transverse" Region "Transverse"

Region

Jet#1

Associated DensityPTmaxT > 2 GeV/c

(not included)

PTmaxT

Polar Plot

0.5

1.0

1.5

2.0

Jet #3

Jet #3

Jet #1

Jet #1

Jet #2

Jet #2

Jet #4

Jet #4

QCD Three Jet TopologyQCD Four Jet Topology

Proton AntiProton

QCD 2-to-4 Scattering

PT(hard)

Outgoing Parton

Outgoing Parton

Underlying Event Underlying Event

Initial-State Radiation

Final-State Radiation

Final-State Radiation

Proton AntiProton

Multiple Parton Interactions

PT(hard)

Outgoing Parton

Outgoing Parton

Underlying Event Underlying Event

Outgoing Parton

Outgoing Parton

IMFP2006 - Day 4 April 6, 2006

Rick Field – Florida/CDF/CMS Page 28

Back-to-Back “Associated”Back-to-Back “Associated”Charged Particle DensityCharged Particle Density

Associated Particle Density: dN/dd

0.1

1.0

10.0

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

95 < ET(jet#1) < 130 GeV

30 < ET(jet#1) < 70 GeV

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

CDF Preliminarydata uncorrected

PTmaxT

PTmaxT > 2.0 GeV/c (not included)

"Jet#1" Region

Back-to-Back

PTmaxT Direction

Jet#1 Region

Jet#2 Region

Look at the dependence of the “associated” charged particle density, dNchg/dd, pT > 0.5 GeV/c, || < 1 (not including PTmaxT) relative to PTmaxT (rotated to 180o) for PTmaxT > 2.0 GeV/c for “back-to-back” events with 30 < ET(jet#1) < 70 GeV and 95 < ET(jet#1) < 130 GeV.

Jet#2 Region

Very little dependence on ET(jet#1) in the “transverse” region for “back-to-back” events!

Log Scale!

IMFP2006 - Day 4 April 6, 2006

Rick Field – Florida/CDF/CMS Page 29

““Back-to-Back” vs “Min-Bias”Back-to-Back” vs “Min-Bias”“Associated” Charge Density“Associated” Charge Density

“Back-to-Back”“Associated” Density

“Min-Bias”“Associated” Density

Associated Particle Density: dN/dd

0.1

1.0

10.0

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(degrees)

As

so

cia

ted

Pa

rtic

le D

en

sit

y PTmaxT > 2.0 GeV/c

PTmax > 2.0 GeV/c

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

30 < ET(jet#1) < 70 GeV

PTmaxTPTmax

PTmaxT, PTmax not included

CDF Preliminarydata uncorrected

Min-Bias

PTmax Direction

Correlations in

PTmaxT Direction

Jet#1 Region

Jet#2 Region

Shows the dependence of the “associated” charged particle density, dNchg/dd for pT > 0.5 GeV/c, || < 1 (not including PTmaxT) relative to PTmaxT (rotated to 180o) for PTmaxT > 2.0 GeV/c, for “back-to-back” events with 30 < ET(jet#1) < 70 GeV.

Shows the data on the dependence of the “associated” charged particle density, dNchg/dd, pT > 0.5 GeV/c, || < 1 (not including PTmax) relative to PTmax (rotated to 180o) for “min-bias” events with PTmax > 2.0 GeV/c.

Associated Particle Density: dN/dd

0.1

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(degrees)

As

so

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rtic

le D

en

sit

y PTmaxT > 2.0 GeV/c

PTmax > 2.0 GeV/c

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

CDF Preliminarydata uncorrected

PTmaxTPTmax

PTmaxT, PTmax not included

30 < ET(jet#1) < 70 GeV

Min-Bias x 1.65

“Birth” of jet#1 in “min-bias” collisions!

“Birth” of jet#3 in the “transverse” region!

Log Scale!

IMFP2006 - Day 4 April 6, 2006

Rick Field – Florida/CDF/CMS Page 31

““Associated” PTsum DensityAssociated” PTsum DensityPYTHIA Tune A vs HERWIGPYTHIA Tune A vs HERWIG

Associated PTsum Density: dPT/dd

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su

m D

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Ge

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)

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PY Tune ABack-to-Back

30 < ET(jet#1) < 70 GeV

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

CDF Preliminarydata uncorrectedtheory + CDFSIM

PTmaxT "Jet#1" Region

PTmaxT not included

Data - Theory: Associated PTsum Density dPT/dd

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(degrees)

Da

ta -

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eo

ry

(Ge

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CDF Preliminarydata uncorrectedtheory + CDFSIM

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

Back-to-Back30 < ET(jet#1) < 70 GeV

PYTHIA Tune A

PTmaxT

PTmaxT not included

"Jet#1" Region

Associated PTsum Density: dPT/dd

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su

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y (

Ge

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)

