“Min-Bias” & “Underlying Event”
at the Tevatron and the LHC
! What happens when a high energy
proton and an antiproton collide?
“Min-Bias”
“Soft” Collision (no hard scattering)
ProtonProton
2 TeV
AntiProton
AntiProton
! Most of the time the proton and
antiproton ooze through each other
and fall apart (i.e. no hard scattering).
“Hard” Scattering Outgoing Parton
The outgoing particles continue in
PT(hard)
roughly the same direction as initial
proton and antiproton. A “Min-Bias” Proton
AntiProton
collision.
Underlying Event
Underlying Event
Initial-State
! Occasionally there will be a “hard”
Radiation
Final-State
parton-parton collision resulting in large
Radiation
transverse momentum outgoing partons.
Outgoing Parton
Also a “Min-Bias” collision.
! The “underlying event” is everything
except the two outgoing hard scattered
“jets”. It is an unavoidable background
to many collider observables.
CPT Week - JetMET
May 5, 2003
“Underlying Event”
Proton
Beam-Beam Remnants
Rick Field - Florida/CDF
AntiProton
Beam-Beam Remnants
Initial-State
Radiation
Page 1
“Min-Bias” & “Underlying Event”
at the Tevatron and the LHC
! What happens when a high energy
proton and an antiproton collide?
“Min-Bias”
“Soft” Collision (no hard scattering)
ProtonProton
AntiProton
AntiProton
2 TeV
! Most of the time the proton and
antiproton ooze through each other
and fall apart (i.e. no hard scattering).
“Hard” Scattering Outgoing Parton
The outgoing particles continue in
PT(hard)
roughly the same direction as initial
Are
proton and antiproton. A “Min-Bias” Proton
these
AntiProton
collision.
the
Underlying Event
Underlying Event
Initial-State
! Occasionally there will be a “hard”
same?
Radiation
Final-State
parton-parton collision resulting in large
Radiation
No!
transverse momentum outgoing partons.
Outgoing Parton
Also a “Min-Bias” collision.
! The “underlying event” is everything
except the two outgoing hard scattered
“jets”. It is an unavoidable background
to many collider observables.
CPT Week - JetMET
May 5, 2003
“Underlying Event”
Proton
AntiProton
Beam-Beam Remnants
Rick Field - Florida/CDF
Beam-Beam Remnants
“underlying event” has
initial-state radiation!
Initial-State
Radiation
Page 2
Beam-Beam Remnants
“Hard” Collision
outgoing parton
“Hard” Component
AntiProton
Proton
initial-state radiation
outgoing parton
initial-state radiation
outgoing jet
final-state radiation
Maybe not all “soft”!
“Soft?” Component
+
Beam-Beam Remnants
final-state radiation
! The underlying event in a hard scattering process has a “hard” component (particles that
arise from initial & final-state radiation and from the outgoing hard scattered partons)
and a “soft?” component (“beam-beam remnants”).
! Clearly? the “underlying event” in a hard scattering process should not look like a “MinBias” event because of the “hard” component (i.e. initial & final-state radiation).
! However, perhaps “Min-Bias” collisions are a good model for the “beam-beam remnant”
component of the “underlying event”.
“Min-Bias” Collision
“Soft?” Component
color string
Are these the same?
Hadron
Hadron
color string
Beam-Beam Remnants
CPT Week - JetMET
May 5, 2003
Rick Field - Florida/CDF
Page 3
Beam-Beam Remnants
“Hard” Collision
outgoing parton
“Hard” Component
AntiProton
Proton
initial-state radiation
outgoing parton
initial-state radiation
outgoing jet
final-state radiation
Maybe not all “soft”!
“Soft?” Component
+
Beam-Beam Remnants
final-state radiation
! The underlying event in a hardIfscattering
process
we are going
to lookhas
at a “hard” component (particles that
arise from initial & final-state“Min-Bias”
radiation and
fromasthe
collisions
a outgoing hard scattered partons)
guide to understanding
the
and a “soft?” component (“beam-beam
remnants”).
“beam-beam remnants”,
! Clearly? the “underlying event” then
in a hard
scattering
we better
study process should not look like a “MinBias” event because of the “hard” component
carefully the(i.e. initial & final-state radiation).
“Min-Bias”
! However, perhaps “Min-Bias” collisions
are data!
a good model for the “beam-beam remnant”
component of the “underlying event”.
“Min-Bias” Collision
“Soft?” Component
color string
Are these the same?
Hadron
Hadron
color string
Beam-Beam Remnants
! The “beam-beam remnant” component is, however, color connected to the “hard”
component so this comparison is (at best) an approximation.
CPT Week - JetMET
May 5, 2003
Rick Field - Florida/CDF
Page 4
CDF Run 1 “Min-Bias” Data
Charged Particle Density
Charged Particle Density: dN/dη
ηdφ
φ
Charged Particle Pseudo-Rapidity Distribution: dN/dη
η
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 1.8 TeV
CDF Min-Bias 630 GeV
1
CDF Min-Bias 630 GeV
CDF Min-Bias 1.8 TeV
all PT
all PT
0.0
0
-4
-3
-2
-1
0
1
2
3
4
-4
-3
-2
-1
0
1
2
3
4
Pseudo-Rapidity η
Pseudo-Rapidity η
<dN
/dη
η> = 4.2
CDF
! chgShows
<dNchg/dη
ηof
dφ
φcharged
> = 0.67 particles per unit pseudo-rapidity
“Min-Bias” data on the number
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
η| < 1, all PT).
ηdφ
φ, by dividing by 2π
π.
! Convert to charged particle density, dNchg/dη
∆ηx∆φ
∆η ∆φ = 1
There are about 0.67 charged particles per unit η-φ
φ in “Min-Bias”
∆φ = 1
collisions at 1.8 TeV (|η
η| < 1, all PT).
0.67
∆η = 1
CPT Week - JetMET
May 5, 2003
Rick Field - Florida/CDF
Page 5
CDF Run 1 “Min-Bias” Data
Charged Particle Density
Charged Particle Density: dN/dη
ηdφ
φ
Charged Particle Pseudo-Rapidity Distribution: dN/dη
η
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 1.8 TeV
CDF Min-Bias 630 GeV
1
CDF Min-Bias 630 GeV
CDF Min-Bias 1.8 TeV
all PT
all PT
0.0
0
-4
-3
-2
-1
0
1
2
3
4
-4
-3
-2
-1
0
1
2
3
4
Pseudo-Rapidity η
Pseudo-Rapidity η
<dN
/dη
η> = 4.2
CDF
! chgShows
<dNchg/dη
ηof
dφ
φcharged
> = 0.67 particles per unit pseudo-rapidity
“Min-Bias” data on the number
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
η| < 1, all PT).
ηdφ
φ, by dividing by 2π
π.
! Convert to charged particle density, dNchg/dη
∆ηx∆φ
∆η ∆φ = 1
There are about 0.67 charged particles per unit η-φ
φ in “Min-Bias”
∆φ = 1
collisions at 1.8 TeV (|η
η| < 1, all PT).
0.67
0.25
! There are about 0.25 charged particles per unit η-φφ in “Min-Bias”
∆η = 1
collisions at 1.8 TeV (|η
η| < 1, PT > 0.5 GeV/c).
