Monte Carlos for the LHC
Tuning the Monte-Carlo Models
and Extrapolations to the LHC
Rick Field
University of Florida
MC4LHC
“Minumum Bias” Collisions
Proton
AntiProton
Outgoing Parton
PT(hard)
Initial-State Radiation
Proton
AntiProton
Underlying Event
Underlying Event
CDF Run 2
Outgoing Parton
Final-State
Radiation
Jet Production, Drell-Yan, Min-Bias
MC4LHC Workshop
July 17-26, 2006
Rick Field – Florida/CDF
Page 1
QCD Monte-Carlo Models:
High Transverse Momentum Jets
Hard Scattering
Hard Scattering
Initial-State Radiation
“Jet”
Initial-State Radiation
Outgoing Parton
PT(hard)
Outgoing Parton
“Jet” PT(hard)
Proton
“Hard Scattering” Component
AntiProton
Underlying Event
Final-State Radiation
Underlying Event
Outgoing Parton
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!
MC4LHC Workshop
July 17-26, 2006
Rick Field – Florida/CDF
Page 2
Distribution of Particles in Jets
 Momentum distribution of charged hadrons in
jets well described by MLLA (A. Kortov and
students)!
CDF Distribution of Particles in Jets
MLLA Curve!
 Dijet mass range 80-600 GeV
 Cutoff Qeff = 230  40 MeV
 Ncharged-hadrons/Npartons = 0.56  0.10
CDF Run 1 Analysis
 Ratio of charged hadron multiplicities in gluon
and quark jets agrees with NNLLA
= ln(Ejet/pparticle)
Both PYTHIA and HERWIG
predict a Gluon-Quark Ratio
that is smaller than the data!
Ratio = Ng-jet / Nq-jet
 Gluon-Quark Ratio = 1.6  0.2
Q = Ejet  qcone
MC4LHC Workshop
July 17-26, 2006
Rick Field – Florida/CDF
Page 3
Charged Multiplicity
in Quark and Gluon Jets
 CDF Run 1 data on the average charged
particle multiplicities in gluon and quark jets
versus Q = Ejet × qcone compared with NLLA,
PYTHIA, and HERWIG.
CDF Run 1 Analysis
 HERWIG and PYTHIA correctly predict the
charged multiplicity for gluon jets.
 Both HERWIG and PYTHIA over-estimate
the charged multiplicity in quark jets by
~30%!
MC4LHC Workshop
July 17-26, 2006
Rick Field – Florida/CDF
Page 4
Distribution of Particles
in Quark and Gluon Jets
Both PYTHIA and HERWIG
predict more charged particles
than the data for quark jets!
CDF Run 1 Analysis
x = 0.37
0.14
0.05
0.02
0.007
pchg = 2 GeV/c
 Momentum distribution of charged particles in gluon jets. HERWIG 5.6 predictions are in a
good agreement with CDF data. PYTHIA 6.115 produces slightly more particles in the region
around the peak of distribution.
 Momentum distribution of charged particles in quark jets. Both HERWIG and PYTHIA
produce more particles in the central region of distribution.
MC4LHC Workshop
July 17-26, 2006
Rick Field – Florida/CDF
Page 5
Evolution of Charged Jets
“Underlying Event”
Charged Particle  Correlations
PT > 0.5 GeV/c |h| < 1
Charged Jet #1
Direction
“Transverse” region
very sensitive to the
“underlying event”!
Look at the charged
particle density in the
“transverse” region!
2p
“Toward-Side” Jet

“Toward”
CDF Run 1 Analysis
Away Region
Charged Jet #1
Direction

Transverse
Region
“Toward”
“Transverse”

Leading
Jet
“Transverse”
Toward Region
“Transverse”
“Transverse”
Transverse
Region
“Away”
“Away”
Away Region
“Away-Side” Jet
0
-1
h
+1
 Look at charged particle correlations in the azimuthal angle  relative to the leading charged
particle jet.
 Define || < 60o as “Toward”, 60o < || < 120o as “Transverse”, and || > 120o as “Away”.
 All three regions have the same size in h- space, hx = 2x120o = 4p/3.
MC4LHC Workshop
July 17-26, 2006
Rick Field – Florida/CDF
Page 6
Run 1 PYTHIA Tune A
CDF Default!
PYTHIA 6.206 CTEQ5L
"Transverse" Charged Particle Density: dN/dhd
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)
MC4LHC Workshop
July 17-26, 2006
1.00
"Transverse" Charged Density
Parameter
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 |h|<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
Page 7
“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

"Transverse"
"Transverse" Charged
Charged Particle
Particle
Density:
dN/dhd
Particle Density:
Density: dN/dhd
dN/dhd
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
|h|<1.0
PT>0.5
GeV
|h|<1.0
|h|<1.0
PT>0.5
PT>0.5
GeV/c
GeV/c
|h|<1.0
PT>0.5
GeV
0.00
0.00
00
10 5 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)
Excellent agreement
between Run 1 and 2!
 Shows the data on the average “transverse” charge particle density (|h|<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 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).
MC4LHC Workshop
July 17-26, 2006
Rick Field – Florida/CDF
Page 8
Charged Multiplicity
in Charged Particle Jets
PYTHIA predict more
charged particles than the
data for charged jets!
Nchg (jet#1) versus PT(charged jet#1)
<Nchg> (Jet#1, R=0.7)
12
CDF Run 1 Analysis
1.8 TeV |eta|<1.0 PT>0.5 GeV
10
8
6
Includes charged particles
from the “underlying event”!
4
CDF
2
data uncorrected
theory corrected
0
0
5
10
15
20
25
30
35
40
45
50
PT(charged jet#1) (GeV)
Herwig
Isajet
Pythia 6.115
CDF Min-Bias
CDF JET20
 Plot shows the average number of charged particles (pT > 0.5 GeV, |h| < 1) within the leading
charged particle jet (R = 0.7) as a function of the PT of the leading charged jet. The solid
(open) points are Min-Bias (JET20) data. The errors on the (uncorrected) data include both
statistical and correlated systematic uncertainties. The QCD “hard scattering” theory curves
(Herwig 5.9, Isajet 7.32, Pythia 6.115) are corrected for the track finding efficiency.
MC4LHC Workshop
July 17-26, 2006
Rick Field – Florida/CDF
Page 9
Run 1 Fragmentation Function
Charged Momentum Distribution Jet#1
Density F(z)=dNchg/dz
100.0
PT(jet#1) > 5 GeV
PYTHIA does not
agree at high z!
CDF
data uncorrected
theory corrected
10.0
1.8 TeV |eta|<1.0 PT>0.5 GeV
CDF Run 1 Analysis
1.0
Herwig
Isajet
Pythia 6.115
CDF Min-Bias
0.1
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
z = p(charged)/P(charged jet#1)
 CDF Run 1 data from on the momentum distribution of charged particles (pT > 0.5 GeV
and |h| < 1) within chgjet#1 (leading charged jet) for PT(chgjet#1) > 5 GeV compared with
the QCD “hard scattering” Monte-Carlo predictions of HERWIG, ISAJET, and
PYTHIA. The points are the charged number density, F(z) = dNchg/dz, where
z = pchg/P(chgjet#1) is the ratio of the charged particle momentum to the charged
momentum of chgjet#1.
MC4LHC Workshop
July 17-26, 2006
Rick Field – Florida/CDF
Page 10
Run 1 Fragmentation Function
Charged Momentum Distribution Jet#1
Density F(z)=dNchg/dz
100.0
PYTHIA does not
agree at high z!
CDF
PT(jet#1) > 30 GeV
data uncorrected
theory corrected
10.0
1.8 TeV |eta|<1.0 PT>0.5 GeV
CDF Run 1 Analysis
1.0
Herwig
Isajet
Pythia 6.115
CDF JET20
0.1
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
z = p(charged)/P(charged jet#1)
 Data from Fig. 3.8 on the momentum distribution of charged particles (pT > 0.5 GeV and
|h| < 1) within chgjet#1 (leading charged jet) for PT(chgjet#1) > 30 GeV compared with the
QCD “hard scattering” Monte-Carlo predictions of HERWIG, ISAJET, and PYTHIA.
The points are the charged number density, F(z) =dNchg/dz, where z = pchg/P(chgjet#1) is
the ratio of the charged particle momentum to the charged momentum of chgjet#1.
MC4LHC Workshop
July 17-26, 2006
Rick Field – Florida/CDF
Page 11
Fragmentation Summary
 Neither HERWIG or PYTHIA describe
Charged
Particle
kT Distribution in Jets
precisely the distribution
charged
particles
Was this Particle
measured in Run 1?
in quark and gluon jets at the Tevatron!
Jet
 To learn about the fragmentation function at large z we should
Comparison
Only
compare the inclusive “jet” cross-sectionShape
to the
inclusive
charged particle cross section!
 We have events with 600 GeV “jets” so we must have events
In 1 fb-1 we have thousands of
with 300 GeV/c charged particles!
charged tracks with p > 100 GeV/c!
T
 I wish I could show you the following:
Charged Particle PT Distribution
100,000,000
CDF Run 2 Pre-Preliminary
Number in 1 GeV/c Bin
 A lot of work has been done in comparing to analytic
MLLA calculations (Korytov and students), but more
work needs to be done in improving the
fragmentation models in HERWIG and PYTHIA!
 CDF measured fragmentation functions at different Q2
compared with PYTHIA and HERWIG.
 The kT distribution of charged particles within “jets”
compared with PYTHIA and HERWIG.
 The ratio of the inclusive charged particle cross-section to the
inclusive “jet” cross-section compared with PYTHIA and
HERWIG.
MC4LHC Workshop
July 17-26, 2006
Rick Field – Florida/CDF
Jet 100 Trigger
10,000,000
1,000,000
100,000
1.96 TeV
10,000
Charged Particles (|h|<1.0)
1,000
0
10
20
30
40
50
60
70
80
90
Charged Particle PT (GeV/c)
Sergo “blessing” this in the
QCD group last week!
Page 12
100
The “Transverse” Regions
as defined by the Leading Jet
Jet #1 Direction
“Transverse” region is
very sensitive to the
“underlying event”!
Charged Particle  Correlations
pT > 0.5 GeV/c |h| < 1
2p
Look at the charged
particle density in the
“transverse” region!
Away Region
“Toward-Side” Jet
Jet #1 Direction