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HERWIGBack-to-Back

30 < ET(jet#1) < 70 GeV

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

CDF Preliminarydata uncorrectedtheory + CDFSIM

PTmaxT "Jet#1" Region

PTmaxT not included

Data - Theory: Associated PTsum Density dPT/dd

-2

-1

0

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2

0 30 60 90 120 150 180 210 240 270 300 330 360

(degrees)

Da

ta -

Th

eo

ry

(Ge

V/c

)

CDF Preliminarydata uncorrectedtheory + CDFSIM

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

Back-to-Back30 < ET(jet#1) < 70 GeV

HERWIG PTmaxT

PTmaxT not included

"Jet#1" Region

HERWIG (without multiple parton interactions) does not produce

enough “associated” PTsum in the direction of PTmaxT!

And HERWIG (without multiple parton interactions) does not

produce enough PTsum in the direction opposite of PTmaxT!

PTmaxT > 0.5 GeV/c

IMFP2006 - Day 4 April 6, 2006

Rick Field – Florida/CDF/CMS Page 32

““Associated” PTsum DensityAssociated” PTsum DensityPYTHIA Tune A vs HERWIGPYTHIA Tune A vs HERWIG

Associated PTsum Density: dPT/dd

0.1

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su

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PY Tune ABack-to-Back

30 < ET(jet#1) < 70 GeV

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

CDF Preliminarydata uncorrectedtheory + CDFSIM

PTmaxT "Jet#1" Region

PTmaxT not included

Associated PTsum Density: dPT/dd

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su

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HERWIGBack-to-Back

30 < ET(jet#1) < 70 GeV

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

CDF Preliminarydata uncorrectedtheory + CDFSIM

PTmaxT "Jet#1" Region

PTmaxT not included

Data - Theory: Associated Particle Density dN/dd

-2.0

-1.0

0.0

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0 30 60 90 120 150 180 210 240 270 300 330 360

(degrees)

Da

ta -

Th

eo

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CDF Preliminarydata uncorrectedtheory + CDFSIM

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

Back-to-Back30 < ET(jet#1) < 70 GeV

PYTHIA Tune A

PTmaxT "Jet#1" Region

PTmaxT > 2.0 GeV/c (not included)

Data - Theory: Associated Particle Density dN/dd

-2

-1

0

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0 30 60 90 120 150 180 210 240 270 300 330 360

(degrees)

Da

ta -

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eo

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CDF Preliminarydata uncorrectedtheory + CDFSIM

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

Back-to-Back30 < ET(jet#1) < 70 GeVHERWIG

PTmaxT "Jet#1" Region

PTmaxT > 2.0 GeV/c (not included)

For PTmaxT > 2.0 GeV both PYTHIA and HERWIG produce

slightly too much “associated” PTsum in the direction of PTmaxT!

But HERWIG (without multiple parton interactions) produces

too few particles in the direction opposite of PTmaxT!

PTmaxT > 2 GeV/c

IMFP2006 - Day 4 April 6, 2006

Rick Field – Florida/CDF/CMS Page 33

Jet MultiplicityJet Multiplicity

Shows the data on the number of jets (JetClu, R = 0.7, || < 2, ET(jet) > 3 GeV) for “back-to-back” events with 30 < ET(jet#1) < 70 GeV and PTmaxT > 2.0 GeV/c.

Jet #1 Direction

“Toward”

“TransMIN” “TransMAX”

PTmaxT

Jet #2 Direction

“Away”

Max pT in the “transverse” region!

Compares the (uncorrected) data with PYTHIA Tune A after CDFSIM.

Jet Multiplicity

0%

10%

20%

30%

40%

50%

0 1 2 3 4 5 6 7 8 9 10

Number of Jets

Pe

rce

nt

of

Ev

en

ts

Data CDF Run 2 Pre-Preliminarydata uncorrectedtheory + CDFSIM

Back-to-Back30 < ET(jet#1) < 70 GeV

PTmaxT > 2.0 GeV/c

Jet Multiplicity

0%

10%

20%

30%

40%

50%

0 1 2 3 4 5 6 7 8 9 10

Number of Jets

Pe

rce

nt

of

Ev

en

ts

Data

PY Tune A

CDF Run 2 Pre-Preliminarydata uncorrectedtheory + CDFSIM

Back-to-Back30 < ET(jet#1) < 70 GeV

PTmaxT > 2.0 GeV/c

Jet Multiplicity

0%

10%

20%

30%

40%

50%

0 1 2 3 4 5 6 7 8 9 10

Number of Jets

Pe

rce

nt

of

Ev

en

ts

Data

HERWIG

CDF Run 2 Pre-Preliminarydata uncorrectedtheory + CDFSIM

Back-to-Back30 < ET(jet#1) < 70 GeV

PTmaxT > 2.0 GeV/c

Compares the (uncorrected) data with HERWIG after CDFSIM.