CPT Week - JetMET
May 5, 2003
Rick Field - Florida/CDF
Page 6
CDF Run 1 “Min-Bias” Data
Energy Dependence
Charged Particle Density: dN/dη
ηdφ
φ
Charged Particle Density: dN/dη
ηdφ
φ
1.4
1.0
CDF Published
Charged density dN/dη
ηdφ
φ
dN/dηdφ
CDF Data
UA5 Data
Fit 2
Fit 1
1.2
0.8
0.6
0.4
0.2
CDF Min-Bias 630 GeV
CDF Min-Bias 1.8 TeV
all PT
1.0
0.8
0.6
0.4
0.2
η=0
0.0
-4
-3
-2
-1
0
1
2
3
4
0.0
10
Pseudo-Rapidity η
100
1,000
10,000
100,000
CM Energy W (GeV)
<dNchg/dη
ηdφ
φ> = 0.51
η = 0 630 GeV
24% increase
<dNchg/dη
ηdφ
φ> = 0.63
η = 0 1.8 TeV
LHC?
ηdφ
φ,
! Shows the center-of-mass energy dependence of the charged particle density, dNchg/dη
for “Min-Bias” collisions at η = 0. Also show a log fit (Fit 1) and a (log)2 fit (Fit 2) to the
CDF plus UA5 data.
! What should we expect for the LHC?
CPT Week - JetMET
May 5, 2003
Rick Field - Florida/CDF
Page 7
Herwig “Soft” Min-Bias
Can
Can we
we believe
believe HERWIG
HERWIG
“soft”
Min-Bias?
“soft”
Min-Bias?
No!
Charged Particle Density: dN/dη
ηdφ
φ
Charged Particle Density: dN/dη
ηdφ
φ
1.4
1.4
14 TeV
Herwig "Soft" Min-Bias
1.2
CDF Data
1.2
Charged density dN/dη
ηdφ
φ
UA5 Data
dN/dηdφ
1.0
0.8
0.6
0.4
0.2
1.8 TeV
630 GeV
-6
-4
-2
0
2
4
HW Min-Bias
0.8
0.6
0.4
0.2
all PT
0.0
Fit 2
Fit 1
1.0
η=0
6
0.0
10
Pseudo-Rapidity η
100
1,000
10,000
100,000
CM Energy W (GeV)
LHC?
ηdφ
φ,
! Shows the center-of-mass energy dependence of the charged particle density, dNchg/dη
for “Min-Bias” collisions compared with the HERWIG “Soft” Min-Bias Monte-Carlo
model. Note: there is no “hard” scattering in HERWIG “Soft” Min-Bias.
! HERWIG “Soft” Min-Bias contains no hard parton-parton interactions and describes
ηdφ
φ, in “Min-Bias” collisions.
fairly well the charged particle density, dNchg/dη
ηdφ
φ at η = 0 in going from the
! HERWIG “Soft” Min-Bias predicts a 45% rise in dNchg/dη
Tevatron (1.8 TeV) to the LHC (14 TeV). 4 charged particles per unit η becomes 6.
CPT Week - JetMET
May 5, 2003
Rick Field - Florida/CDF
Page 8
CDF Run 1 “Min-Bias” Data
PT Dependence
Lots of “hard” scattering
in “Min-Bias”!
Charged Particle Density
Charged Particle Density: dN/dη
ηdφ
φ
1.4
1.0E+01
14 TeV
Herwig "Soft" Min-Bias
CDF Preliminary
1.2
1.0E+00
0.8
0.6
0.4
0.2
1.8 TeV
630 GeV
all PT
0.0
-6
-4
-2
0
2
4
6
Pseudo-Rapidity η
! Shows the energy dependence of the
Charged Density dN/dη
ηdφ
φdPT (1/GeV/c)
1.0
dN/dη
ηdφ
φ
|η
η|<1
1.0E-01
CDF Min-Bias Data at 1.8 TeV
1.0E-02
1.0E-03
HW "Soft" Min-Bias
at 630 GeV, 1.8 TeV, and 14 TeV
1.0E-04
1.0E-05
charged particle density, dNchg/dη
ηdφ
φ, for
1.0E-06
“Min-Bias” collisions compared with
0
2
4
6
8
10
12
14
PT (GeV/c)
HERWIG “Soft” Min-Bias.
ηdφ
φdPT, for “Min-Bias”
! Shows the PT dependence of the charged particle density, dNchg/dη
collisions at 1.8 TeV collisions compared with HERWIG “Soft” Min-Bias.
! HERWIG “Soft” Min-Bias does not describe the “Min-Bias” data! The “Min-Bias” data
contains a lot of “hard” parton-parton collisions which results in many more particles at
large PT than are produces by any “soft” model.
CPT Week - JetMET
May 5, 2003
Rick Field - Florida/CDF
Page 9
Min-Bias: Combining
“Hard” and “Soft” Collisions
No easy way to
“mix” HERWIG “hard”
with HERWIG “soft”.
σHC
Charged Particle Density: dN/dη
ηdφ
φ
1.6
Hard-Scattering Cross-Section
Charged
Particle Density
100.00
CTEQ5L
1.8 TeV
Cross-Section (millibarns)
1.0E+01
Herwig Jet3
Herwig Min-Bias
CDF Min-Bias Data
10.00
CDF Preliminary
1.4
1.2
1.0E+00
1.0
HW PT(hard) > 3 GeV/c
0.8
0.6
0.4
0.2
HW "Soft" Min-Bias
1.8 TeV all PT
0.0
-4
-3
-2
-1
0
1
2
3
4
Pseudo-Rapidity η
CDF Min-Bias Data
Herwig Jet3
Herwig Min-Bias
! HERWIG “hard” QCD with PT(hard) > 3
GeV/c describes well the high PT tail but
produces too many charged particles
overall. Not all of the “Min-Bias” collisions
have a hard scattering with PT(hard) > 3
GeV/c!
Charged Density dN/dη
ηdφ
φdPT (1/GeV/c)
dN/dηdφ
HERWIG diverges!
1.0E-01
1.0E-02
1.00
1.8 TeV |η
η|<1
0.10
PYTHIA
HERWIG
HW PT(hard) > 3 GeV/c
0.01
0
2
4
6
8
10
12
14
16
18
PYTHIA cuts off
the divergence.
HW "Soft" Min-Bias
Can run
PT(hard)>0!
1.0E-03
1.0E-04
1.0E-05
1.0E-06
0
2
4
6
8
10
12
14
PT (GeV/c)
HERWIG “soft”
Min-Bias does not fit
the “Min-Bias” data!
! One cannot run the HERWIG “hard” QCD Monte-Carlo with PT(hard) < 3 GeV/c because
the perturbative 2-to-2 cross-sections diverge like 1/PT(hard)4?
CPT Week - JetMET
May 5, 2003
20
Hard-Scattering Cut-Off PTmin
Rick Field - Florida/CDF
Page 10
PYTHIA Min-Bias
PYTHIA Tune A
“Soft” + ”Hard”
CDF Run 2 Default
Tuned to fit the
“underlying event”!
Charged Particle Density
Charged Particle Density: dN/dη
ηdφ
φ
1.0
1.0E+00
CDF Published
Pythia 6.206 Set A
CDF Min-Bias Data
0.8
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/dη
ηdφ
φdPT (1/GeV/c)
dN/dηdφ
1.0E-01
1.8 TeV |η
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
0
2
4
6
8
10
12
PT(hard)in>“Min-Bias”!
0. One can simulate both “hard”
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)!
