Studying the Underlying Event at
CDF and the LHC
Rick Field
University of Florida
Outline of Talk
¨ Review what we learned about
“min-bias” and the “underlying
event” in Run 1 at CDF.
¨ Discuss using Drell-Yan lepton-pair
production to study the “underlying
event”.
PT(hard)
Initial-State Radiation
Proton
AntiProton
Underlying Event
¨ Explain the various PYTHIA
“underlying event” tunes and
extrapolations to the LHC.
University of Toronto Physics
March 18, 2008
Outgoing Parton
Outgoing Parton
Underlying Event
Final-State
Radiation
¨ “CDF-QCD Data for Theory”: My
latest CDF Run 2 project.
¨ UE&MB@CMS: Plans to measure
“min-bias” and the “underlying
event” at CMS.
University of Toronto
March 18, 2008
CDF Run 2
Rick Field – Florida/CDF/CMS
CMS at the LHC
Page 1
Proton-AntiProton Collisions
at the Tevatron
Elastic Scattering
Single Diffraction
Double Diffraction
M
M2
M1
σtot = σEL + σSD +σDD +σHC
1.8 TeV: 78mb
= 18mb
+ 9mb
+ (4-7)mb + (47-44)mb
CDF “Min-Bias” trigger
1 charged particle in forward BBC
AND
1 charged particle in backward BBC
Hard Core
The “hard core” component
contains both “hard” and
“soft” collisions.
“Hard” Hard Core (hard scattering)
Outgoing Parton
“Soft” Hard Core (no hard scattering)
Proton
PT(hard)
Proton
AntiProton
AntiProton
Underlying Event
Underlying Event
Initial-State
Radiation
Final-State
Radiation
Outgoing Parton
University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 2
Proton-AntiProton Collisions
at the Tevatron
Elastic Scattering
The CDF “Min-Bias” trigger
picks up most of the “hard
core” cross-section plus a
Double
Diffraction
small
amount of single &
double diffraction.
M2
M1
Single Diffraction
M
σtot = σEL + σSD +σDD +σHC
1.8 TeV: 78mb
= 18mb
+ 9mb
+ (4-7)mb + (47-44)mb
CDF “Min-Bias” trigger
1 charged particle in forward BBC
AND
1 charged particle in backward BBC
Hard Core
The “hard core” component
contains both “hard” and
“soft” collisions.
“Hard” Hard Core (hard scattering)
Outgoing Parton
“Soft” Hard Core (no hard scattering)
Proton
AntiProton
Beam-Beam Counters
3.2 < |η| < 5.9
PT(hard)
Proton
AntiProton
Underlying Event
Underlying Event
Initial-State
Radiation
Final-State
Radiation
Outgoing Parton
University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 3
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
Underlying Event
Final-State Radiation
Outgoing Parton
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!
University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 4
Particle Densities
2π
ΔηΔφ = 4π = 12.6
φ
31 charged
charged particles
particle
Charged Particles
pT > 0.5 GeV/c |η| < 1
CDF Run 2 “Min-Bias”
CDF Run 2 “Min-Bias”
Observable
Average
Average Density
per unit η-φ
Nchg
Number of Charged Particles
(pT > 0.5 GeV/c, |η| < 1)
3.17 +/- 0.31
0.252 +/- 0.025
PTsum
(GeV/c)
Scalar pT sum of Charged Particles
(pT > 0.5 GeV/c, |η| < 1)
2.97 +/- 0.23
0.236 +/- 0.018
chg/dηdφ = 1/4π
3/4π = 0.08
0.24
dNchg
13 GeV/c PTsum
0
-1
η
+1
Divide by 4π
dPTsum/dηdφ = 1/4π
3/4π GeV/c = 0.08
0.24 GeV/c
¨Study the charged particles (pT > 0.5 GeV/c, |η| < 1) and form the charged
particle density, dNchg/dηdφ, and the charged scalar pT sum density,
dPTsum/dηdφ.
University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 5
CDF Run 1 “Min-Bias” Data
Charged Particle Density
Charged Particle Density: dN/dηdφ
Charged Particle Pseudo-Rapidity Distribution: dN/dη
1.0
7
CDF Published
CDF Published
6
0.8
dN/dηdφ
dN/dη
5
4
3
0.6
0.4
2
0.2
CDF Min-Bias 630 GeV
CDF Min-Bias 1.8 TeV
1
CDF Min-Bias 1.8 TeV
all PT
CDF Min-Bias 630 GeV
all PT
0.0
0
-4
-3
-2
-1
0
1
2
3
4
-4
-3
-1
0
1
2
3
4
Pseudo-Rapidity η
Pseudo-Rapidity η
<dNchg/dη> = 4.2
-2
<dNchg/dηdφ> = 0.67
¨ Shows CDF “Min-Bias” data on the number of charged particles per unit pseudo-rapidity
at 630 and 1,800 GeV. There are about 4.2 charged particles per unit η in “Min-Bias”
collisions at 1.8 TeV (|η| < 1, all pT).
ΔηxΔφ = 1
¨ Convert to charged particle density, dNchg/dηdφ, by dividing by 2π.
Δφ = 1
There are about 0.67 charged particles per unit η-φ in “Min-Bias”
0.67
collisions at 1.8 TeV (|η| < 1, all pT).
Δη = 1
University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 6
CDF Run 1 “Min-Bias” Data
Charged Particle Density
Charged Particle Density: dN/dηdφ
Charged Particle Pseudo-Rapidity Distribution: dN/dη
1.0
7
CDF Published
CDF Published
6
0.8
dN/dηdφ
dN/dη
5
4
3
0.6
0.4
2
0.2
CDF Min-Bias 630 GeV
CDF Min-Bias 1.8 TeV
1
CDF Min-Bias 1.8 TeV
all PT
CDF Min-Bias 630 GeV
all PT
0.0
0
-4
-3
-2
-1
0
1
2
3
4
-4
-3
-1
0
1
2
3
4
Pseudo-Rapidity η
Pseudo-Rapidity η
<dNchg/dη> = 4.2
-2
<dNchg/dηdφ> = 0.67
¨ Shows CDF “Min-Bias” data on the number of charged particles per unit pseudo-rapidity
at 630 and 1,800 GeV. There are about 4.2 charged particles per unit η in “Min-Bias”
collisions at 1.8 TeV (|η| < 1, all pT).
ΔηxΔφ = 1
¨ Convert to charged particle density, dNchg/dηdφ, by dividing by 2π.
Δφ = 1
There are about 0.67 charged particles per unit η-φ in “Min-Bias”
0.25
0.67
collisions at 1.8 TeV (|η| < 1, all pT).
¨ There are about 0.25 charged particles per unit η-φ in “Min-Bias”
Δη = 1
collisions at 1.96 TeV (|η| < 1, pT > 0.5 GeV/c).
University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 7
CDF Run 2 Min-Bias “Associated”
Charged Particle Density
“Associated” densities do
not include PTmax!
Highest pT
charged particle!
Charged Particle Density: dN/dηdφ
PTmax Direction
0.5
Δφ
Correlations in φ
Charged Particle Density
CDF Preliminary
Associated Density
PTmax not included
data uncorrected
0.4
Charge Density
0.3
0.2
0.1
Charged Particles
(|η|<1.0, PT>0.5 GeV/c)
PTmax
Min-Bias
0.0
0
30
60
90
120
150
180
210
240
270
300
330
360
Δφ (degrees)
¨ Use the maximum pT charged particle in the event, PTmax, to define a direction and look
at the the “associated” density, dNchg/dηdφ, in “min-bias” collisions (pT > 0.5 GeV/c, |η| <
1).
¨ Shows the data on the Δφ dependence of the “associated” charged particle density,
dNchg/dηdφ, for charged particles (pT > 0.5 GeV/c, |η| < 1, not including PTmax) relative
to PTmax (rotated to 180o) for “min-bias” events. Also shown is the average charged
particle density, dNchg/dηdφ, for “min-bias” events.
University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 8
CDF Run 2 Min-Bias “Associated”
Charged Particle Density
“Associated” densities do
not include PTmax!
Highest pT
charged particle!
Charged Particle Density: dN/dηdφ
PTmax Direction
0.5
Δφ
Correlations in φ
Charged Particle Density
CDF Preliminary
Associated Density
PTmax not included
data uncorrected
0.4
Charge Density
0.3
0.2
0.1
Charged Particles
(|η|<1.0, PT>0.5 GeV/c)
PTmax
Min-Bias
0.0
0
30
60
90
120
150
180
210
240
270
300
330
360
Δφ (degrees)
¨ Use the maximum pT charged particle in the event, PTmax, to define a direction and look
It is more probable
to find
a particle
chg/dηdφ,
in “min-bias” collisions (pT > 0.5 GeV/c, |η| <
at the the “associated”
density, dN
accompanying
PTmax
than
it
is
to
1).
find a particle in the central region!
¨ Shows the data
on the Δφ dependence of the “associated” charged particle density,
dNchg/dηdφ, for charged particles (pT > 0.5 GeV/c, |η| < 1, not including PTmax) relative
to PTmax (rotated to 180o) for “min-bias” events. Also shown is the average charged
particle density, dNchg/dηdφ, for “min-bias” events.
University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 9
CDF Run 2 Min-Bias “Associated”
Charged Particle Density Rapid rise in the particle
density in the “transverse”
region as PTmax increases!