“Toward”
“Transverse”
“Transverse”
“Away”
Transverse
Region 1

“Toward”
“Trans 1”

Leading
Jet
“Trans 2”
Toward Region
Transverse
Region 2
“Away”
Away Region
“Away-Side” Jet
0
-1
h
+1
 Look at charged particle correlations in the azimuthal angle  relative to the leading

calorimeter jet (JetClu R = 0.7, |h| < 2).
o
o
o
o
o
Define || < 60 as “Toward”, 60 < - < 120 and 60 <  < 120 as “Transverse 1” and
o
“Transverse 2”, and || > 120 as “Away”. Each of the two “transverse” regions have
o
area h = 2x60 = 4p/6. The overall “transverse” region is the sum of the two
o
transverse regions (h = 2x120 = 4p/3).
MC4LHC Workshop
July 17-26, 2006
Rick Field – Florida/CDF
Page 13
Charged Particle Density  Dependence
Refer to this as a
“Leading Jet” event
Jet #1 Direction
Charged
Particle Density:
Density: dN/dhd
dN/dhd
Charged Particle

10.0
10.0
Subset
“Transverse”
“Transverse”
“Away”
Refer to this as a
“Back-to-Back” event
Jet #1 Direction

“Toward”
“Transverse”
“Transverse”
Charged Particle
Particle Density
Density
Charged
“Toward”
CDF
CDF Preliminary
Preliminary
30 << ET(jet#1)
ET(jet#1) << 70
70 GeV
GeV
30
Back-to-Back
data
data uncorrected
uncorrected
Leading Jet
Min-Bias
"Transverse"
"Transverse"
Region
Region
1.0
1.0
Jet#1
Jet#1
Charged
Charged Particles
Particles
(|h|<1.0,
(|h|<1.0, PT>0.5
PT>0.5 GeV/c)
GeV/c)
0.1
0.1
00
30
30
60
60
90
“Away”
120
150
180
210
210
240
240
270
270
300
300
330
330
360
360
 (degrees)
Jet #2 Direction
 Look at the “transverse” region as defined by the leading jet (JetClu R = 0.7, |h| < 2) or by the
leading two jets (JetClu R = 0.7, |h| < 2). “Back-to-Back” events are selected to have at least
two jets with Jet#1 and Jet#2 nearly “back-to-back” (12 > 150o) with almost equal
transverse energies (ET(jet#2)/ET(jet#1) > 0.8) and with ET(jet#3) < 15 GeV.
 Shows the  dependence of the charged particle density, dNchg/dhd, for charged
particles in the range pT > 0.5 GeV/c and |h| < 1 relative to jet#1 (rotated to 270o) for 30
< ET(jet#1) < 70 GeV for “Leading Jet” and “Back-to-Back” events.
MC4LHC Workshop
July 17-26, 2006
Rick Field – Florida/CDF
Page 14
“Transverse” PTsum Density vs ET(jet#1)
“Leading Jet”
Jet #1 Direction

“Transverse”
“Away”
“Back-to-Back”
Jet #1 Direction

“Toward”
“Transverse”
“Transverse”
"Transverse" PTsum Density (GeV/c)
“Toward”
“Transverse”
"AVE Transverse" PTsum Density: dPT/dhd
1.4
uncorrected
datadata
uncorrected
theory + CDFSIM
PY Tune A
1.0
Hard Radiation!
0.8
0.6
0.4
Back-to-Back
HW
0.2
1.96 TeV
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
0.0
0
50
“Away”
Jet #2 Direction
Leading Jet
CDF Run
2 Preliminary
Preliminary
1.2
100
150
200
250
ET(jet#1) (GeV)
Min-Bias
0.24 GeV/c per unit h-
 Shows the average charged PTsum density, dPTsum/dhd, in the “transverse” region (pT
> 0.5 GeV/c, |h| < 1) versus ET(jet#1) for “Leading Jet” and “Back-to-Back” events.
 Compares the (uncorrected) data with PYTHIA Tune A and HERWIG (without MPI)
after CDFSIM.
MC4LHC Workshop
July 17-26, 2006
Rick Field – Florida/CDF
Page 15
Latest CDF Run 2
“Underlying Event” Results
Jet #1 Direction

“Toward”
“Trans 1”
The “underlying event” consists of the
“beam-beam remnants” and possible
multiple parton interactions, but
inevitably received contributions from
initial and final-state radiation.
Outgoing Parton
PT(hard)
Initial-State Radiation
“Trans 2”
Proton
AntiProton
Underlying Event
Underlying Event
“Away”
“Transverse” region is
very sensitive to the
“underlying event”!
Outgoing Parton
Final-State
Radiation
Latest CDF Run 2 Results (L = 385 pb-1) :
 Two Classes of Events: “Leading Jet” and “Back-to-Back”.
 Two “Transverse” regions: “transMAX”, “transMIN”, “transDIF”.
 Data Corrected to the Particle Level: unlike our previous CDF Run 2 “underlying event”
analysis which used JetClu to define “jets” and compared uncorrected data with the QCD
Monte-Carlo models after detector simulation, this analysis uses the MidPoint jet algorithm and
corrects the observables to the particle level. The corrected observables are then compared
with the QCD Monde-Carlo models at the particle level.
 For the 1st time we study the energy density in the “transverse” region.
MC4LHC Workshop
July 17-26, 2006
Rick Field – Florida/CDF
Page 16
“TransMAX/MIN” PTsum Density
PYTHIA Tune A vs HERWIG
Jet #1 Direction
“TransMAX”
“TransMIN”
“Away”
3.0


“Toward”
"TransMAX" Charged PTsum Density: dPT/dhd
Jet #1 Direction
"Transverse" PTsum Density (GeV/c)
“Leading Jet”
PYTHIA Tune A does a fairly
good job fitting the PTsum
density in the “transverse”
region!
“Back-to-Back”
HERWIG does a poor job!
“Toward”
“TransMAX”
“TransMIN”
“Away”
Jet #2 Direction
CDF Run 2 Preliminary
data corrected to particle level
2.5
"Leading Jet"
1.96 TeV
2.0
PY Tune A
1.5
"Back-to-Back"
1.0
MidPoint R = 0.7 |h(jet#1) < 2
0.5
HW
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
0.0
0
50
100
150
MC4LHC Workshop
July 17-26, 2006
300
350
400
450
"TransMIN" Charged PTsum Density: dPT/dhd
0.6
"Transverse" PTsum Density (GeV/c)

