“Underlying Event” Update
Recent STAR UE Measurements
Rick Field
University of Florida
Outline of Talk
The QCD Monte-Carlo Model tunes.
The Pythia MPI energy scaling
parameter PARP(90).
The “underlying event” at RHIC.
LHC predictions!
Outgoing Parton
PT(hard)
Initial-State Radiation
Proton
AntiProton
Underlying Event
Underlying Event
CDF Run 2
Outgoing Parton
CMS Low PT QCD Meeting
June 5, 2009
Final-State
Radiation
Rick Field – Florida/CDF/CMS
CMS at the LHC
Page 1
Tuning PYTHIA:
Multiple Parton Interaction Parameters
Default
PARP(83)
0.5
PARP(84)
0.2
Description
Double-Gaussian: Fraction of total hadronic
matter within PARP(84)
Double-Gaussian: Fraction of the overall hadron
radius containing the fraction PARP(83) of the
total hadronic matter.
PARP(85)
0.33
Probability that the MPI produces two gluons
with color connections to the “nearest neighbors.
PARP(86)
0.66
Probability that the MPI produces two gluons
either as described by PARP(85) or as a closed
gluon loop. The remaining fraction consists of
quark-antiquark pairs.
PARP(89)
PARP(82)
PARP(90)
PARP(67)
1 TeV
1.9
GeV/c
0.16
1.0
ore
Hard C
Multiple Parton Interaction
Color String
Color String
Multiple PartonDetermine
Interactionby comparing
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.
CMS Low PT QCD Meeting
June 5, 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 2
“Transverse” Charged Densities
Energy Dependence
"Transverse" Charged PTsum Density: dPTsum/dη
ηdφ
φ
"Min Transverse" PTsum Density: dPTsum/dη
ηdφ
φ
0.3
ε = 0.25
HERWIG 6.4
Charged PTsum Density (GeV)
Charged PTsum Density (GeV)
0.60
0.40
ε = 0.16
ε=0
0.20
CTEQ5L
Pythia 6.206 (Set A)
630 GeV |η
η|<1.0 PT>0.4 GeV
Pythia 6.206 (Set A)
HERWIG 6.4
ε = 0.25
0.2
0.1
CTEQ5L
ε = 0.16
ε=0
630 GeV |η
η|<1.0 PT>0.4 GeV
0.0
0.00
0
5
10
15
20
25
30
35
40
45
50
0
5
10
20
25
30
35
40
45
50
PT(charged jet#1) (GeV/c)
PT(charged jet#1) (GeV/c)
Hard-Scattering Cut-Off PT0
Shows the “transverse” charged PTsum density
5
PYTHIA 6.206
ε = 0.25 (Set A))
4
PT0 (GeV/c)
(|η
η|<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, ε = 0, ε =
0.16 (default) and ε = 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.
CMS Low PT QCD Meeting
June 5, 2009
15
3
2
ε = 0.16 (default)
1
100
Rick Field – Florida/CDF/CMS
1,000
10,000
100,000
CM Energy W (GeV)
Reference point
E0 = 1.8 TeV
Page 3
“Transverse” Charged Densities
Energy Dependence
Rick Field Fermilab MC Workshop
October 4, 2002!
"Transverse" Charged PTsum Density: dPTsum/dη
ηdφ
φ
"Min Transverse" PTsum Density: dPTsum/dη
ηdφ
φ
0.3
ε = 0.25
HERWIG 6.4
Charged PTsum Density (GeV)
Charged PTsum Density (GeV)
0.60
0.40
ε = 0.16
ε=0
0.20
HERWIG 6.4
ε = 0.25
0.2
0.1
Increasing ε produces less energy
dependence for the
UE resulting
in
ε = 0.16
ε=0
less UE activity at the LHC!
CTEQ5L
Pythia 6.206 (Set A)
Pythia 6.206 (Set A)
630 GeV |η
η|<1.0 PT>0.4 GeV
CTEQ5L
630 GeV |η
η|<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
ε) increases
charged
PTsum
densityUE activity
resulting in
less energy dependence.
25
30
35
40
45
50
Hard-Scattering Cut-Off PT0
5
PYTHIA 6.206
ε = 0.25 (Set A))
4
PT0 (GeV/c)
(|η
η|<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, ε = 0, ε =
0.16 (default) and ε = 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.
