Monte-Carlo Generators for CMS
High PT Jets
Outgoing Parton
PT(hard)
Initial-State Radiation
Proton
CDF Run 2
AntiProton
CMS
Final-State Radiation
Outline of Talk
Outgoing Parton
Not favored at present!
 Review briefly the CDF Run 1 and Run 2
PYTHIA 6.2 tunes.
UE&MB@CMS
Perugia, Florida, Hamburg, Trieste
 Discuss four NLO structure function
CTEQ6.1M PYTHIA 6.2 tunes, Tune QK
and Tune QKT, Tune QW and Tune QWT.
Drell-Yan Production
Lepton
Proton
AntiProton
Underlying Event
Underlying Event
 Introduce a new CTEQ6L tune Tune D6
and Tune D6T.
Initial-State
Radiation
Anti-Lepton
 Discuss a few early measurements at CMS.
FNAL-CMS MC Generator Meeting
June 7, 2007
Rick Field – Florida/CMS
New CTEQ6L tune!
Page 1
CDF Run 1 PYTHIA Tune A
CDF Default!
PYTHIA 6.206 CTEQ5L
"Transverse" Charged Particle Density: dN/dd
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)
FNAL-CMS MC Generator Meeting
June 7, 2007
Run 1 Analysis
0.50
0.25
CTEQ5L
PYTHIA 6.206 (Set B)
PARP(67)=1
1.8 TeV ||<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/CMS
Page 2
CDF Run 1 PT(Z)
PYTHIA 6.2 CTEQ5L
s = 1.0
Parameter
Tune A
Tune A25
Tune A50
MSTP(81)
1
1
1
MSTP(82)
4
4
4
PARP(82)
2.0 GeV
2.0 GeV
2.0 GeV
PARP(83)
0.5
0.5
0.5
PARP(84)
0.4
0.4
0.4
PARP(85)
0.9
0.9
0.9
PARP(86)
0.95
0.95
0.95
1.8 TeV
1.8 TeV
1.8 TeV
PARP(90)
0.25
0.25
0.25
PARP(67)
4.0
4.0
4.0
MSTP(91)
1
1
1
PARP(91)
1.0
2.5
5.0
PARP(93)
5.0
15.0
25.0
ISR Parameter PARP(89)
Z-Boson Transverse Momentum
0.12
PT Distribution 1/N dN/dPT
UE Parameters
CDF Run 1 Data
PYTHIA Tune A
PYTHIA Tune A25
PYTHIA Tune A50
s = 2.5
0.08
CDF Run 1
published
1.8 TeV
s = 5.0
Normalized to 1
0.04
0.00
0
2
4
6
8
10
12
14
16
18
Z-Boson PT (GeV/c)
 Shows the Run 1 Z-boson pT distribution
(<pT(Z)> ≈ 11.5 GeV/c) compared with PYTHIA
Tune A (<pT(Z)> = 9.7 GeV/c), Tune A25
(<pT(Z)> = 10.1 GeV/c), and
Tune A50
(<pT(Z)> = 11.2 GeV/c).
Vary the intrensic KT!
Intrensic KT
FNAL-CMS MC Generator Meeting
June 7, 2007
20
Rick Field – Florida/CMS
Page 3
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)!
FNAL-CMS MC Generator Meeting
June 7, 2007
20
Rick Field – Florida/CMS
Page 4
CDF Run 1 PT(Z)
Parameter
Tune A
Tune AW
UE Parameters MSTP(81)
1
1
MSTP(82)
4
4
ISR Parameters
PARP(82)
2.0 GeV
2.0 GeV
PARP(83)
0.5
0.5
PARP(84)
0.4
0.4
PARP(85)
0.9
0.9
PARP(86)
0.95
0.95
PARP(89)
1.8 TeV
1.8 TeV
PARP(90)
0.25
0.25
PARP(62)
1.0
1.25
PARP(64)
1.0
0.2
PARP(67)
4.0
4.0
MSTP(91)
1
1
PARP(91)
1.0
2.1
PARP(93)
5.0
15.0
Z-Boson Transverse Momentum
1.0E+00
PT Distribution 1/N dN/dPT
PYTHIA 6.2 CTEQ5L
Tune used by the
CDF-EWK group!