250
PT(jet#1) (GeV/c)
 Shows the charged particle PTsum
density, dPTsum/dhd, in the
“transMAX” and “transMIN”
region (pT > 0.5 GeV/c, |h| < 1)
versus PT(jet#1) for “Leading Jet”
and “Back-to-Back” events.
Compares the (corrected) data with
PYTHIA Tune A (with MPI) and
HERWIG (without MPI) at the
particle level.
200
CDF Run 2 Preliminary
MidPoint R = 0.7 |h(jet#1) < 2
data corrected to particle level
0.5
1.96 TeV
"Leading Jet"
0.4
0.3
"Back-to-Back"
0.2
0.1
PY Tune A
HW
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
0.0
0
50
Rick Field – Florida/CDF
100
150
200
250
300
350
400
450
PT(jet#1) (GeV/c)
Page 17
“TransMAX/MIN” ETsum Density
PYTHIA Tune A vs HERWIG
“Back-to-Back”
Jet #1 Direction
Jet #1 Direction


“Toward”
“TransMAX”
“TransMIN”
“Away”
"TransMAX" ETsum Density: dET/dhd
7.0
“Toward”
Neither PY Tune A or
“TransMIN”
HERWIG
fits the
ETsum density in the
“Away”
“transferse” region!
HERWIG does slightly
than Tune A!
Jet better
#2 Direction
“TransMAX”
"Transverse" ETsum Density (GeV)
“Leading Jet”
CDF Run 2 Preliminary
6.0
"Leading Jet"
1.96 TeV
5.0
4.0
3.0
HW
"Back-to-Back"
2.0
1.0
PY Tune A
MidPoint R = 0.7 |h(jet#1) < 2
Particles (|h|<1.0, all PT)
0.0
 Shows the data on the tower ETsum
0
50
100
150
200
250
300
350
400
450
PT(jet#1) (GeV/c)
density, dETsum/dhd, in the
“transMAX” and “transMIN” region (ET
> 100 MeV, |h| < 1) versus PT(jet#1) for
“Leading Jet” and “Back-to-Back”
events.
Compares the (corrected) data with
PYTHIA Tune A (with MPI) and
HERWIG (without MPI) at the particle
level (all particles, |h| < 1).
"TransMIN" ETsum Density: dET/dhd
3.0
"Transverse" ETsum Density (GeV)

data corrected to particle level
CDF Run 2 Preliminary
MidPoint R = 0.7 |h(jet#1) < 2
data corrected to particle level
2.5
Particles (|h|<1.0, all PT)
1.96 TeV
2.0
HW
"Leading Jet"
1.5
1.0
0.5
"Back-to-Back"
PY Tune A
0.0
0
50
100
150
200
250
300
350
400
450
PT(jet#1) (GeV/c)
MC4LHC Workshop
July 17-26, 2006
Rick Field – Florida/CDF
Page 18
“TransDIF” ETsum Density
PYTHIA Tune A vs HERWIG
“Leading Jet”
Jet #1 Direction

"TransDIF" ETsum Density: dET/dhd
“Toward”
Jet #1 Direction

“TransMIN”
“Away”
“Toward”
“TransMAX”
“TransMIN”
“Away”
Jet #2 Direction
“Back-to-Back”
"Transverse" ETsum Density (GeV)
“TransMAX”
5.0
CDF Run 2 Preliminary
data corrected to particle level
4.0
"Leading Jet"
1.96 TeV
3.0
PY Tune A
2.0
HW
"Back-to-Back"
1.0
MidPoint R = 0.7 |h(jet#1) < 2
Particles (|h|<1.0, all PT)
0.0
“transDIF” is more sensitive to
the “hard scattering” component
of the “underlying event”!
0
50
100
150
200
250
300
350
400
450
PT(jet#1) (GeV/c)
 Use the leading jet to define the MAX and MIN “transverse” regions on an event-byevent basis with MAX (MIN) having the largest (smallest) charged PTsum density.
 Shows the “transDIF” = MAX-MIN ETsum density, dETsum/dhd, for all particles (|h| <
1) versus PT(jet#1) for “Leading Jet” and “Back-to-Back” events.
MC4LHC Workshop
July 17-26, 2006
Rick Field – Florida/CDF
Page 19
Possible Scenario??
 PYTHIA Tune A fits the charged particle
"Transverse" pT Distribution: dN/dpT
1.0E+01
"Transverse" PT Distribution
Sharp Rise at
Low PT?
PTsum density for pT > 0.5 GeV/c, but it
does not produce enough ETsum for
towers with ET > 0.1 GeV.
Possible Scenario??
But I cannot get any
of the Monte-Carlo to
do this perfectly!
1.0E+00
1.0E-01
 It is possible that there is a sharp rise in
Multiple
Parton
Interactions
thesure
number
Warning!? I am not
I of particles in the “underlying
event”density.
at low pT (i.e. pT < 0.5 GeV/c).
believe the data on the energy
Beam-Beam
I am not convienced we are simulating
Remnants
 Perhaps
there are two components, a vary
correctly the “soft” energy
in Calorimeter.
1.0E-02
1.0E-03
1.0E-04
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
pT All Particles (GeV/c)
MC4LHC Workshop
July 17-26, 2006
4.0
4.5
5.0
“soft” beam-beam remnant component
(Gaussian or exponential) and a “hard”
multiple interaction component.
Rick Field – Florida/CDF
Page 20
“TransMAX/MIN” ETsum Density
PYTHIA Tune A vs JIMMY
Jet #1 Direction

“Toward”
“TransMAX”
“TransMIN”
“Away”
"Transverse" ETsum Density (GeV)
“Leading Jet”
JIMMY: MPI
J. M. Butterworth
“Back-to-Back”
"TransMAX" ETsum Density: dET/dhd
Jet #1 Direction J. R. Forshaw
7.0
M. H. Seymour CDF Run 2 Preliminary
“Toward”
“TransMAX”
“TransMIN”
“Away”
Jet #2 Direction
"Leading Jet"
1.96 TeV
5.0
4.0
JIM
3.0
"Back-to-Back"
2.0
1.0
PY Tune A
MidPoint R = 0.7 |h(jet#1) < 2
0
Particles (|h|<1.0, all PT)
50
100
150
200
250
300
350
400
450
PT(jet#1) (GeV/c)
"TransMIN" ETsum Density: dET/dhd
3.0
"Transverse" ETsum Density (GeV)
dETsum/dhd, in the “transMAX”
and “transMIN” region (all particles
|h| < 1) versus PT(jet#1) for
“Leading Jet” and “Back-to-Back”
events.
Compares the (corrected) data with
PYTHIA Tune A (with MPI) and a
tuned version of JIMMY (with MPI,
PTJIM = 3.25 GeV/c) at the particle
level.
MC4LHC Workshop
July 17-26, 2006
data corrected to particle level
0.0
 Shows the ETsum density,

6.0
JIMMY was tuned to fit
the energy density in the
“transverse” region for
“leading jet” events!
CDF Run 2 Preliminary
MidPoint R = 0.7 |h(jet#1) < 2
data corrected to particle level
2.5
Particles (|h|<1.0, all PT)
1.96 TeV
JIM
2.0
"Leading Jet"
1.5
1.0
0.5
"Back-to-Back"
PY Tune A
0.0
0
50
100
Rick Field – Florida/CDF
150
200
250
300
350
400
450
PT(jet#1) (GeV/c)
Page 21
“TransMAX/MIN” Nchg Density
PYTHIA Tune A vs JIMMY
“Leading Jet”
“Back-to-Back”
Jet #1 Direction
Jet #1 Direction