Associated Particle Density: dN/dηdφ
PTmaxDirection
Direction
PTmax
Δφ
“Toward”
“Transverse”
“Transverse”
Correlations in φ
“Away”
Jet #2
Associated Particle Density
Jet #1
Δφ
PTmax > 2.0 GeV/c
1.0
PTmax > 2.0 GeV/c
PTmax > 1.0 GeV/c
PTmax > 0.5 GeV/c
Transverse
Region
0.8
0.6
Charged Particles
(|η|<1.0, PT>0.5 GeV/c)
CDF Preliminary
data uncorrected
Transverse
Region
0.4
0.2
PTmax
PTmax not included
Min-Bias
0.0
0
30
60
90
120
150
180
210
240
270
300
330
360
Δφ (degrees)
Ave Min-Bias
0.25 per unit η-φ
PTmax > 0.5 GeV/c
¨ Shows the data on the Δφ dependence of the “associated” charged particle density,
dNchg/dηdφ, for charged particles (pT > 0.5 GeV/c, |η| < 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.
¨ Shows “jet structure” in “min-bias” collisions (i.e. the “birth” of the leading two jets!).
University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 10
CDF Run 1: Evolution of Charged Jets
“Underlying Event”
Charged Particle Δφ Correlations
PT > 0.5 GeV/c |η| < 1
Charged Jet #1
Direction
“Transverse” region
very sensitive to the
“underlying event”!
2π
CDF Run 1 Analysis
“Toward-Side” Jet
Δφ
“Toward”
Away Region
Charged Jet #1
Direction
Δφ
“Toward”
“Transverse”
Look at the charged
particle density in the
“transverse” region!
Transverse
Region
Leading
Jet
φ
“Transverse”
Toward Region
“Transverse”
“Transverse”
Transverse
Region
“Away”
“Away”
“Away-Side” Jet
Away Region
0
-1
η
+1
¨ Look at charged particle correlations in the azimuthal angle Δφ relative to the leading charged
particle jet.
¨ Define |Δφ| < 60o as “Toward”, 60o < |Δφ| < 120o as “Transverse”, and |Δφ| > 120o as “Away”.
¨ All three regions have the same size in η-φ space, ΔηxΔφ = 2x120o = 4π/3.
University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 11
Run 1 Charged Particle Density
“Transverse” pT Distribution
"Transverse" Charged Particle Density: dN/dηdφ
Charged Particle Density
1.0E+00
CDF Min-Bias
CDF Run 1
CDF JET20
data uncorrected
0.50
Factor of 2!
0.25
1.8 TeV |η|<1.0 PT>0.5 GeV/c
0.00
0
5
10
15
20
25
30
35
40
45
PT(charged jet#1) (GeV/c)
PT(charged jet#1) > 30 GeV/c
“Transverse” <dNchg/dηdφ> = 0.56
“Min-Bias”
CDF Run 1 Min-Bias data
<dNchg/dηdφ> = 0.25
CDF Run 1
"Transverse"
PT(chgjet#1) > 5 GeV/c
0.75
50
Charged Density dN/dηdφdPT (1/GeV/c)
"Transverse" Charged Density
1.00
data uncorrected
1.0E-01
"Transverse"
PT(chgjet#1) > 30 GeV/c
1.0E-02
1.0E-03
1.0E-04
Min-Bias
1.0E-05
1.8 TeV |η|<1 PT>0.5 GeV/c
1.0E-06
0
2
4
6
8
10
12
14
PT(charged) (GeV/c)
¨ Compares the average “transverse” charge particle density with the average “Min-Bias”
charge particle density (|η|<1, pT>0.5 GeV). Shows how the “transverse” charge particle
density and the Min-Bias charge particle density is distributed in pT.
University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 12
ISAJET 7.32
“Transverse” Density
ISAJET uses a naïve leading-log
parton shower-model which does
not agree with the data!
Charged Jet #1
Direction
1.00
Δφ
“Transverse”
“Transverse”
“Away”
CDF Run 1Data
"Transverse" Charged Density
“Toward”
ISAJET
"Transverse" Charged Particle Density: dN/dηdφ
Isajet
data uncorrected
theory corrected
0.75
"Hard"
0.50
0.25
“Hard”
Component
"Remnants"
1.8 TeV |η|<1.0 PT>0.5 GeV
Beam-Beam
Remnants
0.00
0
5
10
15
20
25
30
35
40
45
50
PT(charged jet#1) (GeV/c)
¨ Plot shows average “transverse” charge particle density (|η|<1, pT>0.5 GeV) versus PT(charged jet#1)
compared to the QCD hard scattering predictions of ISAJET 7.32 (default parameters with
PT(hard)>3 GeV/c) .
¨ The predictions of ISAJET are divided into two categories: charged particles that arise from the
break-up of the beam and target (beam-beam remnants); and charged particles that arise from the
outgoing jet plus initial and final-state radiation (hard scattering component).
University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 13
HERWIG 6.4
“Transverse” Density
Δφ
“Toward”
“Transverse”
“Transverse”
“Away”
1.00
CDF Run 1Data
"Transverse" Charged Density
Charged Jet #1
Direction
HERWIG uses a modified leadinglog parton shower-model which
does agrees better with the data!
"Transverse" Charged Particle Density: dN/dηdφ
Total
"Hard"
data uncorrected
theory corrected
0.75
0.50
0.25
"Remnants"
Beam-Beam
Remnants
HERWIG
Herwig 6.4 CTEQ5L
PT(hard) > 3 GeV/c
1.8 TeV |η|<1.0 PT>0.5 GeV
0.00
0
5
10
15
20
25
30
PT(charged jet#1) (GeV/c)
35
40
45
50
“Hard”
Component
¨ Plot shows average “transverse” charge particle density (|η|<1, pT>0.5 GeV) versus PT(charged
jet#1) compared to the QCD hard scattering predictions of HERWIG 5.9 (default parameters with
PT(hard)>3 GeV/c).
¨ The predictions of HERWIG are divided into two categories: charged particles that arise from the
break-up of the beam and target (beam-beam remnants); and charged particles that arise from the
outgoing jet plus initial and final-state radiation (hard scattering component).
University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 14
HERWIG 6.4
“Transverse” PT Distribution
HERWIG has the too steep of a pT
dependence of the “beam-beam remnant”
"Transverse" Chargedcomponent
Particle Density:
dN/dηdφ
of the
“underlying event”!
"Transverse" Charged Particle Density
CDF Data
"Hard"
Total
data uncorrected
theory corrected
0.75
1.0E+00
Herwig 6.4 CTEQ5L
PT(hard) > 3 GeV/c
CDF Data
PT(chgjet#1) > 5 GeV/c
0.50
0.25
"Remnants"
1.8 TeV |η|<1.0 PT>0.5 GeV
0.00
0
5
10
15
20
25
30
35
40
45
PT(charged jet#1) (GeV/c)
Herwig PT(chgjet#1) > 30 GeV/c
“Transverse” <dNchg/dηdφ> = 0.51
50
Charged Density dN/dηdφdPT (1/GeV/c)
"Transverse" Charged Density
1.00
data uncorrected
theory corrected
1.0E-01
1.8 TeV |η|<1 PT>0.5 GeV/c
1.0E-02
1.0E-03
1.0E-04
1.0E-05
PT(chgjet#1) > 30 GeV/c
Herwig 6.4 CTEQ5L
Herwig PT(chgjet#1) > 5 GeV/c
<dNchg/dηdφ> = 0.40
1.0E-06
0
2
4
6
8
10
12
14
PT(charged) (GeV/c)
¨ Compares the average “transverse” charge particle density (|η|<1, pT>0.5 GeV) versus
PT(charged jet#1) and the pT distribution of the “transverse” density, dNchg/dηdφdPT with the
QCD hard scattering predictions of HERWIG 6.4 (default parameters with PT(hard)>3
GeV/c. Shows how the “transverse” charge particle density is distributed in pT.
University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 15
MPI: Multiple Parton
Interactions
“Hard”
Collision
Multiple
Parton
Interaction
outgoing parton
“Hard” Component
“Semi-Hard” MPI
“Soft” Component
AntiProton
Proton
initial-state radiation
outgoing parton
initial-state radiation
final-state radiation
outgoing jet
or
+
final-state radiation
¨ PYTHIA models the “soft” component of the underlying event
with color string fragmentation, but in addition includes a
contribution arising from multiple parton interactions (MPI) in
which one interaction is hard and the other is “semi-hard”.
Beam-Beam Remnants
color string
color string
¨ The probability that a hard scattering events also contains a semi-hard multiple parton
interaction can be varied but adjusting the cut-off for the MPI.
¨ One can also adjust whether the probability of a MPI depends on the PT of the hard
scattering, PT(hard) (constant cross section or varying with impact parameter).
¨ One can adjust the color connections and flavor of the MPI (singlet or nearest neighbor,
q-qbar or glue-glue).
¨ Also, one can adjust how the probability of a MPI depends on PT(hard) (single or double
Gaussian matter distribution).
University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 16
Tuning PYTHIA:
Multiple Parton Interaction Parameters
Parameter
Default
Description
PARP(83)
0.5
Double-Gaussian: Fraction of total hadronic
matter within PARP(84)
PARP(84)
0.2
Double-Gaussian: Fraction of the overall hadron
radius containing the fraction PARP(83) of the
total hadronic matter.
