YETI’11: The Standard Model
at the Energy Frontier
Min-Bias and the Underlying Event at the LHC
Rick Field
University of Florida
1st Lecture
 What is the “underlying event” and
how is it related to “min-bias”
collisions.
 Lessons learned about “min-bias”
and the “underlying event” at the
TEVATRON.
 Predicting the behavior of the
CMS
“underlying event” at the LHC. What
we expected to see.
ATLAS
Outgoing Parton
“Minimum Bias” Collisions
PT(hard)
Initial-State Radiation
Proton
Proton
Proton
Underlying Event
Outgoing Parton
Underlying Event
UE&MB@CMS
Final-State
Radiation
YETI'11 Durham IPPP - Part 1
January 10-12, 2011
Rick Field – Florida/CDF/CMS
Page 1
QCD Monte-Carlo Models:
High Transverse Momentum Jets
Hard Scattering
Initial-State Radiation
Hard Scattering “Jet”
Initial-State Radiation
“Jet”
Outgoing Parton
PT(hard)
Outgoing Parton
PT(hard)
Proton
“Hard Scattering” Component
AntiProton
Final-State Radiation
Outgoing Parton
Underlying Event
Underlying Event
Proton
“Jet”
Final-State Radiation
AntiProton
Underlying Event
Outgoing Parton
Underlying Event
“Underlying Event”
 Start with the perturbative 2-to-2 (or sometimes 2-to-3) parton-parton scattering and add initial and finalstate gluon radiation (in the leading log approximation or modified leading log approximation).
 The “underlying event” consists of the “beam-beam remnants” and from particles arising from soft or
semi-soft multiple parton interactions (MPI).
The “underlying
event” is“jet”
an unavoidable
 Of course the outgoing colored partons fragment
into hadron
and inevitably “underlying event”
background to most collider observables
observables receive contributions from initial
and final-state radiation.
and having good understand of it leads to
more precise collider measurements!
YETI'11 Durham IPPP - Part 1
January 10-12, 2011
Rick Field – Florida/CDF/CMS
Page 2
QCD Monte-Carlo Models:
Lepton-Pair Production
Lepton-Pair
Production
High
PT Z-Boson
Production
Anti-Lepton
Outgoing Parton
Initial-State
Initial-State Radiation
Radiation
High P
T Z-Boson Production
Lepton-Pair
Production
Initial-State
Initial-StateRadiation
Radiation
“Jet”
Proton
Proton
Final-State Radiation
Outgoing
Parton
Anti-Lepton
Final-State Radiation
“Hard Scattering” Component
AntiProton
AntiProton
Underlying Event
Lepton
Z-boson
Underlying Event
Proton
Lepton
Z-boson
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-state radiation.
YETI'11 Durham IPPP - Part 1
January 10-12, 2011
Rick Field – Florida/CDF/CMS
Page 3
MPI, Pile-Up, and Overlap
MPI: Multiple Parton Interactions
Outgoing Parton
PT(hard)
Initial-State Radiation
Proton
Proton
Underlying Event
 MPI: Additional 2-to-2 parton-parton
scatterings within a single hadron-hadron
collision.
Underlying Event
Outgoing Parton
Final-State
Radiation
Proton
Pile-Up
Pile-Up
Proton
Proton
Proton
Primary
Interaction Region Dz
 Pile-Up: More than one hadron-hadron collision in the beam
crossing.
Overlap
 Overlap: An experimental timing issue where a hadron-hadron
collision from the next beam crossing gets included in the hadronhadron collision from the current beam crossing because the next
crossing happened before the event could be read out.
YETI'11 Durham IPPP - Part 1
January 10-12, 2011
Rick Field – Florida/CDF/CMS
Page 4
Proton-Proton Collisions
Elastic Scattering
Single Diffraction
Double Diffraction
M2
M
M1
stot = sEL + sSD
IN +sDD +sHC
ND
“Inelastic Non-Diffractive Component”
Hard Core
The “hard core” component
contains both “hard” and
“soft” collisions.
“Hard” Hard Core (hard scattering)
Outgoing Parton
“Soft” Hard Core (no hard scattering)
Proton
PT(hard)
Proton
Proton
Proton
Underlying Event
Underlying Event
Initial-State
Radiation
Final-State
Radiation
Outgoing Parton
YETI'11 Durham IPPP - Part 1
January 10-12, 2011
Rick Field – Florida/CDF/CMS
Page 5
The Inelastic Non-Diffractive
Cross-Section
Occasionally one of
the parton-parton
collisions is hard
(pT > ≈2 GeV/c)
Proton
Proton
Majority of “minbias” events!
Proton
“Semi-hard” partonparton collision
(pT < ≈2 GeV/c)
Proton
+
Proton
+
Proton
Proton
Proton
+
Proton
Proton
+…
YETI'11 Durham IPPP - Part 1
January 10-12, 2011
Rick Field – Florida/CDF/CMS
Multiple-parton
interactions (MPI)!
Page 6
The “Underlying Event”
Select inelastic non-diffractive events
that contain a hard scattering
Proton
Hard parton-parton
collisions is hard
(pT > ≈2 GeV/c)
Proton
1/(pT)4→ 1/(pT2+pT02)2
The “underlying-event” (UE)!
Proton
Given that you have one hard
scattering it is more probable to
have MPI! Hence, the UE has
more activity than “min-bias”.
YETI'11 Durham IPPP - Part 1
January 10-12, 2011
Proton
+
+
Proton
Proton
Rick Field – Florida/CDF/CMS
“Semi-hard” partonparton collision
(pT < ≈2 GeV/c)
Proton
Proton
+…
Multiple-parton
interactions (MPI)!
Page 7
Allow leading hard
scattering to go to
zero pT with same
cut-off as the MPI!
Model of sND
Proton
Proton
Proton
Proton
Proton
+
Proton
“Semi-hard” partonparton collision
(pT < ≈2 GeV/c)
1/(pT)4→ 1/(pT2+pT02)2
Model of the inelastic nondiffractive cross section!
+
Proton
Proton
Proton
+
Proton
Proton
+…
YETI'11 Durham IPPP - Part 1
January 10-12, 2011
Rick Field – Florida/CDF/CMS
Multiple-parton
interactions (MPI)!
Page 8
UE Tunes
Allow primary hard-scattering to
go to pT = 0 with same cut-off!
“Underlying Event”
Fit the “underlying
event” in a hard
scattering process.
Proton
Proton
All of Rick’s tunes (except X2):
1/(pT)4→ 1/(pT2+pT02)2
A, AW, AWT,DW, DWT,
D6, D6T, CW, X1,
“Min-Bias”
“Min-Bias” (add
(ND)single & double diffraction)
and Tune Z1,
are UE tunes!
Proton
Predict MB (ND)!
Proton
+
+
Proton
Proton
Proton
Single Diffraction
Predict MB (IN)!
+…
YETI'11 Durham IPPP - Part 1
January 10-12, 2011
Proton
+
Proton
Proton
Double Diffraction
M2
M
Rick Field – Florida/CDF/CMS
M1
Page 9
MB Tunes
“Underlying Event”
Predict the “underlying
event” in a hard
scattering process!
Proton
Proton
Most of Peter Skand’s tunes:
S320 Perugia
0, S325 Perugia X,
“Min-Bias”
(ND)
S326 Perugia 6
are MB tunes!
Proton
Fit MB (ND).
Proton
+
Proton
+
Proton
Proton
Proton
+
Proton
Proton
+…
YETI'11 Durham IPPP - Part 1
January 10-12, 2011
Rick Field – Florida/CDF/CMS
Page 10
MB+UE Tunes
“Underlying Event”
Fit the “underlying
event” in a hard
scattering process!
