Chris Quigg Symposium
Predicting MB & UE at the LHC
Rick Field
University of Florida
Outline of Talk
 The inelastic non-diffractive cross section.
 The “underlying event” in a hard
scattering process.
 The QCD Monte-Carlo model tunes.
 Relationship between the “underlying
CDF Run 2
event” in a hard scattering process and
“min-bias” collisions.
 “Min-Bias” and the “underlying event” at
Outgoing Parton
PT(hard)
the LHC.
Initial-State Radiation
Proton
Proton
Underlying Event
UE&MB@CMS
CMS at the LHC
Outgoing Parton
Chris Quigg Symposiun Fermilab
December 14, 2009
Rick Field – Florida/CDF/CMS
Underlying Event
Final-State
Radiation
Page 1
“Older than Dirt” hat!
me
Bob
Cahn
J.D.J. Students
Chris
Quigg
Gordy
Kane
J.D.J
J.D.J
Jimmie & Rick
Chris Quigg Symposiun Fermilab
December 14, 2009
Rick Field – Florida/CDF/CMS
Page 2
Proton-Proton Collisions
Elastic Scattering
Single Diffraction
Double Diffraction
M2
M
M1
stot = sEL + sSD +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
Chris Quigg Symposiun Fermilab
December 14, 2009
Rick Field – Florida/CDF/CMS
Page 3
Inelastic Non-Diffractive Cross-Section
Inelastic Non-Diffractive Cross-Section: sHC
Inelastic Non-Diffractive Cross-Section: sHC
70
70
RDF Preliminary
60
py Tune DW generator level
Cross-Section (mb)
Cross-Section (mb)
60
50
40
My guess!
30
20
10
RDF Preliminary
py Tune DW generator level
50
40
30
20
10
K-Factor = 1.2
K-Factor = 1.2
0
0
0
2
4
6
8
10
12
14
0.1
1.0
100.0
Center-of-Mass Energy (TeV)
Center-of-Mass Energy (TeV)
Linear scale!
10.0
Log scale!
stot = sEL + sSD +sDD +sND
 The inelastic non-diffractive cross section versus center-of-mass energy from PYTHIA (×1.2).
sHC varies slowly.
Only a 13% increase between 7 TeV (≈ 58 mb) and 14 teV (≈ 66 mb). Linear
on a log scale!
Chris Quigg Symposiun Fermilab
December 14, 2009
Rick Field – Florida/CDF/CMS
Page 4
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
Proton
Final-State Radiation
Outgoing Parton
Underlying Event
Underlying Event
Proton
“Jet”
Final-State Radiation
Proton
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!
Chris Quigg Symposiun Fermilab
December 14, 2009
Rick Field – Florida/CDF/CMS
Page 5
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.
Chris Quigg Symposiun Fermilab
December 14, 2009
Rick Field – Florida/CDF/CMS
Page 6
CDF Run 1: Evolution of Charged Jets
“Underlying Event”
Charged Particle D 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
D
“Toward”
CDF Run 1 Analysis
Away Region
Charged Jet #1
Direction
D
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 D relative to the leading charged
particle jet.
 Define |D| < 60o as “Toward”, 60o < |D| < 120o as “Transverse”, and |D| > 120o as “Away”.
 All three regions have the same size in h- space, DhxD = 2x120o = 4p/3.
Chris Quigg Symposiun Fermilab
December 14, 2009
Rick Field – Florida/CDF/CMS
Page 7
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/dhd
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)
Chris Quigg Symposiun Fermilab
December 14, 2009
Default parameters give
very poor description of
the “underlying event”!
Rick Field – Florida/CDF/CMS
Page 8
Tuning PYTHIA:
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.
Chris Quigg Symposiun Fermilab
December 14, 2009
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 9
Run 1 PYTHIA Tune A
CDF Default!
PYTHIA 6.206 CTEQ5L
"Transverse" Charged Particle Density: dN/dhd
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)
Chris Quigg Symposiun Fermilab
December 14, 2009
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 10
CDF Run 1 Min-Bias “Associated”
Charged Particle Density
“Associated” densities do
not include PTmax!
Highest pT
charged particle!