Core
Hard
Multiple Parton Interaction
Color String
Color String
PARP(86)
PARP(89)
PARP(90)
PARP(67)
0.33
0.66
1 TeV
0.16
1.0
Probability that the MPI produces two gluons
with color connections to the “nearest neighbors.
Multiple PartonDetermine
Interactionby comparing
with 630 GeV data!
Probability that the MPI produces two gluons
either as described by PARP(85) or as a closed
gluon
loop.
remaining
fraction consists of
Affects
the The
amount
of
quark-antiquark
pairs.
initial-state radiation!
Color String
Hard-Scattering Cut-Off PT0
5
Determines the reference energy E0.
Determines the energy dependence of the cut-off
PT0 as follows PT0(Ecm) = PT0(Ecm/E0)ε with
ε = PARP(90)
A scale factor that determines the maximum
parton virtuality for space-like showers. The
larger the value of PARP(67) the more initialstate radiation.
PYTHIA 6.206
ε = 0.25 (Set A))
4
PT0 (GeV/c)
PARP(85)
Take E0 = 1.8 TeV
3
2
ε = 0.16 (default)
1
100
1,000
10,000
100,000
CM Energy W (GeV)
Reference point
at 1.8 TeV
University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 17
PYTHIA 6.206 Defaults
MPI constant
probability
scattering
PYTHIA default parameters
6.115
6.125
6.158
6.206
MSTP(81)
1
1
1
1
MSTP(82)
1
1
1
1
PARP(81)
1.4
1.9
1.9
1.9
PARP(82)
1.55
2.1
2.1
1.9
PARP(89)
1,000
1,000
1,000
PARP(90)
0.16
0.16
0.16
4.0
1.0
1.0
PARP(67)
4.0
1.00
"Transverse" Charged Density
Parameter
"Transverse" Charged Particle Density: dN/dηdφ
CDF Data
Pythia 6.206 (default)
MSTP(82)=1
PARP(81) = 1.9 GeV/c
data uncorrected
theory corrected
0.75
0.50
0.25
1.8 TeV |η|<1.0 PT>0.5 GeV
0.00
0
5
10
15
20
25
30
35
40
45
50
PT(charged jet#1) (GeV/c)
CTEQ3L
CTEQ4L
CTEQ5L
CDF Min-Bias
CDF JET20
¨ Plot shows the “Transverse” charged particle density versus PT(chgjet#1) compared to the
QCD hard scattering predictions of PYTHIA 6.206 (PT(hard) > 0) using the default
parameters for multiple parton interactions and CTEQ3L, CTEQ4L, and CTEQ5L.
Note Change
PARP(67) = 4.0 (< 6.138)
PARP(67) = 1.0 (> 6.138)
University of Toronto
March 18, 2008
Default parameters give
very poor description of
the “underlying event”!
Rick Field – Florida/CDF/CMS
Page 18
Run 1 PYTHIA Tune A
PYTHIA 6.206 CTEQ5L
CDF Default!
"Transverse" Charged Particle Density: dN/dηdφ
Parameter
Tune B
Tune A
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(67)
1.0
4.0
New PYTHIA default
(less initial-state radiation)
University of Toronto
March 18, 2008
"Transverse" Charged Density
1.00
CDF Preliminary
PYTHIA 6.206 (Set A)
PARP(67)=4
data uncorrected
theory corrected
0.75
Run 1 Analysis
0.50
0.25
CTEQ5L
PYTHIA 6.206 (Set B)
PARP(67)=1
1.8 TeV |η|<1.0 PT>0.5 GeV
0.00
0
5
10
15
20
25
30
35
40
45
50
PT(charged jet#1) (GeV/c)
¨ Plot shows the “transverse” charged particle density
versus PT(chgjet#1) compared to the QCD hard
scattering predictions of two tuned versions of PYTHIA
6.206 (CTEQ5L, Set B (PARP(67)=1) and Set A
(PARP(67)=4)).
Old PYTHIA default
(more initial-state radiation)
Rick Field – Florida/CDF/CMS
Page 19
PYTHIA Tune A Min-Bias
“Soft” + ”Hard”
Tuned to fit the CDF Run 1
“underlying event”!
PYTHIA Tune A
CDF Run 2 Charged
Default
Particle Density
Charged Particle Density: dN/dηdφ
1.0
CDF Published
1.0E+00
0.8
CDF Min-Bias Data
1.0E-01
0.6
0.4
0.2
Pythia 6.206 Set A
CDF Min-Bias 1.8 TeV
1.8 TeV all PT
0.0
-4
-3
-2
-1
0
1
2
3
4
Pseudo-Rapidity η
¨ PYTHIA regulates the perturbative 2-to-2
Charged Density dN/dηdφdPT (1/GeV/c)
dN/d η d φ
Pythia 6.206 Set A
1.8 TeV |η|<1
1.0E-02
12% of “Min-Bias” events
have PT(hard) > 5 GeV/c!
PT(hard) > 0 GeV/c
1.0E-03
1.0E-04
1% of “Min-Bias” events
have PT(hard) > 10 GeV/c!
1.0E-05
CDF Preliminary
parton-parton cross sections with cut-off
1.0E-06
parameters
which allows one to run with
Lots of “hard” scattering in
0
2
4
6
8
10
12
PT“Min-Bias”
(hard) > at
0. the
One
can simulate both “hard”
Tevatron!
PT(charged) (GeV/c)
and “soft” collisions in one program.
¨ The relative amount of “hard” versus “soft” depends on the cut-off and can be tuned.
14
¨ This PYTHIA fit predicts that 12% of all “Min-Bias” events are a result of a hard 2-to-2
parton-parton scattering with PT(hard) > 5 GeV/c (1% with PT(hard) > 10 GeV/c)!
University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 20
PYTHIA Tune A
LHC Min-Bias Predictions
Hard-Scattering in Min-Bias Events
Charged Particle Density
50%
12% of “Min-Bias”
events
have|η|<1
PT(hard) > 10 GeV/c!
1.0E+00
Pythia 6.206 Set A
Pythia 6.206 Set A
40%
% of Events
Charged Density dN/dηdφdPT (1/GeV/c)
1.0E-01
1.0E-02
PT(hard) > 5 GeV/c
PT(hard) > 10 GeV/c
30%
20%
1.8 TeV
1.0E-03
10%
14 TeV
1.0E-04
0%
100
1,000
10,000
100,000
CM Energy W (GeV)
630 GeV
LHC?
1.0E-05
¨ Shows the center-of-mass energy dependence
CDF Data
1.0E-06
0
2
4
6
8
PT(charged) (GeV/c)
1% of “Min-Bias” events
have PT(hard) > 10 GeV/c!
10
12
14
of the charged particle density,
dNchg/dηdφdPT, 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!
University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 21
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
Underlying Event
AntiProton
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.
University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 22
The “Central” Region
in Drell-Yan Production
Drell-Yan Production
Look at the charged
particle density and the
PTsum density in the
“central” region!
Charged Particles (pT > 0.5 GeV/c, |η| < 1)
Lepton
2π
Proton
AntiProton
Underlying Event
Underlying Event
Initial-State
Radiation
φ
Central Region
Anti-Lepton
Multiple Parton Interactions
Proton
Lepton
AntiProton
Underlying Event
0
Underlying Event
Anti-Lepton
-1
η
+1
After removing the leptonpair everything else is the
“underlying event”!
¨ Look at the “central” region after removing the lepton-pair.
¨ Study the charged particles (pT > 0.5 GeV/c, |η| < 1) and form the charged particle
density, dNchg/dηdφ, and the charged scalar pT sum density, dPTsum/dηdφ, by
dividing by the area in η-φ space.
University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 23
CDF Run 1 PT(Z)
PYTHIA 6.2 CTEQ5L
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
σ = 1.0
Z-Boson Transverse Momentum
0.12
PT Distribution 1/N dN/dPT
UE Parameters Parameter
CDF Run 1 Data
PYTHIA Tune A
σ = 2.5
PYTHIA Tune A25
PYTHIA Tune A50
0.08
CDF Run 1
published
1.8 TeV
σ = 5.0
Normalized to 1
0.04
0.00
ISR Parameter
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),
Tune A25 (<pT(Z)> = 10.1 GeV/c), and
Tune A50 (<pT(Z)> = 11.2 GeV/c).
Vary the intrensic KT!
Intrensic KT
University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 24
20
CDF Run 1 PT(Z)
UE Parameters
ISR Parameters
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
Tune used by the
CDF-EWK group!
Z-Boson Transverse Momentum
0.12
CDF Run 1 Data
PT Distribution 1/N dN/dPT
PYTHIA 6.2 CTEQ5L
CDF Run 1
PYTHIA Tune A
PYTHIA Tune AW
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 αs for space-like showers is scaled by PARP(64)!
University of Toronto
March 18, 2008
20
Rick Field – Florida/CDF/CMS
Page 25
Jet-Jet Correlations (DØ)
Jet#1-Jet#2 Δφ Distribution
Δφ 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).
