studying the “underlying event” at cdf

“Leading Jet” vs Z-BosonInitial-State Radiation Final-State Radiation ¨ The “Towards”, “Away”, and “Transverse” regions of η-φ space.. Transverse Region Transverse Region Away Region

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“Leading Jet” vs Z-Boson

Initial-State Radiation

Final-State Radiation

¨ The “Towards”, “Away”, and “Transverse”

regions of η-φ space.

¨ Four Jet Topologies.

¨ The “transMAX” and “transMIN” regions.

¨ The observables: First look at average quantities Then do

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“Leading Jet” vs Z-Boson

¨ The “Towards”, “Away”, and “Transverse”

regions of η-φ space.

¨ Four Jet Topologies.

¨ The “transMAX” and “transMIN” regions.

¨ The observables: First look at average quantities Then do

collisions.

Rick Field Craig Group Deepak Kar

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QCD Monte-Carlo Models:

High Transverse Momentum Jets

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

Underlying Event Underlying Event

“Hard Scattering” Component

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QCD Monte-Carlo Models:

High Transverse Momentum Jets

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

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Transverse Region

Transverse Region Away Region

“Towards”, “Away”, “Transverse”

¨ Look at correlations in the azimuthal angle Δφ relative to the leading charged particle jet (|η| <

1) or the leading calorimeter jet (| η| < 2).

¨ Define | Δφ| < 60o as “Toward” , 60o < | Δφ| < 120o as “Transverse ” , and | Δφ| > 120o as “Away”

Δφ Correlations relative to the leading jet

Charged particles pT > 0.5 GeV/c | η| < 1

Calorimeter towers ET > 0.1 GeV | η| < 1

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Transverse Region

Transverse Region Away Region

¨ Look at correlations in the azimuthal angle Δφ relative to the leading charged particle jet (|η| <

1) or the leading calorimeter jet (| η| < 2).

¨ Define | Δφ| < 60o as “Toward” , 60o < | Δφ| < 120o as “Transverse ” , and | Δφ| > 120o as “Away”

Δφ Correlations relative to the leading jet

Charged particles pT > 0.5 GeV/c | η| < 1

Calorimeter towers ET > 0.1 GeV | η| < 1

Z-Boson Direction

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Event Topologies

¨ “Leading Jet” events correspond to the leading

calorimeter jet (MidPoint R = 0.7) in the region | η| < 2

with no other conditions.

¨ “Leading ChgJet” events correspond to the leading

charged particle jet (R = 0.7) in the region | η| < 1 with

¨ “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” ( Δφ12> 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” ( Δφ12 > 150o) with almost equal transverse

energies (PT(jet#2)/PT(jet#1) > 0.8) and PT(jet#3) < 15

¨ “Z-Boson” events are Drell-Yan events

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“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 η-φ space of 4π/6.

¨ The “transMIN” region is very sensitive to the “beam-beam remnant” and the soft

multiple parton interaction components of the “underlying event”.

¨ 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).

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

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calorimeter towers (E T > 0.1 GeV, | η| < 1)

(p T > 0.5 GeV/c, | η| < 1)

all particles (all p T , | η| < 1)

per unit η-φ (E T > 0.1 GeV, | η| < 1)

per unit η-φ (all p T , | η| < 1)

(p T > 0.5 GeV/c, | η| < 1) Require Nchg ≥ 1

per unit η-φ (p T > 0.5 GeV/c, | η| < 1)

Number of “good” charged tracks

Number of charged particles

dN chg /d ηdφ

Detector Level Particle Level

Observable

“Leading Jet”

“Leading Jet” Observables at the

Particle and Detector Level

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CDF Run 1 P T (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

2.1

1.0 PARP(91)

1

1 MSTP(91)

1.25 0.25 1.8 TeV 0.95 0.9 0.4 0.5 2.0 GeV 4 1 Tune AW

PARP(62)

PARP(85)

PARP(82) MSTP(82) MSTP(81) Parameter

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

CDF Run 1

published

1.8 TeV Normalized to 1

Tune used by the CDF-EWK group!

