Toward an Understanding of
Hadron-Hadron Collisions
From Feynman-Field to the LHC
XXIèmes Rencontres de Blois
Windows on the Universe
June 21st - 26th, 2009
Rick Field
University of Florida
Outline of Talk
The old days of “Feynman-Field
Phenomenology”.
The present day QCD Monte-Carlo
Outgoing Parton
Model tunes.
Extrapolations from the Tevatron
PT(hard)
CDF Run 2
Initial-State Radiation
Proton
AntiProton
Underlying Event
Underlying Event
to RHIC and the LHC.
The “underlying event” at STAR.
Outgoing Parton
Final-State
Radiation
LHC predictions!
Summary & Conclusions.
XXIèmes Rencontres de Blois, France
June 23, 2009
CMS at the LHC
Rick Field – Florida/CDF/CMS
UE&MB@CMS
Page 1
Toward and Understanding of
Hadron-Hadron Collisions
Feynman-Field Phenomenology1
Feynman
From 7 GeV/c
and
st
hat!
Field
Outgoing Parton
π0’s
to 600 GeV/c
Jets. The early days of trying to
understand and simulate hadronhadron collisions.
PT(hard)
Initial-State Radiation
Proton
AntiProton
Underlying Event
Outgoing Parton
XXIèmes Rencontres de Blois, France
June 23, 2009
Rick Field – Florida/CDF/CMS
Underlying Event
Final-State
Radiation
Page 2
Hadron-Hadron Collisions
FF1 1977
What happens when two hadrons
collide at high energy?
Most of the time the hadrons ooze
through each other and fall apart (i.e.
no hard scattering). The outgoing
particles continue in roughly the same
direction as initial proton and
antiproton.
Occasionally there will be a large
transverse momentum meson.
Question: Where did it come from?
Hadron
Hadron
???
Parton-Parton Scattering
Outgoing Parton
“Soft” Collision (no large transverse momentum)
Hadron
We assumed it came from quark-quark
elastic scattering, but we did not know
how to calculate it!
Hadron
Outgoing Parton
high PT meson
“Black-Box Model”
XXIèmes Rencontres de Blois, France
June 23, 2009
Rick Field – Florida/CDF/CMS
Page 3
Hadron-Hadron Collisions
FF1 1977
What happens when two hadrons
collide at high energy?
Hadron
Hadron
Feynman quote from FF1
???
“The model we shall choose is not a popular one,
Most of the time the hadrons
ooze
so that we will not duplicate too much of the
through each other andwork
fall apart
(i.e.
of others
who are similarly analyzing
no hard scattering). The
outgoing
various models (e.g. constituent interchange
particles continue in roughly
the same
model, multiperipheral
models, etc.). We shall
Parton-Parton Scattering Outgoing Parton
assume
direction as initial proton
andthat the high PT particles arise from
“Soft” constituent
Collision (no large transverse momentum)
direct hard collisions between
antiproton.
quarks in the incoming particles, which
Hadron
Hadron
fragment
or cascade down
into several hadrons.”
Occasionally there will
be a large
transverse momentum meson.
Question: Where did it come from?
We assumed it came from quark-quark
elastic scattering, but we did not know
how to calculate it!
Outgoing Parton
high PT meson
“Black-Box Model”
XXIèmes Rencontres de Blois, France
June 23, 2009
Rick Field – Florida/CDF/CMS
Page 4
Quark-Quark Black-Box Model
No gluons!
Quark Distribution Functions
determined from deep-inelastic
lepton-hadron collisions
FF1 1977
Quark-Quark Cross-Section
Unknown! Deteremined from
hadron-hadron collisions.
XXIèmes Rencontres de Blois, France
June 23, 2009
Rick Field – Florida/CDF/CMS
Quark Fragmentation Functions
determined from e+e- annihilations
Page 5
Quark-Quark Black-Box Model
No gluons!
FF1 1977
Quark Distribution Functions
determined from deep-inelastic
lepton-hadron collisions
Feynman quote from FF1
“Because of the incomplete knowledge of
our functions some things can be predicted
with more certainty than others. Those
experimental results that are not well
predicted can be “used up” to determine
these functions in greater detail to permit
better predictions of further experiments.
Our papers will be a bit long because we
wish to discuss this interplay in detail.”
Quark-Quark Cross-Section
Unknown! Deteremined from
hadron-hadron collisions.