University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 26
CDF Run 1 PT(Z)
PYTHIA 6.2 CTEQ5L
ISR Parameters
Tune DW
Tune AW
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
Intrensic KT
Z-Boson Transverse Momentum
0.12
PT Distribution 1/N dN/dPT
UE Parameters
Parameter
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)!
Tune DW has a lower value of PARP(67) and slightly more MPI!
University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 27
“Transverse” Nchg Density
Parameter
Tune AW
Tune DW
Tune BW
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
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
1.0
MSTP(91)
1
1
1
PARP(91)
2.5
2.5
2/5
PARP(93)
15.0
15.0
15.0
ISR Parameter PARP(89)
Intrensic KT
"Transverse" Charged Particle Density: dN/dηdφ
1.0
RDF Preliminary
"Transverse" Charged Density
UE Parameters
Three different amounts of MPI!
PYTHIA 6.2 CTEQ5L
PY Tune BW
PY Tune DW
generator level
0.8
0.6
PY Tune A
PY Tune AW
0.4
HERWIG
1.96 TeV
0.2
Leading Jet (|η|<2.0)
Charged Particles (|η|<1.0, PT>0.5 GeV/c)
0.0
0
50
100
150
200
250
300
350
400
450
PT(particle jet#1) (GeV/c)
¨ Shows the “transverse” charged particle
density, dN/dηdφ, versus PT(jet#1) for “leading
jet” events at 1.96 TeV for PYTHIA Tune A,
Tune AW, Tune DW, Tune BW, and
HERWIG (without MPI).
Three different amounts of ISR!
University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 28
500
“Transverse” Nchg Density
Parameter
Tune AW
Tune DW
Tune BW
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
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
1.0
MSTP(91)
1
1
1
PARP(91)
2.5
2.5
2/5
PARP(93)
15.0
15.0
15.0
ISR Parameter PARP(89)
Intrensic KT
Three different amounts of ISR!
University of Toronto
March 18, 2008
"Transverse" Charged
Charged Particle
Particle Density:
Density: dN/dηdφ
dN/dηdφ
"Transverse"
1.0
1.0
"Transverse"
"Transverse"Charged
ChargedDensity
Density
UE Parameters
Three different amounts of MPI!
PYTHIA 6.2 CTEQ5L
RDF Preliminary
Preliminary
RDF
PY Tune BW
generator level
level
generator
0.8
0.8
PYPY
Tune
DW
Tune
DW
PY-ATLAS
PY Tune A
0.6
0.6
0.4
0.4
PY Tune AW
HERWIG
HERWIG
1.96 TeV
TeV
1.96
0.2
0.2
Leading Jet
Jet (|η|<2.0)
(|η|<2.0)
Leading
Charged Particles
Particles (|η|<1.0,
(|η|<1.0, PT>0.5
PT>0.5 GeV/c)
GeV/c)
Charged
0.0
0.0
00
50
50
100
100
150
150
200
200
250
250
300
300
350
350
400
400
450
450
500
500
PT(particle jet#1)
jet#1) (GeV/c)
(GeV/c)
PT(particle
¨ Shows the “transverse” charged particle
density, dN/dηdφ, versus PT(jet#1) for “leading
jet” events at 1.96 TeV for PYTHIA Tune A,
Tune AW, Tune DW, Tune BW, and
HERWIG (without MPI).
¨ Shows the “transverse” charged particle
density, dN/dηdφ, versus PT(jet#1) for “leading
jet” events at 1.96 TeV for Tune DW, ATLAS,
and HERWIG (without MPI).
Rick Field – Florida/CDF/CMS
Page 29
“Transverse” PTsum Density
Three different amounts of MPI!
PYTHIA 6.2 CTEQ5L
UE Parameters
Tune AW
Tune DW
Tune BW
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
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
1.0
MSTP(91)
1
1
1
PARP(91)
2.5
2.5
2/5
PARP(93)
15.0
15.0
15.0
ISR Parameter PARP(89)
Intrensic KT
"Transverse" PTsum Density: dPT/dηdφ
1.6
"Transverse" PTsum Density (GeV/c)
Parameter
RDF Preliminary
generator level
1.2
PY Tune BW
PY Tune A
0.8
PY Tune AW
PY Tune DW
1.96 TeV
0.4
HERWIG
Leading Jet (|η|<2.0)
Charged Particles (|η|<1.0, PT>0.5 GeV/c)
0.0
0
50
100
150
200
250
300
350
400
450
PT(particle jet#1) (GeV/c)
¨ Shows the “transverse” charged PTsum
density, dPT/dηdφ, versus PT(jet#1) for
“leading jet” events at 1.96 TeV for PYTHIA
Tune A, Tune AW, Tune DW, Tune BW, and
HERWIG (without MPI).
Three different amounts of ISR!
University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 30
500
“Transverse” PTsum Density
Three different amounts of MPI!
PYTHIA 6.2 CTEQ5L
UE Parameters
Tune AW
Tune DW
Tune BW
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)
PARP(86)
1.0
1.0
0.95
1.0
1.0
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
1.0
MSTP(91)
1
1
1
PARP(91)
2.5
2.5
2/5
PARP(93)
15.0
15.0
15.0
ISR Parameter PARP(89)
Intrensic KT
0.9
Three different amounts of ISR!
University of Toronto
March 18, 2008
"Transverse" PTsum Density: dPT/dηdφ
"Transverse" PTsum
PTsum Density
Density (GeV/c)
(GeV/c)
"Transverse"
Parameter
1.6
RDF Preliminary
generator level
1.2
PY Tune BW
PY Tune A
PY-ATLAS
0.8
PY Tune AW
PY Tune DW
1.96 TeV
0.4
HERWIG
Leading Jet (|η|<2.0)
Charged Particles (|η|<1.0, PT>0.5 GeV/c)
HERWIG
0.0
0
50
100
150
200
250
300
350
400
450
PT(particle jet#1) (GeV/c)
¨ Shows the “transverse” charged PTsum
density, dPT/dηdφ, versus PT(jet#1) for
“leading jet” events at 1.96 TeV for PYTHIA
Tune A, Tune AW, Tune DW, Tune BW, and
HERWIG (without MPI).
¨ Shows the “transverse” charged PTsum
density, dPT/dηdφ, versus PT(jet#1) for
“leading jet” events at 1.96 TeV for Tune DW,
ATLAS, and HERWIG (without MPI).
Rick Field – Florida/CDF/CMS
Page 31
500
PYTHIA 6.2 Tunes
σ(MPI) at 1.96 TeV
σ(MPI) at 14 TeV
Tune A
309.7 mb
484.0 mb
Tune DW
351.7 mb
549.2 mb
Tune DWT
351.7 mb
829.1 mb
ATLAS
324.5 mb
768.0 mb
PYTHIA 6.2 CTEQ5L
Tune A
Tune DW
Tune DWT
ATLAS
MSTP(81)
1
1
1
1
MSTP(82)
4
4
4
4
PARP(82)
2.0 GeV
1.9 GeV
1.9409 GeV
1.8 GeV
PARP(83)
0.5
0.5
0.5
0.5
PARP(84)
0.4
0.4
0.4
0.5
PARP(85)
0.9
1.0
1.0
0.33
PARP(86)
0.95
1.0
1.0
0.66
PARP(89)
1.8 TeV
1.8 TeV
1.96 TeV
1.0 TeV
PARP(90)
0.25
0.25
0.16
0.16
PARP(62)
1.0
1.25
1.25
1.0
PARP(64)
1.0
0.2
0.2
1.0
PARP(67)
4.0
2.5
2.5
1.0
MSTP(91)
1
1
1
1
PARP(91)
1.0
2.1
2.1
1.0
PARP(93)
5.0
15.0
15.0
5.0
Identical to DW at 1.96 TeV but uses
ATLAS extrapolation to the LHC!
University of Toronto
March 18, 2008
"Transverse"
Charged
Particle
Average
pT
"Transverse"
Charged
Particle
Density:
dN/dηdφ
"Transverse"
PTsum
Density:
dPT/dηdφ
"Transverse"
Charged
PTDensity
(GeV/c)
"Transverse"
Charged
"Transverse"
PTsum
Density
(GeV/c)
Parameter
1.6
1.0
1.5
RDF
RDFPreliminary
Preliminary
RDF
Preliminary
generator
generatorlevel
level
generator
level
0.8
1.2
1.3
PY Tune DW
PY Tune DW
0.6
PY Tune DW
PY Tune A
PY Tune A
PY-ATLAS
PY-ATLAS
0.8
1.1
PY Tune A
PY-ATLAS
0.4
1.96TeV
TeV
1.96
1.96 TeV
HERWIG
0.4
0.9
0.2
HERWIG
Leading
JetJet
(|η|<2.0)
Leading
(|η|<2.0)
Leading
Jet (|η|<2.0)
Charged
Particles
(|η|<1.0,
PT>0.5
GeV/c)
Charged
Particles
(|η|<1.0,
PT>0.5
GeV/c)
Charged
Particles
(|η|<1.0,
PT>0.5
GeV/c)
HERWIG
0.0
0.0
0.7
0
00
50
50
50
100
100
100
150
150
150
200
200
200
250
250
250
300
300
300
350
350
350
400
400
400
450
450
450
500
500
500
PT(particle
jet#1)
PT(particle jet#1)
jet#1) (GeV/c)
(GeV/c)
PT(particle
(GeV/c)
¨ Shows
Shows the
the “transverse”
“transverse” charged
charged PTsum
particledensity,
density,
¨
average
p
T,
“leading
dN/dηdφ,
versus
PPTT(jet#1)
(jet#1)for
for
“leading
jet”
dPT/dηdφ,
versusfor
versus
PT(jet#1)
“leading
jet”
eventsjet”
at 1.96
events
atTune
1.96 TeV
TeV
for ATLAS,
Tune A,
A, DW,
DW,HERWIG
ATLAS, and
and
events
at
1.96
for
Tune
ATLAS,
TeV
for
A,
DW,
and
HERWIG
(without MPI).
