Studying the
“Underlying Event” at CDF
“Leading Jet” vs Z-Boson
Rick Field
University of Florida
Outline of Talk
CDF Run 2
goal is to produce data (corrected
to the
“Leading Jet”
 The “Towards”, “Away”,The
and “Transverse”
particle level) that can be used by the theorists to
regions of h-f space.
tune and improve the QCD Monte-Carlo
models
Proton
 Four Jet Topologies.
that are used to simulate hadron-hadron
Underlying Event
collisions.
 The “transMAX” and “transMIN”
regions.
Rick Field
 The “underlying event” in Drell-Yan production.
Outgoing Parton
Group
 The observables: First look at averageCraig
quantities.
Then do
distributions.
Deepak Kar
 Look at <pT> versus Nchg in “min-bias” and
Drell-Yan.
 Show some extrapolations of Drell-Yan to the LHC.
Fourth HERA-LHC Workshop
May 26-30, 2008
Rick Field – Florida/CDF/CMS
Outgoing Parton
PT(hard)
Initial-State Radiation
AntiProton
Underlying Event
Final-State
Radiation
Drell-Yan Production
Proton
Lepton
AntiProton
Underlying Event
Underlying Event
Anti-Lepton
Page 1
QCD Monte-Carlo Models:
High Transverse Momentum Jets
Hard Scattering
Initial-State Radiation
Hard Scattering “Jet”
Initial-State Radiation
“Jet”
Outgoing Parton
PT(hard)
Outgoing Parton
PT(hard)
Proton
“Hard Scattering” Component
AntiProton
Final-State Radiation
Outgoing Parton
Underlying Event
Underlying Event
Proton
“Jet”
Final-State Radiation
AntiProton
Underlying Event
Outgoing Parton
Underlying Event
“Underlying Event”
 Start with the perturbative 2-to-2 (or sometimes 2-to-3) parton-parton scattering and add initial and finalstate gluon radiation (in the leading log approximation or modified leading log approximation).
 The “underlying event” consists of the “beam-beam remnants” and from particles arising from soft or
semi-soft multiple parton interactions (MPI).
The “underlying
event” is“jet”
an unavoidable
 Of course the outgoing colored partons fragment
into hadron
and inevitably “underlying event”
background to most collider observables
observables receive contributions from initial
and final-state radiation.
and having good understand of it leads to
more precise collider measurements!
Fourth HERA-LHC Workshop
May 26-30, 2008
Rick Field – Florida/CDF/CMS
Page 2
QCD Monte-Carlo Models:
Lepton-Pair Production
Lepton-Pair Production
Anti-Lepton
Initial-State Radiation
Lepton-Pair Production
Initial-State Radiation
“Jet”
Proton
Anti-Lepton
“Hard Scattering” Component
AntiProton
Lepton
Underlying Event
Underlying Event
Proton
Lepton
AntiProton
Underlying Event
Underlying Event
“Underlying Event”
 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).
 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.
Fourth HERA-LHC Workshop
May 26-30, 2008
Rick Field – Florida/CDF/CMS
Page 3
“Towards”, “Away”, “Transverse”
Look at the charged
particle density, the
charged PTsum density
and the ETsum density in
all 3 regions!
f Correlations relative to the leading jet
Jet #1 Direction
“Transverse” region is
very sensitive to the
“underlying event”!
Charged particles pT > 0.5 GeV/c |h| < 1
Calorimeter towers ET > 0.1 GeV |h| < 1
“Toward-Side” Jet
2
Away Region
Z-Boson
Direction
Jet #1 Direction
f
f
Transverse
Region
“Toward”
“Toward”
“Transverse”
“Transverse”
“Away”
“Transverse”
“Transverse”
f
Leading
Jet
Toward Region
“Away”
Transverse
Region
“Away-Side” Jet
Away Region
0
-1
h
+1
 Look at correlations in the azimuthal angle frelative to the leading charged particle jet (|h| <
1) or the leading calorimeter jet (|h| < 2).
 Define |f| < 60o as “Toward”, 60o < |f| < 120o as “Transverse ”, and |f| > 120o as “Away”.
o
Each of the three regions have area hf = 2×120 = 4/3.
Fourth HERA-LHC Workshop
May 26-30, 2008
Rick Field – Florida/CDF/CMS
Page 4
Event Topologies
 “Leading Jet” events correspond to the leading
calorimeter jet (MidPoint R = 0.7) in the region |h| < 2
with no other conditions.