CMS Low PT QCD Meeting
June 5, 2009
20
PT(charged jet#1) (GeV/c)
PT(charged jet#1) (GeV/c)
Shows the “transverse”
15
3
2
ε = 0.16 (default)
1
100
Rick Field – Florida/CDF/CMS
1,000
10,000
100,000
CM Energy W (GeV)
Reference point
E0 = 1.8 TeV
Page 4
Peter’s Pythia Tunes WEBsite
http://home.fnal.gov/~skands/leshouches-plots/
CMS Low PT QCD Meeting
June 5, 2009
Rick Field – Florida/CDF/CMS
Page 5
Min-Bias “Associated”
Charged Particle Density
PTmax Direction
Associated Charged Particle Density: dN/dη
ηdφ
φ
∆φ
10.0
Charged Particle Density
RDF Preliminary
py Tune A generator level
“Toward” Region
“Toward”
PTmax > 2.0 GeV/c
PTmax > 5.0 GeV/c
1.0
PTmax > 10.0 GeV/c
“Transverse”
“Transverse”
“Transverse”
“Transverse”
“Away”
0.1
Min-Bias
1.96 TeV
Charged Particles (|η
η|<1.0, PT>0.5 GeV/c)
0.0
0
30
60
PTmax > 0.5 GeV/c
PTmax > 1.0 GeV/c
90
120
150
180
210
240
270
300
330
360
∆φ (degrees)
Shows the ∆φ dependence of the “associated” charged particle density, dNchg/dη
ηdφ
φ, for charged
particles (pT > 0.5 GeV/c, |η
η| < 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).
CMS Low PT QCD Meeting
June 5, 2009
Rick Field – Florida/CDF/CMS
Page 6
Min-Bias “Associated”
Charged Particle Density
PTmax Direction
ηdφ
φ
Associated Charged Particle Density: dN/dη
∆φ
Associated Charged Particle Density: dN/dη
ηdφ
φ
10.0
1.6
py Tune A generator level
“Toward” Region
RDF Preliminary
PTmax > 2.0 GeV/c
PTmax > 5.0 GeV/c
1.0
PTmax > 10.0 GeV/c
Charged Particle Density
Charged Particle Density
RDF Preliminary
“Transverse”
“Transverse”
0.1
Min-Bias
1.96 TeV
PTmax > 0.5 GeV/c
PTmax > 1.0 GeV/c
py Tune A generator level
1.2
Min-Bias
1.96 TeV
“Toward”
"Toward"
“Transverse”
“Transverse”
"Away"
0.8
"Transverse"
“Away”
0.4
Charged Particles (|η
η|<1.0, PT>0.5 GeV/c)
Charged Particles (|η
η|<1.0, PT>0.5 GeV/c)
0.0
0.0
0
30
60
90
120
150
180
210
240
270
300
330
360
0
2
∆φ (degrees)
4
6
8
10
12
14
16
18
PTmax (GeV/c)
Shows the ∆φ dependence of the “associated” charged particle density, dNchg/dη
ηdφ
φ, for charged
particles (pT > 0.5 GeV/c, |η
η| < 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
∆φ
“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, |η
η| < 1, not including PTmax) for “min-bias” events at 1.96 TeV from
PYTHIA Tune A (generator level).
CMS Low PT QCD Meeting
June 5, 2009
Rick Field – Florida/CDF/CMS
Page 7
20
“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).
CMS Low PT QCD Meeting
June 5, 2009
Rick Field – Florida/CDF/CMS
Page 8
“Transverse” Charged Density
PTmax Direction
"Transverse" Charged Particle Density: dN/dη
ηdφ
φ
∆φ
1.6
“Transverse”
“Transverse”
“Away”
ChgJet#1 Direction
∆φ
“Toward”
“Transverse”
“Transverse”
“Away”
"Transverse" Charged Density
“Toward”
RDF Preliminary
14 TeV
py Tune DW generator level
1.2
1.2
0.8
Jet#1
ChgJet#1
0.4
Charged Particles (|η
η|<1.0, PT>0.5 GeV/c)
PTmax
0.0
Jet#1 Direction
∆φ
0
5
10
15
20
25
30
35
40
45
50
55
60
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 14 TeV as defined by PTmax, PT(chgjet#1), and PT(jet#1) from PYTHIA Tune
DW at the particle level (i.e. generator level).
CMS Low PT QCD Meeting
June 5, 2009
Rick Field – Florida/CDF/CMS
Page 9
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!
CMS Low PT QCD Meeting
June 5, 2009
Rick Field – Florida/CDF/CMS
Page 10
Min-Bias “Associated”
Charged Particle Density
About a factor of 2.7 increase in
ηdφ
φ
Associated Charged Particle Density: dN/dη
the
“transverse”
region!