MPI).
HERWIG
(without
(without
MPI).
Rick Field – Florida/CDF/CMS
Page 32
PYTHIA 6.2 Tunes
σ(MPI) at 1.96 TeV
σ(MPI) at 14 TeV
Tune A
309.7 mb
484.0 mb
Tune DW
351.7 mb
549.2 mb
Tune DWT
351.7 mb
829.1 mb
324.5
mbRun 2 Data!
CDF
768.0 mb
PYTHIA 6.2 CTEQ5L
Parameter
Tune A
Tune DW
Tune DWT
ATLAS
MSTP(81)
1
1
1
1
MSTP(82)
4
PARP(82)
2.0 GeV
4
1.7GeV
1.9
PARP(83)
0.5
4"Transverse"
4
1.9409 GeV
ATLAS
1.8 GeV
"Leading Jet"
0.4
PARP(85)
0.9
PARP(86)
0.95
PARP(89)
1.8 TeV
PARP(90)
0.25
PARP(62)
1.0
PARP(64)
1.0
0.2
PARP(67)
4.0
MSTP(91)
1
0.72.5
0
1
1.0
1.3
1.0
1.8 TeV
1.1
0.25
"Transverse"
Charged
Particle
Average
pT
"Transverse"
Charged
Particle
Density:
dN/dηdφ
"Transverse"
PTsum
Density:
dPT/dηdφ
1.0
0.33
1.0
0.66
1.96 TeV
1.0 TeV
0.16
0.16
1.25
1.0
1.25
0.9
1.960.2
TeV
2.5
50
1
100
HERWIG
1.0
1.0
150
1
PARP(91)
1.0
2.1
2.1
1.0
PARP(93)
5.0
15.0
15.0
5.0
Identical to DW at 1.96 TeV but uses
ATLAS extrapolation to the LHC!
"Transverse"
Charged
PTDensity
(GeV/c)
"Transverse"
Charged
"Transverse"
PTsum
Density
(GeV/c)
"Transverse" <PT> (GeV/c)
CDF Run 2 Preliminary
0.5 data corrected
0.5 to particle level
0.5
1.5
0.4
0.5
PY Tune0.4
A, DW
PARP(84)
University of Toronto
March 18, 2008
Charged Average PT
1.6
1.0
1.5
RDF
RDFPreliminary
Preliminary
RDF
Preliminary
generator
generatorlevel
level
generator
level
0.8
1.2
1.3
PY Tune DW
PY Tune DW
0.6
PY Tune DW
PY Tune A
PY Tune A
PY-ATLAS
PY-ATLAS
0.8
1.1
PY-ATLAS
0.4
PY Tune A
MidPoint R = 0.7 |η(jet#1) <PY-ATLAS
2
1.96TeV
TeV
1.96
1.96 TeV
HERWIG
0.4
0.9
HERWIGPT>0.5 GeV/c)
Charged
Particles (|η|<1.0,
0.2
Leading
JetJet
(|η|<2.0)
Leading
(|η|<2.0)
Leading
Jet (|η|<2.0)
Charged
Particles
(|η|<1.0,
PT>0.5
GeV/c)
Charged
Particles
(|η|<1.0,
PT>0.5
GeV/c)
Charged
Particles
(|η|<1.0,
PT>0.5
GeV/c)
HERWIG
0.0
0.0
200 0.7 250
0
00
50
50
50
300
100
100
100
PT(jet#1) (GeV/c)
350
150
150
150
400
200
200
200
250
250
250
450
300
300
300
350
350
350
400
400
400
450
450
450
500
500
500
PT(particle
jet#1)
PT(particle jet#1)
jet#1) (GeV/c)
(GeV/c)
PT(particle
(GeV/c)
¨ Shows
Shows the
the “transverse”
“transverse” charged
charged PTsum
particledensity,
density,
¨
average
p
T,
“leading
dN/dηdφ,
versus
PPTT(jet#1)
(jet#1)for
for
“leading
jet”
dPT/dηdφ,
versusfor
versus
PT(jet#1)
“leading
jet”
eventsjet”
at 1.96
events
atTune
1.96 TeV
TeV
for ATLAS,
Tune A,
A, DW,
DW,HERWIG
ATLAS, and
and
events
at
1.96
for
Tune
ATLAS,
TeV
for
A,
DW,
and
HERWIG
(without MPI).
MPI).
HERWIG
(without
(without
MPI).
Rick Field – Florida/CDF/CMS
Page 33
Use LO αs
with Λ = 192 MeV!
UE Parameters
ISR Parameter
PYTHIA 6.2 Tunes
Parameter
Tune DW
Tune DWT
ATLAS
Tune D6
Tune D6T
PDF
CTEQ5L
CTEQ5L
CTEQ5L
CTEQ6L
CTEQ6L
MSTP(2)
1
1
1
1
1
MSTP(33)
0
0
0
0
1
PARP(31)
1.0
1.0
1.0
1.0
1.0
MSTP(81)
1
1
1
1
1
MSTP(82)
4
4
4
4
4
PARP(82)
1.9 GeV
1.9409 GeV
1.8 GeV
1.8 GeV
1.8387 GeV
PARP(83)
0.5
0.5
0.5
0.5
0.5
PARP(84)
0.4
0.4
0.5
0.4
0.4
PARP(85)
1.0
1.0
0.33
1.0
1.0
PARP(86)
1.0
1.0
0.66
1.0
1.0
PARP(89)
1.8 TeV
1.96 TeV
1.0 TeV
1.8 TeV
1.96 TeV
PARP(90)
0.25
0.16
0.16
0.25
0.16
PARP(62)
1.25
1.25
1.0
1.25
1.25
PARP(64)
0.2
0.2
1.0
0.2
0.2
PARP(67)
2.5
2.5
1.0
2.5
2.5
MSTP(91)
1
1
1
1
1
PARP(91)
2.1
2.1
1.0
2.1
2.1
PARP(93)
15.0
15.0
5.0
15.0
15.0
CTEQ6L Tune
Intrinsic KT
University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 34
Use LO αs
with Λ = 192 MeV!
UE Parameters
ISR Parameter
PYTHIA 6.2 Tunes
Parameter
Tune DW
Tune DWT
ATLAS
Tune D6
Tune D6T
PDF
CTEQ5L
CTEQ5L
CTEQ5L
CTEQ6L
CTEQ6L
MSTP(2)
1
1
1
1
1
MSTP(33)
0
0
0
0
1
PARP(31)
1.0
1.0
1.0
1.0
1.0
MSTP(81)
1
1
1
1
1
MSTP(82)
4
4
4
4
4
PARP(82)
1.9 GeV
1.9409 GeV
1.8 GeV
1.8 GeV
1.8387 GeV
PARP(83)
0.5
0.5
0.5
PARP(84)
0.4
0.4
0.4
PARP(85)
1.0
1.0
0.33
1.0
1.0
PARP(86)
1.0
1.0
0.66
1.0
1.0
PARP(89)
1.8 TeV
1.96 TeV
1.0 TeV
1.8 TeV
1.96 TeV
PARP(90)
0.25
0.16
0.16
0.25
0.16
PARP(62)
1.25
1.25
1.0
1.25
1.25
PARP(64)
0.2
0.2
1.0
0.2
0.2
PARP(67)
2.5
2.5
1.0
2.5
2.5
MSTP(91)
1
1
1
1
1
PARP(91)
2.1
2.1
1.0
2.1
2.1
PARP(93)
15.0
15.0
5.0
15.0
15.0
CMS0.5uses Tune0.5DWT
and
0.4 Tune D6T!
0.5
CTEQ6L Tune
Intrinsic KT
University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 35
Summary
“Minumum Bias” Collisions
Tevatron
LHC
Outgoing Parton
PT(hard)
Initial-State Radiation
Proton
AntiProton
Proton
AntiProton
Underlying Event
Outgoing Parton
Underlying Event
Final-State
Radiation
¨ PYTHIA Tune DW is very similar to Tune A except that it fits the CDF PT(Z) distribution
and it uses the DØ prefered value of PARP(67) = 2.5 (determined from the dijet Δφ
distribution).
¨ PYTHIA Tune DWT is identical to Tune DW at 1.96 TeV but uses the ATLAS energy
extrapolation to the LHC (i.e. PARP(90) = 0.16).
¨ PYTHIA Tune D6 and D6T are similar to Tune DW and DWT, respectively, but use
CTEQ6L (i.e. LHAPDF = 10042).
University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 36
Drell-Yan Production (Run 2 vs LHC)
Drell-Yan Production
Proton
<pT(μ+μ-)> is much
larger at the LHC!
Lepton-Pair Transverse
Momentum
Lepton
AntiProton
Underlying Event
Underlying Event
Shapes of the pT(μ+μ-)
distribution at the Z-boson mass.