XXIèmes Rencontres de Blois, France
June 23, 2009
Rick Field – Florida/CDF/CMS
Quark Fragmentation Functions
determined from e+e- annihilations
Page 6
Quark-Quark Black-Box Model
Predict
particle ratios
FF1 1977
Predict
increase with increasing
CM energy W
The “underlying event”
(Beam-Beam Remnants)!
Predict
overall event topology
(FFF1 paper 1977)
7 GeV/c π0’s!
XXIèmes Rencontres de Blois, France
June 23, 2009
Rick Field – Florida/CDF/CMS
Page 7
Quark-Quark Black-Box Model
Predict
particle ratios
FF1 1977
Predict
increase with increasing
CM energy W
When Jim Cronin’s group at the University
of Chicago measured these rations and we
knew we were on the right track!
The “underlying event”
(Beam-Beam Remnants)!
Predict
overall event topology
(FFF1 paper 1977)
7 GeV/c π0’s!
XXIèmes Rencontres de Blois, France
June 23, 2009
Rick Field – Florida/CDF/CMS
Page 8
QCD Approach: Quarks & Gluons
Quark & Gluon Fragmentation
Functions
Q2 dependence predicted from QCD
FFF2 1978
Parton Distribution Functions
Q2 dependence predicted from
QCD
Quark & Gluon Cross-Sections
Calculated from QCD
XXIèmes Rencontres de Blois, France
June 23, 2009
Rick Field – Florida/CDF/CMS
Page 9
QCD Approach: Quarks & Gluons
Quark & Gluon Fragmentation
Functions
Q2 dependence predicted from QCD
Parton Distribution Functions
Q2 dependence predicted from
QCD
FFF2 1978
Feynman quote from FFF2
“We investigate whether the present
experimental behavior of mesons with
large transverse momentum in hadron-hadron
collisions is consistent with the theory of
quantum-chromodynamics (QCD) with
asymptotic freedom, at least as the theory
is now partially understood.”
Quark & Gluon Cross-Sections
Calculated from QCD
XXIèmes Rencontres de Blois, France
June 23, 2009
Rick Field – Florida/CDF/CMS
Page 10
High PT Jets
CDF (2006)
Feynman, Field, & Fox (1978)
Predict
large “jet”
cross-section
30 GeV/c!
Feynman quote from FFF
600writing,
GeV/c Jets!
“At the time of this
there is
still no sharp quantitative test of QCD.
An important test will come in connection
with the phenomena of high PT discussed here.”
XXIèmes Rencontres de Blois, France
June 23, 2009
Rick Field – Florida/CDF/CMS
Page 11
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!
XXIèmes Rencontres de Blois, France
June 23, 2009
Rick Field – Florida/CDF/CMS
Page 12
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
Underlying Event
AntiProton
Underlying Event
“Underlying Event”
Start with the perturbative Drell-Yan muon pair production and add initial-state gluon radiation (in the
leading log approximation or modified leading log approximation).
The “underlying event” consists of the “beam-beam remnants” and from particles arising from soft or
semi-soft multiple parton interactions (MPI).
Of course the outgoing colored partons fragment into hadron “jet” and inevitably “underlying event”
observables receive contributions from initial-state radiation.
XXIèmes Rencontres de Blois, France
June 23, 2009
Rick Field – Florida/CDF/CMS
Page 13
CDF Run 1: Evolution of Charged Jets
“Underlying Event”
Charged Particle ∆φ Correlations
PT > 0.5 GeV/c |η
η| < 1
Charged Jet #1
Direction
“Transverse” region
very sensitive to the
“underlying event”!
Look at the charged
particle density in the
“transverse” region!
2π
π
CDF Run 1 Analysis
Away Region
Charged Jet #1
Direction
∆φ
Transverse
Region
“Toward-Side” Jet
∆φ
“Toward”
“Toward”
“Transverse”
φ
Leading
Jet
“Transverse”
Toward Region
“Transverse”
“Transverse”
Transverse
Region
“Away”
“Away”
Away Region
“Away-Side” Jet
0
-1
η
+1
Look at charged particle correlations in the azimuthal angle ∆φ relative to the leading charged
particle jet.
o
o
o
o
Define |∆φ
∆φ|
∆φ|
∆φ|
∆φ < 60 as “Toward”, 60 < |∆φ
∆φ < 120 as “Transverse”, and |∆φ
∆φ > 120 as “Away”.
o
All three regions have the same size in η-φφ space, ∆ηx∆φ
π/3.