CDF Run 1 Data
PYTHIA Tune AW
1.0E-01
CDF Run 1
published
1.8 TeV
1.0E-02
Normalized to 1
1.0E-03
1.0E-04
Also fits the high pT tail!
1.0E-05
0
10
20
30
40
50
60
70
80
90
100
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)!
FNAL-CMS MC Generator Meeting
June 7, 2007
Rick Field – Florida/CMS
Page 5
Jet-Jet Correlations (DØ)
Jet#1-Jet#2 D Distribution
D 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).
FNAL-CMS MC Generator Meeting
June 7, 2007
Rick Field – Florida/CMS
Page 6
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!
FNAL-CMS MC Generator Meeting
June 7, 2007
Rick Field – Florida/CMS
Page 7
“Transverse” Nchg Density
Three different amounts of MPI!
UE Parameters
PYTHIA 6.2 CTEQ5L
"Transverse" Charged Particle Density: dN/dd
Parameter
Tune AW
Tune DW
Tune BW
MSTP(81)
1
1
1
MSTP(82)
4
4
4
PARP(82)
2.0 GeV
1.9 GeV
1.8 GeV
PARP(83)
0.5
0.5
0.5
PARP(84)
0.4
0.4
0.4
PARP(85)
0.9
1.0
1.0
PARP(86)
0.95
1.0
1.0
1.8 TeV
1.8 TeV
1.8 TeV
PARP(90)
0.25
0.25
0.25
PARP(62)
1.25
1.25
1.25
PARP(64)
0.2
0.2
0.2
PARP(67)
4.0
2.5
1.0
MSTP(91)
1
1
1
PARP(91)
2.5
2.5
2/5
PARP(93)
15.0
15.0
15.0
1.0
ISR Parameter PARP(89)
Intrensic KT
"Transverse" Charged Density
RDF Preliminary
PY Tune BW
PY Tune DW
generator level
0.8
0.6
PY Tune A
PY Tune AW
0.4
HERWIG
1.96 TeV
0.2
Leading Jet (||<2.0)
Charged Particles (||<1.0, PT>0.5 GeV/c)
0.0
0
50
100
150
200
250
300
350
400
450
PT(particle jet#1) (GeV/c)
 Shows the “transverse” charged particle
density, dN/dd, versus PT(jet#1) for “leading
jet” events at 1.96 TeV for PYTHIA Tune A,
Tune AW, Tune DW, Tune BW, and HERWIG
(without MPI).
Three different amounts of ISR!
FNAL-CMS MC Generator Meeting
June 7, 2007
500
Rick Field – Florida/CMS
Page 8
New PYTHIA 6.2 Tunes
Use LO as
with L = 192 MeV!
UE Parameters
ISR Parameter
Parameter
Tune DW
Tune D6
Tune QW
Tune QK
PDF
CTEQ5L
CTEQ6L
CTEQ6.1
CTEQ6.1
MSTP(2)
1
1
1
1
MSTP(33)
0
0
0
1
PARP(31)
1.0
1.0
1.0
1.8
MSTP(81)
1
1
1
1
MSTP(82)
4
4
4
4
PARP(82)
1.9 GeV
1.8 GeV
1.1 GeV
1.9 GeV
PARP(83)
0.5
0.5
0.5
0.5
PARP(84)
0.4
0.4
0.4
0.4
PARP(85)
1.0
1.0
1.0
1.0
PARP(86)
1.0
1.0
1.0
1.0
PARP(89)
1.8 TeV
1.8 TeV
1.8 TeV
1.8 TeV
PARP(90)
0.25
0.25
0.25
0.25
PARP(62)
1.25
1.25
1.25
1.25
PARP(64)
0.2
0.2
0.2
0.2
PARP(67)
2.5
2.5
2.5
2.5
MSTP(91)
1
1
1
1
PARP(91)
2.1
2.1
2.1
2.1
PARP(93)
15.0
15.0
15.0
15.0
NLO Structure Function!