 “Inclusive 2-Jet Back-to-Back” events are selected to
have at least two jets with Jet#1 and Jet#2 nearly “backto-back” (f12 > 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 “backto-back” (f12 > 150o) with almost equal transverse
energies (PT(jet#2)/PT(jet#1) > 0.8) and PT(jet#3) < 15
GeV/c.
 “Leading ChgJet” events correspond to the leading
charged particle jet (R = 0.7) in the region |h| < 1 with
no other conditions.
 “Z-Boson” events are Drell-Yan events
with 70 < M(lepton-pair) < 110 GeV
with no other conditions.
Fourth HERA-LHC Workshop
May 26-30, 2008
Rick Field – Florida/CDF/CMS
Jet #1 Direction
f
“Leading Jet”
“Toward”
“Transverse”
“Transverse”
subset
“Away”
Jet #1 Direction
f
“Inc2J Back-to-Back”
“Toward”
subset
“Transverse”
“Transverse”
“Away”
“Exc2J Back-to-Back”
Jet #2 Direction
ChgJet #1 Direction
f
“Charged Jet”
“Toward”
“Transverse”
“Transverse”
“Away”
Z-Boson Direction
f
“Toward”
Z-Boson
“Transverse”
“Transverse”
“Away”
Page 5
“transMAX” & “transMIN”
Jet #1 Direction
Jet #1 Direction
f
Area = 4/6
“transMIN” very sensitive to
the “beam-beam remnants”!
“Toward-Side” Jet
f
“Toward”
“TransMAX”
“Toward”
“TransMIN”
“TransMAX”
“Away”
“TransMIN”
Jet #3
“Away”
“Away-Side” Jet
 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 h-f space of 4/6.
 The “transMIN” region is very sensitive to the “beam-beam remnant” and the soft
multiple parton interaction components of the “underlying event”.
 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).
 The overall “transverse” density is the average of the “transMAX” and “transMIN”
densities.
Fourth HERA-LHC Workshop
May 26-30, 2008
Rick Field – Florida/CDF/CMS
Page 6
“Leading Jet” Observables at the
Particle and Detector Level
“Leading Jet”
Jet #1 Direction
Observable
Particle Level
Detector Level
dNchg/dhdf
Number of charged particles
per unit h-f
(pT > 0.5 GeV/c, |h| < 1)
Number of “good” charged tracks
per unit h-f
(pT > 0.5 GeV/c, |h| < 1)
dPTsum/dhdf
Scalar pT sum of charged particles
per unit h-f
(pT > 0.5 GeV/c, |h| < 1)
Scalar pT sum of “good” charged tracks per
unit h-f
(pT > 0.5 GeV/c, |h| < 1)
<pT>
Average pT of charged particles
(pT > 0.5 GeV/c, |h| < 1)
Average pT of “good” charged tracks
(pT > 0.5 GeV/c, |h| < 1)
PTmax
Maximum pT charged particle
(pT > 0.5 GeV/c, |h| < 1)
Require Nchg ≥ 1
Maximum pT “good” charged tracks
(pT > 0.5 GeV/c, |h| < 1)
Require Nchg ≥ 1
dETsum/dhdf
Scalar ET sum of all particles
per unit h-f
(all pT, |h| < 1)
Scalar ET sum of all calorimeter towers
per unit h-f
(ET > 0.1 GeV, |h| < 1)
PTsum/ETsum
Scalar pT sum of charged particles
(pT > 0.5 GeV/c, |h| < 1)
divided by the scalar ET sum of
all particles (all pT, |h| < 1)
Scalar pT sum of “good” charged tracks
(pT > 0.5 GeV/c, |h| < 1)
divided by the scalar ET sum of
calorimeter towers (ET > 0.1 GeV, |h| < 1)
f
“Toward”
“Transverse”
“Transverse”
“Away”
Jet #1 Direction
f
“Toward”
“Transverse”
“Transverse”
“Away”
Jet #2 Direction
“Back-to-Back”
Fourth HERA-LHC Workshop
May 26-30, 2008
Also include the leading jet mass (new)!
Rick Field – Florida/CDF/CMS
Page 7
CDF Run 1 PT(Z)
Parameter
Tune A
Tune AW
UE Parameters 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
ISR Parameters
Z-Boson Transverse Momentum
0.12
PT Distribution 1/N dN/dPT
PYTHIA 6.2 CTEQ5L
Tune used by the
CDF-EWK group!