∆η ∆φ = 2x120 = 4π
XXIèmes Rencontres de Blois, France
June 23, 2009
Rick Field – Florida/CDF/CMS
Page 14
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
ηdφ
φ
"Transverse" Charged Particle Density: dN/dη
CDF Data
Pythia 6.206 (default)
MSTP(82)=1
PARP(81) = 1.9 GeV/c
data uncorrected
theory corrected
0.75
0.50
0.25
1.8 TeV |η
η|<1.0 PT>0.5 GeV
0.00
0
5
10
15
20
25
30
35
40
45
50
PT(charged jet#1) (GeV/c)
CTEQ3L
CTEQ4L
CTEQ5L
CDF Min-Bias
CDF JET20
Plot shows the “Transverse” charged particle density versus PT(chgjet#1) compared to the
QCD hard scattering predictions of PYTHIA 6.206 (PT(hard) > 0) using the default
parameters for multiple parton interactions and CTEQ3L, CTEQ4L, and CTEQ5L.
Note Change
PARP(67) = 4.0 (< 6.138)
PARP(67) = 1.0 (> 6.138)
XXIèmes Rencontres de Blois, France
June 23, 2009
Default parameters give
very poor description of
the “underlying event”!
Rick Field – Florida/CDF/CMS
Page 15
Tuning PYTHIA:
Multiple Parton Interaction Parameters
Default
PARP(83)
0.5
PARP(84)
0.2
PARP(85)
0.33
PARP(86)
0.66
PARP(89)
PARP(82)
PARP(90)
PARP(67)
1 TeV
1.9
GeV/c
0.16
1.0
Description
Double-Gaussian: Fraction of total hadronic
matter within PARP(84)
ore
Hard C
Double-Gaussian: Fraction of the overall hadron
radius containing the fraction PARP(83) of the
total hadronic matter.
Determines the energy
Probability that the MPI produces two gluons
dependence of the MPI!
with color connections to the “nearest neighbors.
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)ε with
ε = PARP(90)
A scale factor that determines the maximum
parton virtuality for space-like showers. The
larger the value of PARP(67) the more initialstate radiation.
XXIèmes Rencontres de Blois, France
June 23, 2009
Rick Field – Florida/CDF/CMS
5
PYTHIA 6.206
ε = 0.25 (Set A))
4
PT0 (GeV/c)
Parameter
Take E0 = 1.8 TeV
3
2
ε = 0.16 (default)
1
100
1,000
10,000
100,000
CM Energy W (GeV)
Reference point
at 1.8 TeV
Page 16
Run 1 PYTHIA Tune A
CDF Default!
PYTHIA 6.206 CTEQ5L
"Transverse" Charged Particle Density: dN/dη
ηdφ
φ
Parameter
Tune B
Tune A
MSTP(81)
1
1
MSTP(82)
4
4
PARP(82)
1.9 GeV
2.0 GeV
PARP(83)
0.5
0.5
PARP(84)
0.4
0.4
PARP(85)
1.0
0.9
PARP(86)
1.0
0.95
PARP(89)
1.8 TeV
1.8 TeV
PARP(90)
0.25
0.25
PARP(67)
1.0
4.0
"Transverse" Charged Density
1.00
CDF Preliminary
0.75
XXIèmes Rencontres de Blois, France
June 23, 2009
Run 1 Analysis
0.50
0.25
CTEQ5L
PYTHIA 6.206 (Set B)
PARP(67)=1
1.8 TeV |η
η|<1.0 PT>0.5 GeV
0.00
0
New PYTHIA default
(less initial-state radiation)
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 17
“Transverse” Charged Density
PTmax Direction
"Transverse" Charged Particle Density: dN/dη
ηdφ
φ
∆φ
0.8
“Transverse”
“Transverse”
“Away”
ChgJet#1 Direction
∆φ
“Toward”
“Transverse”
“Transverse”
“Away”
"Transverse" Charged Density
“Toward”
RDF Preliminary
1.96 TeV
py Tune A generator level
0.6
0.6
0.4
Jet#1
ChgJet#1
0.2
PTmax
Charged Particles (|η
η|<1.0, PT>0.5 GeV/c)
0.0
Jet#1 Direction
∆φ
0
5
10
15
20
25
30
PT(jet#1) or PT(chgjet#1) or PTmax (GeV/c)
“Toward”
“Transverse”
“Transverse”
“Away”
Shows the charged particle density in the “transverse” region for charged particles (pT > 0.5
GeV/c, |η
η| < 1) at 1.96 TeV as defined by PTmax, PT(chgjet#1), and PT(jet#1) from PYTHIA
Tune A at the particle level (i.e. generator level).