“TransMAX”
“TransMIN”
“Away”
CDF Run 2 Preliminary
"Transverse" Charged Density

“Toward”
"TransMAX" Charged Particle Density: dN/dhd
1.4
“Toward”
“TransMAX”
“TransMIN”
“Away”
"Leading Jet"
data corrected to particle level
1.2
JIM
1.0
"Back-to-Back"
0.8
0.6
PY Tune A
MidPoint R = 0.7 |h(jet#1) < 2
0.4
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
1.96 TeV
Jet #2 Direction
0.2
 Shows the charged particle density,
MC4LHC Workshop
July 17-26, 2006
50
100
150
200
250
300
350
400
450
PT(jet#1) (GeV/c)
"TransMIN" Charged Particle Density: dN/dhd
0.6
CDF Run 2 Preliminary
"Transverse" Charged Density

dNchg/dhd, in the “transMAX” and
“transMIN” region (pT > 0.5 GeV/c,
|h| < 1) versus PT(jet#1) for
“Leading Jet” and “Back-to-Back”
events.
Compares the (corrected) data with
PYTHIA Tune A (with MPI) and a
tuned version of JIMMY (with MPI,
PTJIM = 3.25 GeV/c) at the particle
level.
0
JIM
data corrected to particle level
0.5
MidPoint R = 0.7 |h(jet#1) < 2
1.96 TeV
0.4
"Leading Jet"
0.3
0.2
"Back-to-Back"
0.1
PY Tune A
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
0.0
0
50
Rick Field – Florida/CDF
100
150
200
250
300
350
400
450
PT(jet#1) (GeV/c)
Page 22
“Transverse” <PT>
PYTHIA Tune A vs JIMMY
“Leading Jet”
“Back-to-Back”
Jet #1 Direction
Jet #1 Direction
“TransMIN”
“Away”
"Transverse" Charged <PT> (GeV/c)
“TransMAX”
2.0


“Toward”
"Transverse" Charged Particle Mean PT
“Toward”
“TransMAX”
“TransMIN”
“Away”
Jet #2 Direction
CDF Run 2 Preliminary
1.5
1.0
"Back-to-Back"
HW
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
0.5
0
50
100
150
200
250
300
350
400
450
PT(jet#1) (GeV/c)
"Transverse" Charged Particle Mean PT
2.0
"Transverse" Charged <PT> (GeV/c)
the “transverse” (pT > 0.5 GeV/c, |h|
< 1) versus PT(jet#1) for “Leading
Jet” and “Back-to-Back” events.
Compares the (corrected) data with
PYTHIA Tune A (with MPI) and
HERWIG and a tuned version of
JIMMY (with MPI, PTJIM = 3.25
GeV/c) at the particle level.
CDF Run 2 Preliminary
MidPoint R = 0.7 |h(jet#1) < 2
data corrected to particle level
"Leading Jet"
PY Tune A
1.96 TeV
1.5
1.0
"Back-to-Back"
JIM
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
0.5
Both JIMMY and 0
HERWIG are too “soft”
for pT > 0.5 GeV/c!
MC4LHC Workshop
July 17-26, 2006
"Leading Jet"
PY Tune A
1.96 TeV
 Shows the charged particle <PT> in