Charged Particle Density: dN/dhd
PTmax Direction
PTmax Direction
0.5
D
Correlations in 
Charged Particle Density
CDF Preliminary
Associated Density
PTmax not included
data uncorrected
0.4
D
Charge Density
0.3
0.2
0.1
Min-Bias
Correlations
in 
Charged Particles
(|h|<1.0, PT>0.5 GeV/c)
PTmax
0.0
0
30
60
90
120
150
180
210
240
270
300
330
360
D (degrees)
 Use the maximum pT charged particle in the event, PTmax, to define a direction and look
It is more probable
to find
a particle
at the the “associated”
density, dN
chg/dhd,
in “min-bias” collisions (pT > 0.5 GeV/c, |h| <
accompanying
PTmax
than
it
is
to
1).
find a particle in the central region!
 Shows the data
on the D dependence of the “associated” charged particle density,
dNchg/dhd, for charged particles (pT > 0.5 GeV/c, |h| < 1, not including PTmax) relative
to PTmax (rotated to 180o) for “min-bias” events. Also shown is the average charged
particle density, dNchg/dhd, for “min-bias” events.
Chris Quigg Symposiun Fermilab
December 14, 2009
Rick Field – Florida/CDF/CMS
Page 11
CDF Run 1 Min-Bias “Associated”
Charged Particle Density Rapid rise in the particle
density in the “transverse”
region as PTmax increases!
Associated Particle Density: dN/dhd
PTmaxDirection
Direction
PTmax
D
“Toward”
“Transverse”
“Transverse”
Correlations in 
“Away”
Associated Particle Density
Jet #1
D
PTmax > 2.0 GeV/c
1.0
PTmax > 2.0 GeV/c
PTmax > 1.0 GeV/c
0.8
Charged Particles
(|h|<1.0, PT>0.5 GeV/c)
CDF Preliminary
data uncorrected
PTmax > 0.5 GeV/c
Transverse
Region
0.6
Transverse
Region
0.4
0.2
Jet #2
PTmax
PTmax not included
Min-Bias
0.0
0
30
60
90
120
150
180
210
240
270
300
330
360
D (degrees)
Ave Min-Bias
0.25 per unit h-
PTmax > 0.5 GeV/c
 Shows the data on the D dependence of the “associated” charged particle density,
dNchg/dhd, for charged particles (pT > 0.5 GeV/c, |h| < 1, not including PTmax) relative
to PTmax (rotated to 180o) for “min-bias” events with PTmax > 0.5, 1.0, and 2.0 GeV/c.
 Shows “jet structure” in “min-bias” collisions (i.e. the “birth” of the leading two jets!).
Chris Quigg Symposiun Fermilab
December 14, 2009
Rick Field – Florida/CDF/CMS
Page 12
Min-Bias “Associated”
Charged Particle Density
PTmax Direction
Associated Charged
Charged
Particle
Density:
dN/dhd
Associated
"Transverse"
ChargedParticle
ParticleDensity:
Density:dN/dhd
dN/dhd
D
Associated Charged Particle Density: dN/dhd
10.0
Charged Particle Density
py Tune A generator level
“Toward” Region
PTmax > 2.0 GeV/c
PTmax > 5.0 GeV/c
1.0
PTmax > 10.0 GeV/c
“Transverse”
“Transverse”
0.1
Min-Bias
1.96 TeV
PTmax > 0.5 GeV/c
PTmax > 1.0 GeV/c
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
0.0
Density
"Transverse"
Charged
Density
Charged Particle
1.6
2.5
1.2
RDF Preliminary
RDF Preliminary
RDF Preliminary
py Tune A generator level
py Tune A generator level
1.0
2.0
1.2
0.8
1.5
Min-Bias
Min-Bias
Min-Bias
14 TeV
1.96 TeV
“Toward”
14 TeV
"Toward"
"Away"
"Toward"
“Transverse”
~ factor of "Away"
2!
“Transverse”
0.8
0.6
1.0
0.4
0.4
0.5
0.2
1.96 TeV
"Transverse"
"Transverse"
“Away”
Charged
ChargedParticles
Particles(|h|<1.0,
(|h|<1.0,PT>0.5
PT>0.5 GeV/c)
GeV/c)
Charged
Particles
(|h|<1.0,
PT>0.5
GeV/c)
0.0
0.0
0
30
60
90
120
150
180
210
240
270
300
330
360
00
2
D (degrees)
54
6
8
10
10
12
15
14
16
20
18
PTmax (GeV/c)
(GeV/c)
PTmax
 Shows the D dependence of the “associated” charged particle density, dNchg/dhd, for charged
particles (pT > 0.5 GeV/c, |h| < 1, not including PTmax) relative to PTmax (rotated to 180o) for
“min-bias” events at 1.96 TeV with PTmax > 0.5, 1.0, 2.0, 5.0, and 10.0 GeV/c from PYTHIA
Tune A (generator level).