Proton
Proton
Most of Hendrik’s “Professor”
tunes: ProQ20, P329
are MB+UE!
“Min-Bias” (ND)
Simultaneous fit
to both MB & UE
Proton
Fit MB (ND).
Proton
+
Proton
+…
YETI'11 Durham IPPP - Part 1
January 10-12, 2011
+
Proton
Proton
Proton
+
Proton
Proton
The ATLAS AMBT1 Tune is an MB+UE tune, but
because they include in the fit the ATLAS UE data
with PTmax > 10 GeV/c (big errors) the LHC UE data
does not have much pull (hence mostly an MB tune!).
Rick Field – Florida/CDF/CMS
Page 11
Traditional Approach
CDF Run 1 Analysis Charged Particle Df Correlations
Leading Calorimeter Jet or
Charged Jet #1
Leading Charged Particle Jet or
PT > PTmin |h| < hcut
Direction
Leading Charged Particle or
2
“Transverse” region
very sensitive to the
“underlying event”!
Away RegionZ-Boson
“Toward-Side” Jet
Df
“Toward”
“Transverse”
“Transverse”
“Away”
Leading Object
Direction
Df
“Toward”
“Transverse”
“Transverse”
Transverse
Region
f
Leading
Object
Toward Region
Transverse
Region
“Away”
Away Region
0
-hcut
“Away-Side” Jet
h
+hcut
 Look at charged particle correlations in the azimuthal angle Df relative to a leading object (i.e.
CaloJet#1, ChgJet#1, PTmax, Z-boson). For CDF PTmin = 0.5 GeV/c hcut = 1.
 Define |Df| < 60o as “Toward”, 60o < |Df| < 120o as “Transverse”, and |Df| > 120o as

“Away”.
o
All three regions have the same area in h-f space, Dh×Df = 2hcut×120 = 2hcut×2/3. Construct
densities by dividing by the area in h-f space.
YETI'11 Durham IPPP - Part 1
January 10-12, 2011
Rick Field – Florida/CDF/CMS
Page 12
ISAJET 7.32 (without MPI)
“Transverse” Density
ISAJET uses a naïve leading-log
parton shower-model which does
not agree with the data!
Charged Jet #1
Direction
"Transverse" Charged Particle Density: dN/dhdf
1.00
Df
“Transverse”
“Transverse”
“Away”
CDF Run 1Data
"Transverse" Charged Density
“Toward”
ISAJET
Isajet
data uncorrected
theory corrected
0.75
"Hard"
0.50
0.25
“Hard”
Component
"Remnants"
1.8 TeV |h|<1.0 PT>0.5 GeV
Beam-Beam
Remnants
0.00
0
5
10
15
20
25
30
35
40
45
50
PT(charged jet#1) (GeV/c)
 Plot shows average “transverse” charge particle density (|h|<1, pT>0.5 GeV) versus PT(charged
jet#1) compared to the QCD hard scattering predictions of ISAJET 7.32 (default parameters with
PT(hard)>3 GeV/c) .
 The predictions of ISAJET are divided into two categories: charged particles that arise from the
break-up of the beam and target (beam-beam remnants); and charged particles that arise from the
outgoing jet plus initial and final-state radiation (hard scattering component).
YETI'11 Durham IPPP - Part 1
January 10-12, 2011
Rick Field – Florida/CDF/CMS
Page 13
HERWIG 6.4 (without MPI)
“Transverse” Density
Df
“Toward”
“Transverse”
“Transverse”
“Away”
1.00
1.00
CDF Run 1Data
CDF
"Transverse" Charged Density
Charged Jet #1
Direction
HERWIG uses a modified leadinglog parton shower-model which
does agrees better with the data!
"Transverse"
"Transverse"Charged
ChargedParticle
ParticleDensity:
Density:dN/dhdf
dN/dhdf
Isajet
Total
"Hard"
data uncorrected
theory corrected
0.75
0.75
"Hard"
0.50
0.50
0.25
0.25
"Remnants"
"Remnants"
Beam-Beam
Remnants
HERWIG
Herwig 6.4 CTEQ5L
PT(hard) > 3 GeV/c
1.8TeV
TeV|h|<1.0
|h|<1.0PT>0.5
PT>0.5GeV
GeV
1.8
0.00
0.00
0
5
10
10
15
15
20
20
25
25
30
30
3535
PT(chargedjet#1)
jet#1) (GeV/c)
(GeV/c)
PT(charged
4040
4545
5050
“Hard”
Component
 Plot shows average “transverse” charge particle density (|h|<1, pT>0.5 GeV) versus PT(charged
jet#1) compared to the QCD hard scattering predictions of HERWIG 5.9 (default parameters with
PT(hard)>3 GeV/c without MPI).
 The predictions of HERWIG are divided into two categories: charged particles that arise from the
break-up of the beam and target (beam-beam remnants); and charged particles that arise from the
outgoing jet plus initial and final-state radiation (hard scattering component).
YETI'11 Durham IPPP - Part 1
January 10-12, 2011
Rick Field – Florida/CDF/CMS
Page 14
HERWIG 6.4 (without MPI)
“Transverse” PT Distribution
HERWIG has the too steep of a pT
dependence of the “beam-beam remnant”
"Transverse" Chargedcomponent
Particle Density:
dN/dhdf
of the
“underlying event”!
"Transverse" Charged Particle Density
Charged Jet #1
Direction
CDF Data
"Hard"
Total
data uncorrected
theory corrected
0.75
1.0E+00
Herwig 6.4 CTEQ5L
PT(hard) > 3 GeV/c
Df
0.50
0.25
"Remnants"
1.8 TeV |h|<1.0 PT>0.5 GeV
0.00
0
5
10
CDF Data
PT(chgjet#1) > 5 GeV/c
15
20
25
30
35
40
45
PT(charged jet#1) (GeV/c)
Herwig PT(chgjet#1) > 30 GeV/c
“Transverse” <dNchg/dhdf> = 0.51
50
Charged Density dN/dhdfdPT (1/GeV/c)
"Transverse" Charged Density
1.00
data uncorrected
theory corrected
1.0E-01
“Toward”
1.8 TeV |h|<1 PT>0.5 GeV/c
1.0E-02
“Transverse”
1.0E-03
“Transverse”
“Away”
1.0E-04
1.0E-05
PT(chgjet#1) > 30 GeV/c
Herwig 6.4 CTEQ5L
1.0E-06
Herwig PT(chgjet#1) > 5 GeV/c
<dNchg/dhdf> = 0.40
0
2
4
6
8
10
12
14
PT(charged) (GeV/c)
 Compares the average “transverse” charge particle density (|h|<1, pT>0.5 GeV) versus
PT(charged jet#1) and the pT distribution of the “transverse” density, dNchg/dhdfdPT with the
QCD hard scattering predictions of HERWIG 6.4 (default parameters with PT(hard)>3
GeV/c without MPI). Shows how the “transverse” charge particle density is distributed in pT.
YETI'11 Durham IPPP - Part 1
January 10-12, 2011
Rick Field – Florida/CDF/CMS
Page 15
MPI: Multiple Parton
Interactions
“Hard”
Collision
Multiple
Parton
Interaction
outgoing parton
“Hard” Component
“Semi-Hard” MPI
“Soft” Component
AntiProton
Proton
initial-state radiation
initial-state radiation
outgoing parton
final-state radiation
or
+
outgoing jet
final-state radiation
 PYTHIA models the “soft” component of the underlying event
with color string fragmentation, but in addition includes a
contribution arising from multiple parton interactions (MPI)
in which one interaction is hard and the other is “semi-hard”.