1.6
py Tune DW generator level
RDF Preliminary
Min-Bias
1.96 TeV
Charged Particle Density
RDF Preliminary
Charged Particle Density
ηdφ
φ
Associated Charged Particle Density: dN/dη
1.2
1.2
"Toward"
"Away"
0.8
"Transverse"
0.4
Charged Particles (|η
η|<1.0, PT>0.5 GeV/c)
py Tune DW generator level
Min-Bias
0.2 TeV
"Away"
0.8
"Toward"
0.4
"Transverse"
Charged Particles (|η
η|<1.0, PT>0.5 GeV/c)
0.0
0.0
0
2
4
6
8
10
12
16
18
20
0
2
4
6
8
10
PTmax (GeV/c)
PTmax (GeV/c)
PTmax Direction
PTmax Direction
∆φ
∆φ
“Toward”
Tevatron
14
“Transverse”
1.96 TeV ← 0.2 TeV
(~factor of 10 increase)
“Transverse”
12
14
“Toward”
RHIC
“Transverse”
“Transverse”
“Away”
“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, |η
η| < 1, not including PTmax) for
“min-bias” events at 1.96 TeV and at 0.2 TeV from PYTHIA Tune DW at the particle level (i.e.
generator level).
CMS Low PT QCD Meeting
June 5, 2009
Rick Field – Florida/CDF/CMS
Page 11
Min-Bias “Associated”
Charged Particle Density
About a factor of 2 increase in
ηdφ
φ
Associated Charged Particle Density: dN/dη
the
“transverse”
region!
1.6
py Tune DW generator level
Min-Bias
14 TeV
RDF Preliminary
Min-Bias
1.96 TeV
Charged Particle Density
RDF Preliminary
Charged Particle Density
Charged Particle Density: dN/dη
ηdφ
φ
2.5
1.2
"Toward"
"Away"
0.8
"Transverse"
0.4
py Tune DW generator level
2.0
"Toward"
"Away"
1.5
"Transverse"
1.0
0.5
η|<1.0, PT>0.5 GeV/c)
Charged Particles (|η
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
5
10
PTmax (GeV/c)
PTmax Direction
PTmax Direction
∆φ
∆φ
“Toward”
Tevatron
15
“Transverse”
20
25
PTmax (GeV/c)
1.96 TeV → 14 TeV
(~factor of 7 increase)
“Transverse”
“Toward”
LHC
“Transverse”
“Transverse”
“Away”
“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, |η
η| < 1, not including PTmax) for
“min-bias” events at 1.96 TeV and at 14 TeV from PYTHIA Tune DW at the particle level (i.e.
generator level).
CMS Low PT QCD Meeting
June 5, 2009
Rick Field – Florida/CDF/CMS
Page 12
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).
CMS Low PT QCD Meeting
June 5, 2009
Rick Field – Florida/CDF/CMS
Page 13
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 with Pythia Tune A.
CMS Low PT QCD Meeting
June 5, 2009
Rick Field – Florida/CDF/CMS
Page 14
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 with Pythia Tune A.
CMS Low PT QCD Meeting
June 5, 2009
Rick Field – Florida/CDF/CMS
Page 15
The “Underlying Event” at STAR
Charged PTsum Density
Charged PTsum Density (GeV/c)
Charged PTsum Density: dPT/dη
ηdφ
φ
“Back-to-Back”
Charged Particles (|η
η|<1.0, PT>0.2 GeV/c)
Data uncorrected
PYTHIA Tune A + STAR-SIM
100.0
CDF Run 2 Preliminary
data corrected
pyA generator level
10.0
"Toward"
"Away"
“Toward”
"Transverse"
1.0
"Leading Jet"
MidPoint R=0.7 |η
η(jet#1)|<2
“Away”
Charged Particles (|η
η|<1.0, PT>0.5 GeV/c)
0.1
0
50
100
150
200
250
300
350
400
Preliminary
Preliminary
PT(jet#1) (GeV/c)
Jet #1 Direction
∆φ
∆φ
“Leading Jet”
“Toward”
“Transverse”
“Transverse”
“Away”
“Transverse”
Jet #1 Direction
“Toward”
“Transverse”
PT(jet#1) (GeV/c)
“Transverse”
“Away”
“Back-to-Back”
Jet #2 Direction
Data on the charged particle scalar pT sum density, dPT/dη
ηdφ
φ, as a function of the leading jet pT for the
“toward”, “away”, and “transverse” regions compared with PYTHIA Tune A.