PTmax Direction
D
“Toward”
“Transverse”
“Transverse”
“Away”
 Shows the “associated” charged particle density in the “toward”, “away” and
“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 1.96 TeV from
PYTHIA Tune A (generator level).
Chris Quigg Symposiun Fermilab
December 14, 2009
Rick Field – Florida/CDF/CMS
Page 13
25
20
25
Charged Particle Multiplicity
Charged Multiplicity Distribution
Charged Multiplicity Distribution
1.0E+00
1.0E+00
CDF Run 2 Preliminary
CDF Run 2 Preliminary
1.0E-01
1.0E-01
CDF Run 2 <Nchg>=4.5
CDF Run 2 <Nchg>=4.5
1.0E-02
1.0E-02
1.0E-03
1.0E-03
py64 Tune A <Nchg> = 4.1
Probability
Probability
pyAnoMPI <Nchg> = 2.6
1.0E-04
1.0E-05
1.0E-04
1.0E-05
1.0E-06
1.0E-06
HC 1.96 TeV
Min-Bias 1.96 TeV
1.0E-07
1.0E-07
Normalized to 1
Normalized to 1 Charged Particles (|h|<1.0, PT>0.4 GeV/c)
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
20
25
30
35
40
No MPI!
“Minumum Bias” Collisions
Proton
15
45
50
55
Number of Charged Particles
Number of Charged Particles
7 decades!
10
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.
 The data are compared with PYTHIA Tune A and Tune A without multiple parton
interactions (pyAnoMPI).
Chris Quigg Symposiun Fermilab
December 14, 2009
Rick Field – Florida/CDF/CMS
Page 14
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
“Semi-hard” partonparton collision
(pT < ≈2 GeV/c)
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”.
Chris Quigg Symposiun Fermilab
December 14, 2009
Proton
+
+
Proton
Proton
Rick Field – Florida/CDF/CMS
Proton
Proton
+…
Multiple-parton
interactions (MPI)!
Page 15
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
+…
Chris Quigg Symposiun Fermilab
December 14, 2009
Rick Field – Florida/CDF/CMS
Multiple-parton
interactions (MPI)!
Page 16
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
“Semi-hard” partonparton collision
(pT < ≈2 GeV/c)
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”.
Chris Quigg Symposiun Fermilab
December 14, 2009
Proton
+
+
Proton
Proton
Rick Field – Florida/CDF/CMS
Proton
Proton
+…
Multiple-parton
interactions (MPI)!
Page 17
Min-Bias Correlations
Average PT versus Nchg
Average PT (GeV/c)
1.4
CDF Run 2 Preliminary
pyDW
data corrected
generator level theory
“Minumum Bias” Collisions
1.2
Min-Bias
1.96 TeV
pyA
Proton
1.0
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
 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).
Chris Quigg Symposiun Fermilab
December 14, 2009
Rick Field – Florida/CDF/CMS
Page 18
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
Chris Quigg Symposiun Fermilab
December 14, 2009
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 19
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
pyAnoMPI <Nchg> = 2.6
1.0E-03
CDF Run 2 <Nchg>=4.5
1.0E-02
py Tune A <Nchg> = 4.3
Probability
Probability
1.0E-02
CDF Run 2 Preliminary
1.0E-01
1.0E-04
1.0E-05
py Tune A <Nchg> = 4.3
pyA 900 GeV <Nchg> = 3.3
1.0E-03
1.0E-04
1.0E-05
1.0E-06
1.0E-06
Min-Bias 1.96
1.0E-07
Normalized to 1
Min-Bias
1.0E-07
Normalized to 1
Charged Particles (|h|<1.0, PT>0.4 GeV/c)
Charged Particles (|h|<1.0, PT>0.4 GeV/c)
1.0E-08
1.0E-08
0
5
No MPI!
10
15
20
25
30
35
40
45
50
55
0
5
Tune A prediction at
900 GeV!
Number of Charged Particles
“Minumum Bias” Collisions
Proton
10
15
20
25
30
35
40
45
50
Number of Charged Particles
“Minumum Bias” Collisions
Tune A!