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Jet-Jet Correlations (DØ)

¨ 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) =

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CDF Run 1 P T (Z)

¨ Shows the Run 1 Z-boson pT distribution (<pT(Z)>

≈ 11.5 GeV/c) compared with PYTHIA Tune DW , and HERWIG

4.0 2.5

2.1

2.1 PARP(91)

1

1 MSTP(91)

1.25 0.25 1.8 TeV 0.95 0.9 0.4 0.5 2.0 GeV 4 1 Tune AW

PARP(62)

PARP(85)

PARP(82) MSTP(82) MSTP(81)

CDF Run 1

published

1.8 TeV Normalized to 1

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

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PYTHIA 6.2 Tunes

15.0 2.1 1 4.0 0.2 1.25 0.25 1.8 TeV 0.95 0.9 0.4 0.5 2.0 GeV 4 1 CTEQ5L Tune AW

15.0 2.1 1 2.5 0.2 1.25 0.25 1.8 TeV 1.0 1.0 0.4 0.5 1.8 GeV 4 1

CTEQ6L

Tune D6

CTEQ5L PDF

1.25 PARP(62)

0.2 PARP(64)

0.4 PARP(84)

0.25 PARP(90)

1.0 PARP(86)

1.8 TeV PARP(89)

2.5

1.0

1.9 GeV 4 1 Tune DW

PARP(67)

PARP(85)

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PYTHIA 6.2 Tunes

15.0 2.1 1 2.5 0.2 1.25 0.16 1.96 TeV 1.0 1.0 0.4 0.5 1.8387 GeV 4 1

CTEQ6L Tune D6T

5.0 1.0 1 1.0 1.0 1.0 0.16 1.0 TeV 0.66 0.33 0.5 0.5 1.8 GeV 4 1 CTEQ5L

ATLAS CTEQ5L

PDF

1.25 PARP(62)

0.2 PARP(64)

0.4 PARP(84)

0.16 PARP(90)

1.0 PARP(86)

1.96 TeV PARP(89)

2.5

1.0

1.9409 GeV 4 1 Tune DWT

PARP(67)

PARP(85)

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scalarp T sum of charged particles (p T > 0.5 GeV/c, |η| < 1) and the overall scalarET sum of all

Overall Totals versus PT(jet#1)

1 10 100 1000

"Leading Jet"

MidPoint R=0.7 | η(jet#1)|<2

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

Stable Particles (| η|<1.0, all PT)

ETsum (GeV)

PTsum (GeV/c)

Nchg

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scalarp T sum of charged particles (p T > 0.5 GeV/c, |η| < 1) and the overall scalarET sum of all

Overall Totals versus PT(jet#1)

1 10 100 1000

"Leading Jet"

Stable Particles (| η|<1.0, all PT)

ETsum (GeV)

PTsum (GeV/c)

Nchg

Nchg = 30 PTsum = 190 GeV/c

ETsum = 330 GeV

ETsum = 775 GeV!

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Overall Number of Charged Particles

0 10 20 30 40

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0 10 20 30 40

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0 10 20 30 40

Overall ETsum versus PT(jet#1)

0 200 400 600 800

PY Tune A

HW

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0 1 2 3 4 5

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0 1 2 3 4 5

level).

Factor of ~4.5

0.1 1.0 10.0 100.0

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0 1 2 3 4 5

level).

Factor of ~4.5

0.1 1.0 10.0 100.0

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Deepak Kar’s Thesis

Charged Particle Density: dN/d ηdφ

0 1 2 3

excluding the lepton-pair

Factor of ~3

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level).

Deepak Kar’s Thesis

Charged Particle Density: dN/d ηdφ

0 1 2 3

Factor of ~3

Charged PTsum Density: dPT/d ηdφ

0.1 1.0 10.0

Factor of ~11

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0 1 2 3 4

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0 1 2 3 4

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0 1 2 3 4

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0 1 2 3 4 5

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0 1 2 3 4 5

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0 1 2 3 4 5

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"Transverse" Average PTmax

0.0 1.0 2.0 3.0 4.0

"Leading Jet"

Excludes events with no "Transverse" Charged Particles

PY Tune A

HW

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“Charged Particle Density”

“transverse” regions The data are corrected to the particle level (with errors that include both the statistical

"Transverse"

"Toward"

"Drell-Yan Production"

70 < M(pair) < 110 GeV

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"Transverse"

"Toward"

70 < M(pair) < 110 GeV

"Transverse" Charged Particle Density: dN/d ηdφ

"Leading Jet"

"Z-Boson"

"Away" Charged Particle Density: dN/d ηdφ

0 1 2 3 4

"Leading Jet"

"Z-Boson"

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"Transverse" Charged PTsum Density: dPT/d ηdφ

"Leading Jet"

"Z-Boson"

"Away" Charged PTsum Density: dPT/d ηdφ

0 5 10 15 20

"Leading Jet"

"Z-Boson"

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HERWIG (without MPI).