MidPoint R = 0.7 |h(jet#1) < 2
data corrected to particle level
50
100
Rick Field – Florida/CDF
150
200
250
300
350
400
450
PT(jet#1) (GeV/c)
Page 23
CDF Run 1 PT(Z)
PYTHIA 6.2 CTEQ5L
Parameter
Tune A
Tune A25
s = 1.0
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
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
CDF Run 1 Data
PYTHIA Tune A
PYTHIA Tune A25
PYTHIA Tune A50
s = 2.5
0.08
CDF Run 1
published
1.8 TeV
s = 5.0
Normalized to 1
0.04
0.00
0
ISR Parameter PARP(89)
Z-Boson Transverse Momentum
0.12
PT Distribution 1/N dN/dPT
UE Parameters
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
MC4LHC Workshop
July 17-26, 2006
20
Rick Field – Florida/CDF
Page 24
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
Z-Boson Transverse
Transverse Momentum
Momentum
Z-Boson
0.12
1.0E+00
PTDistribution
Distribution1/N
1/NdN/dPT
dN/dPT
PT
PYTHIA 6.2 CTEQ5L
Tune used by the
CDF-EWK group!
CDF Run 1 Data
CDFPYTHIA
Run 1 Data
Tune A
PYTHIA
Tune
AW AW
PYTHIA
Tune
1.0E-01
CDF Run
Run 11
CDF
published
published
0.08
1.8 TeV
1.8 TeV
1.0E-02
Normalized
to 1to 1
Normalized
1.0E-03
0.04
1.0E-04
Also fits the high pT tail!
0.00
1.0E-05
0
0
2
10
4
20
6
30
8
40
10
50
12
60
14
70
16
80
18
90
Z-Boson PT (GeV/c)
Z-Boson PT (GeV/c)
 Shows the Run 1 Z-boson pT distribution (<pT(Z)>
≈ 11.5 GeV/c) compared with PYTHIA Tune A
(<pT(Z)> = 9.7 GeV/c), and PYTHIA Tune AW
(<pT(Z)> = 11.7 GeV/c).
Effective Q cut-off, below which space-like showers are not evolved.
Intrensic KT
The Q2 = kT2 in as for space-like showers is scaled by PARP(64)!
MC4LHC Workshop
July 17-26, 2006
20
100
Rick Field – Florida/CDF
Page 25
Jet-Jet Correlations (DØ)
Jet#1-Jet#2  Distribution
 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).
MC4LHC Workshop
July 17-26, 2006
Rick Field – Florida/CDF
Page 26
CDF Run 1 PT(Z)
PYTHIA 6.2 CTEQ5L
Z-Boson Transverse Momentum
UE Parameters
ISR Parameters
Parameter
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
PT
PTDistribution
Distribution 1/N
1/N dN/dPT
dN/dPT
1.0E+00
0.12
1 Data
CDFCDF
Run Run
1 Data
PYTHIA
Tune
PYTHIA Tune DW DW
HERWIG
1.0E-01
CDF
CDFRun
Run1 1
published
published
1.8 TeV
1.8 TeV
0.08
1.0E-02
Normalized to 1
Normalized to 1
1.0E-03
0.04
1.0E-04
Also fits the high pT tail!
1.0E-05
0.00
0 0
2 10
4 20
6 30
840
50
10
60
12
70
14
80
16
90
18
100
20
Z-BosonPT
PT(GeV/c)
(GeV/c)
Z-Boson
 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!
MC4LHC Workshop
July 17-26, 2006
Rick Field – Florida/CDF
Page 27
“Transverse” Nchg Density
Parameter
Intrensic KT
Tune AW
Tune DW
"Transverse" Charged
Charged Particle
Particle Density:
Density: dN/dhd
dN/dhd
"Transverse"
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)
ISR Parameter
Three different amounts of MPI!
PYTHIA 6.2 CTEQ5L
0.4
0.4
0.4
PARP(85)
0.9
1.0
1.0
PARP(86)
0.95
1.0
1.0
PARP(89)
1.8 TeV
1.8 TeV
1.8 TeV
PARP(90)
0.25
0.25
0.25
PARP(62)
1.25
1.25
1.25
PARP(64)
0.2
0.2
0.2
PARP(67)
4.0
2.5
1.0
MSTP(91)
1
1
1
PARP(91)
2.5
2.5
2/5
PARP(93)
15.0
15.0
15.0
Three different amounts of ISR!
MC4LHC Workshop
July 17-26, 2006
1.0
1.0
"Transverse"
"Transverse"Charged
ChargedDensity
Density
UE Parameters
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 (|h|<2.0)
(|h|<2.0)
Leading
Charged Particles
Particles (|h|<1.0,
(|h|<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/dhd, 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/dhd, versus PT(jet#1) for “leading
jet” events at 1.96 TeV for Tune DW, ATLAS,
and HERWIG (without MPI).
Rick Field – Florida/CDF
Page 28
“Transverse” PTsum Density
ISR Parameter
Intrensic KT
Three different amounts of MPI!
PYTHIA 6.2 CTEQ5L
"Transverse" PTsum Density: dPT/dhd
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
PARP(89)
1.8 TeV
1.8 TeV
1.8 TeV
PARP(90)
0.25
0.25
0.25
PARP(62)
1.25
1.25
1.25
PARP(64)
0.2
0.2
0.2
PARP(67)
4.0
2.5
1.0
MSTP(91)
1
1
1
PARP(91)
2.5
2.5
2/5
PARP(93)
15.0
15.0
15.0
Three different amounts of ISR!
MC4LHC Workshop
July 17-26, 2006
"Transverse" PTsum
PTsum Density
Density (GeV/c)
(GeV/c)
"Transverse"
UE Parameters
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 (|h|<2.0)
Charged Particles (|h|<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/dhd, 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/dhd, versus PT(jet#1) for
“leading jet” events at 1.96 TeV for Tune DW,
ATLAS, and HERWIG (without MPI).
Rick Field – Florida/CDF
Page 29
500
PYTHIA 6.2 Tunes
s(MPI) at 1.96 TeV
s(MPI) at 14 TeV
Tune A
309.7 mb
484.0 mb
351.7 mb
549.2 mb
351.7 mb
CDF
324.5
mbRun 2 Data!
829.1 mb
PYTHIA 6.2 CTEQ5L
Parameter
Tune A
Tune DW
Tune DWT
ATLAS
MSTP(81)
1
1
1
1
Tune DW
MSTP(82)
4
4
4
4
Tune DWT
PARP(82)
2.0 GeV
1.9 GeV
1.9409 GeV
1.8 GeV
ATLAS
PARP(83)
0.5
0.5
0.5
0.5
PARP(84)
0.4
0.4
PARP(85)
0.9
PARP(86)
0.95
PARP(62)
1.0
PARP(64)
1.0
PARP(67)
4.0
MSTP(91)
1
PARP(91)
1.0
PARP(93)
5.0
1.96 TeV
0.25
1.1
0.9
0.16
0.16
1.25
1.25
1.0
0.2
0.2
1.0
2.5
2.5
1.0
1
1
1
PY-ATLAS
0.7
15.0
50
15.0
100
Identical to DW at 1.96 TeV but uses
ATLAS extrapolation to the LHC!
generator
generatorlevel
level
generator
level
0.8
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
HERWIG
0.0
0.0
0.7
MidPoint R = 0.7 |h(jet#1) < 2
00
0
2.1 1.96 TeV2.1 HERWIG 1.0
0
MC4LHC Workshop
July 17-26, 2006
1.0 TeV
PY Tune A, DW
1.3
RDF
RDFPreliminary
Preliminary
RDF
Preliminary
1.2 Jet"
"Leading
1.3
data corrected to particle level
1.8 TeV 1.5 1.8 TeV
0.25
0.33
"Transverse"
Charged
PTDensity
(GeV/c)
"Transverse"
Charged
"Transverse"
PTsum
Density
(GeV/c)
PARP(90)
1.0
CDF
1.0 Run 2 Preliminary