XXIèmes Rencontres de Blois, France
June 23, 2009
Rick Field – Florida/CDF/CMS
Page 18
All use LO αs
with Λ = 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!
Intrinsic KT
XXIèmes Rencontres de Blois, France
June 23, 2009
Rick Field – Florida/CDF/CMS
Page 19
All use LO αs
with Λ = 192 MeV!
PYTHIA 6.2 Tunes
UE Parameters
ISR Parameter
Parameter
Tune DWT
Tune D6T
ATLAS
PDF
CTEQ5L
CTEQ6L
CTEQ5L
MSTP(81)
1
1
1
MSTP(82)
4
4
4
PARP(82)
1.9409 GeV
1.8387 GeV
1.8 GeV
PARP(83)
0.5
0.5
0.5
PARP(84)
0.4
0.4
0.5
PARP(85)
1.0
1.0
0.33
PARP(86)
1.0
1.0
0.66
PARP(89)
1.96 TeV
1.96 TeV
1.0 TeV
PARP(90)
0.16
0.16
0.16
PARP(62)
1.25
1.25
1.0
PARP(64)
0.2
0.2
1.0
PARP(67)
2.5
2.5
1.0
MSTP(91)
1
1
1
PARP(91)
2.1
2.1
1.0
PARP(93)
15.0
15.0
5.0
ATLAS energy dependence!
Intrinsic KT
XXIèmes Rencontres de Blois, France
June 23, 2009
Rick Field – Florida/CDF/CMS
Page 20
All use LO αs
with Λ = 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
PARP(84)
Tune
AW
Tune ISR
A Parameter
0.4
0.4
Tune
B
0.5
PARP(85)
1.0
1.0
0.33
PARP(86)
1.0
1.0
0.66
PARP(89)
1.96 TeV
1.96 TeV
1.0 TeV
PARP(90)
0.16
0.16
0.16
PARP(62)
1.25
1.25
1.0
PARP(64)
0.2
0.2
1.0
PARP(67)
2.5
2.5
1.0
MSTP(91)
1
1
1
PARP(91)
PARP(93)
Tune 2.1
DW
15.0
2.1
15.0
Tune BW
1.0
Tune
D6
5.0
Tune D
Tune D6T
Intrinsic KT
XXIèmes Rencontres de Blois, France
June 23, 2009
ATLAS energy dependence!
Rick Field – Florida/CDF/CMS
Page 21
All use LO αs
with Λ = 192 MeV!
PYTHIA 6.2 Tunes
UE Parameters
Tune ISR
A Parameter
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
ATLAS energy dependence!
PARP(84)
0.4
0.4
Tune
B 0.5
Tune
AW
Tune BW
These are 1.0
“old” PYTHIA
6.2
PARP(85)
1.0
0.33 tunes!
PARP(86)There 1.0
1.0
0.66 by
are new 6.420
tunes
PARP(89)
1.96 TeV
TeV
1.0 TeV
Peter Skands
(Tune1.96S320,
update
of S0)
PARP(90)
0.16
0.16
Peter Skands
(Tune
N324,0.16N0CR)
PARP(62)
1.25
1.0
Hendrik
Hoeth
(Tune1.25P329, “Professor”)
PARP(64)
0.2
0.2
1.0
PARP(67)
2.5
2.5
1.0
MSTP(91)
1
1
1
PARP(91)
PARP(93)
Tune 2.1
DW
15.0
2.1
15.0
Tune D
Tune D6T
Intrinsic KT
XXIèmes Rencontres de Blois, France
June 23, 2009
1.0
Tune
D6
5.0
Rick Field – Florida/CDF/CMS
Page 22
Min-Bias “Associated”
Charged Particle Density
35% more at RHIC means
ηdφ
φ less at the LHC!