Initial-State
Radiation
Anti-Lepton
Lepton-Pair Transverse Momentum
Drell-Yan PT(μ+μ-) Distribution
80
0.10
Drell-Yan
Drell-Yan
LHC
60
1/N dN/dPT (1/GeV)
Average Pair PT
generator level
40
Tevatron Run 2
20
0
0.08
PY Tune DW (solid)
HERWIG (dashed)
0.06
70 < M(μ-pair) < 110 GeV
|η(μ-pair)| < 6
0.04
0.02
PY Tune DW (solid)
HERWIG (dashed)
Z
generator level
Tevatron Run2
LHC
Normalized to 1
0.00
0
100
200
300
400
500
600
700
800
900
1000
0
5
Lepton-Pair Invariant Mass (GeV)
10
15
20
25
30
35
40
PT(μ+μ-) (GeV/c)
¨ Average Lepton-Pair transverse momentum ¨ Shape of the Lepton-Pair pT distribution at the
Z-boson mass at the Tevatron and the LHC for
at the Tevatron and the LHC for PYTHIA
PYTHIA Tune DW and HERWIG (without MPI).
Tune DW and HERWIG (without MPI).
University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 37
The “Underlying Event” in
Drell-Yan Production
Drell-Yan Production
The “Underlying Event”
Lepton
Proton
HERWIG (without MPI)
is much less active than
PY Tune AW (with MPI)!
Underlying Event
Charged particle density
versus M(pair)
AntiProton
Underlying Event
“Underlying event” much
more active at the LHC!
Initial-State
Radiation
Anti-Lepton
Charged Particle Density: dN/dηdφ
Charged Particle Density: dN/dηdφ
1.5
1.0
RDF Preliminary
generator level
PY Tune AW
0.8
0.6
0.4
HERWIG
0.2
Drell-Yan
1.96 TeV
Z
Charged Particles (|η|<1.0, PT>0.5 GeV/c)
(excluding lepton-pair )
Charged Particle Density
Charged Particle Density
RDF Preliminary
generator level
Z
LHC
1.0
PY Tune AW
CDF
0.5
Drell-Yan
Charged Particles (|η|<1.0, PT>0.5 GeV/c)
(excluding lepton-pair )
HERWIG
0.0
0.0
0
50
100
150
200
250
0
50
100
150
200
250
Lepton-Pair Invariant Mass (GeV)
Lepton-Pair Invariant Mass (GeV)
¨ Charged particle density versus the lepton- ¨ Charged particle density versus the lepton-pair
pair invariant mass at 1.96 TeV for PYTHIA invariant mass at 14 TeV for PYTHIA Tune AW
and HERWIG (without MPI).
Tune AW and HERWIG (without MPI).
University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 38
Most Recent CDF
“Underlying Event” Studies
Fermilab 2008
CDF-QCD Data for Theory
Outline of the Project
The goal is to produce data (corrected to the
particle level) that can be used by the theorists to
tune and improve the QCD Monte-Carlo models
that are used to simulate hadron-hadron
collisions.
¨ The “Towards”, “Away”, and
“Transverse” regions of η-φ space.
¨ Four Jet Topologies.
¨ The “transMAX”, “transMIN”, and
Rick Field
Craig Group
Deepak Kar
“transDIF” regions.
¨ Also, study the “underlying event”
in Drell-Yan production.
¨ 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
Proton
Proton
plots.
¨ We plan to construct a “CDF-QCD
Jet #1 Direction
Lepton Parton
Outgoing
Δφ
PT(hard)
Initial-State Radiation
AntiProton
AntiProton
UnderlyingEvent
Event
Underlying
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.
University of Toronto
March 18, 2008
Drell-Yan Production
Anti-Lepton
Outgoing
Parton
UnderlyingEvent
Event
Underlying
Final-State
Radiation
Rick Field – Florida/CDF/CMS
“Toward”
“Transverse”
“Transverse”
“Away”
Page 39
“Towards”, “Away”, “Transverse”
Jet #1 Direction
“Transverse” region is
very sensitive to the
“underlying event”!
Look at the charged
particle density, the
charged PTsum density
and the ETsum density in
all 3 regions!
Δφ Correlations relative to the leading jet
Charged particles pT > 0.5 GeV/c |η| < 1
Calorimeter towers ET > 0.1 GeV |η| < 1
“Toward-Side” Jet
2π
Z-Boson
Direction
Jet #1 Direction
Δφ
Away Region
Δφ
Transverse
Region
“Toward”
“Toward”
“Transverse”
“Transverse”
“Away”
“Transverse”
“Transverse”
φ
Leading
Jet
Toward Region
“Away”
Transverse
Region
“Away-Side” Jet
Away Region
0
-1
η
+1
¨ 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”.
Each of the three regions have area ΔηΔφ = 2×120o = 4π/3.
University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 40
Event Topologies
¨ “Leading Jet” events correspond to the leading
calorimeter jet (MidPoint R = 0.7) in the region |η| < 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” (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 “backto-back” (Δφ12 > 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 |η| < 1 with
no other conditions.
¨ “Z-Boson” events are Drell-Yan events
with 70 < M(lepton-pair) < 110 GeV
with no other conditions.
University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Jet #1 Direction
Δφ
“Leading Jet”
“Toward”
“Transverse”
“Transverse”
subset
“Away”
Jet #1 Direction
Δφ
“Toward”
“Transverse”
“Inc2J Back-to-Back”
subset
“Transverse”
“Away”
“Exc2J Back-to-Back”
Jet #2 Direction
ChgJet #1 Direction
Δφ
“Toward”
“Transverse”
“Charged Jet”
“Transverse”
“Away”
Z-Boson Direction
Δφ
“Toward”
“Transverse”
“Transverse”
Z-Boson
“Away”
Page 41
“Leading Jet” Observables at the
Particle and Detector Level
“Leading Jet”
Jet #1 Direction
Observable
Particle Level
Detector Level
dNchg/dηdφ
Number of charged particles
per unit η-φ
(pT > 0.5 GeV/c, |η| < 1)
Number of “good” charged tracks
per unit η-φ
(pT > 0.5 GeV/c, |η| < 1)
dPTsum/dηdφ
Scalar pT sum of charged particles
per unit η-φ
(pT > 0.5 GeV/c, |η| < 1)
Scalar pT sum of “good” charged tracks per
unit η-φ
(pT > 0.5 GeV/c, |η| < 1)
<pT>
Average pT of charged particles
(pT > 0.5 GeV/c, |η| < 1)
Average pT of “good” charged tracks
(pT > 0.5 GeV/c, |η| < 1)
PTmax
Maximum pT charged particle
(pT > 0.5 GeV/c, |η| < 1)
Require Nchg ≥ 1
Maximum pT “good” charged tracks
(pT > 0.5 GeV/c, |η| < 1)
Require Nchg ≥ 1
dETsum/dηdφ
Scalar ET sum of all particles
per unit η-φ
(all pT, |η| < 1)
Scalar ET sum of all calorimeter towers
per unit η-φ
(ET > 0.1 GeV, |η| < 1)
PTsum/ETsum
Scalar pT sum of charged particles
(pT > 0.5 GeV/c, |η| < 1)
divided by the scalar ET sum of
all particles (all pT, |η| < 1)
Scalar pT sum of “good” charged tracks
(pT > 0.5 GeV/c, |η| < 1)
divided by the scalar ET sum of
calorimeter towers (ET > 0.1 GeV, |η| < 1)
Δφ
“Toward”
“Transverse”
“Transverse”
“Away”
Jet #1 Direction
Δφ
“Toward”
“Transverse”
“Transverse”
“Away”
Jet #2 Direction
“Back-to-Back”
University of Toronto
March 18, 2008
Also include the leading jet mass (new)!
Rick Field – Florida/CDF/CMS
Page 42
Overall Totals (|η| < 1)
ETsum = 775 GeV!
“Leading Jet”
Overall Totals versus PT(jet#1)
ETsum = 330 GeV
1000
CDF Run 2 Preliminary
Jet #1 Direction
ETsum (GeV)
data corrected
pyA generator level
Δφ
PTsum (GeV/c)
Average
100
“Overall”
Nchg
"Leading Jet"
MidPoint R=0.7 |η(jet#1)|<2
10
PTsum = 190 GeV/c
Charged Particles (|η|<1.0, PT>0.5 GeV/c)
Stable Particles (|η|<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, |η| < 1) and the overall
scalar pT sum of charged particles (pT > 0.5 GeV/c, |η| < 1) and the overall scalar ET sum of all
particles (|η| < 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)..
University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 43
Overall Totals (|η| < 1)
“Leading Jet”
Overall Number of Charged Particles
Jet #1 Direction
Δφ
“Overall”
Average Number of Charged
Particles
40
CDF Run 2 Preliminary
PY Tune A
data corrected
generator level theory
30
20
10
"Leading Jet"
MidPoint R=0.7 |η(jet#1)|<2
HW
Charged Particles (|η|<1.0, PT>0.5 GeV/c)
0
0
50
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, |η| < 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 and HERWIG
(without MPI) at the particle level (i.e. generator level).