Beam-Beam Remnants
color string
color string
 The probability that a hard scattering events also contains a semi-hard multiple parton
interaction can be varied but adjusting the cut-off for the MPI.
 One can also adjust whether the probability of a MPI depends on the PT of the hard
scattering, PT(hard) (constant cross section or varying with impact parameter).
 One can adjust the color connections and flavor of the MPI (singlet or nearest neighbor,
q-qbar or glue-glue).
 Also, one can adjust how the probability of a MPI depends on PT(hard) (single or double
Gaussian matter distribution).
YETI'11 Durham IPPP - Part 1
January 10-12, 2011
Rick Field – Florida/CDF/CMS
Page 16
Tuning PYTHIA 6.2:
Multiple Parton Interaction Parameters
Parameter
Default
PARP(83)
0.5
Double-Gaussian: Fraction of total hadronic
matter within PARP(84)
PARP(84)
0.2
Double-Gaussian: Fraction of the overall hadron
radius containing the fraction PARP(83) of the
total hadronic matter.
Determines the energy
Probability
that of
thethe
MPI
produces two gluons
dependence
MPI!
with color connections to the “nearest neighbors.
0.33
PARP(86)
0.66
PARP(89)
PARP(82)
PARP(90)
PARP(67)
1 TeV
1.9
GeV/c
0.16
1.0
Multiple Parton Interaction
Color String
Color String
Multiple PartonDetermine
Interactionby comparing
Probability thatAffects
the MPI
theproduces
amount two
of gluons
either as described
by PARP(85)
or as a closed
initial-state
radiation!
gluon loop. The remaining fraction consists of
quark-antiquark pairs.
with 630 GeV data!
Color String
Hard-Scattering Cut-Off PT0
Determines the reference energy E0.
The cut-off PT0 that regulates the 2-to-2
scattering divergence 1/PT4→1/(PT2+PT02)2
Determines the energy dependence of the cut-off
PT0 as follows PT0(Ecm) = PT0(Ecm/E0)e with
e = 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.
YETI'11 Durham IPPP - Part 1
January 10-12, 2011
Rick Field – Florida/CDF/CMS
5
PYTHIA 6.206
e = 0.25 (Set A))
4
PT0 (GeV/c)
PARP(85)
Description
Take E0 = 1.8 TeV
3
2
e = 0.16 (default)
1
100
1,000
10,000
100,000
CM Energy W (GeV)
Reference point
at 1.8 TeV
Page 17
PYTHIA 6.206 Defaults
MPI constant
probability
scattering
PYTHIA default parameters
6.115
6.125
6.158
6.206
MSTP(81)
1
1
1
1
MSTP(82)
1
1
1
1
PARP(81)
1.4
1.9
1.9
1.9
PARP(82)
1.55
2.1
2.1
1.9
PARP(89)
1,000
1,000
1,000
PARP(90)
0.16
0.16
0.16
4.0
1.0
1.0
PARP(67)
4.0
1.00
"Transverse" Charged Density
Parameter
"Transverse" Charged Particle Density: dN/dhdf
CDF Data
Pythia 6.206 (default)
MSTP(82)=1
PARP(81) = 1.9 GeV/c
data uncorrected
theory corrected
0.75
0.50
0.25
1.8 TeV |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)
CTEQ3L
CTEQ4L
CTEQ5L
CDF Min-Bias
CDF JET20
 Plot shows the “Transverse” charged particle density versus PT(chgjet#1) compared to
the QCD hard scattering predictions of PYTHIA 6.206 (PT(hard) > 0) using the default
parameters for multiple parton interactions and CTEQ3L, CTEQ4L, and CTEQ5L.
Note Change
PARP(67) = 4.0 (< 6.138)
PARP(67) = 1.0 (> 6.138)
YETI'11 Durham IPPP - Part 1
January 10-12, 2011
Default parameters give
very poor description of
the “underlying event”!
Rick Field – Florida/CDF/CMS
Page 18
Run 1 PYTHIA Tune A
CDF Default!
PYTHIA 6.206 CTEQ5L
"Transverse" Charged Particle Density: dN/dhdf
Parameter
Tune B
Tune A
MSTP(81)
1
1
MSTP(82)
4
4
PARP(82)
1.9 GeV
2.0 GeV
PARP(83)
0.5
0.5
PARP(84)
0.4
0.4
PARP(85)
1.0
0.9
"Transverse" Charged Density
1.00
CDF Preliminary
0.75
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)
YETI'11 Durham IPPP - Part 1
January 10-12, 2011
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
PARP(86)
PYTHIA 6.206 (Set A)
PARP(67)=4
data uncorrected
theory corrected
5
10
15
20
25
30
35
40
45
50
PT(charged jet#1) (GeV/c)
 Plot shows the “transverse” charged particle density
versus PT(chgjet#1) compared to the QCD hard
scattering predictions of two tuned versions of
PYTHIA 6.206 (CTEQ5L, Set B (PARP(67)=1) and
Set A (PARP(67)=4)).
Old PYTHIA default
(more initial-state radiation)
Rick Field – Florida/CDF/CMS
Page 19
“Transverse” Cones
vs “Transverse” Regions
“Cone Analysis”
2
2
Transverse
Cone:
(0.7)2=0.49
Away Region
Transverse
Region
f
(Tano, Kovacs, Huston, Bhatti)
Cone 1
f
Leading
Jet
Leading
Jet
Toward Region
Transverse
Region:
2/3=0.67
Transverse
Region
Cone 2
Away Region
0
0
-1


h
+1
-1
h
+1
Sum the PT of charged particles in two cones of
radius 0.7 at the same h as the leading jet but with
|DF| = 90o.
Plot the cone with the maximum and minimum PTsum
versus the ET of the leading (calorimeter) jet.
YETI'11 Durham IPPP - Part 1
January 10-12, 2011
Rick Field – Florida/CDF/CMS
Page 20
Energy Dependence
of the “Underlying Event”
“Cone Analysis”
(Tano, Kovacs, Huston, Bhatti)
630 GeV
1,800 GeV
PYTHIA 6.115
PT0 = 1.4 GeV
PYTHIA 6.115
PT0 = 2.0 GeV



Sum the PT of charged particles (pT > 0.4 GeV/c) in two cones of radius 0.7 at the same h as the
leading jet but with |DF| = 90o. Plot the cone with the maximum and minimum PTsum versus the ET
of the leading (calorimeter) jet.
Note that PYTHIA 6.115 is tuned at 630 GeV with PT0 = 1.4 GeV and at 1,800 GeV with PT0 = 2.0
GeV. This implies that e = PARP(90) should be around 0.30 instead of the 0.16 (default).
For the MIN cone 0.25 GeV/c in radius R = 0.7 implies a PTsum density of dPTsum/dhdf = 0.16 GeV/c
and 1.4 GeV/c in the MAX cone implies dPTsum/dhdf = 0.91 GeV/c (average PTsum density of 0.54
GeV/c per unit h-f).
YETI'11 Durham IPPP - Part 1
January 10-12, 2011
Rick Field – Florida/CDF/CMS
Page 21
“Transverse” Charged Densities
Energy Dependence
"Transverse" Charged PTsum Density: dPTsum/dhdf
"Min Transverse" PTsum Density: dPTsum/dhdf
0.60
0.3
Charged PTsum Density (GeV)
Charged PTsum Density (GeV)
e = 0.25
HERWIG 6.4
0.40
e = 0.16
e=0
0.20
630 GeV |h|<1.0 PT>0.4 GeV
0.2
0.1
CTEQ5L
630 GeV |h|<1.0 PT>0.4 GeV
0.0
0.00
0
5
10
15
20
25
30
35
40
45
50
0
5
10
Lowering PT0 at 630 GeV (i.e.
increasing e) increases UE activity
charged
PT density
resulting insum
less energy dependence.