CDF Run 1 Data
PYTHIA Tune A
PYTHIA Tune AW
CDF Run 1
published
0.08
1.8 TeV
Normalized to 1
0.04
0.00
0
2
4
6
8
10
12
14
16
18
Z-Boson PT (GeV/c)
 Shows the Run 1 Z-boson pT distribution (<pT(Z)>
≈ 11.5 GeV/c) compared with PYTHIA Tune A
(<pT(Z)> = 9.7 GeV/c), and PYTHIA Tune AW
(<pT(Z)> = 11.7 GeV/c).
Effective Q cut-off, below which space-like showers are not evolved.
Intrensic KT
The Q2 = kT2 in as for space-like showers is scaled by PARP(64)!
Fourth HERA-LHC Workshop
May 26-30, 2008
20
Rick Field – Florida/CDF/CMS
Page 8
Jet-Jet Correlations (DØ)
Jet#1-Jet#2 f Distribution
f Jet#1-Jet#2
 MidPoint Cone Algorithm (R = 0.7, fmerge = 0.5)
 L = 150 pb-1 (Phys. Rev. Lett. 94 221801 (2005))
 Data/NLO agreement good. Data/HERWIG agreement
good.
 Data/PYTHIA agreement good provided PARP(67) =
1.0→4.0 (i.e. like Tune A, best fit 2.5).
Fourth HERA-LHC Workshop
May 26-30, 2008
Rick Field – Florida/CDF/CMS
Page 9
CDF Run 1 PT(Z)
PYTHIA 6.2 CTEQ5L
Tune DW
Tune AW
UE Parameters MSTP(81)
1
1
MSTP(82)
4
4
PARP(82)
1.9 GeV
2.0 GeV
PARP(83)
0.5
0.5
PARP(84)
0.4
0.4
PARP(85)
1.0
0.9
PARP(86)
1.0
0.95
PARP(89)
1.8 TeV
1.8 TeV
PARP(90)
0.25
0.25
PARP(62)
1.25
1.25
PARP(64)
0.2
0.2
PARP(67)
2.5
4.0
MSTP(91)
1
1
PARP(91)
2.1
2.1
PARP(93)
15.0
15.0
ISR Parameters
PT Distribution 1/N dN/dPT
Parameter
Z-Boson Transverse Momentum
0.12
CDF Run 1 Data
PYTHIA Tune DW
HERWIG
CDF Run 1
published
0.08
1.8 TeV
Normalized to 1
0.04
0.00
0
2
4
6
8
10
12
14
16
18
20
Z-Boson PT (GeV/c)
 Shows the Run 1 Z-boson pT distribution (<pT(Z)>
≈ 11.5 GeV/c) compared with PYTHIA Tune DW,
and HERWIG.
Tune DW uses D0’s perfered value of PARP(67)!
Intrensic KT
Tune DW has a lower value of PARP(67) and slightly more MPI!
Fourth HERA-LHC Workshop
May 26-30, 2008
Rick Field – Florida/CDF/CMS
Page 10
All use LO as
with L = 192 MeV!
UE Parameters
ISR Parameter
PYTHIA 6.2 Tunes
Parameter
Tune AW
Tune DW
Tune D6
PDF
CTEQ5L
CTEQ5L
CTEQ6L
MSTP(81)
1
1
1
MSTP(82)
4
4
4
PARP(82)
2.0 GeV
1.9 GeV
1.8 GeV
PARP(83)
0.5
0.5
0.5
PARP(84)
0.4
0.4
0.4
PARP(85)
0.9
1.0
1.0
PARP(86)
0.95
1.0
1.0
PARP(89)
1.8 TeV
1.8 TeV
1.8 TeV
PARP(90)
0.25
0.25
0.25
PARP(62)
1.25
1.25
1.25
PARP(64)
0.2
0.2
0.2
PARP(67)
4.0
2.5
2.5
MSTP(91)
1
1
1
PARP(91)
2.1
2.1
2.1
PARP(93)
15.0
15.0
15.0
Uses CTEQ6L
Tune A energy dependence!
Intrinsic KT
Fourth HERA-LHC Workshop
May 26-30, 2008
Rick Field – Florida/CDF/CMS
Page 11
All use LO as
with L = 192 MeV!