CPT Week - JetMET
May 5, 2003
Rick Field - Florida/CDF
Page 11
Studying the “Underlying Event”
at CDF
Outgoing Parton
The Underlying Event:
beam-beam remnants
initial-state radiation
multiple-parton interactions
PT(hard)
Initial-State Radiation
Proton
AntiProton
Underlying Event
Run II CDF
Underlying Event
“Evolution of
Charged Particle Jets
Final-State
and Calorimeter
Jets”
! The underlying event in a hard scattering
process is a complicated and not very well
Radiation
Outgoing Parton
Rick Field
understood object. It is an interesting
Run I CDF
region since it probes the interface
“Evolution of Charged Jets”
between perturbative and nonRick Field
perturbative physics.
David Stuart
! There are now four CDF analyses which
Rich Haas
quantitatively study the underlying event Run I CDF
and compare with the QCD Monte-Carlo “Cone Analysis”
Valeria Tano
models (2 Run I and 2 Run II).
Run II CDF
Eve Kovacs
! It is important to model this region well
“Jet Shapes & Energy Flow”
Joey Huston
since it is an unavoidable background to
Mario Martinez
all collider observables. Also, we need a
Anwar Bhatti
good model of “min-bias” collisions.
CPT Week - JetMET
May 5, 2003
Rick Field - Florida/CDF
Page 12
“Underlying Event”
as defined by “Charged particle Jets”
Charged Jet #1
“Transverse” regionDirection
is
very sensitive to the
“underlying event”!
Look at the charged
particle density in the
“transverse” region!
Charged Particle ∆φ Correlations
PT > 0.5 GeV/c |η
η| < 1
Toward-side
“Toward-Side”
Jet
∆φ
“jet”
(always)
2π
π
Charged Jet #1
Direction
∆φ
Away Region
Transverse
Region
“Toward”
“Toward”
Leading
ChgJet
φ
“Transverse”
“Transverse”
“Transverse”
“Transverse”
Toward Region
“Away”
Transverse
Region
“Away”
“Away-Side” Jet
Away-side “jet”
(sometimes)
Perpendicular to the plane of the
2-to-2 hard scattering
Away Region
0
-1
η
+1
! Look at charged particle correlations in the azimuthal angle ∆φ relative to the leading
charged particle jet.
o
o
o
o
∆φ|
∆φ|
∆φ|
! Define |∆φ
∆φ < 60 as “Toward”, 60 < |∆φ
∆φ < 120 as “Transverse”, and |∆φ
∆φ > 120 as
“Away”.
o
π/3.
! All three regions have the same size in η-φφ space, ∆ηx∆φ
∆η ∆φ = 2x120 = 4π
CPT Week - JetMET
May 5, 2003
Rick Field - Florida/CDF
Page 13
“Transverse”
Charged Particle Density
“Transverse” region as
defined by the leading
“charged particle jet”
“Toward”
“Transverse”
“Transverse”
“Away”
1.25
"Transverse" Charged Density
Charged Particle Jet #1
Direction
∆φ
"Transverse" Charged Particle Density: dN/dη
ηdφ
φ
CDF Run 1 Min-Bias
CDF Run 1 Data
CDF Run 1 JET20
data uncorrected
1.00
0.75
0.50
0.25
1.8 TeV |η
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)
η|<1, PT>0.5 GeV) as
! Shows the data on the average “transverse” charge particle density (|η
a function of the transverse momentum of the leading charged particle jet from Run 1.
CPT Week - JetMET
May 5, 2003
Rick Field - Florida/CDF
Page 14
“Transverse”
Charged Particle Density
“Transverse” region as
defined by the leading
“charged particle jet”
“Toward”
“Transverse”
“Transverse”
“Away”
1.25
1.25
1.25
"Transverse"Charged
ChargedDensity
Density
"Transverse"
"Transverse"
Charged
Density
Charged Particle Jet #1
Direction
∆φ
"Transverse"
ηηηdφ
φφφ
"Transverse" Charged
Charged Particle
Particle
Density:
dN/dη
dφ
Particle Density:
Density: dN/dη
dN/dη
dφ
CDF Run 1 Min-Bias
CDF Run 1 Min-Bias
CDF
Run
1 JET20
CDF
Run
1 Published
CDF Run 1 JET20
CDF Run 2 Preliminary
CDF Run 2
CDFPreliminary
Run 1 Data
CDF
CDFdata
Preliminary
uncorrected
1.00
1.00
1.00
data
datauncorrected
uncorrected
0.75
0.75
0.75
0.50
0.50
0.25
0.25
1.8
|η
|<1.0
PT>0.5
GeV
ηPT>0.5
|η
PT>0.5
η|<1.0
|η
|<1.0
GeVGeV/c
ηTeV
0.00
0.00
00
10 5 20
10
30
4015 50
20
60
70 25 80
80
30
40 130
50
90
90 100
10035110
110 120
120
13045140
140 150
150
PT(charged
PT(charged jet#1)
jet#1) (GeV/c)
(GeV/c)
(GeV/c)
Excellent agreement
between Run 1 and 2!
η|<1, PT>0.5 GeV) as
! Shows the data on the average “transverse” charge particle density (|η
a function of the transverse momentum of the leading charged particle jet from Run 1.
! Compares the Run 2 data (Min-Bias, JET20, JET50, JET70, JET100) with Run 1.
The errors on the (uncorrected) Run 2 data include both statistical and correlated
systematic uncertainties.
CPT Week - JetMET
May 5, 2003
Rick Field - Florida/CDF
Page 15
“Transverse”
Charged Particle Density
“Transverse” region as
defined by the leading
“charged particle jet”
“Toward”
“Transverse”
“Transverse”
“Away”
1.25
1.25
1.25
"Transverse"Charged
ChargedDensity
Density
Charged
Density
"Transverse"
"Transverse"
Charged Particle Jet #1
Direction
∆φ
"Transverse"
ηηηdφ
φφφ
"Transverse" Charged
Charged Particle
Particle
Density:
dN/dη
dφ
Particle Density:
Density: dN/dη
dN/dη
dφ
CDF Run 1 Min-Bias
CDFRun
Run11Published
Min-Bias
CDF
CDF
Run
1 JET20
CDF
Run
1 Published
CDFRun
Run21Preliminary
JET20
CDF
CDF Run 2 Preliminary
PYTHIA
Tune
CDF
RunA2
CDFPreliminary
Run 1 Data
CDF
CDF
Preliminary
CDFdata
Preliminary
uncorrected
1.00
1.00
1.00
data
uncorrected
data
uncorrected
data
uncorrected
theory corrected
0.75
0.75
0.75
0.50
0.50
0.25
0.25
1.8
TeV
|η
|<1.0
PT>0.5
GeV
ηPT>0.5
|η
PT>0.5
PT>0.5
GeV/c
GeV/c
η|<1.0
η|<1.0
|η
|<1.0
GeV
η|η
0.00
0.00
00
10 5 20
20
10
30
30
40
4015 50
50
20
60
60
70
702580
80
30
40 130
50
90
90 100
10035110
110 120
120
13045140
140 150
150
PT(charged
PT(charged jet#1)
jet#1) (GeV/c)
(GeV/c)
(GeV/c)
η|<1, PT>0.5 GeV) as
! Shows the data on the average “transverse” charge particle density (|η
a function of the transverse momentum of the leading charged particle jet from Run 1.
! Compares the Run 2 data (Min-Bias, JET20, JET50, JET70, JET100) with Run 1.
The errors on the (uncorrected) Run 2 data include both statistical
and Tune
correlated
PYTHIA
A was tuned to fit
the
“underlying
event” in Run I!
systematic uncertainties.
! Shows the prediction of PYTHIA Tune A at 1.96 TeV after detector simulation (i.e. after
CDFSIM).