University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 44
Overall Totals (|η| < 1)
“Leading Jet”
OverallOverall
Number
of Charged
Particles
Charged
PTsum
Jet #1 Direction
Δφ
AverageNumber
PTsumof(GeV/c)
Average
Charged
Particles
40040
CDF
CDFRun
Run2 2Preliminary
Preliminary
30030
PY Tune A
HW
data
corrected
data
corrected
generator
level
theory
generator
level
theory
PY Tune A
20020
“Overall”
10010
"Leading Jet"
"Leading Jet"
MidPoint R=0.7 |η(jet#1)|<2
MidPoint R=0.7 |η(jet#1)|<2
HW
ChargedParticles
Particles(|η|<1.0,
(|η|<1.0,PT>0.5
PT>0.5GeV/c)
GeV/c)
Charged
00
00
5050
100
100
150
150
200
200
250
250
300
300
350
350
400
400
PT(jet#1) (GeV/c)
(GeV/c)
PT(jet#1)
¨ Data
Data at
at 1.96
1.96 TeV
TeV on
on the
the overall
overall scalar
number
charged
particles
(pT > (p
0.5 GeV/c,
|η| < 1) for “leading jet” events
¨
pTofsum
of charged
particles
T > 0.5 GeV/c, |η| < 1) for “leading jet”
as a function
of the leading
jet pT. The
are corrected to the particle level (with errors that include both
events
as a function
of the leading
jet pdata
T. The data are corrected to the particle level (with errors that include
the statistical
errorerror
and the
uncertainty
) and) are
with with
PYTHIA
TuneTune
A and
both
the statistical
andsystematic
the systematic
uncertainty
andcompared
are compared
PYTHIA
A HERWIG
and
generator level).
HERWIG
(without
at the
particle
level (i.e. level).
(without MPI)
at theMPI)
particle
level
(i.e. generator
University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 45
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University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 46
CDF DiJet Event: M(jj) ≈ 1.4 TeV
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University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 47
“Towards”, “Away”, “Transverse”
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University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 48
“Towards”, “Away”, “Transverse”
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University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 49
“Towards”, “Away”, “Transverse”
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University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 50
The “Toward” Region
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University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 51
The “Toward” Region
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University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 52
The “Toward” Region
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University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 53
The “Away” Region
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University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 54
The “Away” Region
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University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 55
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University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 56
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March 18, 2008
Rick Field – Florida/CDF/CMS
Page 57
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University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 58
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March 18, 2008
Rick Field – Florida/CDF/CMS
Page 59
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March 18, 2008
Rick Field – Florida/CDF/CMS
Page 60
The “Transverse” Region
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March 18, 2008
Rick Field – Florida/CDF/CMS
Page 61
The “Transverse” Region
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March 18, 2008
Rick Field – Florida/CDF/CMS
Page 62
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University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 63
The “Transverse” Region
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University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 64
The “Transverse” Region
“Leading Jet”
Jet #1 Direction
Δφ
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University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 65
“transMAX” & “transMIN”
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radiation).
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densities.
University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 66
The “TransMAX/MIN” Regions
“Leading Jet”
"TransMAX"
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dN/dηdφ
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University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 67
The “TransMAX/MIN” Regions
“Leading Jet”
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dN/dηdφ
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University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 68
The “TransMAX/MIN” Regions
“Leading Jet”
Jet #1 Direction
Δφ
“Toward”
“TransMAX”
“TransMIN”
“Away”
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University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 69
The “TransMAX/MIN” Regions
“Leading Jet”
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level).
University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 70
The “TransMAX/MIN” Regions
“Leading Jet”
Jet #1 Direction
Δφ
“Toward”
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HERWIG
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MPI) at level
the particle
level (i.e.
University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 71
The “TransMAX/MIN” Regions
“Leading Jet”
Jet #1 Direction
Δφ
“Toward”
“TransMAX”
“TransMIN”
“Away”
"TransMAX"
Density
(GeV)
"Transverse"
Density
(GeV)
TransMAX ETsum
-ETsum
TransMIN
(GeV)
"TransveMIN"
ETsum
Density
(GeV)
"TransMAX"
"TransMIN"
ETsum
Density:
dET/dηdφ
"TransMAX/MIN"
ETsum
Density:
dET/dηdφ
"TransDIF" ETsum
Density:
dET/dηdφ
6.0
3.0
6.0
5.0
CDF
"Leading Jet"
CDF Run
Run 22 Preliminary
Preliminary
CDF
Run
4.0
4.0
2.0
4.0
3.0
PY Tune A
2.0
2.0
1.0
2.0
HW
data corrected
generator level theory
HW
PY
PYTune
TuneAA
"Leading Jet"
MidPoint R=0.7 |η(jet#1)|<2
"Leading Jet"
"transMIN"
Jet"
MidPoint "Leading
R=0.7 |η(jet#1)|<2
MidPoint
R=0.7 |η(jet#1)|<2
PY Tune
A
Stable Particles (|η|<1.0, all PT)
Stable
Particles
(|η|<1.0,
all PT)
Stable
Particles
(|η|<1.0,
all PT)
HW
1.0
HW
0.0
0.0
0.0
0.0
CDF Run 2 Preliminary
data
MidPoint R=0.7 |η(jet#1)|<2
datacorrected
corrected
data
corrected
"transMAX"
generator
theory
generatorlevel
level
theory
generator
level
theory
Stable
Particles (|η|<1.0, all PT)
00
0
50
50
50
100
100
100
150
150
150
200
200
200
250
250
250
250
300
300
300
300
350
350
350
350
400
400
400
400
PT(jet#1)
PT(jet#1) (GeV/c)
(GeV/c)
(GeV/c)
PT(jet#1)
(GeV/c)
¨
¨ Data
Data at
at 1.96
1.96 TeV
TeV on
on the
the scalar
scalar E
ETTT sum
sum density,
density, dET/dηdφ,
dET/dηdφ, with
with |η|
|η| <
< 11 for
for “leading
“leading jet”
jet” events
events as
as aa function
function of
of
of
leading
“transMAX”
region.
corrected
to the
particle
(with
errors
the
leading
jet
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thethe
“transMIN”
region.
TheThe
datadata
are are
corrected
to the
particle
levellevel
(with
errors
thatthat
T for
thethe
leading
jetjet
T for “transDIF” = “transMAX”-”transMIN. The data are corrected to the particle level (with
include
both
the statistical
and the
systematic
) and are compared
PYTHIA
A and
errors that
include
both theerror
statistical
error
and the uncertainty
systematic uncertainty
) and are with
compared
withTune
PYTHIA
level).
HERWIG
MPI)
at the particle
(i.e. generator
generator level).
Tune A and(without
HERWIG
(without
MPI) at level
the particle
level (i.e.
University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 72
“TransMIN” Nchg Density
"TransMIN" Charged Particle Density: dN/dηdφ
0.6
Jet #1 Direction
“Toward”
“TransMAX”
“TransMIN”
“Away”
"TransMIN" Charged Density
Δφ
CDF Run 2 Preliminary
"Leading Jet"
MidPoint R=0.7 |η(jet#1)|<2
data corrected
generator level theory
HW
0.4
0.2
PY Tune A
Charged Particles (|η|<1.0, PT>0.5 GeV/c)
0.0
0
50
100
These are the key plots!
Tune A does not produce
enough activity in the
“transMIN” region!
150
200
250
300
350
400
PT(jet#1) (GeV/c)
¨ Data at 1.96 TeV on the density of charged particles, dN/dηdφ, with pT > 0.5 GeV/c and |η| < 1 for “leading
jet” events as a function of the leading jet pT for the “transMIN” 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 A and HERWIG (without MPI) at the particle level (i.e. generator level).
University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 73
“TransMIN” PTsum Density
"TransMIN" Charged PTsum Density: dPT/dηdφ
Jet #1 Direction
Δφ
“Toward”
“TransMAX”
“TransMIN”
“Away”
"TransMIN" PTsum Density (GeV/c)
0.6
CDF Run 2 Preliminary
"Leading Jet"
MidPoint R=0.7 |η(jet#1)|<2
data corrected
generator level theory
0.4
0.2
PY Tune A
HW
Charged Particles (|η|<1.0, PT>0.5 GeV/c)
0.0
0
50
100
These are the key plots!
Tune A does not produce
enough activity in the
“transMIN” region!
150
200
250
300
350
400
PT(jet#1) (GeV/c)
¨ Data at 1.96 TeV on the charged scalar PTsum density, dPT/dηdφ, with pT > 0.5 GeV/c and |η| < 1 for “leading
jet” events as a function of the leading jet pT for the “transMIN” 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 A and HERWIG (without MPI) at the particle level (i.e. generator level).
University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 74
“TransMIN” ETsum Density
"TransMIN" ETsum Density: dET/dηdφ
Δφ
“Toward”
“TransMAX”
“TransMIN”
“Away”
"TransveMIN" ETsum Density (GeV)
3.0
Jet #1 Direction
"Leading Jet"
MidPoint R=0.7 |η(jet#1)|<2
CDF Run 2 Preliminary
data corrected
generator level theory
Stable Particles (|η|<1.0, all PT)
2.0
HW
1.0
PY Tune A
0.0
0
50
100
These are the key plots!
Tune A does not produce
enough activity in the
“transMIN” region!