UE Parameters
ISR Parameter
PYTHIA 6.2 Tunes
Parameter
Tune DWT
Tune D6T
ATLAS
PDF
CTEQ5L
CTEQ6L
CTEQ5L
MSTP(81)
1
1
1
MSTP(82)
4
4
4
PARP(82)
1.9409 GeV
1.8387 GeV
1.8 GeV
PARP(83)
0.5
0.5
0.5
PARP(84)
0.4
0.4
0.5
PARP(85)
1.0
1.0
0.33
PARP(86)
1.0
1.0
0.66
PARP(89)
1.96 TeV
1.96 TeV
1.0 TeV
PARP(90)
0.16
0.16
0.16
PARP(62)
1.25
1.25
1.0
PARP(64)
0.2
0.2
1.0
PARP(67)
2.5
2.5
1.0
MSTP(91)
1
1
1
PARP(91)
2.1
2.1
1.0
PARP(93)
15.0
15.0
5.0
ATLAS energy dependence!
Intrinsic KT
Fourth HERA-LHC Workshop
May 26-30, 2008
Rick Field – Florida/CDF/CMS
Page 12
Overall Totals (|h| < 1)
ETsum = 775 GeV!
“Leading Jet”
Overall Totals versus PT(jet#1)
ETsum = 330 GeV
1000
CDF Run 2 Preliminary
ETsum (GeV)
data corrected
pyA generator level
Jet #1 Direction
f
PTsum (GeV/c)
Average
100
“Overall”
Nchg
"Leading Jet"
MidPoint R=0.7 |h(jet#1)|<2
10
PTsum = 190 GeV/c
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
Stable Particles (|h|<1.0, all PT)
1
0
50
Nchg = 30
100
150
200
250
300
350
400
PT(jet#1) (GeV/c)
 Data at 1.96 TeV on the overall number of charged particles (pT > 0.5 GeV/c, |h| < 1) and the overall
scalar pT sum of charged particles (pT > 0.5 GeV/c, |h| < 1) and the overall scalar ET sum of all
particles (|h| < 1) for “leading jet” events as a function of the leading jet pT. The data are corrected to
the particle level (with errors that include both the statistical error and the systematic uncertainty) and
are compared with PYTHIA Tune A at the particle level (i.e. generator level)..
Fourth HERA-LHC Workshop
May 26-30, 2008
Rick Field – Florida/CDF/CMS
Page 13
Overall Totals (|h| < 1)
“Leading Jet”
Overall
Number
ofversus
Charged
Particles
Overall
Charged
PTsum
Overall
ETsum
PT(jet#1)
Jet #1 Direction
f
Average
PTsum
Average
ETsum
(GeV)
Average
Number
of(GeV/c)
Charged
Particles
400
80040
CDF
Run
CDF
Run
2Preliminary
Preliminary
CDF
Run
22 Preliminary
300
60030
PY Tune A
data
corrected
data
corrected
data
corrected
generator
level
theory
generator
level
theory
generator
level
theory
HW
PY Tune A
PY Tune A
200
40020
“Overall”
20010
100
"Leading Jet"
"Leading Jet"
MidPoint R=0.7 |h(jet#1)|<2
MidPoint R=0.7 |h(jet#1)|<2
HW
HW
00 0
00 0
50
50
50
100
100
150
150
ChargedStable
Particles
(|h|<1.0,
PT>0.5
GeV/c)
Particles
(|h|<1.0,
all
PT)
Charged
Particles
(|h|<1.0,
PT>0.5
GeV/c)
200
200
250
250
300
300
350
350
400
400
PT(jet#1)
PT(jet#1) (GeV/c)
(GeV/c)
Data
at
1.96
TeV
on
the
overall
number
ofsum
charged
(p(|h|
0.5
|h| < 1)
“leading
events
 Data
ofofcharged
particles
>
GeV/c,
|h|for
<events
1)
for as
“leading
jet”
T ><(p
Data at
at 1.96
1.96 TeV
TeV on
on the
the overall
overall scalar
scalar pET
allparticles
particles
1)T GeV/c,
for0.5
“leading
jet”
ajet”
function
T sum
as
function
ofjetthe
jet are
pT. The
are
corrected
tolevel
the particle
levelthat
(with
errors
that
include
both
events
as a function
thedata
leading
jet pdata
data
are
corrected
to theerrors
particle
level
(withboth
errors
that
include
of athe
leading
pTleading
.of
The
corrected
the
particle
(with
include
the
statistical
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both
the
error
and
the systematic
uncertainty)
and
are
compared
with
PYTHIA
AHERWIG
and MPI)
the
statistical
and the
systematic
uncertainty)
and are
compared
with
PYTHIA
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A and
error
andstatistical
the error
systematic
uncertainty)
and
are
compared
with
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A and
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at the
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generator level).