AntiProton
Proton
Proton
 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.
 The data are compared with PYTHIA Tune A and Tune A without multiple parton interactions
(pyAnoMPI).
 Prediction from PYTHIA Tune A for proton-proton collisions at 900 GeV.
Chris Quigg Symposiun Fermilab
December 14, 2009
Rick Field – Florida/CDF/CMS
Page 20
55
Peter’s Pythia Tunes WEBsite
 http://home.fnal.gov/~skands/leshouches-plots/
Chris Quigg Symposiun Fermilab
December 14, 2009
Rick Field – Florida/CDF/CMS
Page 21
Min-Bias “Associated”
Charged Particle Density
35% more at RHIC means
"Transverse" Charged Particle Density: dN/dhd
26% less at the LHC!
1.6
RDF Preliminary
"Transverse" Charged Density
0.3
"Transverse" Charged Density
"Transverse" Charged Particle Density: dN/dhd
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
D
“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”
D
“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!
Chris Quigg Symposiun Fermilab
December 14, 2009
Rick Field – Florida/CDF/CMS
Page 22
Min-Bias “Associated”
Charged Particle Density
"Transverse" Charged Particle Density: dN/dhd
"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
D
“Toward”
RHIC
“Transverse”
“Transverse”
0.2 TeV → 1.96 TeV
(UE increase ~2.7 times)
Tevatron
“Away”
PTmax Direction
D
“Toward”
“Transverse”
PTmax Direction
1.96 TeV → 14 TeV
(UE increase ~1.9 times)
LHC
“Transverse”
“Away”
D
“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).
Chris Quigg Symposiun Fermilab
December 14, 2009
Rick Field – Florida/CDF/CMS
Page 23
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.
Chris Quigg Symposiun Fermilab
December 14, 2009
Rick Field – Florida/CDF/CMS
Page 24
LHC Predictions: 900 GeV
Charged Particle Density: dN/dh
Charged Particle Density: dN/dh
5
5
RDF Preliminary
Charged Particle Density
Charged Particle Density
RDF Preliminary
4
3
2
ALICE INEL
UA5 INEL
INEL = HC+DD+SD
900 GeV
1
pyDW INEL (2.67)
4
3
2
1
pyS320 INEL (2.70)
Charged Particles (all pT)
UA5
ALICE
NSD = HC+DD
900 GeV
pyDW_10mm (3.04)
pyS320_10mm (3.09)
0
0
-3.0
-2.5
-2.0
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
2.0
2.5
3.0
-3.0
-2.5
-2.0
-1.0
-0.5
0.0
0.5
1.0
1.5
2.0
2.5
PseudoRapidity h
PseudoRapidity h
“Minumum Bias” Collisions
“Minumum Bias” Collisions
Proton
-1.5
Proton
(SD + DD)/INEL = 28±8%
Proton
DD/NSD = 12±4%
Proton
 Compares the 900 GeV data with my favorite PYTHIA Tunes (Tune DW and Tune
S320 Perugia 0). Tune DW uses the old Q2-ordered parton shower and the old
MPI model. Tune S320 uses the new pT-ordered parton shower and the new MPI
model. The numbers in parentheses are the average value of dN/dh for the region
|h| < 0.6.
Chris Quigg Symposiun Fermilab
December 14, 2009
Rick Field – Florida/CDF/CMS
Page 25
3.0
LHC Predictions: 900 GeV
Off by 11%!