"Transverse" Charged Particle Density: dN/dη
26%
RDF Preliminary
"Transverse" Charged Density
0.3
"Transverse" Charged Density
ηdφ
φ
"Transverse" Charged Particle Density: dN/dη
1.6
PY Tune DW
generator level
0.2
~1.35
PY Tune DWT
0.1
Min-Bias
0.2 TeV
Charged Particles (|η
η|<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 (|η
η|<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 (GeV/c)
PTmax Direction
∆φ
“Toward”
RHIC
“Transverse”
10
12
14
16
18
20
PTmax (GeV/c)
PTmax Direction
0.2 TeV → 14 TeV
(~factor of 70 increase)
“Transverse”
“Away”
∆φ
“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, |η
η| < 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!
XXIèmes Rencontres de Blois, France
June 23, 2009
Rick Field – Florida/CDF/CMS
Page 23
Min-Bias “Associated”
Charged Particle Density
ηdφ
φ
"Transverse" Charged Particle Density: dN/dη
"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 (|η
η|<1.0, PT>0.5 GeV/c)
0.0
0
5
10
15
20
25
PTmax (GeV/c)
PTmax Direction
∆φ
“Toward”
RHIC
“Transverse”
“Transverse”
PTmax Direction
PTmax Direction
0.2 TeV → 1.96 TeV
(UE increase ~2.7 times)
Tevatron
“Away”
∆φ
“Toward”
“Transverse”
1.96 TeV → 14 TeV
(UE increase ~1.9 times)
LHC
∆φ
“Toward”
“Transverse”
“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, |η
η| < 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).
XXIèmes Rencontres de Blois, France
June 23, 2009
Rick Field – Florida/CDF/CMS
Page 24
The “Underlying Event” at STAR
At STAR they have measured the “underlying event at W = 200 GeV (|η
η| < 1, pT > 0.2 GeV)
and compared their uncorrected data with PYTHIA Tune A + STAR-SIM.
XXIèmes Rencontres de Blois, France
June 23, 2009
Rick Field – Florida/CDF/CMS
Page 25
The “Underlying Event” at STAR
At STAR they have measured the “underlying event at W = 200 GeV (|η
η| < 1, pT > 0.2 GeV)
and compared their uncorrected data with PYTHIA Tune A + STAR-SIM.
XXIèmes Rencontres de Blois, France
June 23, 2009
Rick Field – Florida/CDF/CMS
Page 26
Min-Bias “Associated”
Charged Particle Density
RDF LHC Prediction!
ηdφ
φ
"Transverse" Charged Particle Density: dN/dη
"Transverse" Charged Particle Density: dN/dη
ηdφ
φ
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
Charged Particles (|η
η|<1.0, PT>0.5 GeV/c)
0.0
PY ATLAS
RDF Preliminary
PY Tune DWT
generator level
1.2
0.8
PY64 Tune P329
PY Tune A
PY Tune DW
PY64 Tune S320
0.4
Min-Bias
14 TeV
Charged Particles (|η
η|<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)
15
PTmax Direction
∆φ
∆φ
“Toward”
“Toward”
“Transverse”
25
PTmax (GeV/c)
PTmax Direction
“Transverse”
20
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, |η
η| < 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.
XXIèmes Rencontres de Blois, France
June 23, 2009
Rick Field – Florida/CDF/CMS
Page 27
Min-Bias “Associated”
Charged Particle Density
RDF LHC Prediction!
ηdφ
φ
"Transverse" Charged Particle Density: dN/dη
"Transverse" Charged Particle Density: dN/dη
ηdφ
φ
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
Charged Particles (|η
η|<1.0, PT>0.5 GeV/c)
0.0
PY ATLAS
RDF Preliminary
PY Tune DWT
generator level
1.2
0.8
PY64 Tune P329
PY Tune A
PY Tune DW
PY64 Tune S320
0.4
Min-Bias
14 TeV
Charged Particles (|η
η|<1.0, PT>0.5 GeV/c)
If the LHC data are not in
the range shown here then
we learn new (QCD) physics!
0.0
0
2
4
6
8
10
12
14
16
18
20
0
5
10
PTmax (GeV/c)
PTmax Direction
∆φ
“Transverse”
20
25
PTmax (GeV/c)
PTmax Direction
∆φ
“Toward”
“Toward”
“Transverse”
15
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, |η
η| < 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.