(without
MPI)
at theMPI)
particle
level
(i.e. generator
at the particle
level
(i.e.
generator
level).
Fourth HERA-LHC Workshop
May 26-30, 2008
Rick Field – Florida/CDF/CMS
Page 14
“Towards”, “Away”, “Transverse”
“Leading Jet”
Jet #1 Direction
f
“Toward”
“Transverse”
“Transverse”
“Away”
ETsum
Density
(GeV)
Charged
PTsum
Density
(GeV/c)
Average
Charged
Density
Charged
Particle
Density:
dN/dhdf
Charged
PTsum
Density:
dPT/dhdf
ETsum
Density:
dET/dhdf
5
100.0
100.0
CDFCDF
RunRun
2 Preliminary
2 Preliminary
4
data corrected
data"Toward"
corrected
pyA generator level
pyA generator level
10.0
3
"Toward"
"Away"
"Away"
Factor of ~13
"Toward"
"Transverse"
Factor of ~16
"Away"
"Transverse" "Leading Jet"
Factor of MidPoint
~4.5 R=0.7 |h(jet#1)|<2
2
1.0
1.0
1
0 0.1
0.1
0 0
0
"Transverse"
CDF Run 2 Preliminary
data corrected
pyA generator level
50 50
50
100100
100
150
150
150
"Leading Jet"
"Leading Jet"
MidPoint R=0.7 |h(jet#1)|<2
MidPoint R=0.7 |h(jet#1)|<2
ChargedStable
Particles
(|h|<1.0,
PT>0.5
GeV/c)
Charged
Particles
(|h|<1.0,
PT>0.5
GeV/c)
Particles
(|h|<1.0,
all
PT)
200
200
200
250
250
250
300
300
300
350
350
350
400
400
400
PT(jet#1)
PT(jet#1)(GeV/c)
(GeV/c)
PT(jet#1)
(GeV/c)
 Data
Data at
at 1.96
1.96 TeV
TeV on
on the
the charged
density ofparticle
charged
particles,
dN/dhdf,
p > 0.5 GeV/c
and |h| < 1 for

pT sum
density, with
dPT/dhdf,
and“leading
|h|
T > 0.5 GeV/c

Data at
1.96 TeV
on the
particle scalar
ETscalar
sum density,
dET/dhdf,
forT|h| < with
1 for p“leading
jet” events
as<a1
jet” events as a function of the leading jet p for the “toward”, “away”, and “transverse” regions. The
for “leading
jet”
eventsjet
as pa function
of the Tleading
jet pand
the “toward”,
“away”,The
anddata
“transverse”
T for“transverse”
function
of the
leading
“toward”,
“away”,
regions.
are corrected
T for the
data
are
corrected
to
the
particle
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(with
errors
that
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regions.
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data
are
corrected
to
the
particle
level
(with
errors
that
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andare
to the particle level (with errors that include both the statistical error and the systematic uncertainty)
uncertainty)
and
are
compared
with
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A
at
the
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(i.e.
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level).
the systematic
and A
are
with
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at the particle level (i.e. generator
compared
withuncertainty)
PYTHIA Tune
at compared
the particle
level
(i.e. generator
level).