CPT Week - JetMET
May 5, 2003
Rick Field - Florida/CDF
Page 16
“Transverse”
Charged PTsum Density
“Transverse” region as
defined by the leading
“charged particle jet”
“Toward”
“Transverse”
“Transverse”
“Away”
1.25
"Transverse" PTsum Density (GeV)
Charged Particle Jet #1
Direction
∆φ
"Transverse" Charged PTsum Density: dPTsum/dη
ηdφ
φ
CDF JET20
CDF Run 1 Data
CDF Min-Bias
data uncorrected
1.00
0.75
0.50
0.25
1.8 TeV |η
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)
η|<1, PT>0.5 GeV)
! Shows the data on the average “transverse” charged PTsum density (|η
as a function of the transverse momentum of the leading charged particle jet from Run 1.
CPT Week - JetMET
May 5, 2003
Rick Field - Florida/CDF
Page 17
“Transverse”
Charged PTsum Density
“Transverse” region as
defined by the leading
“charged particle jet”
“Toward”
“Transverse”
“Transverse”
“Away”
"Transverse"
PTsum
Density
(GeV)
"Transverse"
"Transverse"PTsum
PTsumDensity
Density(GeV/c)
(GeV)
Charged Particle Jet #1
Direction
∆φ
sum/dη
ηdφ
φ
"Transverse" Charged
Charged PTsum
PTsum Density:
Density: dPT
dPTsum
"Transverse"
1.25
1.25
CDFPreliminary
Preliminary
CDF
CDF
Run
1 Data
CDF JET20
CDF Min-Bias
data
uncorrected
data
datauncorrected
uncorrected
1.00
1.00
0.75
0.75
CDF
Run 2
CDF Run
1 Published
CDF
CDF
RunJET20
2 Preliminary
CDF Min-Bias
0.50
0.50
0.25
0.25
|η
|<1.0
PT>0.5
η|η
PT>0.5GeV
GeV/c
η|<1.0GeV
1.8 TeV |η
η|<1.0 PT>0.5
0.00
0.00
00
! Shows the
10 5 20
20
10
30
30
10
40 15 50
60
20
70 2580
90
140
10035110
110 120
120
13045
140 150
150
30 100
40 130
50
PT(charged jet#1)
jet#1) (GeV/c)
(GeV/c)
Excellent agreement
between
Run average
1 and 2!
data
on the
“transverse” charged PTsum density (|η
η|<1, PT>0.5 GeV)
as a function of the transverse momentum of the leading charged particle jet from Run 1.
! Compares the Run 2 data (Min-Bias, JET20, JET50, JET70, JET100) with Run 1. The
errors on the (uncorrected) Run 2 data include both statistical and correlated systematic
uncertainties.
CPT Week - JetMET
May 5, 2003
Rick Field - Florida/CDF
Page 18
“Transverse”
Charged PTsum Density
“Transverse” region as
defined by the leading
“charged particle jet”
“Toward”
“Transverse”
“Transverse”
“Away”
"Transverse"
PTsum
Density
(GeV)
"Transverse"
"Transverse"PTsum
PTsumDensity
Density(GeV/c)
(GeV)
Charged Particle Jet #1
Direction
∆φ
ηηdφ
φφ
sum/dη
"Transverse" Charged
Charged PTsum
PTsum Density:
Density: dPT
dPTsum
"Transverse"
1.25
1.25
1.25
CDFPreliminary
Preliminary
CDF
CDF
Run
1 Data
CDF JET20
CDF Min-Bias
data
uncorrected
data
datauncorrected
uncorrected
1.00
1.00
1.00
theory corrected
0.75
0.75
0.75
CDF Run
1Run
Published
CDF
2
CDF Run
1 Published
CDF Run 2 Preliminary
CDF
CDF
RunJET20
2 Preliminary
PYTHIA Tune A
CDF Min-Bias
0.50
0.50
0.50
0.25
0.25
0.25
|η
|<1.0
PT>0.5
η|η
PT>0.5GeV
GeV/c
η |<1.0GeV
1.8 TeV |η
η|<1.0 PT>0.5
0.00
0.00
0.00
000
10 5 20
20
10
30
30
10
40
4015 50
50
60
60
20
70
70 2580
80
90
140
90
10035110
110 120
120
13045
140 150
150
30 100
40 130
50
PT(charged
PT(charged jet#1)
jet#1) (GeV/c)
(GeV/c)
η|<1, PT>0.5 GeV)
! Shows the data on the average “transverse” charged PTsum density (|η
as a function of the transverse momentum of the leading charged particle jet from Run 1.
! Compares the Run 2 data (Min-Bias, JET20, JET50, JET70, JET100) with Run 1. The
errors on the (uncorrected) Run 2 data include both statistical and
correlated
systematic
PYTHIA
Tune A was
tuned to fit
the
“underlying
event”
in Run I!
uncertainties.
! Shows the prediction of PYTHIA Tune A at 1.96 TeV after detector simulation (i.e. after
CDFSIM).
CPT Week - JetMET
May 5, 2003
Rick Field - Florida/CDF
Page 19
Run 1 Charged Particle Density
“Transverse” PT Distribution
ηdφ
φ
"Transverse" Charged Particle Density: dN/dη
Charged Particle Density
1.0E+00
CDF Min-Bias
CDF JET20
CDF Run 1
data uncorrected
0.50
Factor of 2!
0.25
1.8 TeV |η
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/dη
ηdφ
φ> = 0.56
“Min-Bias”
CDF Run 1 Min-Bias data
<dNchg/dη
ηdφ
φ> = 0.25
CDF Run 1
"Transverse"
PT(chgjet#1) > 5 GeV/c
0.75
50
Charged Density dN/dη
ηdφ
φdPT (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
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
η|<1, PT>0.5 GeV). Shows how the “transverse” charge particle
density and the Min-Bias charge particle density is distributed in PT.
CPT Week - JetMET
May 5, 2003
Rick Field - Florida/CDF
Page 20
Tuned PYTHIA 6.206
Run 1 Tune A
1.00
"Transverse" Charged Density
CDF Run 1
PYTHIA 6.206 Set A
data uncorrected
theory corrected
0.75
0.50
0.25
η|<1.0 PT>0.5 GeV/c
1.8 TeV |η
0.00
0
5
10
15
20
25
30
35
PT(charged jet#1) (GeV/c)
40
45
50
Charged Density dN/dη
ηdφ
φdPT (1/GeV/c)
Describes the rise
from “Min-Bias” to
1.0E+00
“underlying event”!
"Transverse" Charged Particle Density: dN/dη
ηdφ
φ
Set A PT(charged jet#1) > 30 GeV/c
“Transverse” <dNchg/dη
ηdφ
φ> = 0.60
“Min-Bias”
Charged Particle Density
PYTHIA 6.206 Set A
CDF Run 1
data uncorrected
theory corrected
"Transverse"
PT(chgjet#1) > 5 GeV/c
1.0E-01
"Transverse"
PT(chgjet#1) > 30 GeV/c
1.0E-02
1.0E-03
1.0E-04
CDF Min-Bias
CTEQ5L
1.8 TeV |η
η |<1 PT>0.5 GeV/c
1.0E-05
Set A Min-Bias
<dNchg/dη
ηdφ
φ> = 0.24
0
2
4
6
8
10
12
14
PT(charged) (GeV/c)
η|<1, PT>0.5 GeV) versus
! Compares the average “transverse” charge particle density (|η
PT(charged jet#1) and the PT distribution of the “transverse” and “Min-Bias” densities with
the QCD Monte-Carlo predictions of a tuned version of PYTHIA 6.206 (PT(hard) > 0,
CTEQ5L, Set A). Describes “Min-Bias” collisions! Describes the “underlying event”!