(|h|<1, PT>0.4 GeV) versus PT(charged jet#1) at
630 GeV predicted by HERWIG 6.4 (PT(hard) > 3
GeV/c, CTEQ5L) and a tuned version of PYTHIA
6.206 (PT(hard) > 0, CTEQ5L, Set A, e = 0, e =
0.16 (default) and e = 0.25 (preferred)).
Also shown are the PTsum densities (0.16 GeV/c
and 0.54 GeV/c) determined from the Tano,
Kovacs, Huston, and Bhatti “transverse” cone
analysis at 630 GeV.
20
25
30
40
45
50
Hard-Scattering Cut-Off PT0
PYTHIA 6.206
e = 0.25 (Set A))
3
2
e = 0.16 (default)
1
100
1,000
Rick Field Fermilab MC Workshop
Reference point
E = 1.8 TeV
October 4, 2002!
YETI'11 Durham IPPP - Part 1
January 10-12, 2011
35
5
4
PT0 (GeV/c)
 Shows the “transverse”
15
PT(charged jet#1) (GeV/c)
PT(charged jet#1) (GeV/c)

HERWIG 6.4
e = 0.25
Increasing e produces less energy
dependence for the
UE resulting
in
e = 0.16
e=0
less UE activity at the LHC!
CTEQ5L
Pythia 6.206 (Set A)
Pythia 6.206 (Set A)
Rick Field – Florida/CDF/CMS
10,000
100,000
CM Energy W (GeV)
0
Page 22
Run 1 vs Run 2: “Transverse”
Charged Particle Density
“Transverse” region as
defined by the leading
“charged particle jet”
"Transverse"
"Transverse" Charged
Charged Particle
Particle Density:
Density: dN/dhdf
dN/dhdf
"Transverse"
Charged
Particle
Density:
dN/dhdf
"Transverse"
Charged
Particle
Density:
dN/dhdf
Charged Particle Jet #1
Direction
Df
“Toward”
“Transverse”
“Transverse”
“Away”
"Transverse"
ChargedDensity
Density
"Transverse"Charged
Charged
Density
"Transverse"
"Transverse"
Charged
Density
1.25
1.25
1.25
CDF Run 1 Min-Bias
CDF Run 1 Min-Bias
CDF
Run
11Published
CDF
Run
JET20
CDF
Run
1 Published
CDF
Run
1 JET20
CDF Run 2 Preliminary
CDF Run 2 Preliminary
PYTHIA Tune A
CDF Run 2
CDFPreliminary
Run 1 Data
CDF
CDF
Preliminary
CDF
Preliminary
data
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
0.50
0.25
0.25
0.25
|h|<1.0
PT>0.5
GeV/c
|h|<1.0
PT>0.5
GeV/c
1.8
TeV
|h|<1.0
|h|<1.0
PT>0.5PT>0.5
GeV GeV
0.00
0.00
0.00
0.00
000
0
10
20
10
10 5 20
20
30
30
10
30
40
50
40
4015 50
50
60
70 2580
60
20
60 70
70 80
80
PT(charged
jet#1)
PT(charged jet#1)
90
10035110
120
140 150
90
130
30
40 130
50
90 100
100 110
110 120
120
13045140
140 150
150
(GeV/c)
PT(charged jet#1) (GeV/c)
(GeV/c)
 Shows the
Excellent agreement
between
Run average
1 and 2!
data
on the
“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).
YETI'11 Durham IPPP - Part 1
January 10-12, 2011
Rick Field – Florida/CDF/CMS
Page 23
Run 1 vs Run 2: “Transverse”
Charged PTsum Density
“Transverse” region as
defined by the leading
“charged particle jet”
“Toward”
“Transverse”
“Transverse”
“Away”
1.25
1.25
1.25
"Transverse"
PTsum
Density
(GeV)
"Transverse"
"Transverse"PTsum
PTsumDensity
Density(GeV/c)
(GeV)
Charged Particle Jet #1
Direction
Df
"Transverse" Charged PTsum Density: dPTsum
sum/dhdf
sum
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
|h|<1.0
PT>0.5
|h|<1.0GeV
PT>0.5GeV
GeV/c
1.8 TeV |h|<1.0 PT>0.5
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
130 45
140 150
150
30 100
40 130
50
PT(charged
PT(charged jet#1)
jet#1) (GeV/c)
(GeV/c)
 Shows the
Excellent agreement
between
Run average
1 and 2!
data on the
“transverse” charged PTsum 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
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).
YETI'11 Durham IPPP - Part 1
January 10-12, 2011
Rick Field – Florida/CDF/CMS
Page 24
“Underlying Event”
as defined by “Calorimeter Jets”
Charged Particle Df Correlations
JetClu Jet #1
Direction
pT > 0.5 GeV/c |h| < 1
“Transverse” region is
2
very sensitive to the
JetClu
Jet
#1
“Toward-Side” Jet
“underlying event”!
Direction
Df
“Toward”
Look at the charged
particle density in the
“transverse” region!
Away Region
Df
Transverse
Region
“Toward”
f
“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
h
+1
 Look at charged particle correlations in the azimuthal angle Df relative to the leading


JetClu jet.
o
o
o
o
Define |Df| < 60 as “Toward”, 60 < |Df| < 120 as “Transverse”, and |Df| > 120 as
“Away”.
o
All three regions have the same size in h-f space, DhxDf = 2x120 = 4/3.
YETI'11 Durham IPPP - Part 1
January 10-12, 2011
Rick Field – Florida/CDF/CMS
Page 25
“Transverse”
Charged Particle Density
Direction
“Transverse” region as
defined by the leading
“calorimeter jet”
Df
“Toward”
“Toward”
“Transverse”
“Transverse”
“Transverse”
“Transverse”
“Away”
“Away”
"Transverse"
Charged Particle
Particle Density: dN/dhdf
"Transverse" Charged
1.00
1.00
1.00
Df
Density
"Transverse"
"Transverse" Charged
Charged Density
Density
JetClu Jet #1
or ChgJet#1
Direction
JetClu Jet #1
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 |h(jet)|<2)
= 0.7,|h(jet)|<2)
CDF Run 2 Preliminary
0.50
0.50
ChgJet#1 R = 0.7
PYTHIA
Tune A 1.96
JetClu (R
= 0.7, |h(jet#1)|
< 2)TeV
ChgJet#1 R = 0.7
0.25
0.25
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)
0.00
0.00
00
25
25
50
50
75
75
100
100
125
125
150
150
175
175
200
225
250
ET(jet#1)
(GeV) (GeV)
PT(chgjet#1)
or ET(jet#1)
 Shows the data on the average “transverse” charge particle density (|h|<1, PT>0.5 GeV)
as a function of the transverse energy of the leading JetClu jet (R = 0.7, |h(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.