Fourth HERA-LHC Workshop
May 26-30, 2008
Rick Field – Florida/CDF/CMS
Page 15
“Towards”, “Away”, “Transverse”
“Drell-Yan Producetion”
ParticleDensity:
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May 26-30, 2008
Rick Field – Florida/CDF/CMS
Page 16
The “Toward” Region
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Fourth HERA-LHC Workshop
May 26-30, 2008
Rick Field – Florida/CDF/CMS
Page 17
The “Away” Region
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Fourth HERA-LHC Workshop
May 26-30, 2008
Rick Field – Florida/CDF/CMS
Page 18
The “Transverse” Region
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Fourth HERA-LHC Workshop
May 26-30, 2008
Rick Field – Florida/CDF/CMS
Page 19
“Charged Particle Density”
Charged
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Fourth HERA-LHC Workshop
May 26-30, 2008
Rick Field – Florida/CDF/CMS
Page 20
“Charged PTsum Density”
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Fourth HERA-LHC Workshop
May 26-30, 2008
Rick Field – Florida/CDF/CMS
Page 21
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Fourth HERA-LHC Workshop
May 26-30, 2008
Rick Field – Florida/CDF/CMS
Page 22
“Charged Particle Density”
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Fourth HERA-LHC Workshop
May 26-30, 2008
Rick Field – Florida/CDF/CMS
Page 23
The “Transverse” Region
Jet #1 Direction
f
“Toward”
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Fourth HERA-LHC Workshop
May 26-30, 2008
Rick Field – Florida/CDF/CMS
Page 24
“Charged PTsum Density”
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Fourth HERA-LHC Workshop
May 26-30, 2008
Rick Field – Florida/CDF/CMS
Page 25
The “Transverse” Region
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Fourth HERA-LHC Workshop
May 26-30, 2008
Rick Field – Florida/CDF/CMS
Page 26
The Leading Jet Mass
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Fourth HERA-LHC Workshop
May 26-30, 2008
Rick Field – Florida/CDF/CMS
Page 27
The “Transverse” Region
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Fourth HERA-LHC Workshop
May 26-30, 2008
Rick Field – Florida/CDF/CMS
Page 28
The “TransMAX/MIN” Regions
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Fourth HERA-LHC Workshop
May 26-30, 2008
Rick Field – Florida/CDF/CMS
Page 29
The “TransMAX/MIN” Regions
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Fourth HERA-LHC Workshop
May 26-30, 2008
Rick Field – Florida/CDF/CMS
Page 30
The “TransMAX/MIN” Regions
“Leading Jet”
Jet #1 Direction
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Fourth HERA-LHC Workshop
May 26-30, 2008
Rick Field – Florida/CDF/CMS
Page 31
Z-Boson: “Towards” Region
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(|h|<1.0, PT>0.5
PT>0.5 GeV/c)
GeV/c)
Charged
excluding the
the lepton-pair
lepton-pair
excluding
0.0
0.0
00
2520
50
40
60
75
100
80125
100
150
00
PT(Z-Boson)
PT(Z-Boson) (GeV/c)
(GeV/c)
2520
50
75
40
60
f
f
“Transverse”
80125
Z-BosonDirection
Z-BosonDirection
“Toward”
100
PT(Z-Boson) (GeV/c)
(GeV/c)
PT(Z-Boson)
HW without MPI
“Toward”
“Transverse”
“Transverse”
“Transverse”
“Away”
“Away”
 Data at 1.96 TeV on the density of charged particles, dN/dhdf, with pT > 0.5 GeV/c and |h| < 1 for “ZBoson” events as a function of PT(Z) for the “toward” region. The data are corrected to the particle
level (with errors that include both the statistical error and the systematic uncertainty) and are
compared with PYTHIA Tune AW and HERWIG (without MPI) at the particle level (i.e. generator
level).
Fourth HERA-LHC Workshop
May 26-30, 2008
Rick Field – Florida/CDF/CMS
Page 32
150
100
Z-Boson: “Towards” Region
"Toward" Average PT Charged
"Toward" Average PT Charged
1.6
1.6
data corrected
generator level theory
"Toward" <PT> (GeV/c)
CDF Run 2 Preliminary
"Toward" <PT> (GeV/c)
CDF Run 2 Preliminary
"Drell-Yan Production"
70 < M(pair) < 110 GeV
pyDW
1.2
0.8
pyAW
ATLAS
HW
pyDWT LHC14
data corrected
generator level theory
"Drell-Yan Production"
70 < M(pair) < 110 GeV
1.2
DWT
0.8
HW LHC14
HW Tevatron
pyDWT Tevatron
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
excluding the lepton-pair
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
excluding the lepton-pair
0.4
0.4
0
20
40
60
80
100
0
20
40
60
Z-BosonDirection
Z-BosonDirection
f
f
“Transverse”
“Transverse”
100
PT(Z-Boson) (GeV/c)
PT(Z-Boson) (GeV/c)
“Toward”
80
HW (without MPI)
almost no change!
“Toward”
“Transverse”
“Transverse”
“Away”
“Away”
 Data at 1.96 TeV on the average pT of charged particles with pT > 0.5 GeV/c and |h| < 1 for “Z-Boson”
events as a function of PT(Z) for the “toward” region. The data are corrected to the particle level
(with errors that include both the statistical error and the systematic uncertainty) and are compared
with PYTHIA Tune AW and HERWIG (without MPI) at the particle level (i.e. generator level).