CPT Week - JetMET
May 5, 2003
Rick Field - Florida/CDF
Page 21
HERWIG 6.4
“Transverse” PT Distribution
HERWIG has the too steep of a PT
dependence of the “beam-beam remnant”
ηdφ
φ
"Transverse" Chargedcomponent
Particle Density:
dN/dη
of the
“underlying
event”!
CDF Data
"Hard"
Total
data uncorrected
theory corrected
0.75
CDF Data
PT(chgjet#1) > 5 GeV/c
0.50
0.25
"Remnants"
1.8 TeV |η
η|<1.0 PT>0.5 GeV
0.00
0
5
10
"Transverse" Charged Particle Density
1.0E+00
Herwig 6.4 CTEQ5L
PT(hard) > 3 GeV/c
15
20
25
30
35
40
45
PT(charged jet#1) (GeV/c)
Herwig PT(chgjet#1) > 30 GeV/c
“Transverse” <dNchg/dη
ηdφ
φ> = 0.51
Herwig PT(chgjet#1) > 5 GeV/c
<dNchg/dη
ηdφ
φ> = 0.40
50
Charged Density dN/dη
ηdφ
φdPT (1/GeV/c)
"Transverse" Charged Density
1.00
data uncorrected
theory corrected
1.0E-01
1.8 TeV |η
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
1.0E-06
0
2
4
6
8
10
12
14
PT(charged) (GeV/c)
η|<1, PT>0.5 GeV) versus
! Compares the average “transverse” charge particle density (|η
PT(charged jet#1) and the PT distribution of the “transverse” density, dNchg/dη
ηdφ
φdPT 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.
CPT Week - JetMET
May 5, 2003
Rick Field - Florida/CDF
Page 22
“Underlying Event”
as defined by “Calorimeter Jets”
JetClu Jet #1
Charged Particle ∆φ Correlations
Direction
η| < 1
PT > 0.5 GeV/c |η
“Transverse” region is
2π
π
very sensitive to the
JetClu Jet #1
“Toward-Side” Jet
“underlying event”!
Direction
∆φ
“Toward”
Look at the charged
particle density in the
“transverse” region!
Away Region
∆φ
Transverse
Region
“Toward”
φ
“Transverse”
“Transverse”
“Transverse”
Leading
Jet
“Transverse”
Toward Region
“Away”
Transverse
Region
“Away”
“Away-Side” Jet
Away-side “jet”
(sometimes)
Away Region
Perpendicular to the plane of the
2-to-2 hard scattering
0
-1
η
+1
! Look at charged particle correlations in the azimuthal angle ∆φ relative to the leading
JetClu jet.
o
o
o
o
∆φ|
∆φ|
∆φ|
! Define |∆φ
∆φ < 60 as “Toward”, 60 < |∆φ
∆φ < 120 as “Transverse”, and |∆φ
∆φ > 120 as
“Away”.
o
π/3.
! All three regions have the same size in η-φφ space, ∆ηx∆φ
∆η ∆φ = 2x120 = 4π
CPT Week - JetMET
May 5, 2003
Rick Field - Florida/CDF
Page 23
“Transverse”
Charged Particle Density
∆φ
∆φ
“Toward”
“Toward”
“Transverse”
“Transverse”
“Transverse”
“Transverse”
“Away”
“Away”
"Transverse" Charged Particle Density: dN/dη
ηdφ
φ
1.00
1.00
"Transverse" Charged Density
JetClu Jet #1
JetClu
Jet #1
or
ChgJet#1
Direction
Direction
“Transverse” region as
defined by the leading
“calorimeter jet”
CDF
CDF Preliminary
PYTHIA Tune A
CDF Run 2 Preliminary
data
data uncorrected
uncorrected
theory corrected
0.75
0.75
0.50
0.50
JetClu (R = 0.7, |η
η(jet#1)| < 2)
0.25
0.25
Charged Particles (|η
η|<1.0, PT>0.5 GeV/c)
0.00
0.00
0
25
50
75
100
125
150
175
200
225
250
ET(jet#1) (GeV)
η|<1, PT>0.5 GeV)
! Shows the data on the average “transverse” charge particle density (|η
as a function of the transverse energy of the leading JetClu jet (R = 0.7, |η
η(jet)| < 2)
from Run 2., compared with PYTHIA Tune A after CDFSIM.
CPT Week - JetMET
May 5, 2003
Rick Field - Florida/CDF
Page 24
“Transverse”
Charged Particle Density
∆φ
∆φ
“Toward”
“Toward”
“Transverse”
“Transverse”
“Transverse”
“Transverse”
“Away”
“Away”
"Transverse"
ηdφ
φ
Charged Particle
Particle Density: dN/dη
"Transverse" Charged
1.00
1.00
1.00
Density
"Transverse"
"Transverse" Charged
Charged Density
Density
JetClu Jet #1
JetClu
Jet #1
or
ChgJet#1
Direction
Direction
“Transverse” region as
defined by the leading
“calorimeter jet”
CDF
CDF
Preliminary
CDFPreliminary
CDF
data Preliminary
uncorrected
data
data uncorrected
uncorrected
data uncorrected
theory
theorycorrected
corrected
0.75
0.75
0.75
PYTHIA
Tune A
JetCluJetClu
Jet#1 (R
= 0.7,
Jet#1
(R |η
=η(jet)|<2)
0.7,|η
η(jet)|<2)
CDF Run 2 Preliminary
0.50
0.50
0.50
ChgJet#1 R = 0.7
PYTHIA
Tune
A 1.96
JetClu (R
= 0.7, |η
η(jet#1)|
< 2)TeV
ChgJet#1 R = 0.7
0.25
0.25
0.25
Charged
Particles
(|η
ηη|<1.0,
PT>0.5
GeV/c)
Charged
Particles
(|η
|<1.0,
PT>0.5
GeV/c)
Charged
Particles
(|η
PT>0.5
GeV/c)
η|<1.0,
0.00
0.00
0.00
00
25
25
50
50
75
75
100
100
125
125
150
150
175
200
225
250
ET(jet#1)
(GeV) (GeV)
PT(chgjet#1)
or ET(jet#1)
η|<1, PT>0.5 GeV)
! Shows the data on the average “transverse” charge particle density (|η
as a function of the transverse energy of the leading JetClu jet (R = 0.7, |η
η(jet)| < 2)
from Run 2., compared with PYTHIA Tune A after CDFSIM.
! Compares the “transverse” region of the leading “charged particle jet”, chgjet#1, with
the “transverse” region of the leading “calorimeter jet” (JetClu R = 0.7), jet#1.
CPT Week - JetMET
May 5, 2003
Rick Field - Florida/CDF
Page 25
“Transverse”
Charged PTsum Density
“Transverse” region as
defined by the leading
“calorimeter jet”
ηdφ
φ
"Transverse" Charged PTsum Density: dPTsum/dη
JetClu Jet #1
JetClu
Jet #1
or ChgJet#1
Direction
∆φ
∆φ
“Toward”
“Transverse”
“Transverse”
“Transverse”
“Away”
"Transverse"
"Transverse" PTsum
PTsum Density
Density (GeV/c)
(GeV/c)
1.5
CDF Preliminary
data uncorrected
theory corrected
1.0
0.5
PYTHIA Tune A
CDF Run 2 Preliminary
JetClu (R = 0.7, |η
η(jet#1)| < 2)
Charged Particles (|η
η|<1.0, PT>0.5 GeV/c)
0.0
0
25
50
75
100
125
150
175
200
225
250
ET(jet#1) (GeV)
η|<1, PT>0.5
! Shows the data on the average “transverse” charged PTsum density (|η
GeV) as a function of the transverse energy of the leading JetClu jet (R = 0.7, |η
η(jet)| <
2) from Run 2., compared with PYTHIA Tune A after CDFSIM.