K-factor
(T. Sjostrand)
Tune A energy dependence!
Intrinsic KT
FNAL-CMS MC Generator Meeting
June 7, 2007
Rick Field – Florida/CMS
Page 9
New PYTHIA 6.2 Tunes
Use LO as
with L = 192 MeV!
UE Parameters
ISR Parameter
Parameter
Tune DWT
ATLAS
Tune D6T
Tune QWT
Tune QKT
PDF
CTEQ5L
CTEQ5L
CTEQ6L
CTEQ6.1
CTEQ6.1
MSTP(2)
1
1
1
1
1
MSTP(33)
0
0
1
1
1
PARP(31)
1.0
1.0
1.0
1.0
1.8
MSTP(81)
1
1
1
1
1
MSTP(82)
4
4
4
4
4
PARP(82)
1.9409 GeV
1.8 GeV
1.8387 GeV
1.1237 GeV
1.9409 GeV
PARP(83)
0.5
0.5
0.5
0.5
0.5
PARP(84)
0.4
0.5
0.4
0.4
0.4
PARP(85)
1.0
0.33
1.0
1.0
1.0
PARP(86)
1.0
0.66
1.0
1.0
1.0
PARP(89)
1.96 TeV
1.0 TeV
1.96 TeV
1.96 TeV
1.96 TeV
PARP(90)
0.16
0.16
0.16
0.16
0.16
PARP(62)
1.25
1.0
1.25
1.25
1.25
PARP(64)
0.2
1.0
0.2
0.2
0.2
PARP(67)
2.5
1.0
2.5
2.5
2.5
MSTP(91)
1
1
1
1
1
PARP(91)
2.1
1.0
2.1
2.1
2.1
PARP(93)
15.0
5.0
15.0
15.0
15.0
NLO Structure Function!
K-factor
(T. Sjostrand)
ATLAS energy dependence!
Intrinsic KT
FNAL-CMS MC Generator Meeting
June 7, 2007
Rick Field – Florida/CMS
Page 10
New PYTHIA 6.2 Tunes
1.96 TeV
"Transverse" Charged Particle Density: dN/dd
1.0
"Transverse" Charged Density
PT0(MPI)
GeV
s(MPI)
mb
PT0(MPI)
GeV
s(MPI)
mb
Tune DW
1.9409
351.7
3.1730
549.2
Tune DWT
1.9409
351.7
2.6091
829.1
ATLAS
2.0046
324.5
2.7457
768.0
Tune D6
1.8387
306.3
3.0059
546.1
Tune D6T
1.8387
306.3
2.5184
786.5
Tune QK
1.9409
259.5
3.1730
422.0
Tune QKT
1.9409
259.5
2.6091
588.0
PY Tune DW
RDF Preliminary
generator level
0.8
0.6
PY Tune D6
0.4
PY Tune QK
1.96 TeV
14 TeV
0.2
Leading Jet (||<2.0)
Charged Particles (||<1.0, PT>0.5 GeV/c)
0.0
0
50
100
150
200
250
300
350
400
450
500
PT(particle jet#1) (GeV/c)
"Transverse" PTsum Density (GeV/c)
"Transverse" PTsum Density: dPT/dd
1.6
RDF Preliminary
PY Tune QK
 Average charged particle density and
PTsum density in the “transverse”
region (pT > 0.5 GeV/c, || < 1) versus
PT(jet#1) at 1.96 TeV for PY Tune DW,
Tune D6, and Tune QK.