YETI'11 Durham IPPP - Part 1
January 10-12, 2011
Rick Field – Florida/CDF/CMS
Page 26
“Transverse”
Charged PTsum Density
Direction
“Transverse” region as
defined by the leading
“calorimeter jet”
"Transverse" Charged PTsum Density: dPTsum/dhdf
Df
Df
“Toward”
“Toward”
“Transverse”
“Transverse”
“Transverse”
“Transverse”
“Away”
“Away”
1.5
"Transverse"
"Transverse" PTsum
PTsum Density
Density (GeV/c)
(GeV/c)
JetClu Jet #1
or ChgJet#1
Direction
JetClu
Jet #1
CDF Preliminary
CDF
Preliminary
data uncorrected
data
uncorrected
theory
corrected
1.0
JetClu Jet#1 (R = 0.7,|h(jet)|<2)
JetClu Jet#1 (R = 0.7,|h(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
JetClu (R = 0.7, |h(jet#1)| < 2)
Charged Particles
Particles (|h|<1.0,
(|h|<1.0, PT>0.5
PT>0.5 GeV/c)
GeV/c)
Charged
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
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)
 Shows the data on the average “transverse” charged PTsum density (|h|<1, PT>0.5
GeV) as a function of the transverse energy of the leading JetClu jet (R = 0.7, |h(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.
YETI'11 Durham IPPP - Part 1
January 10-12, 2011
Rick Field – Florida/CDF/CMS
Page 27
Rick Field University of Chicago
July 11, 2006
“Leading Jet”
“Back-to-Back”
Jet #1 Direction
Jet #1 Direction
“Toward”
“Toward”
“TransMAX”
“TransMIN”
“TransMAX”
“Away”
“TransMIN”
“Away”
"Transverse" ETsum Density (GeV)
Df
Df
"TransMAX" ETsum Density: dET/dhdf
7.0
Jet #2 Direction
CDF Run 2 Preliminary
6.0
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
0
50
100
150
200
250
300
350
400
450
PT(jet#1) (GeV/c)
"TransMIN" ETsum Density: dET/dhdf
3.0
"Transverse" ETsum Density (GeV)

"Leading Jet"
1.96 TeV
5.0
 Shows the data on the tower ETsum
density, dETsum/dhdf, 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).
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)
YETI'11 Durham IPPP - Part 1
January 10-12, 2011
Rick Field – Florida/CDF/CMS
Page 28
Rick Field University of Chicago
July 11, 2006
“Leading Jet”
“Back-to-Back”
Jet #1 Direction
Jet #1 Direction
“Toward”
“TransMAX”
“TransMIN”
“Away”
Neither PY Tune A or
“Toward”
HERWIG fits the
ETsum
density in the
“TransMAX”
“TransMIN”
“transferse” region!
HERWIG
does slightly
“Away”
better than Tune A!
"Transverse" ETsum Density (GeV)
Df
Df
"TransMAX" ETsum Density: dET/dhdf
7.0
Jet #2 Direction
CDF Run 2 Preliminary
6.0
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
0
50
100
150
200
250
300
350
400
450
PT(jet#1) (GeV/c)
"TransMIN" ETsum Density: dET/dhdf
3.0
"Transverse" ETsum Density (GeV)

"Leading Jet"
1.96 TeV
5.0
 Shows the data on the tower ETsum
density, dETsum/dhdf, 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).
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)
YETI'11 Durham IPPP - Part 1
January 10-12, 2011
Rick Field – Florida/CDF/CMS
Page 29
Rick Field University of Chicago
July 11, 2006
“Leading Jet”
Jet #1 Direction
Df
"TransDIF" ETsum Density: dET/dhdf
“Toward”
Jet #1 Direction
Df
“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/dhdf, for all particles (|h| <
1) versus PT(jet#1) for “Leading Jet” and “Back-to-Back” events.
YETI'11 Durham IPPP - Part 1
January 10-12, 2011
Rick Field – Florida/CDF/CMS
Page 30
Rick Field University of Chicago
July 11, 2006
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
the number of particles in the “underlying
event” at low pT (i.e. pT < 0.5 GeV/c).
1.0E-02
Beam-Beam
Remnants
1.0E-03
 Perhaps there are two components, a vary
1.0E-04
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
pT All Particles (GeV/c)
YETI'11 Durham IPPP - Part 1
January 10-12, 2011
4.0
4.5
5.0
“soft” beam-beam remnant component
(Gaussian or exponential) and a “hard”
multiple interaction component.
Rick Field – Florida/CDF/CMS
Page 31
Charged Particle Multiplicity
Charged Multiplicity Distribution
Charged Multiplicity Distribution
1.0E+00
1.0E+00
CDF Run 2 Preliminary
1.0E-01
CDF Run 2 <Nchg>=4.5
CDF Run 2 <Nchg>=4.5
1.0E-02
Probability
Probability
1.0E-02
CDF Run 2 Preliminary
1.0E-01
1.0E-03
1.0E-04
1.0E-05
py Tune A <Nchg> = 4.3
pyAnoMPI <Nchg> = 2.6
1.0E-03
1.0E-04
1.0E-05
1.0E-06
1.0E-06
Min-Bias 1.96
1.0E-07
Min-Bias 1.96
1.0E-07
Charged Particles (|h|<1.0, PT>0.4 GeV/c)
Normalized to 1
Normalized to 1
Charged Particles (|h|<1.0, PT>0.4 GeV/c)
1.0E-08
1.0E-08
0
5
10
15
20
25
30
35
40
45
50
55
0
5
10
Number of Charged Particles
i
20
25
30
35
40
45
50
Number of Charged Particles
“Minimum Bias” Collisions
Proton
15
No MPI!
Tune A!
AntiProton
 Data at 1.96 TeV on the charged particle multiplicity (pT > 0.4 GeV/c, |h| < 1) for “min-bias”
collisions at CDF Run 2 (non-diffractive cross-section).
 The data are compared with PYTHIA Tune A and Tune A without multiple parton
interactions (pyAnoMPI).
YETI'11 Durham IPPP - Part 1
January 10-12, 2011
Rick Field – Florida/CDF/CMS
Page 32
55
PYTHIA Tune A Min-Bias
“Soft” + ”Hard”
Charged Particle Density
1.0E+00
Pythia 6.206 Set A
CDF Min-Bias Data
Charged Density dN/dhdfdPT (1/GeV/c)
1.0E-01
Ten decades!
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
PT(charged) (GeV/c)
10
12
14
Lots of “hard” scattering in
“Min-Bias” at the Tevatron!
 Comparison of PYTHIA Tune A with the pT distribution of charged particles for “min-bias”
collisions at CDF Run 1 (non-diffractive cross-section).
pT = 50 GeV/c!
 PYTHIA Tune A 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)!
YETI'11 Durham IPPP - Part 1
January 10-12, 2011
Rick Field – Florida/CDF/CMS
Page 33
CDF: Charged pT Distribution
Erratum November 18, 2010
Excess
No excess
events
atat
large
large
pTp! T!
“Minimum Bias” Collisions
Proton
AntiProton
50 GeV/c!
 Published CDF data on the pT distribution
of charged particles in Min-Bias collisions
(ND) at 1.96 TeV compared with PYTHIA
Tune A.
YETI'11 Durham IPPP - Part 1
January 10-12, 2011
CDF
CDFinconsistent
consistent with
withCMS
CMSand
andUA1!
UA1!
Rick Field – Florida/CDF/CMS
Page 34
Min-Bias Correlations
Average PT versus Nchg
Average PT (GeV/c)
1.4
CDF Run 2 Preliminary
1.2
Min-Bias
1.96 TeV
pyDW
data corrected
generator level theory
pyA
“Minumum
Bias” Collisions
1.0
Proton
AntiProton
ATLAS
0.8
Charged Particles (|h|<1.0, PT>0.4 GeV/c)
0.6
0
10
20
30
40
50
Number of Charged Particles
“Minimum Bias” Collisions
Proton
AntiProton
 Data at 1.96 TeV on the average pT of charged particles versus the number of charged
particles (pT > 0.4 GeV/c, |h| < 1) for “min-bias” collisions at CDF Run 2. The data are
corrected to the particle level and are compared with PYTHIA Tune A at the particle
level (i.e. generator level).