CPT Week - JetMET
May 5, 2003
Rick Field - Florida/CDF
Page 26
“Transverse”
Charged PTsum Density
“Transverse” region as
defined by the leading
“calorimeter jet”
ηdφ
φ
"Transverse" Charged PTsum Density: dPTsum/dη
JetClu Jet #1
JetClu
Jet #1
or ChgJet#1
Direction
∆φ
∆φ
“Toward”
“Transverse”
“Transverse”
“Transverse”
“Away”
"Transverse"
"Transverse" PTsum
PTsum Density
Density (GeV/c)
(GeV/c)
1.5
CDF Preliminary
CDF
Preliminary
data uncorrected
data
uncorrected
theory
corrected
1.0
JetClu Jet#1 (R = 0.7,|η
η(jet)|<2)
JetClu Jet#1 (R = 0.7,|η
η(jet)|<2)
0.5
PYTHIA Tune A
ChgJet#1 RR= =0.7
0.7
CDF ChgJet#1
Run 2 Preliminary
PYTHIA Tune A 1.96 TeV
η(jet#1)| < 2)
JetClu (R = 0.7, |η
Charged Particles
Particles (|η
(|η
η|<1.0,
|<1.0, PT>0.5
PT>0.5 GeV/c)
GeV/c)
Charged
ηη|<1.0,
PT>0.5 GeV/c)
Charged Particles (|η
0.0
0
25
50
75
100
125
150
175
200
225
250
PT(chgjet#1)
or ET(jet#1)
ET(jet#1)
(GeV) (GeV)
η|<1, PT>0.5
! Shows the data on the average “transverse” charged PTsum density (|η
GeV) as a function of the transverse energy of the leading JetClu jet (R = 0.7, |η
η(jet)| <
2) from Run 2., compared with PYTHIA Tune A after CDFSIM.
! Compares the “transverse” region of the leading “charged particle jet”, chgjet#1, with
the “transverse” region of the leading “calorimeter jet” (JetClu R = 0.7), jet#1.
CPT Week - JetMET
May 5, 2003
Rick Field - Florida/CDF
Page 27
Charged Particle Density
“Transverse” PT Distribution
ηdφ
φ
"Transverse" Charged Particle Density: dN/dη
"Transverse" Charged Particle Density
CDF Preliminary
data uncorrected
theory corrected
0.75
1.0E+00
PYTHIA Tune A
CDF Run 2 Preliminary
CDF Preliminary
JetClu R = 0.7 |η
η(jet)| < 2
0.50
JetClu (R = 0.7, |η
η(jet#1)| < 2)
0.25
Charged Particles (|η
η|<1.0, PT>0.5 GeV/c)
0.00
0
25
50
75
100
125
150
175
200
225
250
ET(jet#1) (GeV)
95 < ET(jet#1) > 130 GeV
“Transverse” <dNchg/dη
ηdφ
φ> = 0.65
30 < ET(jet#1) < 70 GeV/c
“Transverse” <dNchg/dη
ηdφ
φ> = 0.61
Charged Density dN/dη
ηdφ
φdPT (1/GeV/c)
"Transverse" Charged Density
1.00
data uncorrected
theory corrected
1.0E-01
PYTHIA Tune A 1.96 TeV
1.0E-02
95 < ET(jet#1) < 130 GeV
1.0E-03
1.0E-04
1.0E-05
30 < ET(jet#1) < 70 GeV
Charged Particles |η
η| < 1.0
1.0E-06
0
5
10
15
20
25
PT(charged) (GeV/c)
η|<1, PT>0.5 GeV) versus
! Compares the average “transverse” charge particle density (|η
ET(jet#1) with the PT distribution of the “transverse” density, dNchg/dη
ηdφ
φdPT.
! Shows the prediction of PYTHIA Tune A at 1.96 TeV after detector simulation (i.e. after
CDFSIM).
CPT Week - JetMET
May 5, 2003
Rick Field - Florida/CDF
Page 28
Relationship Between
“Calorimeter” and “Charged Particle” Jets
PT(chgjet#1)/ET(matched jet) vs PT(chgjet#1)
ET(matched jet) vs PT(charged jet#1)
1.2
160
CDF Preliminary
140
data uncorrected
theory corrected
120
PYTHIA Tune A
CDF Run 2 Preliminary
100
80
60
JetClu (R = 0.7, |η
η(jet#1)| < 2)
40
Charged Particles (|η
η|<1.0, PT>0.5 GeV/c)
20
PT(chgjet#1)/ET(matched jet)
Matched Jet ET (GeV)
180
1.0
0.8
PYTHIA Tune A
CDF Run 2 Preliminary
0.6
JetClu (R = 0.7, |η
η(jet#1)| < 2)
CDF Preliminary
0.4
data uncorrected
theory corrected
Charged Particles (|η
η|<1.0, PT>0.5 GeV/c)
0.2
0
0
10
20
30
40
50
60
70
80
90
100 110 120 130 140 150
0
10
20
30
40
50
60
70
80
90
100 110 120 130 140 150
PT(charged jet#1) (GeV/c)
PT(charged jet#1) (GeV/c)
! Shows the “matched” JetClu jet ET
versus the transverse momentum of the
leading “charged particle jet” (closest
jet within R = 0.7 of the leading chgjet).
! Shows the ratio of PT(chgjet#1) to the
“matched” JetClu jet ET versus
PT(chgjet#1).
The leading chgjet comes from a
JetClu jet that is, on the average,
about 90% charged!
CPT Week - JetMET
May 5, 2003
Rick Field - Florida/CDF
Page 29
Relationship Between
“Calorimeter” and “Charged Particle” Jets
PT(chgjet#1)/ET(matched jet) vs PT(chgjet#1)
ET(matched jet) vs PT(charged jet#1)
1.2
160
CDF Preliminary
140
data uncorrected
theory corrected
120
PYTHIA Tune A
CDF Run 2 Preliminary
100
80
60
JetClu (R = 0.7, |η
η(jet#1)| < 2)
40
Charged Particles (|η
η|<1.0, PT>0.5 GeV/c)
20
PT(chgjet#1)/ET(matched jet)
Matched Jet ET (GeV)
180
1.0
0.8
PYTHIA Tune A
CDF Run 2 Preliminary
0.6
JetClu (R = 0.7, |η
η(jet#1)| < 2)
CDF Preliminary
0.4
data uncorrected
theory corrected
Charged Particles (|η
η|<1.0, PT>0.5 GeV/c)
0.2
0
0
10
20
30
40
50
60
70
80
90
0
100 110 120 130 140 150
10
20
30
40
50
60
70
80
90
100 110 120 130 140 150
PT(charged jet#1) (GeV/c)
PT(charged jet#1) (GeV/c)
versus the transverse momentum of the
leading “charged particle jet” (closest
jet within R = 0.7 of the leading chgjet).
! Shows the EM fraction of the “matched”
JetClu jet and the EM fraction of a
typical JetClu jet.