Fourth HERA-LHC Workshop
May 26-30, 2008
Rick Field – Florida/CDF/CMS
Page 33
Charged <PT> versus Nchg
The charged <PT>
rises with Nchg!
Average PT versus Nchg
1.6
CDF Preliminary
Average PT (GeV/c)
PYTHIA Tune A 1.96 TeV
data uncorrected
theory + CDFSIM
1.4
Min-Bias
1.2
1.0
0.8
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
0.6
0
2
4
6
8
10
12
14
16
18
20
22
24
26
28
Number of Charged Particles
Shows the average transverse momentum of charged particles (|h|<1, pT>0.5 GeV)
versus the number of charged particles, Nchg, at the detector level for the CDF Run
2 Min-Bias events.
Fourth HERA-LHC Workshop
May 26-30, 2008
Rick Field – Florida/CDF/CMS
Page 34
Min-Bias Correlations
Average PT versus Nchg
Average PT (GeV/c)
1.4
CDF Run 2 Preliminary
pyDW
data corrected
generator level theory
“Minumum Bias” Collisions
1.2
Min-Bias
1.96 TeV
pyA
Proton
1.0
AntiProton
ATLAS
0.8
Charged Particles (|h|<1.0, PT>0.4 GeV/c)
0.6
0
10
20
30
40
50
Number of Charged Particles
 Data at 1.96 TeV on the average pT of charged particles versus the number of charged particles (pT >
0.4 GeV/c, |h| < 1) for “min-bias” collisions at CDF Run 2. The data are corrected to the particle level
and are compared with PYTHIA Tune A at the particle level (i.e. generator level).
Fourth HERA-LHC Workshop
May 26-30, 2008
Rick Field – Florida/CDF/CMS
Page 35
Average PT versus Nchg
Average PT versus Nchg
Average
Nchg
CDF Run 2 Preliminary
Min-Bias
1.96 TeV
pyDW
data corrected
pyAW
generator level theory
1.2
Average PT versus Nchg
2.6
Average PT (GeV/c)
Average
Average PT
PT (GeV/c)
1.4
1.4
"Drell-Yan Production" pyA
70 < M(pair) < 110 GeV
PT(pair) < 5 GeV/c
1.0
ATLAS
0.8
Generator Level Theory
1.96 TeV
2.2
"Drell-Yan Production"
70 < M(pair) < 110 GeV
pyAW
HW
1.8
1.4
ATLAS
1.0
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
excluding the lepton-pair
Charged Particles (|h|<1.0, PT>0.4 GeV/c)
Charged Particles (|h|<1.0, PT>0.4 GeV/c)
0.6
0.6
0
10
20
30
40
Number of Charged Particles
Particles
50
0
10
Z-Boson with PT(Z) < 5 GeV
compared with “min-bias”!
20
30
40
50
Number of Charged Particles
Drell-Yan Production
Lepton
“Minumum Bias” Collisions
Proton
AntiProton
Proton
AntiProton
Underlying Event
Underlying Event
Anti-Lepton
 Data at 1.96 TeV on the average pT of charged particles versus the number of charged particles (pT > 0.4 GeV/c, |h| <
1) for “min-bias” collisions at CDF Run 2. The data are corrected to the particle leveland are compared with PYTHIA
Tune A, Tune DW, and the ATLAS tune at the particle level (i.e. generator level).
 Particle level predictions for the average pT of charged particles versus the number of charged particles (pT > 0.5
GeV/c, |h| < 1, excluding the lepton-pair) for for Drell-Yan production (70 < M(pair) < 110 GeV) at CDF Run 2.
Fourth HERA-LHC Workshop
May 26-30, 2008
Rick Field – Florida/CDF/CMS
Page 36
Summary
 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!
 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!
 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!
 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.
 I plan to construct a “CDF-QCD Data for Theory”
WEBsite with the “blessed” plots together with
tables of the data points and errors so that people
can have access to the results .
Fourth HERA-LHC Workshop
May 26-30, 2008
Outgoing Parton
PT(hard)
Initial-State Radiation
Proton
AntiProton
Underlying Event
Underlying Event
Outgoing Parton
Final-State
Radiation
Drell-Yan Production
Proton
Lepton
AntiProton
Underlying Event
Underlying Event
Anti-Lepton
CDF-QCD Data for Theory
Rick Field – Florida/CDF/CMS
Page 37