1.0
0.66
"Transverse" <PT> (GeV/c)
PARP(89)
"Transverse"
Charged
Particle
Average
pT
"Transverse"
Charged
Particle
Density:
dN/dhd
"Transverse"
PTsum
Density:
dPT/dhd
0.4
0.5Charged 1.6
"Transverse"
Average PT
1.0
1.5
1.0
1.7
768.0 mb
50
50
50
100
100
100
150
150
150
200
200
200
Leading
JetJet
(|h|<2.0)
Leading
(|h|<2.0)
Leading
Jet (|h|<2.0)
Charged
Particles
(|h|<1.0,
PT>0.5
GeV/c)
Charged
Particles
(|h|<1.0,
PT>0.5
GeV/c)
Charged Particles (|h|<1.0, PT>0.5
GeV/c)
250
250
250
300
300
300
350
350
350
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
PT(particle
jet#1)
PT(particle jet#1)
jet#1) (GeV/c)
(GeV/c)
PT(particle
(GeV/c)
400
400
400
450
450
450
500
500
500
5.0
150
250
Shows
charged particle
density,
300the “transverse”
350
400
450
 Shows
the “transverse”
charged PTsum
averagedensity,
pT,
dN/dhd,
versus
P
(jet#1)
for
“leading
jet”
PT(jet#1) (GeV/c)
dPT/dhd,
versusfor
P
(jet#1) for
“leading
jet”
T T“leading
versus PT(jet#1)
jet”
events at
1.96
events at 1.96 TeV for Tune A, DW, ATLAS, and
TeV for Tune A, DW, ATLAS, and HERWIG
HERWIG (without MPI).
(without MPI).
200
Rick Field – Florida/CDF
Page 30
PYTHIA 6.2 Tunes
s(MPI) at 1.96 TeV
s(MPI) at 14 TeV
Tune A
309.7 mb
484.0 mb
PYTHIA 6.2 CTEQ5L
Parameter
Tune A
Tune DW
Tune DWT
ATLAS
MSTP(81)
1
1
1
1
Tune DW
351.7 mb
549.2 mb
MSTP(82)
4
4
4
4
Tune DWT
351.7 mb
829.1 mb
PARP(82)
2.0 GeV
1.9 GeV
1.9409 GeV
1.8 GeV
ATLAS
324.5 mb
768.0 mb
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
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
"Transverse"
Charged
Density
"Transverse"
PTsum
Density
(GeV/c)
"Transverse"
Charged
PT
(GeV/c)
PARP(62)
"Transverse"
PTsum
Density:
dPT/dhd
"Transverse"
Charged
Particle
Average
pT
"Transverse"
Charged
Particle
Density:
dN/dhd
8.0
2.5
2.5
MC4LHC Workshop
July 17-26, 2006
PY-ATLAS
generator level
level
generator
2.0
6.0
PY Tune DW
PY Tune DW
2.0
1.5
4.0
PY-ATLAS
HERWIG
PY Tune DW
1.0
1.5
2.0
0.5
14 TeV
14
14 TeV
TeV
HERWIG
PY-ATLAS
HERWIG
LeadingJet
Jet(|h|<2.0)
(|h|<2.0)
Leading
Leading Jet
(|h|<2.0)
ChargedParticles
Particles(|h|<1.0,
(|h|<1.0,PT>0.5
PT>0.5GeV/c)
GeV/c)
Charged
Charged Particles
(|h|<1.0, PT>0.5
GeV/c)
0.0
0.0
1.0
000
Identical to DW at 1.96 TeV but uses
ATLAS extrapolation to the LHC!
PY Tune DWT
PY Tune DWT
PY Tune DWT
RDF Preliminary
RDFgenerator
Preliminary
Preliminary
level
250
250
500
500
750
750
1000
1250
1500
1750
1750
2000
2000
PT(particle
(GeV/c)
PT(particle jet#1)
jet#1) (GeV/c)
 Shows the “transverse” charged PTsum
particle density,
 Shows the “transverse” charged averagedensity,
pT,
dN/dhd,
versus
P
(jet#1)
for
“leading
jet”
dPT/dhd,
versusfor
PT T(jet#1)
forjet”
“leading
versus PT(jet#1)
“leading
eventsjet”
at 14
events
at
14
TeV
for
Tune
A,
DW,
ATLAS,
and
TeV for Tune A, DW, ATLAS, and HERWIG
HERWIG
(without MPI).
(without MPI).
Rick Field – Florida/CDF
Page 31
PYTHIA 6.2 Tunes
s(MPI) at 1.96 TeV
s(MPI) at 14 TeV
Tune A
309.7 mb
484.0 mb
Tune DW
351.7 mb
549.2 mb
Tune QW
296.5 mb
568.7 mb
PYTHIA 6.2
Tune A
Tune DW
Tune QW
PDF
CTEQ5L
CTEQ5L
CTEQ6.1
MSTP(81)
1
1
1
MSTP(82)
4
4
4
PARP(82)
2.0 GeV
1.9 GeV
1.1 GeV
PARP(83)
0.5
0.5
0.5
PARP(84)
0.4
0.4
0.4
PARP(85)
0.9
1.0
1.0
PARP(86)
0.95
1.0
1.0
PARP(89)
1.8 TeV
1.8 TeV
1.8 TeV
PARP(90)
0.25
0.25
0.25
PARP(62)
1.0
1.25
1.25
PARP(64)
1.0
0.2
0.2
PARP(67)
4.0
2.5
2.5
MSTP(91)
1
1
1
PARP(91)
1.0
2.1
2.1
PARP(93)
5.0
15.0
15.0
Uses LO as with L = 192 MeV!
MC4LHC Workshop
July 17-26, 2006
"Transverse"
PTsum
Density:
dPT/dhd
"Transverse"
Charged
Particle
Density:
dN/dhd
"Transverse"
Charged
Density
"Transverse"
PTsum
Density
(GeV/c)
Parameter
1.6
1.0
RDFPreliminary
Preliminary
RDF
PY Tune QW
PY Tune DW
generatorlevel
level
generator
0.8
1.2
PY Tune DW
PY Tune A
0.6
0.8
PY Tune A
0.4
1.96 TeV
1.96 TeV
PY Tune QW
0.4
0.2
Leading Jet (|h|<2.0)
Leading Jet (|h|<2.0)
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
0.0
0.0
00
50
50
100
100
150
150
200
200
250
250
300
300
350
350
400
450
500
(GeV/c)
PT(particle jet#1) (GeV/c)
 Shows the “transverse” charged PTsum
particledensity,
density,
dN/dhd, versus
dPT/dhd,
versusPP
for“leading
“leadingjet”
jet”events
events
T(jet#1)
T(jet#1)for
at 1.96 TeV for Tune A, DW, and Tune QW
(CTEQ6.1M).
Rick Field – Florida/CDF
Page 32
PYTHIA 6.2 Tunes
s(MPI) at 1.96 TeV
s(MPI) at 14 TeV
Tune A
309.7 mb
484.0 mb
PYTHIA 6.2
Parameter
Tune A
Tune DW
Tune DWT
Tune QW
PDF
CTEQ5L
CTEQ5L
CTEQ5L
CTEQ6.1
Tune DW
351.7 mb
549.2 mb
MSTP(81)
1
1
1
1
Tune DWT
351.7 mb
829.1 mb
MSTP(82)
4
4
4
4
Tune QW
296.5 mb
568.7 mb
PARP(82)
2.0 GeV
1.9 GeV
1.9409 GeV
1.1 GeV
PARP(83)
0.5
0.5
0.5
0.5
0.4
0.4
0.4
0.4
PARP(85)
0.9
1.0
1.0
1.0
PARP(86)
0.95
1.0
1.0
1.0
PARP(89)
1.8 TeV
1.8 TeV
1.96 TeV
1.8 TeV
PARP(90)
0.25
0.25
0.16
0.25
PARP(62)
1.0
1.25
1.25
1.25
PARP(64)
1.0
0.2
0.2
0.2
PARP(67)
4.0
2.5
2.5
2.5
MSTP(91)
1
1
1
1
PARP(91)
1.0
2.1
2.1
2.1
PARP(93)
5.0
15.0
15.0
15.0
Uses LO as with L = 192 MeV!
MC4LHC Workshop
July 17-26, 2006
"Transverse"
Charged
Density
"Transverse"
PTsum
Density
(GeV/c)
PARP(84)
"Transverse"
Charged
Particle
Density:
dN/dhd
"Transverse"
PTsum
Density:
dPT/dhd
8.0
2.5
RDFPreliminary
Preliminary
RDF
PY Tune DWT
PY Tune DWT
generator
level
generator
level
2.0
6.0
1.5
4.0
PY Tune DW
PY Tune DW
1.0
14 TeV
PY Tune QW
14 TeV
PY Tune QW
2.0
0.5
Leading Jet (|h|<2.0)
Leading(|h|<1.0,
Jet (|h|<2.0)
Charged Particles
PT>0.5 GeV/c)
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
0.0
0.0
00
250
250
500
500
750
750
1000
1000
1250
1250
1500
1500
1750
2000
(GeV/c)
PT(particle jet#1) (GeV/c)