"Calorimeter Jet" EM Fraction
ratio of PT(chgjet#1) to the
! Shows the
0.8
Electromagnetic Fraction
! Shows the “matched” JetClu jet ET
0.7
0.6
PYTHIA Tune A 1.96 TeV
CDF Preliminary
“matched”
JetClu jet ET versus
PT(chgjet#1).
Leading Jet
|η
η (jet)| < 0.7
data uncorrected
theory corrected
0.5
0.4
Jet matching
ChgJet#1
0.3
JetClu R = 0.7
0.2
0
25
50
75
100
125
150
175
200
225
250
PT(chgjet#1) or ET(jet#1) (GeV)
CPT Week - JetMET
May 5, 2003
Rick Field - Florida/CDF
Page 30
PYTHIA: Multiple Parton
Interaction Parameters
Multiple Parton Interactions
Outgoing Parton
PT(hard)
Proton
AntiProton
Underlying Event
Underlying Event
ParameterOutgoingValue
Parton
MSTP(81)
MSTP(82)
Same parameter that
cuts-off the hard 2-to-2
parton cross sections!
Pythia uses multiple parton
interactions to enhance
the underlying event.
Description
0
Multiple-Parton Scattering off
1
Multiple-Parton Scattering on
1
Multiple interactions assuming the same probability, with
an abrupt cut-off PTmin=PARP(81)
3
Multiple interactions assuming a varying impact
parameter and a hadronic matter overlap consistent with
a single Gaussian matter distribution, with a smooth turnoff PT0=PARP(82)
4
Multiple interactions assuming a varying impact
parameter and a hadronic matter overlap consistent with
a double Gaussian matter distribution (governed by
PARP(83) and PARP(84)), with a smooth turn-off
PT0=PARP(82)
CPT Week - JetMET
May 5, 2003
Rick Field - Florida/CDF
and now
HERWIG!
Jimmy: MPI
J. M. Butterworth
J. R. Forshaw
M. H. Seymour
Multiple parton
interaction more
likely in a hard
(central) collision!
Hard Core
Page 31
PYTHIA: Multiple Parton
Interaction Parameters
Parameter
Default
PARP(83)
0.5
PARP(84)
0.2
Description
Double-Gaussian: Fraction of total hadronic
matter within PARP(84)
Hard
Core
Double-Gaussian: Fraction of the overall hadron
radius containing the fraction PARP(83) of the
total hadronic matter.
Multiple Parton Interaction
Color String
Color String
PARP(86)
0.33
0.66
PARP(89)
1 TeV
PARP(90)
0.16
PARP(67)
1.0
CPT Week - JetMET
May 5, 2003
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. The remaining fraction consists of
quark-antiquark pairs.
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.
Rick Field - Florida/CDF
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
Page 32
PYTHIA Tune A
LHC Predictions
"Transverse" Charged PTsum Density: dPTsum/dη
ηdφ
φ
"Transverse" Charged Particle Density: dN/dη
ηdφ
φ
2.5
3.0
"Transverse" PTsum Density (GeV)
"Transverse" Charged Density
HERWIG 6.4
14 TeV
2.5
2.0
1.5
1.8 TeV
1.0
PYTHIA 6.206 Set A
0.5
CTEQ5L
|η
η|<1.0 PT>0 GeV
PYTHIA 6.206 Set A
2.0
14 TeV
Factor of 2!
HERWIG 6.4
1.5
1.0
1.8 TeV
0.5
CTEQ5L
|η
η|<1.0 PT>0 GeV
0.0
0.0
0
5
10
15
20
25
30
35
40
45
50
0
5
10
15
20
25
30
35
40
45
50
PT(charged jet#1) (GeV/c)
PT(charged jet#1) (GeV/c)
η|<1, PT>0) versus
! Shows the average “transverse” charge particle and PTsum density (|η
PT(charged jet#1) predicted by HERWIG 6.4 (PT(hard) > 3 GeV/c, CTEQ5L). and a tuned
versions of PYTHIA 6.206 (PT(hard) > 0, CTEQ5L, Set A) at 1.8 TeV and 14 TeV.
! At 14 TeV tuned PYTHIA (Set A) predicts roughly 2.3 charged particles per unit η-φφ (PT > 0)
in the “transverse” region (14 charged particles per unit η) which is larger than the HERWIG
prediction.
! At 14 TeV tuned PYTHIA (Set A) predicts roughly 2 GeV/c charged PTsum per unit η-φφ (PT
> 0) in the “transverse” region at PT(chgjet#1) = 40 GeV/c which is a factor of 2 larger than
at 1.8 TeV and much larger than the HERWIG prediction.
CPT Week - JetMET
May 5, 2003
Rick Field - Florida/CDF
Page 33
PYTHIA Tune A
LHC Predictions
"Transverse" Charged Particle Density: dN/dη
ηdφ
φ
"Transverse" Charged PTsum Density: dPTsum/dη
ηdφ
φ
3.0
PYTHIA 6.206 (default)
"Transverse" PTsum Density (GeV)
"Transverse" Charged Density
3.5
HERWIG 6.4
3.0
14 TeV
2.5
2.0
1.5
1.8 TeV
1.0
PYTHIA 6.206 Set A
0.5
CTEQ5L
|η
η|<1.0 PT>0 GeV
0.0
PYTHIA 6.206 Set A
2.5
PYTHIA 6.206 (default)
14 TeV
2.0
HERWIG 6.4
1.5
1.0
1.8 TeV
0.5
|η
η|<1.0 PT>0 GeV
CTEQ5L
0.0
0
5
10
15
20
25
30
35
40
45
50
0
5
PT(charged jet#1) (GeV/c)
10
15
20
25
30
35
40
45
50
PT(charged jet#1) (GeV/c)
η|<1, PT>0) versus
! Shows the average “transverse” charge particle and PTsum density (|η
PT(charged jet#1) predicted by HERWIG 6.4 (PT(hard) > 3 GeV/c, CTEQ5L). and a tuned
versions of PYTHIA 6.206 (PT(hard) > 0, CTEQ5L, Set A) at 1.8 TeV and 14 TeV. Also
shown is the 14 TeV prediction of PYTHIA 6.206 with the default value ε = 0.16.
! Tuned PYTHIA (Set A) predicts roughly 2.3 charged particles per unit η-φφ (PT > 0) in
the “transverse” region (14 charged particles per unit η) which is larger than the
HERWIG prediction and much less than the PYTHIA default prediction.
CPT Week - JetMET
May 5, 2003
Rick Field - Florida/CDF
Page 34
PYTHIA Tune A
LHC Predictions
"Transverse" Charged Particle Density: dN/dη
ηdφ
φ
"Transverse" Charged PTsum Density: dPTsum/dη
ηdφ
φ
2.5
"Transverse" PTsum Density (GeV)
"Transverse" Charged Density
3.0
PYTHIA 6.206 Set A
2.5
2.0
1.5
HERWIG 6.4
1.0
0.5
CTEQ5L
14 TeV |η
η|<1.0 PT>0 GeV
0.0
PYTHIA 6.206 Set A
2.0
Big difference!
1.5
1.0
HERWIG 6.4
0.5
14 TeV |η
η|<1.0 PT>0 GeV
CTEQ5L
0.0
0
10
20
30
40
50
60
70
80
90
100
0
10
PT(charged jet#1) (GeV/c)
20
30
40
50
60
70
80
90
100
PT(charged jet#1) (GeV/c)
η|<1, PT>0) versus
! Shows the average “transverse” charge particle and PTsum density (|η
PT(charged jet#1) predicted by HERWIG 6.4 (PT(hard) > 3 GeV/c, CTEQ5L). and a tuned
versions of PYTHIA 6.206 (PT(hard) > 0, CTEQ5L, Set A) at 1.8 TeV and 14 TeV. Also
shown is the 14 TeV prediction of PYTHIA 6.206 with the default value ε = 0.16.