XXIèmes Rencontres de Blois, France
June 23, 2009
Rick Field – Florida/CDF/CMS
Page 28
Z-Boson: “Towards” Region
RDF LHC
"Toward" Charged Particle Density:
dN/dη
ηPrediction!
dφ
φ
"Toward" Charged Particle Density: dN/dη
ηdφ
φ
RDF Preliminary
PY Tune AW
PY Tune DW
generator level
RDF Preliminary
Drell-Yan
1.96 TeV
"Toward" Charged Density
"Toward" Charged Density
PY ATLAS
1.6
0.8
0.6
0.4
PY64 Tune P329
PY64 Tune S320
0.2
70 < M(pair) < 110 GeV
Charged Particles (|η
η|<1.0, PT>0.5 GeV/c)
PY Tune DWT
generator level
1.2
0.8
PY Tune DW
PY64 Tune P329
PY64 Tune S320
0.4
70 < M(pair) < 110 GeV
Drell-Yan
14 TeV
Charged Particles (|η
η|<1.0, PT>0.5 GeV/c)
0.0
0.0
0
25
50
75
100
125
150
0
25
50
75
Z-BosonDirection
Z-BosonDirection
∆φ
∆φ
“Toward”
“Toward”
“Transverse”
125
Lepton-Pair PT (GeV/c)
Lepton-Pair PT (GeV/c)
“Transverse”
100
Tevatron
LHC
“Transverse”
“Transverse”
“Away”
“Away”
Data at 1.96 TeV on the density of charged particles, dN/dη
ηdφ
φ, with pT > 0.5 GeV/c and |η
η| < 1 for “ZBoson” events as a function of PT(Z) for the “toward” region from PYTHIA Tune AW, Tune DW, Tune
S320, and Tune P329 at the particle level (i.e. generator level).
Extrapolations of PYTHIA Tune AW, Tune DW, Tune DWT, Tune S320, and Tune P329 to the LHC.
XXIèmes Rencontres de Blois, France
June 23, 2009
Rick Field – Florida/CDF/CMS
Page 29
150
Z-Boson: “Towards” Region
RDF LHC
"Toward" Charged Particle Density:
dN/dη
ηPrediction!
dφ
φ
"Toward" Charged Particle Density: dN/dη
ηdφ
φ
RDF Preliminary
PY Tune AW
PY Tune DW
generator level
RDF Preliminary
Drell-Yan
1.96 TeV
"Toward" Charged Density
"Toward" Charged Density
PY ATLAS
1.6
0.8
0.6
0.4
PY64 Tune P329
PY64 Tune S320
0.2
70 < M(pair) < 110 GeV
Charged Particles (|η
η|<1.0, PT>0.5 GeV/c)
PY Tune DWT
generator level
1.2
0.8
PY Tune DW
PY64 Tune P329
PY64 Tune S320
0.4
70 < M(pair) < 110 GeV
Drell-Yan
14 TeV
If the LHC data are not in
the range shown here then
we learn new (QCD) physics!
Charged Particles (|η
η|<1.0, PT>0.5 GeV/c)
0.0
0.0
0
25
50
75
100
125
150
0
25
∆φ
“Transverse”
100
125
Z-BosonDirection
∆φ
“Toward”
“Toward”
“Transverse”
75
Lepton-Pair PT (GeV/c)
Lepton-Pair PT (GeV/c)
Z-BosonDirection
50
Tevatron
LHC
“Transverse”
“Transverse”
“Away”
“Away”
Data at 1.96 TeV on the density of charged particles, dN/dη
ηdφ
φ, with pT > 0.5 GeV/c and |η
η| < 1 for “ZBoson” events as a function of PT(Z) for the “toward” region from PYTHIA Tune AW, Tune DW, Tune
S320, and Tune P329 at the particle level (i.e. generator level).
Extrapolations of PYTHIA Tune AW, Tune DW, Tune DWT, Tune S320, and Tune P329 to the LHC.
XXIèmes Rencontres de Blois, France
June 23, 2009
Rick Field – Florida/CDF/CMS
Page 30
150
Charged Particle Density: dN/dη
RDF LHC Prediction!
