lpc cms workshop june 8, 2007 rick field – florida/cmspage 1 lpc mini-workshop on early cms...

LPC CMS Workshop June 8, 2007

Rick Field – Florida/CMS

LPC Mini-Workshop on LPC Mini-Workshop on Early CMS PhysicsEarly CMS Physics

Proton AntiProton

“Minumum Bias” Collisions

Proton AntiProton

Drell-Yan Production Lepton

Underlying Event Underlying Event

Initial-State Radiation

Anti-Lepton

UE&MB@CMSUE&MB@CMS

Rick FieldUniversity of Florida

(for the UE&MB@CMS Group)

University of Florida

D. Acosta, P. Bartalini, R. Field, K. Kotov

University of Perugia

F. Ambroglini, G. Bilei, L. Fano'

CERN

A. De Roeck

Hamburg

F.Bechtel, P. Schleper, G. Steinbrueck

University of Trieste

D. Treleani et al.

DESY

H. Jung, K. Borras

Summer Student

E. Izaguirre

“Min-Bias” and the “Underlying Event” at the LHC

Proton AntiProton

High PT Jets

PT(hard)

Outgoing Parton

Outgoing Parton


Final-State Radiation

Study charged particlesand muons during the

early running of the LHC!



-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



Charged Particle Density: dN/dd

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

-6 -4 -2 0 2 4 6

Pseudo-Rapidity

dN

/d

d

all PT

CDF Data Pythia 6.206 Set A

630 GeV

1.8 TeV

14 TeV

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


0.0

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0.8

1.0

1.2

1.4

10 100 1,000 10,000 100,000

CM Energy W (GeV)

Ch

arg

ed d

ensi

ty d

N/d

d

Pythia 6.206 Set ACDF DataUA5 DataFit 2Fit 1

= 0

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

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

LHC?

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



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)

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!

1% of “Min-Bias” events have PT(hard) > 10 GeV/c!

12% of “Min-Bias” events have PT(hard) > 10 GeV/c!

LHC?

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



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

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

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

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

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Pa

rtic

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sity

pyA

pyDW

pyDWT

ATLAS

Charged Particles (all pT)

Generator Level14 TeV

Charged Particle Density: dN/dY

0

2

4

6

8

10

12

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

Rapidity Y

Ch

arg

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Pa

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en

sity

pyA

pyDW

pyDWT

ATLAS


Charged Particles (all pT)

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



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

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

min (|| < 1).

Charged PT Distribution

0.1

1.0

10.0

100.0

0.0 0.5 1.0 1.5 2.0 2.5 3.0

Charged Particle PT (GeV/c)

1/N

ev d

N/d

PT

(1/

GeV

/c)

pyA <PT> = 641 MeV/c

pyDW <PT> = 665 MeV/c

pyDWT <PT> = 693 MeV/c

ATLAS <PT> = 548 MeV/c

Charged Particles (||<1.0)

Generator LevelMin-Bias 14 TeV

Average Number of Charged Particles vs PTmin

0

5

10

15

20

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0

Minimum PT (GeV/c)

<N

chg

>

pyA

pyDW

pyDWT

ATLAS

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

Generator LevelMin-Bias 14 TeV

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



TOTEM+CMS: pTOTEM+CMS: pTT-- coverage coverage

RPRP

0-12 -10 -8 -6 -4 -2 +2 +4 +6 +8 +10 +12

0.1

1

10

100

1000 CMSCentral

Detectors

T1T1

T2 T2

pTmax ~ s exp(-)

CA

STO

R

CA

STO

R ZD

C

ZD

C

HFHF

pp TT (

GeV

) (

GeV

)CMS Forward detectors:Hadron Forward Calorimeter HF: 3 ≤|| ≤ 5Castor Calorimeter: 5.2 ≤|| ≤ 6.5Beam Scintillation counters BSCZero-Degree Calorimeter ZDC

Extended Tracking

TOTEM detectors:T1 (CSC) in CMS endcaps, T2 (GEM) behind HFT1 + T2: 3 ≤ || ≤ 6.8Roman Pots with Si det. up to 220 m



A CMS “Min-Bias” TriggerA CMS “Min-Bias” Trigger3<|η|<5

18 wedges/side

0.175×0.175

towers

Cut on the numberof calorimeter cells:

>10 cells hit99% efficient>10 forward cells and>10 backward cells

>15 → 86%

>20 → 66% Use towers or fired cells

Prescaling by a factor 4×107 an HF trigger with high efficiency (e.g.: at least 10 cells fired in + and - detector) → 1 Hz

Tracking Efficiency pT > 0.9 GeV/cversus pseudorapidity

Tracking Efficiency pT > 0.9 GeV/cversus transverse momentum



Detector AlignmentDetector Alignment

Early track studieswill help align the detector!