CMS Low PT QCD Meeting
June 5, 2009
Rick Field – Florida/CDF/CMS
Page 16
The “Underlying Event” at STAR
Charged PTsum Density
Charged PTsum
"Transverse"
PTsumDensity
Density (GeV/c)
(GeV/c)
"Transverse"
PTsum Density:
dPT/dη
ηdφ
φ
ChargedCharged
PTsum Density:
dPT/dη
ηdφ
φ
2.0
100.0
1.6
“Back-to-Back”
Charged Particles (|η
η|<1.0, PT>0.2 GeV/c)
Data uncorrected
PYTHIA Tune A + STAR-SIM
CDF
Run
2 Preliminary
CDF
Run
2 Preliminary
data corrected
particle level
datatocorrected
10.0
1.2
pyA
generator level
1.96
TeV
"Leading Jet"
"Toward"
PY Tune A
"Away"
“Toward”
"Transverse"
0.8
1.0
"Back-to-Back"
"Leading Jet"
MidPoint R=0.7 |η
η(jet#1)|<2
0.4
0.1
0.0
0
0
MidPoint
R = Particles
0.7 |η
η(jet#1)
< 2 PT>0.5 GeV/c)
Charged
(|η
η|<1.0,
Charged Particles (|η
η|<1.0, PT>0.5 GeV/c)
HW
50
50
“Away”
0.55
100
150
200
250
100
150
200
250
300
300
350
350
400
400
450
Preliminary
Preliminary
~1.5
PT(jet#1) (GeV/c)
PT(jet#1) (GeV/c)
Jet #1 Direction
∆φ
∆φ
“Leading Jet”
“Toward”
“Transverse”
“Transverse”
“Away”
“Transverse”
Jet #1 Direction
0.37
“Toward”
“Transverse”
PT(jet#1) (GeV/c)
“Transverse”
“Away”
“Back-to-Back”
Jet #2 Direction
Data on the charged particle scalar pT sum density, dPT/dη
ηdφ
φ, as a function of the leading jet pT for the
“toward”, “away”, and “transverse” regions compared with PYTHIA Tune A.
CMS Low PT QCD Meeting
June 5, 2009
Rick Field – Florida/CDF/CMS
Page 17
Min-Bias “Associated”
Charged Particle Density
"Transverse" Charged Particle Density: dN/dη
ηdφ
φ
"Transverse" Charged Density
0.8
RDF Preliminary
PY64 Tune P329
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
0
2
4
6
8
10
12
14
16
18
20
PTmax (GeV/c)
PTmax Direction
∆φ
“Toward”
“Transverse”
“Transverse”
Tevatron
“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).
CMS Low PT QCD Meeting
June 5, 2009
Rick Field – Florida/CDF/CMS
Page 18
Min-Bias “Associated”
Charged Particle Density
RDF LHC Prediction!
"Transverse" Charged Particle Density: dN/dη
ηdφ
φ
ηdφ
φ
"Transverse" Charged Particle Density: dN/dη
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
PTmax Direction
∆φ
∆φ
“Transverse”
25
“Toward”
“Toward”
“Transverse”
20
PTmax (GeV/c)
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.
CMS Low PT QCD Meeting
June 5, 2009
Rick Field – Florida/CDF/CMS
Page 19
Z-Boson: “Towards” Region
"Toward" Charged Particle Density: dN/dη
ηdφ
φ
"Toward" Charged Density
0.8
RDF Preliminary
PY Tune AW
PY Tune DW
generator level
Drell-Yan
1.96 TeV
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)
0.0
0
25
50
75
100
125
150
Lepton-Pair PT (GeV/c)
Z-BosonDirection
∆φ
“Toward”
“Transverse”
“Transverse”
Tevatron
“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).
CMS Low PT QCD Meeting
June 5, 2009
Rick Field – Florida/CDF/CMS
Page 20
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.
CMS Low PT QCD Meeting
June 5, 2009
Rick Field – Florida/CDF/CMS
Page 21
150
LHC Predictions
“Minumum Bias” Collisions
Proton
AntiProton
Charged Particle Density: dN/dη
η
4.0
RDF Preliminary
Charged Particle Density
I believe because of the STAR analysis we are now
in a position to make some predictions at the LHC!