Charged Particle Density: dN/dh
5
Charged Particle Density: dN/dhCharged Particle Density: dN/dh
4
5
3
2
INEL = HC+DD+SD
900 GeV
1
times 1.11
4
3
2
1
Charged Particles (all pT)
0
-3.0
-2.5
-2.0
-1.5
-1.0
-0.5
0.0
RDF Preliminary
ALICE INEL
UA5
INEL
INEL
= HC+DD+SD
pyDW times
900 1.11
GeV(2.97)
pyS320
times
1.11 (3.00)
Charged
Particles
(all pT)
900 GeV
3
pyDW HC (3.30)
pyS320 HC (3.36)
pyDW SD (0.61)
2
pyS320 SD (0.53)
ALICE INEL
pyDW DD (0.59)
UA5 INEL
pyS320 DD (0.53)
Only DD
pyS320 INEL NPT1>0 (4.48)
pyDW INEL (2.67)
0
pyS320 INEL (2.70)
0.0-6 0.5-5 1.0-4 1.5-3 2.0 -2 2.5 -1 3.0 0
PseudoRapidity h
“Minumum Bias” Collisions
Proton
(SD + DD)/INEL = 28±8%
Only SD
pyDW INEL NPT1>0 (4.24)
1
Charged Particles (all pT)
0
0.5-3.0 1.0-2.5 1.5-2.0 2.0-1.5 2.5-1.0 3.0-0.5
PseudoRapidity h
Proton
Charged Particle Density
Charged Particle Density
Charged Particle Density
4
Only HC
RDF Preliminary
RDF Preliminary
1
2
3
4
5
PseudoRapidity h
“Minumum Bias” Collisions
Require at least one
charged
particleProton
to have pT > 1 GeV/c.
This is > 99% HC only!
Proton
 Shows the individual HC, DD, and SD predictions of PYTHIA Tune DW and Tune
S320 Perugia 0. The numbers in parentheses are the average value of dN/dh for the
region |h| < 0.6. I do not trust PYTHIA to model correctly the DD and SD
contributions! I would like to know how well these tunes model the HC component.
We need to look at observables where only HC contributes!
Chris Quigg Symposiun Fermilab
December 14, 2009
Rick Field – Florida/CDF/CMS
Page 26
6
Min-Bias “Associated”
Charged Particle Density
"Transverse" Charged Particle Density: dN/dhd
"Transverse" Charged Particle Density: dN/dhd
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
D
“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
D
“Toward”
“Transverse”
PTmax Direction
1.96 TeV → 14 TeV
(UE increase ~1.9 times)
LHC
“Transverse”
“Away”
D
“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 level
Linear scale!
(i.e. generator level).
Chris Quigg Symposiun Fermilab
December 14, 2009
Rick Field – Florida/CDF/CMS
Page 27
Min-Bias “Associated”
Charged Particle Density
"Transverse" Charged Particle Density: dN/dhd
"Transverse" Charged Particle Density: dN/dhd
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
D
“Toward”
LHC7
“Transverse”
100.0
PTmax Direction
7 TeV → 14 TeV
(UE increase ~20%)
D
“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 level
Log scale!
(i.e. generator level).
Chris Quigg Symposiun Fermilab
December 14, 2009
Rick Field – Florida/CDF/CMS
Page 28
“Transverse” Charge Density
"Transverse" Charged Particle Density: dN/dhd
"Transverse" Charged Particle Density: dN/dhd
1.2
"Transverse" Charged Density
"Transverse" Charged Density
0.6
RDF Preliminary
generator level
pyDW
0.4
pyS320
0.2
HC 900 GeV
Charged Particles (|h|<2.0, PT>0.5 GeV/c)
RDF Preliminary
py Tune DW generator level
7 TeV
0.8
factor of 2!
900 GeV
0.4
Charged Particles (|h|<2.0, PT>0.5 GeV/c)
0.0
0.0
0
2
4
6
8
10
12
14
16
18
20
0
2
4
D
LHC
900 GeV
“Toward”
“Transverse”
8
10
12
14
16
18
20
PTmax (GeV/c)
PTmax (GeV/c)
PTmax Direction
6
PTmax Direction
900 GeV → 7 TeV
(UE increase ~ factor of 2.1)
“Transverse”
“Away”
D
“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 as defined by PTmax from PYTHIA Tune DW and Tune S320 at the
particle level (i.e. generator level).
Chris Quigg Symposiun Fermilab
December 14, 2009
Rick Field – Florida/CDF/CMS
Page 29
Important 900 GeV Measurements
“Minumum Bias” Collisions
Proton
Charged Multiplicity Distribution
0.08
0.16
Proton
pyA <Nchg>
= 5.0 STdev = 4.5
RDF
Preliminary
RDF Preliminary
pyDW
900
GeV
<Nchg>==14.2
5.3
pyA
900
GeV
<Nchg>
pyS320
900GeV
GeV<Nchg>
<Nchg> = 5.2
pyDW
900
14.4
pyS320
GeV<Nchg>
<Nchg>= =5.3
14.2
pyP329 900
900 GeV
pyP329 900 GeV <Nchg> = 14.7
 The amount of activity in “min-bias” collisions (multiplicity distribution,
Probability
0.06
0.12
pT distribution, PTsum distribution, dNchg/dh).