Shows
Showsthe
the“transverse”
“transverse”charged
chargedPTsum
particledensity,
dPT/dhd,
density, dN/dhd,
versus Pversus
PTfor
(jet#1)
“leading
for “leading
jet”
T(jet#1)
events
jet” events
at 1.96
atTeV
1.96for
TeV
Tune
for Tune
A, DW,
A, and
DW,Tune
and
QW
Tune(CTEQ6.1M).
QW (CTEQ6.1M).
Rick Field – Florida/CDF
Page 33
MIT Search Scheme 12
Exclusive 3 Jet Final State Challenge
At least 1 Jet (“trigger” jet)
(PT > 40 GeV/c, |h| < 1.0)
CDF Data
Normalized to 1
PYTHIA
Tune A
Exactly 3 jets
(PT > 20 GeV/c, |h| < 2.5)
R(j2,j3)
R(j) = 0.4
Order Jets by PT
Jet1 highest PT, etc.
Bruce Knuteson
Khaldoun
Makhoul
MC4LHC Workshop
July 17-26, 2006
Georgios
Choudalakis
Markus
Klute
Conor
Henderson
Rick Field – Florida/CDF
Ray
Culbertson
Gene
Flanagan
Page 34
3Jexc R(j2,j3) Normalized
The data have more
3 jet events with
small R(j2,j3)!?
 Let Ntrig40 equal the number of events
Exclusive 3-Jet Production: R(j2,j3)
with at least one jet with PT > 40 geV and
|h| < 1.0 (this is the “offline” trigger).
0.16
 Let N3Jexc20 equal the number of events
0.12
with exactly three jets with PT > 20 GeV/c
and |h| < 2.5 which also have at least one
jet with PT > 40 GeV/c and |h| < 1.0.
 Let N3JexcFr = N3Jexc20/Ntrig40. The is
the fraction of the “offline” trigger events
that are exclusive 3-jet events.
Initial-State Radiation
0.08
Normalized to
N3JexcFr
0.04
0.00
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
Underlying Event
 PARP(67) affects the initial-state radiation which
contributes primarily to the region R(j2,j3) > 1.0.
“Jet 3”
Outgoing Parton
Initial-State Radiation
“Jet 2”
R > 1.0
MC4LHC Workshop
July 17-26, 2006
5.0
R(j2,j3)
with PYTHIA Tune AW (PARP(67)=4), Tune DW
(PARP(67)=2.5), Tune BW (PARP(67)=1).
AntiProton
Underlying Event
Data R(j2,j3)
pyAW
pyDW
pyBW
data uncorrected
generator level theory
 The CDF data on dN/dR(j2,j3) at 1.96 TeV compared
Outgoing Parton
“Jet 1”
Proton
dN/dR(j2,j3)
CDF Run 2 Preliminary
Rick Field – Florida/CDF
Page 35
3Jexc R(j2,j3) Normalized
 Let Ntrig40 equal the number of events
Exclusive
Exclusive 3-Jet
3-Jet Production:
Production: R(j2,j3)
R(j2,j3)
0.16
0.80
0.16
with at least one jet with PT > 40 geV and
|h| < 1.0 (this is the “offline” trigger).
0.12
0.60
0.12
dN/dR(j2,j3)
dN/dR(j2,j3)
dN/dR(j2,j3)
 Let N3Jexc20 equal the number of events
CDF Run
Run 22 Preliminary
Preliminary
CDF
with exactly three jets with PT > 20 GeV/c
0.08
0.40
0.08
I do not understand
the
and |h| < 2.5 which also have at least one
excess number
of events
0.04
jet with PT > 40 GeV/c and |h| < 1.0.
0.20
0.04
data
uncorrected
datauncorrected
uncorrected
data
generator
level
theory
generatorlevel
leveltheory
theory
generator
CDF Data
Data
Data R(j2,j3)
R(j2,j3)
hw05
pyDW
pyDW
pyDW
pyDWnoFSR
hw05
pyBW
Normalized to
N3JexcFr
with R(j2,j3) < 1.0.
Normalized to 1
 Let N3JexcFr = N3Jexc20/Ntrig40.
The is this0.00
Perhaps
is
related
to the
0.00
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
the fraction of the “offline” trigger“soft
eventsenergy”
0.0 problem??
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
R(j2,j3)
R(j2,j3)
that are exclusive 3-jet events.
For now the best tune is
 The Tune
CDF data
PYTHIA
DW.on dN/dR(j2,j3) at 1.96 TeV compared
Final-State Radiation
Outgoing Parton
“Jet 1”
with PYTHIA Tune DW (PARP(67)=2.5) and
HERWIG (without MPI).
Proton
AntiProton
Underlying Event
Underlying Event
Outgoing Parton
Final-State Radiation
“Jet “Jet
2” 3”
R < 1.0
MC4LHC Workshop
July 17-26, 2006
 Final-State radiation contributes to the region R(j2,j3)
< 1.0.
 If you ignore the normalization and normalize all the
distributions to one then the data prefer Tune BW, but
I believe this is misleading.
Rick Field – Florida/CDF
Page 36
QCD Monte-Carlo Models:
Lepton-Pair Production
Lepton-Pair Production
Anti-Lepton
Initial-State Radiation
Lepton-Pair Production
Initial-State Radiation
Anti-Lepton
“Hard Scattering” Component
“Jet”
Proton
AntiProton
Lepton
Underlying Event
Underlying Event
Proton
Lepton
AntiProton
Underlying Event
Underlying Event
“Underlying Event”