YETI'11 Durham IPPP - Part 1
January 10-12, 2011
Rick Field – Florida/CDF/CMS
Page 35
Min-Bias: Average PT versus Nchg
 Beam-beam remnants (i.e. soft hard core) produces
Average PT versus Nchg
Average PT (GeV/c)
1.4
CDF Run 2 Preliminary
Min-Bias
1.96 TeV
data corrected
generator level theory
1.2
low multiplicity and small <pT> with <pT>
independent of the multiplicity.
 Hard scattering (with no MPI) produces large
pyA
multiplicity and large <pT>.
pyAnoMPI
1.0
 Hard scattering (with MPI) produces large
0.8
multiplicity and medium <pT>.
ATLAS
Charged Particles (|h|<1.0, PT>0.4 GeV/c)
0.6
0
5
10
15
20
25
30
35
40
This observable is sensitive
to the MPI tuning!
Number of Charged Particles
“Hard” Hard Core (hard scattering)
Outgoing Parton
“Soft” Hard Core (no hard scattering)
PT(hard)
CDF “Min-Bias”
=
Proton
+
AntiProton
Proton
AntiProton
Underlying Event
Underlying Event
Initial-State
Radiation
Final-State
Radiation
Multiple-Parton Interactions
+
Proton
AntiProton
Underlying Event
Outgoing Parton
YETI'11 Durham IPPP - Part 1
January 10-12, 2011
Outgoing Parton
PT(hard)
Initial-State
Radiation
The CDF “min-bias” trigger
picks up most of the “hard
core” component!
Outgoing Parton
Underlying Event
Final-State
Radiation
Rick Field – Florida/CDF/CMS
Page 36
CDF Run 1 PT(Z)
Parameter
Tune A
Tune AW
UE Parameters MSTP(81)
1
1
MSTP(82)
4
4
PARP(82)
2.0 GeV
2.0 GeV
PARP(83)
0.5
0.5
PARP(84)
0.4
0.4
PARP(85)
0.9
0.9
PARP(86)
0.95
0.95
PARP(89)
1.8 TeV
1.8 TeV
PARP(90)
0.25
0.25
PARP(62)
1.0
1.25
PARP(64)
1.0
0.2
PARP(67)
4.0
4.0
MSTP(91)
1
1
PARP(91)
1.0
2.1
PARP(93)
5.0
15.0
ISR Parameters
Z-Boson Transverse Momentum
0.12
PT Distribution 1/N dN/dPT
PYTHIA 6.2 CTEQ5L
Tune used by the
CDF-EWK group!
CDF Run 1 Data
PYTHIA Tune A
PYTHIA Tune AW
CDF Run 1
published
0.08
1.8 TeV
Normalized to 1
0.04
0.00
0
2
4
6
8
10
12
14
16
18
Z-Boson PT (GeV/c)
 Shows the Run 1 Z-boson pT distribution (<pT(Z)>
≈ 11.5 GeV/c) compared with PYTHIA Tune A
(<pT(Z)> = 9.7 GeV/c), and PYTHIA Tune AW
(<pT(Z)> = 11.7 GeV/c).
Effective Q cut-off, below which space-like showers are not evolved.
Intrensic KT
The Q2 = kT2 in as for space-like showers is scaled by PARP(64)!
YETI'11 Durham IPPP - Part 1
January 10-12, 2011
20
Rick Field – Florida/CDF/CMS
Page 37
Jet-Jet Correlations (DØ)
Jet#1-Jet#2 Df Distribution
Df 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).
YETI'11 Durham IPPP - Part 1
January 10-12, 2011
Rick Field – Florida/CDF/CMS
Page 38
CDF Run 1 PT(Z)
PYTHIA 6.2 CTEQ5L
Tune DW
Tune AW
UE Parameters MSTP(81)
1
1
MSTP(82)
4
4
PARP(82)
1.9 GeV
2.0 GeV
PARP(83)
0.5
0.5
PARP(84)
0.4
0.4
PARP(85)
1.0
0.9
PARP(86)
1.0
0.95
PARP(89)
1.8 TeV
1.8 TeV
PARP(90)
0.25
0.25
PARP(62)
1.25
1.25
PARP(64)
0.2
0.2
PARP(67)
2.5
4.0
MSTP(91)
1
1
PARP(91)
2.1
2.1
PARP(93)
15.0
15.0
ISR Parameters
PT Distribution 1/N dN/dPT
Parameter
Z-Boson Transverse Momentum
0.12
CDF Run 1 Data
PYTHIA Tune DW
HERWIG
CDF Run 1
published
0.08
1.8 TeV
Normalized to 1
0.04
0.00
0
2
4
6
8
10
12
14
16
18
20
Z-Boson PT (GeV/c)
 Shows the Run 1 Z-boson pT distribution (<pT(Z)>
≈ 11.5 GeV/c) compared with PYTHIA Tune DW,
and HERWIG.
Tune DW uses D0’s perfered value of PARP(67)!
Intrensic KT
Tune DW has a lower value of PARP(67) and slightly more MPI!
YETI'11 Durham IPPP - Part 1
January 10-12, 2011
Rick Field – Florida/CDF/CMS
Page 39
All use LO as
with L = 192 MeV!
PYTHIA 6.2 Tunes
UE Parameters
ISR Parameter
Parameter
Tune AW
Tune DW
Tune D6
PDF
CTEQ5L
CTEQ5L
CTEQ6L
MSTP(81)
1
1
1
MSTP(82)
4
4
4
PARP(82)
2.0 GeV
1.9 GeV
1.8 GeV
PARP(83)
0.5
0.5
0.5
PARP(84)
0.4
0.4
0.4
PARP(85)
0.9
1.0
1.0
PARP(86)
0.95
1.0
1.0
PARP(89)
1.8 TeV
1.8 TeV
1.8 TeV
PARP(90)
0.25
0.25
0.25
PARP(62)
1.25
1.25
1.25
PARP(64)
0.2
0.2
0.2
PARP(67)
4.0
2.5
2.5
MSTP(91)
1
1
1
PARP(91)
2.1
2.1
2.1
PARP(93)
15.0
15.0
15.0
Uses CTEQ6L
Tune A energy dependence!
(not the default)
Intrinsic KT
YETI'11 Durham IPPP - Part 1
January 10-12, 2011
Rick Field – Florida/CDF/CMS
Page 40
All use LO as
with L = 192 MeV!
PYTHIA 6.2 Tunes
UE Parameters
Parameter
Tune DWT
Tune D6T
ATLAS
PDF
CTEQ5L
CTEQ6L
CTEQ5L
MSTP(81)
1
1
1
MSTP(82)
4
4
4
PARP(82)
1.9409 GeV
1.8387 GeV
1.8 GeV
PARP(83)
0.5
0.5
0.5
Tune A
ISR Parameter
PARP(62)
1.25
1.25
1.0
PARP(64)
0.2
0.2
1.0
PARP(67)
2.5
2.5
1.0
MSTP(91)
1
1
1
PARP(91)
Tune D
PARP(93)
Tune 2.1
DW
15.0
2.1
15.0
Tune BW
1.0
Tune D6
5.0
Tune D6T
Intrinsic KT
YETI'11 Durham IPPP - Part 1
January 10-12, 2011
Old ATLAS energy dependence!