0.04
0.08
Charged Particles (|h|<2.0, PT>0.5 GeV/c)
0.02
0.04
Normalized to 1
Normalized to 1
PTmax Direction
0
D
25
4
10
“Transverse”
12
30
14
35
16
40
Final-State
Radiation
0.6
0.18
“Transverse”
“Away”
T
"Transverse"
Charged Density
Probability
Outgoing Parton
10
25
"Transverse"
Charged
Particle
Density:
dN/dhd
"Transverse"
Charged
Particle
Multiplicity
Proton
Underlying Event
8
20
“Toward”
Initial-State Radiation
Underlying Event
6
15
Number of Charged Particles
PT(hard)
Proton
Charged Particles (|h|<2.0, all pT)
0.00
It is very important to measure
BOTH “min-bias” and the and the
“underlying event” at 900 GeV!
To do this
we need to collect
 The amount of activity in the “underlying
event” in hard scattering
events (“transverse” Nchg distribution,
“transverse”
p distribution,
about
5,000,000
CMS
“transverse” PTsum distribution for events with PTmax > 5 GeV/c).
min-bias triggers!
Outgoing Parton
For every 1,000
events here
HC HC
900900
GeVGeV
RDF Preliminary
generator level
py64DW <Nchg> = 3.5 <NchgDen> = 0.42
pyS320 <Nchg> = 3.4 <NchgDen> = 0.41
pyDW
0.4
0.12
RDF Preliminary
generator level
We get 3 events
here!
pyS320
0.2
0.06
HC 900 GeV PTmax > 5 GeV/c
HC 900 GeV
Charged Particles (|h|<2.0, PT>0.5 GeV/c)
Charged Particles (|h|<2.0, PT>0.5 GeV/c)
0.0
0.00
00
12
2 4 3
PTmax Direction
64
58
6
107
812
9 1410
16
11
1218 13
20
14
PTmax
(GeV/c)Particles
Number
of Charged
D
Outgoing Parton
PT(hard)
Initial-State Radiation
Proton
"Transverse" Charged Particle Density: dN/dhd
“Toward”
1.2
Underlying Event
Underlying Event
“Transverse”
Outgoing Parton
Final-State
Radiation
“Transverse”
“Away”
 We should map out the energy dependence of the “underlying
event” in a hard scattering process from 900 GeV to 14 TeV!
"Transverse" Charged Density
Proton
RDF Preliminary
py Tune DW generator level
0.8
0.4
PTmax = 5.25 GeV/c
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
0.0
0.1
1.0
10.0
100.0
Center-of-Mass Energy (TeV)
Chris Quigg Symposiun Fermilab
December 14, 2009
Rick Field – Florida/CDF/CMS
Page 30
The “Underlying Event” at 900 GeV
"Transverse" Charged Particle Density: dN/dhd
"Transverse" Charged Particle Density: dN/dhd
0.6
"Transverse" Charged Density
"Transverse" Charged Density
0.6
RDF Preliminary
pyDW generator level
0.4
0.2
900 GeV
10 Million MB Collisions
Charged Particles (|h|<2.0, PT>0.5 GeV/c)
RDF Preliminary
pyDW generator level
0.4
0.2
900 GeV
1 Million MB Collisions
Charged Particles (|h|<2.0, PT>0.5 GeV/c)
0.0
0.0
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
0
15
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
PTmax (GeV/c)
PTmax (GeV/c)
"Transverse" Charged Particle Density: dN/dhd
0.6
"Transverse" Charged Density
 Show how well we could measure the
“transverse” charged particle density versus
PTmax with 10 M, 1 M, and 0.5 M “minbias” (MB) events collected by CMS.
Assumes that for all the events that the
tracker is working well! The goal is to see
how well the data (red squares) agree with
the QCD MC prediction (black curve).
RDF Preliminary
pyDW generator level
0.4
0.2
900 GeV
0.5 Million MB Collisions
Charged Particles (|h|<2.0, PT>0.5 GeV/c)
0.0
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
PTmax (GeV/c)
Unfortunately, looks like
this is all we will get!
Chris Quigg Symposiun Fermilab
December 14, 2009
Rick Field – Florida/CDF/CMS
Page 31