PY64 Tune P329
generator level
3.0
PY64 Tune S320
2.0
PY Tune A
1.0
Min-Bias
14 TeV
Charged Particles (PT>0.5 GeV/c)
0.0
The amount of activity in “min-bias” collisions.
Outgoing Parton
-8
-6
∆φ
“Transverse”
Outgoing Parton
“Transverse”
Final-State
Radiation
“Away”
The amount of activity in the “underlying event” in hard
scattering events.
Drell-Yan Production
4
PY ATLAS
RDF Preliminary
“Toward”
Underlying Event
2
6
8
"Transverse" Charged Particle Density: dN/dη
ηdφ
φ
1.6
"Transverse" Charged Density
Underlying Event
0
PseudoRapidity η
Initial-State Radiation
AntiProton
-2
PTmax Direction
PT(hard)
Proton
-4
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
5
10
Z-BosonDirection
15
20
25
PTmax (GeV/c)
∆φ
Lepton
"Toward" Charged Particle Density: dN/dη
ηdφ
φ
“Toward”
Underlying Event
Underlying Event
PY ATLAS
RDF Preliminary
AntiProton
“Transverse”
“Transverse”
“Away”
Anti-Lepton
The amount of activity in the “underlying event” in DrellYan events.
"Toward" Charged Density
Proton
1.6
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
25
50
75
100
125
150
Lepton-Pair PT (GeV/c)
CMS Low PT QCD Meeting
June 5, 2009
Rick Field – Florida/CDF/CMS
Page 22
LHC Predictions
“Minumum Bias” Collisions
Proton
AntiProton
Charged Particle Density: dN/dη
η
4.0
RDF Preliminary
Charged Particle Density
I believe because of the STAR analysis we are now
in a position to make some predictions at the LHC!
PY64 Tune P329
generator level
3.0
PY64 Tune S320
2.0
PY Tune A
1.0
Min-Bias
14 TeV
Charged Particles (PT>0.5 GeV/c)
0.0
The amount of activity in “min-bias” collisions.
Outgoing Parton
Underlying Event
If the LHC data are not in
the range shown here then
we learn new physics!
Outgoing Parton
“Transverse”
“Away”
The amount of activity in the “underlying event” in hard
scattering events.
Drell-Yan Production
0
2
4
PY ATLAS
RDF Preliminary
“Toward”
“Transverse”
Final-State
Radiation
-2
6
8
"Transverse" Charged Particle Density: dN/dη
ηdφ
φ
1.6
"Transverse" Charged Density
AntiProton
-4
PseudoRapidity η
∆φ
Initial-State Radiation
Underlying Event
-6
PTmax Direction
PT(hard)
Proton
-8
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
5
10
Z-BosonDirection
15
20
25
PTmax (GeV/c)
∆φ
Lepton
"Toward" Charged Particle Density: dN/dη
ηdφ
φ
“Toward”
Underlying Event
Underlying Event
PY ATLAS
RDF Preliminary
AntiProton
“Transverse”
“Transverse”
“Away”
Anti-Lepton
The amount of activity in the “underlying event” in DrellYan events.
"Toward" Charged Density
Proton
1.6
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
25
50
75
100
125
150
Lepton-Pair PT (GeV/c)
CMS Low PT QCD Meeting
June 5, 2009
Rick Field – Florida/CDF/CMS
Page 23
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!
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
5
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!
CMS Low PT QCD Meeting
June 5, 2009
Rick Field – Florida/CDF/CMS
PYTHIA 6.206
ε = 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.
3
2
ε = 0.16 (default)
1
100
1,000
10,000
100,000
CM Energy W (GeV)
UE&MB@CMS
Page 24
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!
PT(hard)
Initial-State Radiation
Proton
AntiProton
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
More work needs to be done
preferred!
Underlying Event
Underlying Event
Outgoing Parton
Final-State
Radiation
Hard-Scattering Cut-Off PT0
5
It is clear now that the default
value PARP(90)
= 0.16 is using
studying
the tunes
not correct and the value should be closer to the Tune A
LO* structure functions!
value of 0.25.
PYTHIA 6.206
ε = 0.25 (Set A))
PT0 (GeV/c)
4
3
(Tune DW, S320, and P329 have been studied
All tunes with the default value PARP(90)
0.16 detail!)
in much=more
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!
CMS Low PT QCD Meeting
June 5, 2009
Rick Field – Florida/CDF/CMS
2
ε = 0.16 (default)
1
100
1,000
10,000
100,000
CM Energy W (GeV)
UE&MB@CMS
Page 25