generator level
1.2
PY Tune DW
PY Tune D6
0.8
1.96 TeV
0.4
Leading Jet (||<2.0)
Charged Particles (||<1.0, PT>0.5 GeV/c)
0.0
0
50
100
150
200
250
300
350
400
450
500
PT(particle jet#1) (GeV/c)
FNAL-CMS MC Generator Meeting
June 7, 2007
Rick Field – Florida/CMS
Page 11
New PYTHIA 6.2 Tunes
1.96 TeV
"Transverse" Charged Particle Density: dN/dd
"Transverse" Charged Density
2.5
PT0(MPI)
GeV
s(MPI)
mb
PT0(MPI)
GeV
s(MPI)
mb
Tune DW
1.9409
351.7
3.1730
549.2
Tune DWT
1.9409
351.7
2.6091
829.1
ATLAS
2.0046
324.5
2.7457
768.0
14 TeV
Tune D6
1.8387
306.3
3.0059
546.1
Leading Jet (||<2.0)
Charged Particles (||<1.0, PT>0.5 GeV/c)
Tune D6T
1.8387
306.3
2.5184
786.5
Tune QK
1.9409
259.5
3.1730
422.0
Tune QKT
1.9409
259.5
2.6091
588.0
PY Tune DWT
RDF Preliminary
generator level
2.0
1.5
PY Tune QKT
PY Tune D6T
1.0
0.5
0.0
0
250
500
750
14 TeV
1000
1250
1500
1750
2000
PT(particle jet#1) (GeV/c)
"Transverse" PTsum Density (GeV/c)
"Transverse" PTsum Density: dPT/dd
8.0
 Average charged particle density and
PTsum density in the “transverse”
region (pT > 0.5 GeV/c, || < 1) versus
PT(jet#1) at 14 TeV for PY Tune DWT,
Tune D6T, and Tune QKT.
PY Tune DWT
RDF Preliminary
generator level
6.0
PY Tune QKT
4.0
14 TeV
2.0
Leading Jet (||<2.0)
Charged Particles (||<1.0, PT>0.5 GeV/c)
PY Tune D6T
0.0
0
250
500
750
1000
1250
1500
1750
2000
PT(particle jet#1) (GeV/c)
FNAL-CMS MC Generator Meeting
June 7, 2007
Rick Field – Florida/CMS
Page 12
PYTHIA 6.2 Tunes
LHC Min-Bias Predictions
Charged Particle Density: dN/dY
Charged Particle Density: dN/d
12
pyA
pyDW
pyDWT
ATLAS
Generator Level
14 TeV
8
Charged Particle Density
Charged Particle Density
10
6
4
2
pyA
pyDW
pyDWT
ATLAS
Generator Level
14 TeV
10
8
6
4
2
Charged Particles (all pT)
Charged Particles (all pT)
0
0
-10
-8
-6
-4
-2
0
2
4
6
8
10
-10
-8
-6
-4
PseudoRapidity 
-2
0
2
4
6
8
10
Rapidity Y
 Shows the predictions of PYTHIA Tune A, Tune DW, Tune DWT, and the ATLAS tune for
the charged particle density dN/d and dN/dY at 14 TeV (all pT).
 PYTHIA Tune A and Tune DW predict about 6 charged particles per unit  at  = 0, while
the ATLAS tune predicts around 9.
 PYTHIA Tune DWT is identical to Tune DW at 1.96 TeV, but extrapolates to the LHC using
the ATLAS energy dependence.
FNAL-CMS MC Generator Meeting
June 7, 2007
Rick Field – Florida/CMS
Page 13
PYTHIA 6.2 Tunes
LHC Min-Bias Predictions
Average Number of Charged Particles vs PTmin
Charged PT Distribution
20
100.0
Generator Level
Min-Bias 14 TeV
pyA <PT> = 641 MeV/c
Generator Level
Min-Bias 14 TeV
pyDW <PT> = 665 MeV/c
15
pyA
pyDW
pyDWT
ATLAS
<Nchg>
1/Nev dN/dPT (1/GeV/c)
pyDWT <PT> = 693 MeV/c
ATLAS <PT> = 548 MeV/c
10.0
10
5
Charged Particles (||<1.0, PT>PTmin)
1.0
0
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
Minimum PT (GeV/c)
Charged Particles (||<1.0)
0.1
0.0
0.5
1.0
1.5
2.0
2.5
3.0
Charged Particle PT (GeV/c)
 Shows the predictions of PYTHIA Tune A, Tune DW, Tune DWT, and the ATLAS tune for
the charged particle pT distribution at 14 TeV (|| < 1) and the average number of charged
particles with pT > pTmin (|| < 1).