(PYTHIA default)
These are all
0.4 old PYTHIA
0.4
0.5 Tunes!
Tune
B6.2
Tune AW
PARP(85)are now
1.0 many PYTHIA
1.0
0.33
There
6.4 tunes
PARP(86) (S320 1.0
0.66
Perugia 1.0
0, Tune Z1)
PARP(89)
1.96 TeV
1.96 TeV
1.0 TeV
and some
PYTHIA
8 tunes
PARP(90)
0.16
0.16
(Tune0.161, Hendrik
tunes).
PARP(84)
Rick Field – Florida/CDF/CMS
Page 41
Min-Bias “Associated”
Charged Particle Density
35% more at RHIC means
"Transverse" Charged Particle Density: dN/dhdf
26% less at the LHC!
1.6
RDF Preliminary
"Transverse" Charged Density
0.3
"Transverse" Charged Density
"Transverse" Charged Particle Density: dN/dhdf
PY Tune DW
generator level
0.2
~1.35
PY Tune DWT
0.1
Min-Bias
0.2 TeV
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
RDF Preliminary
PY Tune DWT
generator level
1.2
~1.35
0.8
PY Tune DW
0.4
Min-Bias
14 TeV
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
0.0
0.0
0
2
4
6
8
10
12
14
16
18
20
0
2
4
6
8
PTmax Direction
Df
“Toward”
“Transverse”
12
14
16
18
20
PTmax (GeV/c)
PTmax (GeV/c)
RHIC
10
PTmax Direction
0.2 TeV → 14 TeV
(~factor of 70 increase)
“Transverse”
“Away”
Df
“Toward”
LHC
“Transverse”
“Transverse”
“Away”
 Shows the “associated” charged particle density in the “transverse” regions as a function of
PTmax for charged particles (pT > 0.5 GeV/c, |h| < 1, not including PTmax) for “min-bias” events
at 0.2 TeV and 14 TeV from PYTHIA Tune DW and Tune DWT at the particle level (i.e. generator
level). The STAR data from RHIC favors Tune DW!
YETI'11 Durham IPPP - Part 1
January 10-12, 2011
Rick Field – Florida/CDF/CMS
Page 42
Min-Bias “Associated”
Charged Particle Density
"Transverse" Charged Particle Density: dN/dhdf
"Transverse" Charged Density
1.2
RDF Preliminary
14 TeV
Min-Bias
py Tune DW generator level
0.8
~1.9
0.4
1.96 TeV
~2.7
0.2 TeV
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
0.0
0
5
10
15
20
25
PTmax (GeV/c)
PTmax Direction
Df
“Toward”
RHIC
“Transverse”
“Transverse”
0.2 TeV → 1.96 TeV
(UE increase ~2.7 times)
Tevatron
“Away”
PTmax Direction
Df
“Toward”
“Transverse”
PTmax Direction
1.96 TeV → 14 TeV
(UE increase ~1.9 times)
LHC
“Transverse”
“Away”
Df
“Toward”
“Transverse”
“Transverse”
“Away”
 Shows the “associated” charged particle density in the “transverse” region as a function of
PTmax for charged particles (pT > 0.5 GeV/c, |h| < 1, not including PTmax) for “min-bias” events
at 0.2 TeV, 1.96 TeV and 14 TeV predicted by PYTHIA Tune DW at the particle level (i.e.
generator level).
YETI'11 Durham IPPP - Part 1
January 10-12, 2011
Rick Field – Florida/CDF/CMS
Page 43
The “Underlying Event” at STAR
 At STAR they have measured the “underlying event at W = 200 GeV (|h| < 1, pT > 0.2 GeV)
and compared their uncorrected data with PYTHIA Tune A + STAR-SIM.
YETI'11 Durham IPPP - Part 1
January 10-12, 2011
Rick Field – Florida/CDF/CMS
Page 44
Min-Bias “Associated”
Charged Particle Density
RDF LHC Prediction!
"Transverse" Charged Particle Density: dN/dhdf
"Transverse" Charged Particle Density: dN/dhdf
1.6
RDF Preliminary
PY64 Tune P329
"Transverse" Charged Density
"Transverse" Charged Density
0.8
generator level
0.6
0.4
PY Tune A
PY64 Tune N324
0.2
PY64 Tune S320
Min-Bias
1.96 TeV
PY Tune DWT
generator level
1.2
0.8
PY64 Tune P329
PY Tune A
0.4
PY Tune DW
PY64 Tune S320
If the LHC data are not in
the range shown here then
we learn new (QCD) physics!
Rick Field October 13, 2009
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
0.0
PY ATLAS
RDF Preliminary
Min-Bias
14 TeV
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
0.0
0
2
4
6
8
10
12
14
16
18
20
0
5
10
PTmax (GeV/c)
PTmax Direction
Df
“Toward”
“Transverse”
“Transverse”
15
20
25
PTmax (GeV/c)
PTmax Direction
Df
“Toward”
Tevatron
LHC
“Transverse”
“Transverse”
“Away”
“Away”
 Shows the “associated” charged particle density in the “transverse” region as a function of
PTmax for charged particles (pT > 0.5 GeV/c, |h| < 1, not including PTmax) for “min-bias” events
at 1.96 TeV from PYTHIA Tune A, Tune S320, Tune N324, and Tune P329 at the particle level (i.e.
generator level).
 Extrapolations of PYTHIA Tune A, Tune DW, Tune DWT, Tune S320, Tune P329, and pyATLAS to the
LHC.
YETI'11 Durham IPPP - Part 1
January 10-12, 2011
Rick Field – Florida/CDF/CMS
Page 45
“Transverse” Charged Density
PTmax Direction
"Transverse" Charged Particle Density: dN/dhdf
Df
1.6
“Transverse”
“Transverse”
“Away”
ChgJet#1 Direction
Df
“Toward”
“Transverse”
“Transverse”
“Away”
"Transverse" Charged Density
“Toward”
RDF Preliminary
7 TeV
py Tune DW generator level
1.2
PTmax
0.8
ChgJet#1
DY(muon-pair)
70 < M(pair) < 110 GeV
0.4
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
0.0
Muon-Pair Direction
Df
0
5
10
15
20
25
30
35
40
45
50
PT(chgjet#1) or PTmax or PT(pair) (GeV/c)
“Toward”
“Transverse”
“Transverse”
“Away”
 Shows the charged particle density in the “transverse” region for charged particles (pT > 0.5
GeV/c, |h| < 1) at 7 TeV as defined by PTmax, PT(chgjet#1), and PT(muon-pair) from PYTHIA
Tune DW at the particle level (i.e. generator level). Charged particle jets are constructed using
the Anti-KT algorithm with d = 0.5.
YETI'11 Durham IPPP - Part 1
January 10-12, 2011
Rick Field – Florida/CDF/CMS
Page 46
Min-Bias “Associated”
Charged Particle Density
"Transverse" Charged Particle Density: dN/dhdf
"Transverse" Charged Particle Density: dN/dhdf
1.2
RDF Preliminary
14 TeV
Min-Bias
"Transverse" Charged Density
"Transverse" Charged Density
1.2
py Tune DW generator level
10 TeV
7 TeV
0.8
1.96 TeV
0.9 TeV
0.4
0.2 TeV
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
RDF Preliminary
LHC14
py Tune DW generator level
0.8
LHC10
LHC7
Tevatron
900 GeV
0.4
PTmax = 5.25 GeV/c
RHIC
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
0.0
0.0
0
5
10
15
20
0
25
2
Df
“Toward”
RHIC
“Transverse”
“Transverse”
0.2 TeV → 1.96 TeV
(UE increase ~2.7 times)
Tevatron
“Away”
6
8
10
12
14
Center-of-Mass Energy (TeV)
PTmax (GeV/c)
PTmax Direction
4
PTmax Direction
Df
“Toward”
“Transverse”
PTmax Direction
1.96 TeV → 14 TeV
(UE increase ~1.9 times)
LHC
“Transverse”
“Away”
Df
“Toward”
“Transverse”
“Transverse”
“Away”
 Shows the “associated” charged particle density in the “transverse” region as a function of
PTmax for charged particles (pT > 0.5 GeV/c, |h| < 1, not including PTmax) for “min-bias” events
at 0.2 TeV, 0.9 TeV, 1.96 TeV, 7 TeV, 10 TeV, 14 TeV predicted by PYTHIA Tune DW at the particle
Linear scale!
level (i.e. generator level).