! Tuned PYTHIA (Set A) predicts roughly 2.5 GeV/c per unit η-φφ
(PT > 0) from charged particles in the “transverse” region for
3.8 GeV/c (charged)
PT(chgjet#1) = 100 GeV/c. Note, however, that the “transverse”
in cone of
radius R=0.7
charged PTsum density increases as PT(chgjet#1) increases.
at 14 TeV
CPT Week - JetMET
May 5, 2003
Rick Field - Florida/CDF
Page 35
PYTHIA Tune A
LHC Predictions
Charged Particle Density: dN/dη
ηdφ
φ
Charged Particle Density: dN/dη
ηdφ
φ
1.4
1.4
Pythia 6.206 Set A
CDF Data
14 TeV
Charged density dN/dη
η dφ
φ
dN/dηdφ
1.0
1.8 TeV
0.8
0.6
0.4
0.2
0.0
-4
-2
0
Pseudo-Rapidity η
2
1.0
0.8
0.6
0.4
0.2
all PT
630 GeV
-6
Pythia 6.206 Set A
CDF Data
UA5 Data
Fit 2
Fit 1
1.2
1.2
4
6
η=0
0.0
10
100
1,000
10,000
LHC?
100,000
CM Energy W (GeV)
ηdφ
φ,
! Shows the center-of-mass energy dependence of the charged particle density, dNchg/dη
for “Min-Bias” collisions compared with the a tuned version of PYTHIA 6.206 (Set A) with
PT(hard) > 0.
! PYTHIA was tuned to fit the “underlying event” in hard-scattering processes at 1.8 TeV
and 630 GeV.
ηdφ
φ at η = 0 in going from the Tevatron (1.8
! PYTHIA (Set A) predicts a 42% rise in dNchg/dη
TeV) to the LHC (14 TeV).
CPT Week - JetMET
May 5, 2003
Rick Field - Florida/CDF
Page 36
PYTHIA Tune A
LHC Predictions
Charged Particle Density
12% of “Min-Bias” events
50%
have PT(hard) > 10 GeV/c!
1.0E+00
|η
η|<1
Pythia 6.206 Set A
Pythia 6.206 Set A
40%
% of Events
1.0E-01
Charged Density dN/dη
ηdφ
φdPT (1/GeV/c)
Hard-Scattering in Min-Bias Events
1.0E-02
1.8 TeV
PT(hard) > 5 GeV/c
PT(hard) > 10 GeV/c
30%
20%
1.0E-03
10%
14 TeV
1.0E-04
0%
100
1.0E-06
2
100,000
LHC?
! Shows the center-of-mass energy
CDF Data
0
10,000
CM Energy W (GeV)
630 GeV
1.0E-05
1,000
4
6
8
PT(charged) (GeV/c)
1% of “Min-Bias” events
have PT(hard) > 10 GeV/c!
10
12
14
dependence of the charged particle density,
ηdφ
φdPT, for “Min-Bias” collisions
dNchg/dη
compared with the a tuned version of
PYTHIA 6.206 (Set A) with PT(hard) > 0.
! This PYTHIA fit 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!
CPT Week - JetMET
May 5, 2003
Rick Field - Florida/CDF
Page 37
The “Underlying Event”
Summary & Conclusions
Outgoing Parton
PT(hard)
Initial-State Radiation
Proton
AntiProton
Underlying Event
Outgoing Parton
Underlying Event
The “Underlying Event”
Final-State
Radiation
! There is excellent agreement between the Run 1 and the Run 2. The
!
!
“underlying event” is the same in Run 2 as in Run 1 but the Run 2 analysis
extends the evolution out to much higher energies!
PYTHIA Tune A does a good job of describing the “underlying event” in the
Run 2 data as defined by “charged particle jets” and as defined by
“calorimeter jets”. HERWIG Run 2 comparisons will be coming soon!
Lots more CDF Run 2 data to come including MAX/MIN “transverse” and
MAX/MIN “cones”.
CPT Week - JetMET
May 5, 2003
Rick Field - Florida/CDF
Page 38
LHC Predictions
Summary & Conclusions
Outgoing Parton
PT(hard)
Initial-State Radiation
Proton
AntiProton
Underlying Event
Outgoing Parton
Underlying Event
Tevatron
LHC
Final-State
Radiation
ηdφ
φ at η
! Both HERWIG and the tuned PYTHIA (Set A) predict a 40-45% rise in dNchg/dη
= 0 in going from the Tevatron (1.8 TeV) to the LHC (14 TeV). 4 charged particles per
unit η at the Tevatron becomes 6 per unit η at the LHC.
! The tuned PYTHIA (Set A) predicts that 1% of all “Min-Bias” events at the Tevatron
(1.8 TeV) are the result of a hard 2-to-2 parton-parton scattering with PT(hard) > 10
GeV/c which increases to 12% at LHC (14 TeV)!
! For the “underlying event” in hard scattering processes the predictions of HERWIG and
the tuned PYTHIA (Set A) differ greatly (factor of 2!). HERWIG predicts a smaller
increase in the activity of the “underlying event” in going from the Tevatron to the LHC.
! The tuned PYTHIA (Set A) predicts about a factor of two increase at the LHC in the
charged PTsum density of the “underlying event” at the same PT(jet#1) (the “transverse”
charged PTsum density increases rapidly as PT(jet#1) increases).
CPT Week - JetMET
May 5, 2003
Rick Field - Florida/CDF
Page 39
LHC Predictions
Summary & Conclusions
Outgoing Parton
PT(hard)
Initial-State Radiation
Proton
AntiProton
Underlying Event
!
!
Underlying Event
Tevatron
LHC
12 times more likely
Final-State
Radiation
“Min-Bias” at the LHC contains
to find a 10 GeV
much more
hard (Set
collisions
than at the
Both HERWIG and the tuned
PYTHIA
A) predict
a 40-45% rise
ηdφ
φ at η
“jet”inindN
“Min-Bias”
chg/dη
Tevatron!
At the
at theparticles
LHC!
= 0 in going from the Tevatron
(1.8 TeV)
to Tevatron
the LHCthe
(14 TeV). 4 charged
per
“underlying
event”
factor
of 2
unit η at the Tevatron becomes
6 per unit
η is
atathe
LHC.
more active than “Tevatron Min-Bias”.
Twice as much
The tuned PYTHIA (SetAt
A)the
predicts
that
1% of allevent”
“Min-Bias”
events at the Tevatron
LHC the
“underlying
will
activity in the
(1.8 TeV) are the result of a hard
> 10
be at2-to-2
least a parton-parton
factor of 2 more scattering with PT(hard)
“underlying event”
active
than “LHC
Min-Bias”!
GeV/c which increases to 12%
at LHC
(14 TeV)!
at the LHC!
Outgoing Parton
! For the “underlying event” in hard scattering processes the predictions of HERWIG and
the tuned PYTHIA (Set A) differ greatly (factor of 2!). HERWIG predicts a smaller
increase in the activity of the “underlying event” in going from the Tevatron to the LHC.
! The tuned PYTHIA (Set A) predicts about a factor of two increase at the LHC in the
charged PTsum density of the “underlying event” at the same PT(jet#1) (the “transverse”
charged PTsum density increases rapidly as PT(jet#1) increases).
CPT Week - JetMET
May 5, 2003
Rick Field - Florida/CDF
Page 40