“transverse” region!

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“toward” region for “Z-Boson” and the “transverse” region for “Leading Jet” events as a function of

70 < M(pair) < 110 GeV Charged Particles (| η|<1.0, PT>0.5 GeV/c)

pyDW ATLAS

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“Charged PTsum Density”

70 < M(pair) < 110 GeV

excluding the lepton-pair HW

pyAW

ATLAS pyDW

the “toward” region for “Z-Boson” and the “transverse” region for “Leading Jet” events as a

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“transverse” region!

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The Leading Jet Mass

PY Tune A

HW

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The Leading Jet Mass

PY Tune A

HW

Leading Jet Invariant Mass

-4.0 0.0 4.0 8.0 12.0

"Leading Jet"

Off by ~2 GeV

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and ETsum (all p T , |η| < 1) and for PTsum (p T > 0.5 GeV/c, |η| < 1) and ETsum (all p T , |η| < 1) for “leading

ETsum Stable Particles (| η|<1.0, all PT)

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

PTsum Charged Particles (| η|<1.0, all PT)

PY Tune A

HW

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and ETsum (all p T , |η| < 1) and for PTsum (p T > 0.5 GeV/c, |η| < 1) and ETsum (all p T , |η| < 1) for “leading

PTsum Charged Particles (| η|<1.0, all PT)

"Leading Jet"

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The “TransMAX/MIN” Regions

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Z-Boson: “Towards” Region

excluding the lepton-pair HW

pyAW

pyDW ATLAS

70 < M(pair) < 110 GeV

Tevatron LHC10

LHC14

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HW

pyAW

pyDW ATLAS

70 < M(pair) < 110 GeV

Tevatron LHC10

LHC14

"Toward" Charged Particle Density: dN/d ηdφ

0.0 0.3 0.6 0.9

HW generator level

70 < M(pair) < 110 GeV

excluding the lepton-pair Tevatron

HW LHC14 pyDWT LHC14

pyDWT Tevatron

HW Tevatron DWT

HW without MPI

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pyDWT Tevatron

HW Tevatron HW LHC14

CDF Run 2 Preliminary data corrected generator level theory

DWT

HW (without MPI) almost no change!

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¨ Shows the average transverse momentum of charged particles (| η|<1, pT>0.5 GeV)

PYTHIA Tune A 1.96 TeV

Min-Bias

Charged <P T > versus N chg

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Average PT versus Nchg

0.6 0.8 1.0 1.2 1.4 1.6

PYTHIA Tune A 1.96 TeV

Min-Bias

2 Min-Bias events.

The charged <PT>

rises with Nchg!

Charged <P T > versus N chg

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Min-Bias Correlations

generator level theory

Min-Bias 1.96 TeV

ATLAS pyA

pyDW

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ATLAS pyA

0.6 1.0 1.4 1.8 2.2 2.6

PYTHIA Tune A, Tune DW, and the ATLAS tune at the particle level (i.e generator level).

¨

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ATLAS pyA

0.6 1.0 1.4 1.8 2.2 2.6

PYTHIA Tune A, Tune DW, and the ATLAS tune at the particle level (i.e generator level).

compared with “min-bias”!

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¨ 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 to

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” in jet production and

in Drell-Yan Tune A and Tune AW describe the data

very well, although not perfect However, we do not

yet have a perfect fit to all the features of the CDF

“underlying event” data!

¨ I plan to construct a “CDF-QCD Data for Theory”

WEBsite with the “blessed” plots together with CDF-QCD Data for Theory

¨ Perhaps looking at <pT> versus Nchg in Drell-Yan with

70 < Mpair) < 110 GeV and PT(pair) < 5 GeV is a good

way to look at the color connections Data coming soon! Proton AntiProton

Drell-Yan Production

Anti-Lepton

Lepton

Tiêu đề	Studying the “Underlying Event” at CDF
Trường học	University of Florida
Chuyên ngành	High Energy Physics / Particle Physics
Thể loại	presentation
Năm xuất bản	2008
Thành phố	Gainesville

Định dạng
Số trang	67
Dung lượng	1,42 MB