150
200
250
300
350
400
PT(jet#1) (GeV/c)
¨ Data at 1.96 TeV on the scalar ETsum density, dET/dηdφ, with |η| < 1 for “leading jet” events as a function of
the leading jet pT for the “transMIN” 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 A and
HERWIG (without MPI) at the particle level (i.e. generator level).
University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 75
The Leading Jet Mass
“Leading Jet”
Leading Jet Invariant Mass
70
“Toward”
“Transverse”
“Transverse”
“Away”
Jet Mass (GeV)
Jet #1 Direction
Δφ
CDF Run 2 Preliminary
data corrected
generator level theory
60
50
40
PY Tune A
30
20
10
"Leading Jet"
MidPoint R=0.7 |η(jet#1)|<2
HW
0
0
50
100
150
200
250
300
350
400
PT(jet#1) (GeV/c)
¨
1.96
TeV- on
the leading
invariant
mass formass
“leading
jet” events
a function
of the leading
pT
¨ Data
Showsatthe
Data
Theory
for thejet
leading
jet invariant
for “leading
jet”asevents
as a function
of thejet
leading
for
“transverse” region. The data are corrected to the particle level (with errors that include both the
jet pthe
T for the “transverse” region for PYTHIA Tune A and HERWIG (without MPI).
statistical error and the systematic uncertainty) and are compared with PYTHIA Tune A and HERWIG
(without MPI) at the particle level (i.e. generator level).
University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 76
The Leading Jet Mass
“Leading Jet”
Leading Jet Invariant
Off by ~2Mass
GeV
12.0
70
“Toward”
“Transverse”
“Transverse”
“Away”
Data
Theory
(GeV)
Jet-Mass
(GeV)
Jet #1 Direction
Δφ
CDF
CDFRun
Run22Preliminary
Preliminary
"Leading Jet"
MidPoint R=0.7 |η(jet#1)|<2
data
datacorrected
corrected
generator
generatorlevel
leveltheory
theory
60
8.0
50
HW
PY Tune A
40
4.0
30
PY Tune A
20
0.0
10
"Leading Jet"
MidPoint R=0.7 |η(jet#1)|<2
HW
-4.0
0
00
5050
100
100
150
150
200
200
250
250
300
300
350
400
PT(jet#1
uncorrected)
PT(jet#1)
(GeV/c)(GeV/c)
¨
1.96
TeV- on
the leading
invariant
mass formass
“leading
jet” events
a function
of the leading
pT
¨ Data
Showsatthe
Data
Theory
for thejet
leading
jet invariant
for “leading
jet”asevents
as a function
of thejet
leading
for
“transverse” region. The data are corrected to the particle level (with errors that include both the
jet pthe
T for the “transverse” region for PYTHIA Tune A and HERWIG (without MPI).
statistical error and the systematic uncertainty) and are compared with PYTHIA Tune A and HERWIG
(without MPI) at the particle level (i.e. generator level).
University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 77
The “Underlying Event” in
High PT Jet Production (LHC)
High PT Jet Production
Outgoing Parton
PT(hard)
Initial-State
Radiation
The “Underlying Event” Proton
Underlying Event
Underlying Event
“Underlying event” much
more active at the LHC!
Final-State
Radiation
Outgoing Parton
"Transverse" Charged Particle Density: dN/dηdφ
"Transverse" Charged Particle Density: dN/dηdφ
1.0
2.0
RDF Preliminary
LHC
RDF Preliminary
generator level
0.8
0.6
PY Tune AW
HERWIG
0.4
1.96 TeV
0.2
"Leading Jet"
Charged Particles (|η|<1.0, PT>0.5 GeV/c)
0.0
"Transverse" Charged Density
"Transverse" Charged Density
Charged particle density
versus PT(jet#1)
AntiProton
generator level
1.5
PY Tune AW
HERWIG
1.0
CDF
0.5
"Leading Jet"
Charged Particles (|η|<1.0, PT>0.5 GeV/c)
0.0
0
50
100
150
200
250
300
350
400
450
500
0
250
500
PT(particle jet#1) (GeV/c)
750
1000
1250
1500
1750
2000
2250
2500
PT(particle jet#1) (GeV/c)
¨ Charged particle density in the “Transverse” ¨ Charged particle density in the “Transverse”
region versus PT(jet#1) at 1.96 TeV for PY
region versus PT(jet#1) at 14 TeV for PY Tune
Tune AW and HERWIG (without MPI).
AW and HERWIG (without MPI).
University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 78
Min-Bias at the LHC
¨ We have learned a lot about “Min-Bias” at the
Tevatron, but we do not know what to expect at
the LHC. This will depend on the Min-Bias Trigger!
¨ We are making good progress in understanding
and modeling the “underlying event”. However,
we do not yet have a perfect fit to all the features
of the CDF “underlying event” data!
“Minumum Bias” Collisions
Proton
AntiProton
Charged Particle Density: dN/dη
10
Charged Particle Density
¨ “Min-Bias” is not well defined. What you
see depends on what you trigger on! Every
trigger produces some biases.
pyA
pyDW
pyDWT
ATLAS
Generator Level
14 TeV
8
6
4
2
Charged Particles (all pT)
0
-10
-8
-6
-4
-2
0
2
4
6
8
10
PseudoRapidity η
Outgoing Parton
PT(hard)
¨ Need to measure “Min-Bias” and the “underlying
event” at the LHC as soon as possible and tune the
Monte-Carlo modles and compare with CDF!
Initial-State Radiation
Proton
AntiProton
Underlying Event
Outgoing Parton
University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Underlying Event
Final-State
Radiation
Page 79
UE&MB@CMS
UE&MB@CMS
“Minimum-Bias” Collisions
Proton
Proton
High PT Jet Production
Outgoing Parton
PT(hard)
Initial-State
Radiation
Proton
Proton
Underlying Event
Outgoing Parton
¨ 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)
Underlying Event
Final-State
Radiation
Drell-Yan Production
Lepton
Proton
Proton
Underlying Event
Underlying Event
¨ “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 DrellYan)
Initial-State
Radiation
Anti-Lepton
Drell-Yan Production
Lepton-Pair
PT(pair)
Proton
Proton
Underlying Event
Underlying Event
Initial-State
Radiation
Final-State
Radiation
¨ Drell-Yan Studies: Transverse momentum distribution of
the lepton-pair versus the mass of the lepton-pair,
<pT(pair)>, <pT2(pair)>, dσ/dpT(pair) (only requires
muons). Event structure for large lepton-pair pT (i.e. μμ
+jets, requires muons).
Outgoing Parton
University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 80
UE&MB@CMS
UE&MB@CMS
“Minimum-Bias” Collisions
Proton
Proton
High PT Jet Production
Outgoing Parton
PT(hard)
Initial-State
Radiation
Proton
Proton
Underlying Event
Outgoing Parton
¨ 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)
Underlying Event
Final-State
Radiation
Drell-Yan Production
Lepton
Proton
Proton
Underlying Event
Underlying Event
Study charged
particles
¨ “Underlying
Event”
Studies: The “transverse region” in
and“leading
muons using
the
CMS
detector charged particle jet
Jet” and “back-to-back”
atproduction
the LHC (as
soon
possible)!
and
theas“central
region” in Drell-Yan
production. (requires charged tracks and muons for DrellYan)
Initial-State
Radiation
Anti-Lepton
Drell-Yan Production
Lepton-Pair
PT(pair)
Proton
Proton
Underlying Event
Underlying Event
Initial-State
Radiation
Final-State
Radiation
¨ Drell-Yan Studies: Transverse momentum distribution of
the lepton-pair versus the mass of the lepton-pair,
<pT(pair)>, <pT2(pair)>, dσ/dpT(pair) (only requires
muons). Event structure for large lepton-pair pT (i.e. μμ
+jets, requires muons).
Outgoing Parton
University of Toronto
March 18, 2008
Rick Field – Florida/CDF/CMS
Page 81
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”. However, we do not
yet have a perfect fit to all the features of the CDF
“underlying event” data!
¨ There are over 128 plots to get “blessed” and then
published. So far we have only looked at average
quantities. We plan to also produce distributions and
flow plots
¨ I will 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 .
PT(hard)
Initial-State Radiation
Proton
AntiProton
Underlying Event
Outgoing Parton
Underlying Event
Final-State
Radiation
CDF-QCD Data for Theory
¨ Need to measure “Min-Bias” and the “underlying
event” at the LHC as soon as possible and tune the
Monte-Carlo modles and compare with CDF!
University of Toronto
March 18, 2008
Outgoing Parton
Rick Field – Florida/CDF/CMS
UE&MB@CMS
Page 82
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”. However, we do not
analysis approval
in December 2007!
Proton
yet have a perfect fit to allCMS
the features
of the CDF
“underlying event” data!
Outgoing Parton
PT(hard)
Initial-State Radiation
AntiProton
Underlying Event
¨ There are over 128 plots to get “blessed” and then
published. So far we have only looked at average
quantities. We plan to also produce distributions and
flow plots
¨ I will 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 .
Final-State
Radiation
CDF-QCD Data for Theory
¨ Need to measure “Min-Bias” and the “underlying
event” at the LHC as soon as possible and tune the
Monte-Carlo modles and compare with CDF!
University of Toronto
March 18, 2008
Outgoing Parton
Underlying Event
Rick Field – Florida/CDF/CMS
UE&MB@CMS
Page 83