Start with the perturbative Drell-Yan muon pair production and add initial-state gluon radiation (in the
leading log approximation or modified leading log approximation).
 The “underlying event” consists of the “beam-beam remnants” and from particles arising from soft or
semi-soft multiple parton interactions (MPI).
 Of course the outgoing colored partons fragment into hadron “jet” and inevitably “underlying event”
observables receive contributions from initial and final-state radiation.
MC4LHC Workshop
July 17-26, 2006
Rick Field – Florida/CDF
Page 37
The “Central” Region
in Drell-Yan Production
Look at the charged
particle density and the
PTsum density in the
“central” region!
Charged Particles (pT > 0.5 GeV/c, |h| < 1)
Drell-Yan Production
Lepton
2p
Proton
AntiProton
Underlying Event
Underlying Event
Initial-State
Radiation

Central Region
Anti-Lepton
Multiple Parton Interactions
Proton
Lepton
AntiProton
Underlying Event
0
Underlying Event
Anti-Lepton
-1
After removing the leptonpair everything else is the
“underlying event”!
h
+1
 Look at the “central” region after removing the lepton-pair.
 Study the charged particles (pT > 0.5 GeV/c, |h| < 1) and form the charged particle
density, dNchg/dhd, and the charged scalar pT sum density, dPTsum/dhd, by
dividing by the area in h- space.
MC4LHC Workshop
July 17-26, 2006
Rick Field – Florida/CDF
Page 38
Drell-Yan Production (Run 2 vs LHC)
Drell-Yan Production
Lepton-Pair Transverse
Momentum
Lepton
Proton
<pT(m+m-)> is much
larger at the LHC!
AntiProton
Underlying Event
Drell-Yan PT(m+m-) Distribution
Underlying Event
1.0E+02
Shapes of the pT(m+m-)
distribution at the Z-boson mass.
Initial-State
Radiation
Drell-Yan
generator level
1.0E+01
ds/dPT (pb/GeV)
Anti-Lepton
PY Tune DW (solid)
HERWIG (dashed)
1.0E+00
Lepton-Pair Transverse Momentum
Drell-Yan
Average Pair PT
generator level
LHC
60
Drell-Yan PT(m+m-) Distribution
0.10
Drell-Yan
1.0E-01
1/N dN/dPT (1/GeV)
80
1.0E-02
40
Tevatron Run 2
1.0E-03
70 < M(m-pair) < 110 GeV
|h(m-pair)| < 6
20
PY Tune DW (solid)
HERWIG (dashed)
Z
0
0
100
300
400
500
600
7000
Lepton-Pair Invariant Mass (GeV)
0.08
generator level
LHC
PY Tune DW (solid)
HERWIG (dashed)
0.06
70 < M(m-pair) < 110 GeV
|h(m-pair)| < 6
0.04
0.02 Tevatron Run2
LHC
Normalized to 1
1.0E-04
200
Tevatron Run2
800
50 1000
900
0.00
100
0
1505
PT (m+m-) (GeV/c)
200
10
15
250
20
25
30
35
40
PT(m+m-) (GeV/c)
 Average Lepton-Pair transverse momentum  Shape of the Lepton-Pair pT distribution at the
at the Tevatron and the LHC for PYTHIA
Z-boson mass at the Tevatron and the LHC for
Tune DW and HERWIG (without MPI).
PYTHIA Tune DW and HERWIG (without MPI).
MC4LHC Workshop
July 17-26, 2006
Rick Field – Florida/CDF
Page 39
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/dhd
Charged Particle Density: dN/dhd
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 (|h|<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 (|h|<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
invariant mass at 14 TeV for PYTHIA Tune AW
pair invariant mass at 1.96 TeV for PYTHIA
and HERWIG (without MPI).
Tune AW and HERWIG (without MPI).
MC4LHC Workshop
July 17-26, 2006
Rick Field – Florida/CDF
Page 40
Extrapolations to the LHC:
Drell-Yan Production
Drell-Yan Production
Charged particle density
versus M(pair)
Lepton
The “Underlying Event”
Proton
AntiProton
Underlying Event
Tune DW and DWT are
identical at 1.96 TeV, but
have different MPI energy
dependence!
Underlying Event
Initial-State
Radiation
Anti-Lepton
Charged Particle Density: dN/dhd
Charged Particle
Particle Density:
Density: dN/dhd
dN/dhd
Charged
2.5
1.0
1.0
Charged
Charged Particle
Particle Density
Density
PY Tune BW
PY-ATLAS
generator
generatorlevel
level
0.8
0.8
PY Tune
PYDW
Tune DW
0.6
0.6
0.4
0.4
PY Tune A
PY Tune A
HERWIG
HERWIG
0.2
0.2
00
50
50
100
100
1.96 TeV Drell-Yan
1.96 TeV
Charged Particles
Particles (|h|<1.0,
(|h|<1.0, PT>0.5
PT>0.5 GeV/c)
GeV/c)
Charged
(excluding lepton-pair
lepton-pair))
(excluding
Z
0.0
0.0
PY Tune AW
Charged Particle Density
RDF Preliminary
RDF
RDF Preliminary
Preliminary
generator level
PY-ATLAS
PY Tune DWT
2.0
1.5
PY Tune DW
1.0
14 TeV
0.5
Z
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
(excluding lepton-pair )
HERWIG
0.0
150
150
200
200
250
250
300
300
350
350
400
400
450
450
500
500
0
100
200
300
400
500
600
700
800
900
1000
Lepton-Pair Invariant Mass (GeV)
Lepton-Pair Invariant
Invariant Mass
Mass (GeV)
(GeV)
Lepton-Pair
 Average charged particle density versus the  Average charged particle density versus the
lepton-pair invariant mass at 1.96 TeV for
lepton-pair invariant mass at 14 TeV for
PYTHIA Tune A, Tune AW,
DW, Tune
ATLAS
BW,
and
Tune
PYTHIA Tune DW, Tune DWT, ATLAS and
DW and HERWIG
HERWIG
(without MPI
(without
).
MPI).
HERWIG (without MPI).
MC4LHC Workshop
July 17-26, 2006
Rick Field – Florida/CDF
Page 41
Extrapolations to the LHC:
Drell-Yan Production
Drell-Yan Production
The “Underlying Event”
Charged particle charged
PTsum density versus M(pair)
Lepton
Proton
AntiProton
Underlying Event
The ATLAS tune has a much “softer”
distribution of charged particles than
the CDF Run 2 Tunes!
Underlying Event
Initial-State
Radiation
Anti-Lepton
Charged
Charged PTsum
PTsum Density:
Density: dPT/dhd
dPT/dhd
Charged PTsum Density: dPT/dhd
5.0
PY Tune BW
PY Tune DW
RDF
RDFPreliminary
Preliminary
generator level
generator level
0.9
0.9
PYPY
Tune
A A
Tune
0.6
0.6
PY Tune
AW
PY-ATLAS
PY Tune
DW TeV
1.96
Drell-Yan
1.96 TeV
0.3
0.3
HERWIG
HERWIG
Charged Particles
Particles (|h|<1.0,
(|h|<1.0, PT>0.9
PT>0.5 GeV/c)
GeV/c)
Charged
(excluding lepton-pair
lepton-pair))
(excluding
Z
0.0
0.0
00
50
50
Charged PTsum Density (GeV/c)
Charged PTsum
PTsum Density
Density (GeV/c)
(GeV/c)
Charged
1.2
1.2
RDF Preliminary
PY Tune DWT
generator level
PY Tune DW
4.0
PY-ATLAS
3.0
2.0
14 TeV Drell-Yan
1.0
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
(excluding lepton-pair )
HERWIG
Z
0.0
100
100
150
150
200
200
250
250
300
300
350
350
400
400
450
450
500
500
0
100
Lepton-Pair
Lepton-Pair Invariant
Invariant Mass
Mass (GeV)
(GeV)
200
300
400
500
600
700
800
900
1000
Lepton-Pair Invariant Mass (GeV)
 Average charged PTsum density versus the  Average charged PTsum density versus the
lepton-pair invariant mass at 1.96 TeV for
lepton-pair invariant mass at 14 TeV for
PYTHIA Tune A, Tune
DW, ATLAS,
AW, Tune
and
BW, Tune
PYTHIA Tune DW, Tune DWT, ATLAS, and
DW and HERWIG
HERWIG
(without MPI
(without
).
MPI).
HERWIG (without MPI).
MC4LHC Workshop
July 17-26, 2006
Rick Field – Florida/CDF
Page 42
Extrapolations to the LHC:
Drell-Yan Production
The “Underlying Event”
Charged Particles
(|h|<1.0, pT > 0.5 GeV/c)
Drell-Yan Production
Charged particle density
versus M(pair)
Lepton
The ATLAS tune has a much “softer”
distribution of charged particles than
the CDF Run 2 AntiProton
Tunes!
Proton
Underlying Event
Underlying Event
Charged Particles
(|h|<1.0, pT > 0.9 GeV/c)
Initial-State
Radiation
Anti-Lepton
Charged Particle Density: dN/dhd
Charged Particle Density: dN/dhd
Drell-Yan
PY Tune DWT
Generator Level
14 TeV
Charged Particle
4.0 Density: dN/dhd
PY-ATLAS
generator level
2.0
1.5
1.0
0.5
Z
HERWIG
100
200
0.0
0
Charged Particle Density
Charged Particle Density
RDF Preliminary
300
1.2
PY-ATLAS
PY Tune DWT
3.0
PY Tune DW
PY Tune DW
2.0
14 TeV
1.0
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
(excluding lepton-pair )
Charged Particle Density
2.5
0.8
Charged Particles (pT > min, |h|<1.0)
(excluding lepton-pair
PY Tune DW )
0.4
PY-ATLAS
70 < M(m+m-) < 110 GeV
Z
Generator Level
14 TeV
HERWIG
Charged Particles (|h|<1.0, PT>0.9 GeV/c)
(excluding lepton-pair )
0.0
400
500
600
HERWIG
700
800
900
1000
0
100
200
300
400
500
600
700
800
900
1000
Lepton-Pair Invariant Mass (GeV)
Lepton-Pair Invariant Mass (GeV)
0.0
particle
0.0
0.2
0.4(pT >0.60.5 0.8  Average
1.0
1.2charged
1.4
1.6
1.8density (pT > 0.9 GeV/c)
 Average charged particle
density
the lepton-pair invariant mass at 14 TeV
GeV/c) versus the lepton-pair invariantMinimum
mass pversus
T (GeV/c)
at 14 TeV for PYTHIA Tune DW, Tune DWT, for PYTHIA Tune DW, Tune DWT, ATLAS and
HERWIG (without MPI).
ATLAS and HERWIG (without MPI).
MC4LHC Workshop
July 17-26, 2006
Rick Field – Florida/CDF
Page 43
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
stot = sEL + sIN
SD +sDD +sHC
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 < |h| < 5.9
PT(hard)
Proton
AntiProton
Underlying Event
Underlying Event
Initial-State
Radiation
Final-State
Radiation
Outgoing Parton
MC4LHC Workshop
July 17-26, 2006
Rick Field – Florida/CDF
Page 44
PYTHIA Tune A Min-Bias
“Soft” + ”Hard”
Tuned to fit the
“underlying event”!
PYTHIA Tune A
CDF Run 2 Default
Charged Particle Density: dN/dhd
Charged Particle Density
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
1.8 TeV all PT
CDF Min-Bias 1.8 TeV
0.0
-4
-3
-2
-1
0
1
2
3
4
Pseudo-Rapidity h
 PYTHIA regulates the perturbative 2-to-2
parton-parton cross sections with cut-off
parameters
which allows one to run with
Lots of “hard” scattering
PT(hard)in>“Min-Bias”!
0. One can simulate both “hard”
and “soft” collisions in one program.
Charged Density dN/dhddPT (1/GeV/c)
dN/dhd
Pythia 6.206 Set A
1.8 TeV |h|<1
1.0E-02
12% of “Min-Bias” events
have PT(hard) > 5 GeV/c!
PT(hard) > 0 GeV/c
1.0E-03
1% of “Min-Bias” events
have PT(hard) > 10 GeV/c!
1.0E-04
1.0E-05
CDF Preliminary
1.0E-06
0
2
4
6
8
10
12
14
PT(charged) (GeV/c)
 The relative amount of “hard” versus “soft” depends on the cut-off and can be tuned.
 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)!
MC4LHC Workshop
July 17-26, 2006
Rick Field – Florida/CDF
Page 45
PYTHIA Tune A
LHC Min-Bias Predictions
Hard-Scattering in Min-Bias Events
Charged Particle Density
12% of “Min-Bias”
50% events
have PT(hard) > 10 GeV/c!
1.0E+00
|h|<1
Pythia 6.206 Set A
Pythia 6.206 Set A
40%
% of Events
Charged Density dN/dhddPT (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
1.0E-05
 Shows the center-of-mass energy
CDF Data
1.0E-06
0
2
LHC?
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,
dNchg/dhddPT, 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!
MC4LHC Workshop
July 17-26, 2006
Rick Field – Florida/CDF
Page 46
PYTHIA 6.2 Tunes
LHC Min-Bias Predictions
Charged Particle Density: dN/dY
Charged Particle Density: dN/dh
12
pyA
pyDW
pyDWT
ATLAS
Generator Level
14 TeV
8
Charged Particle Density
Charged Particle Density
10
6
4
2
pyA
pyDW
pyDWT
ATLAS
Generator Level
14 TeV
10
8
6
4
2
Charged Particles (all pT)
Charged Particles (all pT)
0
0
-10
-8
-6
-4
-2
0
2
4
6
8
10
-10
-8
-6
-4
PseudoRapidity h
-2
0
2
4
6
8
10
Rapidity Y
 Shows the predictions of PYTHIA Tune A, Tune DW, Tune DWT, and the ATLAS tune for
the charged particle density dN/dh and dN/dY at 14 TeV (all pT).
 PYTHIA Tune A and Tune DW predict about 6 charged particles per unit h at h = 0, while
the ATLAS tune predicts around 9.
 PYTHIA Tune DWT is identical to Tune DW at 1.96 TeV, but extrapolates to the LHC using
the ATLAS energy dependence.
MC4LHC Workshop
July 17-26, 2006
Rick Field – Florida/CDF
Page 47
PYTHIA 6.2 Tunes
LHC Min-Bias Predictions
Average Number of Charged Particles vs PTmin
Charged PT Distribution
20
100.0
Generator Level
Min-Bias 14 TeV
pyA <PT> = 641 MeV/c
Generator Level
Min-Bias 14 TeV
pyDW <PT> = 665 MeV/c
15
pyA
pyDW
pyDWT
ATLAS
<Nchg>
1/Nev dN/dPT (1/GeV/c)
pyDWT <PT> = 693 MeV/c
ATLAS <PT> = 548 MeV/c
10.0
10
5
Charged Particles (|h|<1.0, PT>PTmin)
1.0
0
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
Minimum PT (GeV/c)
Charged Particles (|h|<1.0)
0.1
0.0
0.5
1.0
1.5
2.0
2.5
3.0
Charged Particle PT (GeV/c)
 Shows the predictions of PYTHIA Tune A, Tune DW, Tune DWT, and the ATLAS tune for
the charged particle pT distribution at 14 TeV (|h| < 1) and the average number of charged
particles with pT > pTmin (|h| < 1).
 The ATLAS tune has many more “soft” particles than does any of the CDF Tunes. The
ATLAS tune has <pT> = 548 MeV/c while Tune A has <pT> = 641 MeV/c (100 MeV/c more
per particle)!
MC4LHC Workshop
July 17-26, 2006
Rick Field – Florida/CDF
Page 48
Summary
Tevatron
Outgoing Parton
LHC
PT(hard)
“Minumum Bias” Collisions
Initial-State Radiation
Proton
Proton
AntiProton
AntiProton
Underlying Event
Underlying Event
I am not sure I
believe the data!?
Outgoing Parton
Final-State
Radiation
The ATLAS tune cannot be right
 PYTHIA Tune A does not produce
in the “underlying event”!
becauseenough
it does“soft”
not fitenergy
the Tevatron
JIMMY 325 (PTJIM = 3.25 GeV/c)
fits the
energy
the “underlying
event” but does so by
data. Right
now
I likeinTune
DW.
producing too many particles
(i.e. itno
is too
Probably
tunesoft).
will fit the LHC data.
That is why we plan to measure MB&UE
 The ATLAS tune is “goofy”!
It produces too many “soft” particles. The charged
at CMS and retune the Monte-Carlo
particle <pT> is too low and does not agree with the CDF Run 2 data. The ATLAS tune
models!
agrees with <Nchg> but not with <PTsum> at the Tevatron.
 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 
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).
MC4LHC Workshop
July 17-26, 2006
Rick Field – Florida/CDF
Page 49