η
Charged Particle Density: dN/dη
η
Charged Particle Density: dN/dη
5.0
8.0
Charged Particle Density
Charged Particle Density
PY Tune A
RDF Preliminary
generator level
4.0
3.0
PY Tune DW
2.0
PY64 Tune S320
PY64 Tune P329
1.0
Min-Bias
1.96 TeV
Charged Particles (all PT)
0.0
PY64 Tune P329
RDF Preliminary
generator level
PY Tune DWT
6.0
PY ATLAS
4.0
PY Tune DW
PY Tune A
PY64 Tune S320
2.0
0.0
-8
-6
-4
-2
0
2
4
6
8
-8
-6
-4
-2
PseudoRapidity η
0
2
4
6
PseudoRapidity η
“Minumum Bias” Collisions
Proton
Min-Bias
14 TeV
Charged Particles (all PT)
“Minumum Bias” Collisions
AntiProton
Tevatron
Proton
Proton
LHC
Charged particle (all pT) pseudo-rapidity distribution, dNchg/dη
ηdφ
φ, at 1.96 TeV for
inelastic non-diffractive collisions from PYTHIA Tune A, Tune DW, Tune S320, and
Tune P324.
Extrapolations (all pT) of PYTHIA Tune A, Tune DW, Tune S320, Tune P324. and
ATLAS to the LHC.
XXIèmes Rencontres de Blois, France
June 23, 2009
Rick Field – Florida/CDF/CMS
Page 31
8
Charged Particle Density: dN/dη
RDF LHC Prediction!
η
Charged Particle Density: dN/dη
η
Charged Particle Density: dN/dη
5.0
8.0
Charged Particle Density
Charged Particle Density
PY Tune A
RDF Preliminary
generator level
4.0
3.0
PY Tune DW
2.0
PY64 Tune S320
PY64 Tune P329
1.0
Min-Bias
1.96 TeV
Charged Particles (all PT)
0.0
PY64 Tune P329
RDF Preliminary
generator level
PY Tune DWT
6.0
PY ATLAS
4.0
PY Tune DW
PY Tune A
PY64 Tune S320
2.0
If the LHC data are not in
the range shown here then
we learn new (QCD) physics!
0.0
-8
-6
-4
-2
0
2
4
6
8
-8
-6
-4
-2
PseudoRapidity η
“Minumum Bias” Collisions
Proton
Min-Bias
14 TeV
Charged Particles (all PT)
2
4
6
PseudoRapidity η
AntiProton
Tevatron
0
Proton
“Minumum Bias” Collisions
Proton
LHC
Charged particle (all pT) pseudo-rapidity distribution, dNchg/dη
ηdφ
φ, at 1.96 TeV for
inelastic non-diffractive collisions from PYTHIA Tune A, Tune DW, Tune S320, and
Tune P324.
Extrapolations (all pT) of PYTHIA Tune A, Tune DW, Tune S320, Tune P324. and
ATLAS to the LHC.
XXIèmes Rencontres de Blois, France
June 23, 2009
Rick Field – Florida/CDF/CMS
Page 32
8
Summary & Conclusions
We are making good progress in understanding and modeling the
“underlying event”. RHIC data at 200 GeV are very important!
PT(hard)
Initial-State Radiation
Proton
AntiProton
Underlying Event
PT0 (GeV/c)
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!
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!
Outgoing Parton
Underlying Event
Outgoing Parton
Final-State
Radiation
Hard-Scattering Cut-Off PT0
5
PYTHIA 6.206
ε = 0.25 (Set A))
4
3
2
ε = 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 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!
XXIèmes Rencontres de Blois, France
June 23, 2009
Rick Field – Florida/CDF/CMS
100
1,000
10,000
100,000
CM Energy W (GeV)
UE&MB@CMS
Page 33
However, I believe that the
better fits to the LEP
fragmentation data at high z
will lead to small improvements
Outgoing Parton
of Tune A at the
Tevatron!
Summary & Conclusions
We are making good progress in understanding and modeling the
“underlying event”. RHIC data at 200 GeV are very important!
Initial-State Radiation
Proton
AntiProton
Underlying Event
PT0 (GeV/c)
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!
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!
PT(hard)
Underlying Event
Outgoing Parton
Final-State
Radiation
Hard-Scattering Cut-Off PT0
5
PYTHIA 6.206
ε = 0.25 (Set A))
4
3
2
ε = 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 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!
XXIèmes Rencontres de Blois, France
June 23, 2009
Rick Field – Florida/CDF/CMS
100
1,000
10,000
100,000
CM Energy W (GeV)
UE&MB@CMS
Page 34