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


0.0

0.1

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0.4

0.5

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

(degrees)

Ch

arg

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Pa

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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!




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

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en

sit

y

PTmax > 2.0 GeV/c

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!




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

PTmax Direction

Correlations in

Associated Particle Density: dN/dd

0.0

0.2

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0.8

1.0

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

(degrees)

As

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PTmax > 2.0 GeV/c

PY Tune A

PTmax > 0.5 GeV/c

PY Tune A

CDF Preliminarydata uncorrectedtheory + CDFSIM

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

PY Tune A 1.96 TeV

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

PTmax > 2.0 GeV/c

PTmax > 0.5 GeV/c

PTmax Direction

“Toward”


“Away”

Transverse Region Transverse

Region

PY Tune A



QCD Monte-Carlo Models:QCD Monte-Carlo Models:High Transverse Momentum JetsHigh Transverse Momentum Jets

Start with the perturbative 2-to-2 (or sometimes 2-to-3) parton-parton scattering and add initial and final-state gluon radiation (in the leading log approximation or modified leading log approximation).

Hard Scattering

PT(hard)

Outgoing Parton

Outgoing Parton



Hard Scattering

PT(hard)

Outgoing Parton

Outgoing Parton



Proton AntiProton


Proton AntiProton


“Hard Scattering” Component

“Jet”

“Jet”

“Underlying Event”

The “underlying event” consists of the “beam-beam remnants” and from particles arising from soft or semi-soft multiple parton interactions (MPI).

Of course the outgoing colored partons fragment into hadron “jet” and inevitably “underlying event” observables receive contributions from initial and final-state radiation.

“Jet”

The “underlying event” is an unavoidable background to most collider observables and having good understand of it leads to

more precise collider measurements!



Charged Jet #1Direction


“Toward”

“Away”

“Toward-Side” Jet

“Away-Side” Jet

Look at charged particle correlations in the azimuthal angle relative to the leading charged particle jet.

Define || < 60o as “Toward”, 60o < || < 120o as “Transverse”, and || > 120o as “Away”.All three regions have the same size in - space, x = 2x120o = 4/3.

Charged Jet #1Direction

“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

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

CDF Run 1 Analysis

The Evolution of Charged JetsThe Evolution of Charged Jetsand the “Underlying Event”and the “Underlying Event”

-1 +1

2

0

Leading Jet

Toward Region

Transverse Region

Transverse Region

Away Region

Away Region

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

-2 +2

UE&MB@CMS



The Evolution of Charged JetsThe Evolution of Charged Jetsand the “Underlying Event” at the LHCand the “Underlying Event” at the LHC

Shows average “transverse” charge particle density (|| < 1, pT> 0.9 GeV) versus PT(charged jet#1) prediced by PYTHIA Tune DW, HERWIG, and the ATLAS PYTHIA Tune at the LHC .

"Transverse" Charged Particle Density: dN/dd

0.0

0.3

0.6

0.9

1.2

0 25 50 75 100 125 150 175 200

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

"Tra

nsv

erse

" C

har

ge

d D

ensi

ty


Leading Charged Jet (||<1.0)Charged Particles (||<1.0, PT>0.9 GeV/c)

PY Tune DW

HERWIG

PY-ATLAS

"Transverse" PTsum Density: dPT/dd

0.0

1.0

2.0

3.0

0 25 50 75 100 125 150 175 200

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

"Tra

nsv

erse

" P

Tsu

m D

ens

ity

(Ge

V/c

)


Leading Charged Jet (||<1.0)Charged Particles (||<1.0, PT>0.9 GeV/c)

PY Tune DW

HERWIG

PY-ATLASMCMBJET60JET120

PT>0.9, ||<1 MCMBJET60JET120

PT>0.9, ||<1MCMBJET60JET120

Ratio PT>0.9GeV/PT>0.5GeV

MCMBJET60JET120

Ratio PT>0.9GeV/PT>0.5GeV

Shows average “transverse” charge particle PTsum density (|| < 1, pT> 0.9 GeV) versus PT(charged jet#1) prediced by PYTHIA Tune DW, HERWIG, and the ATLAS PYTHIA Tune at the LHC .

Shows average “transverse” charge particle PTsum density (|| < 1, pT> 0.9 GeV) versus PT(charged jet#1) at the generator level and at the detector level .

Shows average “transverse” charge particle density (|| < 1, pT> 0.9 GeV) versus PT(charged jet#1) at the generator level and at the detector level .

Shows the ratio, (pT>0.9 GeV/c)/(pT>0.5 GeV/c), for the “transverse” charge particle and PTsum density (|| < 1) versus PT(charged jet#1) at the generator level and at the detector level .