YETI'11 Durham IPPP - Part 1
January 10-12, 2011
Rick Field – Florida/CDF/CMS
Page 47
Min-Bias “Associated”
Charged Particle Density
"Transverse" Charged Particle Density: dN/dhdf
"Transverse" Charged Particle Density: dN/dhdf
1.2
RDF Preliminary
14 TeV
Min-Bias
"Transverse" Charged Density
"Transverse" Charged Density
1.2
py Tune DW generator level
10 TeV
7 TeV
0.8
1.96 TeV
0.9 TeV
0.4
0.2 TeV
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
RDF Preliminary
py Tune DW generator level
LHC14
LHC10
LHC7
0.8
Tevatron
0.4
900 GeV
RHIC
PTmax = 5.25 GeV/c
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
0.0
0.0
0
5
10
15
20
25
0.1
Df
“Toward”
LHC7
“Transverse”
100.0
PTmax Direction
7 TeV → 14 TeV
(UE increase ~20%)
Df
“Toward”
LHC14
“Transverse”
“Away”
10.0
Center-of-Mass Energy (TeV)
PTmax (GeV/c)
PTmax Direction
1.0
Linear on a log plot!
“Transverse”
“Transverse”
“Away”
 Shows the “associated” charged particle density in the “transverse” region as a function of
PTmax for charged particles (pT > 0.5 GeV/c, |h| < 1, not including PTmax) for “min-bias” events
at 0.2 TeV, 0.9 TeV, 1.96 TeV, 7 TeV, 10 TeV, 14 TeV predicted by PYTHIA Tune DW at the particle
Log scale!
level (i.e. generator level).
YETI'11 Durham IPPP - Part 1
January 10-12, 2011
Rick Field – Florida/CDF/CMS
Page 48
Conclusions November 2009
 We are making good progress in understanding and modeling the
“underlying event”. RHIC data at 200 GeV are very important!
Outgoing Parton
PT(hard)
Initial-State Radiation
Proton
 The new Pythia pT ordered tunes (py64 S320 and py64 P329)
are very similar to Tune A, Tune AW, and Tune DW. At present
the new tunes do not fit the data better than Tune AW and Tune
DW. However, the new tune are theoretically preferred!
AntiProton
Underlying Event
Underlying Event
Outgoing Parton
Final-State
Radiation
Hard-Scattering Cut-Off PT0
PYTHIA 6.206
e = 0.25 (Set A))
4
PT0 (GeV/c)
 It is clear now that the default value PARP(90) = 0.16 is
not correct and the value should be closer to the Tune A
value of 0.25.
 The new and old PYTHIA tunes are beginning to
converge and I believe we are finally in a position to make
some legitimate predictions at the LHC!
5
3
2
e = 0.16 (default)
1
 All tunes with the default value PARP(90) = 0.16 are
wrong and are overestimating the activity of min-bias and
the underlying event at the LHC! This includes all my
“T” tunes and the (old) ATLAS tunes!
 Need to measure “Min-Bias” and the “underlying
event” at the LHC as soon as possible to see if there is
new QCD physics to be learned!
YETI'11 Durham IPPP - Part 1
January 10-12, 2011
Rick Field – Florida/CDF/CMS
100
1,000
10,000
100,000
CM Energy W (GeV)
UE&MB@CMS
Page 49
“Transverse” Charged Particle Density
PT(chgjet#1) Direction
"Transverse" Charged Particle Density: dN/dhdf
"Transverse" Charged Density
0.8
Df
RDF Preliminary
Fake Data
pyDW generator level
ChgJet#1
“Toward”
0.6
PTmax
“Transverse”
“Transverse”
0.4
Leading Charged
Particle Jet, chgjet#1.
“Away”
0.2
900 GeV
Prediction!
Charged Particles (|h|<2.0, PT>0.5 GeV/c)
PTmax Direction
0.0
0
2
4
6
8
10
12
14
16
PTmax or PT(chgjet#1) (GeV/c)
“Toward”
 Fake data (from MC) at 900 GeV on the
“transverse” charged particle density,
dN/dhdf, as defined by the leading
charged particle (PTmax) and the leading
charged particle jet (chgjet#1) for charged
particles with pT > 0.5 GeV/c and |h| < 2.
The fake data (from PYTHIA Tune DW)
are generated at the particle level (i.e.
generator level) assuming 0.5 M min-bias
events at 900 GeV (361,595 events in the
plot).
YETI'11 Durham IPPP - Part 1
January 10-12, 2011
Df
18
Rick Field – Florida/CDF/CMS
“Transverse”
“Transverse”
Leading Charged
Particle, PTmax.
“Away”
Rick Field
MB&UE@CMS Workshop
CERN, November 6, 2009
Page 50
“Transverse” Charge Density
"Transverse" Charged Particle Density: dN/dhdf
Rick Field
MB&UE@CMS Workshop
CERN, November 6, 2009
"Transverse" Charged Density
1.2
RDF Preliminary
py Tune DW generator level
7 TeV
0.8
factor of 2!
900 GeV
0.4
Prediction!
Charged Particles (|h|<2.0, PT>0.5 GeV/c)
4
10
0.0
0
2
6
8
12
14
16
18
20
PTmax (GeV/c)
PTmax Direction
Df
LHC
900 GeV
“Toward”
“Transverse”
PTmax Direction
900 GeV → 7 TeV
(UE increase ~ factor of 2)
“Transverse”
“Away”
~0.4 → ~0.8
Df
“Toward”
LHC
7 TeV
“Transverse”
“Transverse”
“Away”
 Shows the charged particle density in the “transverse” region for charged particles (pT > 0.5
GeV/c, |h| < 2) at 900 GeV and 7 TeV as defined by PTmax from PYTHIA Tune DW and at the
particle level (i.e. generator level).
YETI'11 Durham IPPP - Part 1
January 10-12, 2011
Rick Field – Florida/CDF/CMS
Page 51
YETI’11: The Standard Model
at the Energy Frontier
Min-Bias and the Underlying Event at the LHC
Rick Field
University of Florida
2nd Lecture
 How well did we do at predicting the
behavior of the “underlying event” at
the LHC (900 GeV and 7 TeV)?


CMS
In lecture 2 we will examine how
well we did at predicting the
How well did we do at predicting the
“underlying event” and “minbehavior of “min-bias” collisions at
bias” at the LHC and look at
the LHC (900 GeV and 7 TeV)?
some new tunes that came after
PYTHIA 6.4 Tune Z1: New CMS 6.4 tune
seeing ATLAS
the LHC data.
(pT-ordered parton showers and new MPI).
 New Physics in Min-Bias??
Observation of long-range same-side
correlations at 7 TeV.
 Strange particle production:
A problem for the models?
YETI'11 Durham IPPP - Part 1
January 10-12, 2011
UE&MB@CMS
Rick Field – Florida/CDF/CMS
Page 52