Data have about equal amounts of 3 and 4 jet topologies!

HERWIG (without multiple parton interactions) does not have equal amounts of 3 and 4 jet topologies!

IMFP2006 - Day 4 April 6, 2006

Rick Field – Florida/CDF/CMS Page 36

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

Underlying Event Underlying Event

Initial-State Radiation

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

Underlying Event Underlying Event

-1 +1

2

0

Central Region

Look at the charged particle density and the

PTsum density in the “central” region!

IMFP2006 - Day 4 April 6, 2006

Rick Field – Florida/CDF/CMS Page 37

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

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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 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

IMFP2006 - Day 4 April 6, 2006

Rick Field – Florida/CDF/CMS Page 38

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

IMFP2006 - Day 4 April 6, 2006

Rick Field – Florida/CDF/CMS Page 39

DrellDrell--Yan ProductionYan Productionat the Tevatronat the Tevatron

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

Underlying Event Underlying Event

Initial-State Radiation

Final-State Radiation

Lepton-Pair Transverse Momentum

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DrellDrell--Yan ProductionYan Productionat the LHCat the LHC

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

Drell-Yan Production

PT(pair)

Lepton-Pair

Outgoing Parton

Underlying Event Underlying Event

Initial-State Radiation

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

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

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

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The “Underlying Event”

Proton AntiProton

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Underlying Event Underlying Event

Initial-State Radiation

Anti-Lepton

Charged Particle Density: dN/dd

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HERWIG (without MPI) is much less active than

PY Tune AW (with MPI)!

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Rick Field – Florida/CDF/CMS Page 42

The “Underlying Event” inThe “Underlying Event” inDrellDrell--Yan Production (LHC)Yan Production (LHC)

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

Drell-Yan Production Lepton

Underlying Event Underlying Event

Initial-State Radiation

Anti-Lepton

Charged Particle Density: dN/dd

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(excluding lepton-pair )

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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)!

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IMFP2006 - Day 4 April 6, 2006

Rick Field – Florida/CDF/CMS Page 43

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”

"Transverse" Charged Particle Density: dN/dd

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Charged particle density versus PT(jet#1)

“Underlying event” much more active at the LHC!

Proton AntiProton

High PT Jet Production

PT(hard)

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Outgoing Parton

Underlying Event Underlying Event

Final-State Radiation

Initial-State Radiation

IMFP2006 - Day 4 April 6, 2006

Rick Field – Florida/CDF/CMS Page 45

UE&MB@CMSUE&MB@CMS

Measure Min-Bias and the “Underlying Event” at CMS The plan involves two phases. Phase 1 would be to measure min-bias and the “underlying event”

as soon as possible (when the luminosity is low), perhaps during commissioning. We would then tune the QCD Monte-Carlo models for all the other CMS analyses. Phase 1 would be a service to the rest of the collaboration. As the measurements become more reliable we would re-tune the QCD Monte-Carlo models if necessary and begin Phase 2.

Phase 2 is “physics” and would include comparing the min-bias and “underlying event” measurements at the LHC with the measurements we have done (and am doing now) at CDF and then writing a physics publication.

Me at CMS!

Darin

UE&MB@CMSRick Field (Florida)

Darin Acosta (Florida) Paolo Bartalini (Florida)Albert De Roeck (CERN)

Livio Fano' (INFN/Perugia at CERN)Filippo Ambroglini (INFN/Perugia at CERN)

Khristian Kotov (UF Student, Acosta)

UE&MB@CMSUE&MB@CMS

IMFP2006 - Day 4 April 6, 2006

Rick Field – Florida/CDF/CMS Page 46

Proton Proton

High PT Jet Production

PT(hard)

Outgoing Parton

Outgoing Parton

Underlying Event Underlying Event

Final-State Radiation

Initial-State Radiation

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)>, ds/dpT(pair) (only requires muons). Event structure for large lepton-pair pT (i.e. +jets, requires muons).

Min-Bias Studies: Charged particle distributions and correlations. Construct “charged particle jets” and look at “mini-jet” structure and the onset of the “underlying event”. (requires only charged tracks)

Proton Proton

Drell-Yan Production Lepton

Underlying Event Underlying Event

Initial-State Radiation

Anti-Lepton

Proton Proton

“Minimum-Bias” Collisions

Proton Proton

Drell-Yan Production

PT(pair)

Lepton-Pair

Outgoing Parton

Underlying Event Underlying Event

Initial-State Radiation

Final-State Radiation

UE&MB@CMSUE&MB@CMS

Study charged particles and muons using the CMS detector

at the LHC (during the pilot run)!