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

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

Proton AntiProton


Proton AntiProton


“Hard Scattering” Component

Lepton-Pair Production

Lepton

Anti-Lepton


Lepton-Pair Production

Lepton

Anti-Lepton


“Underlying Event”

The “underlying event” consists of the “beam-beam remnants” and from particles arising from soft or semi-soft multiple parton interactions (MPI).

Of course the outgoing colored partons fragment into hadron “jet” and inevitably “underlying event” observables receive contributions from initial and final-state radiation.

“Jet”



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

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

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

Proton AntiProton




Anti-Lepton

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

After removing the lepton-pair everything else is the

“underlying event”!

Proton AntiProton

Multiple Parton Interactions

Anti-Lepton

Lepton


-1 +1

2

0

Central Region

Look at the charged particle density and the

PTsum density in the “central” region!



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).

Proton AntiProton




Anti-Lepton

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).

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


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

Normalized to 1LHC

Tevatron Run2

Z

Drell-Yan PT(+-) Distribution

1.0E-04

1.0E-03

1.0E-02

1.0E-01

1.0E+00

1.0E+01

1.0E+02

0 50 100 150 200 250

PT (+-) (GeV/c)

ds /

dP

T (

pb

/GeV

)

Drell-Yangenerator level

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

LHC

Tevatron Run2




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


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0 50 100 150 200 250


Ch

arg

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arti

cle

De

nsi

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RDF Preliminarygenerator level

Drell-Yan1.96 TeV

PY Tune AW

HERWIG

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


0.0

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RDF Preliminarygenerator level

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

(excluding lepton-pair )

PY Tune AW

HERWIG

LHC

CDF

Charged particle density versus M(pair)

“Underlying event” much more active at the LHC!

HERWIG (without MPI) is much less active than

PY Tune AW (with MPI)!

Z

Z



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

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

Proton AntiProton




Anti-Lepton

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

The “Underlying Event”Charged particle density

versus M(pair)

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

dependence!


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1.0

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2.0

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0 100 200 300 400 500 600 700 800 900 1000


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Den

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RDF Preliminary generator level

14 TeV

HERWIG

PY-ATLAS

PY Tune DW

PY Tune DWT

Z


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HERWIG

PY Tune BWPY Tune DW

PY Tune A PY Tune AW

1.96 TeV

Z


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1.96 TeV Drell-Yan


HERWIG

PY Tune DWPY-ATLAS

PY Tune A

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




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

Proton AntiProton




Anti-Lepton

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

The “Underlying Event”Charged particle charged

PTsum density versus M(pair)

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

the CDF Run 2 Tunes!

Charged PTsum Density: dPT/dd

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1.2

0 50 100 150 200 250 300 350 400 450 500


Ch

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Tsu

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ensi

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GeV

/c)

HERWIG

PY Tune BWRDF Preliminary generator level

PY Tune A

PY Tune AWPY Tune DW


1.96 TeV

Z Z


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1.0

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5.0

0 100 200 300 400 500 600 700 800 900 1000


Ch

arg

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PT

sum

De

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GeV

/c)

14 TeV Drell-Yan


HERWIG

PY-ATLAS

PY Tune DWPY Tune DWT



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0 50 100 150 200 250 300 350 400 450 500


Ch

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PT

sum

De

nsi

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GeV

/c)


1.96 TeV Drell-Yan


HERWIG

PY-ATLAS

PY Tune DW

PY Tune A

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




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

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

The “Underlying Event”

Proton AntiProton




Anti-Lepton

Charged particle density versus M(pair)

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


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0.5

1.0

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14 TeV

HERWIG

PY-ATLAS

PY Tune DW

PY Tune DWT

Z Z


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Ch

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HERWIG

PY-ATLASPY Tune DW

PY Tune DWT

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


0.0

1.0

2.0

3.0

4.0

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8

Minimum pT (GeV/c)

Ch

arg

ed P

arti

cle

Den

sity

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

(excluding lepton-pair )

Drell-YanGenerator Level

14 TeV

70 < M(+-) < 110 GeV

HERWIG

PY Tune DW

PY-ATLAS

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

the CDF Run 2 Tunes!



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 chgjet” and “back-to-back” chgjet production and in 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. +chgjets, requires muons and charged tracks).

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




Paolo

Filippo

Gian Mario Me (Jimmy) Livio

Perugia, March 2006

lpc cms workshop june 8, 2007 rick field – florida/cmspage 1 lpc mini-workshop on early cms...

Documents

bias predictionspythia

pythia tune dwt

pythia tune alhc

predictions of pythia

bias predictionsthe

charged particles pt

gevc h

bias events