 The ATLAS tune has many more “soft” particles than does any of the CDF Tunes. The
ATLAS tune has <pT> = 548 MeV/c while Tune A has <pT> = 641 MeV/c (100 MeV/c more
per particle)!
FNAL-CMS MC Generator Meeting
June 7, 2007
Rick Field – Florida/CMS
Page 14
New PYTHIA 6.2 Tunes
14 TeV (pT > 0.5 GeV/c, || < 1)
Charged Particle Density: dN/d
Charged Particle Density
4
<Nchg>
<PTsum>
(GeV/c)
<PT>
(GeV/c)
Tune DWT
6.268
7.091
1.131
Tune D6T
5.743
6.467
1.126
Tune QKT
5.361
6.115
0.982
pyDWT LHC
pyD6T LHC
pyQKT LHC
Min-Bias
(Hard Core)
3
No Trigger
MSTJ(22)=1
14 TeV
2
1
Charged Particles (PT > 0.5 GeV/c)
Numbers for pT > 0.5 GeV/c, || < 1.
0
-10
-8
-6
-4
-2
0
2
4
6
8
10
PseudoRapidity 
 PseudoRapidity distribution, dN/d, for charged
particles with pT > 0.5 GeV/c at 14 TeV for PY
Tune DWT, Tune D6T, and Tune QKT. Note this is
“hard core” (i.e. MSEL=1, PT(hard) = 0) with no
trigger and with only stable particles (i.e.
MSTJ(22)=1). Tune D6T uses CTEQ6L (i.e.
LHAPDF = 10042) and Tune QKT uses
CTEQ6.1M (i.e. LHAPDF = 10100 or 10150 which
are the same).
FNAL-CMS MC Generator Meeting
June 7, 2007
Rick Field – Florida/CMS
We now have CTEQ6L
Tune D6T!
Page 15
The Evolution of Charged Jets
and the “Underlying Event”
Charged Particle D Correlations
PT > 0.5 GeV/c || < 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

+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 - space, DxD = 2x120o = 4p/3.
FNAL-CMS MC Generator Meeting
June 7, 2007
Rick Field – Florida/CMS
Page 16
CDF Run 2 Min-Bias “Associated”
Charged Particle Density
“Associated” densities do
not include PTmax!
Highest pT
charged particle!
Charged Particle Density: dN/dd
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
(||<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

is “associated”
more probable
to finddN
a chg
particle
look at the It
the
density,
/dd, in “min-bias” collisions (pT > 0.5
accompanying
PTmax
than
it
is to
GeV/c, || < 1).
find a particle in the central region!
Shows the data on the D dependence of the “associated” charged particle density,
dNchg/dd, for charged particles (pT > 0.5 GeV/c, || < 1, not including PTmax) relative
to PTmax (rotated to 180o) for “min-bias” events. Also shown is the average charged
particle density, dNchg/dd, for “min-bias” events.
FNAL-CMS MC Generator Meeting
June 7, 2007
Rick Field – Florida/CMS
Page 17
CDF Run 2 Min-Bias “Associated”
Rapid rise in the particle
Charged Particle Density
density in the “transverse”
region as PTmax increases!
Associated Particle Density: dN/dd
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
(||<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 -
PTmax > 0.5 GeV/c
 Shows the data on the D dependence of the “associated” charged particle density,
dNchg/dd, for charged particles (pT > 0.5 GeV/c, || < 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!).
FNAL-CMS MC Generator Meeting
June 7, 2007
Rick Field – Florida/CMS
Page 18
CDF Run 2 Min-Bias “Associated”
Charged Particle Density
PY Tune A
PTmax > 2.0 GeV/c
PTmax Direction
Direction
PTmax
D
“Toward”
“Transverse”
“Transverse”
Correlations in 
“Away”
PTmax > 2.0 GeV/c
Associated Particle Density
D
Associated Particle Density: dN/dd
1.0
CDF Preliminary
PY Tune A
0.8
data uncorrected
theory + CDFSIM
PTmax > 0.5 GeV/c
PY Tune A
Transverse
Region
0.6
PY Tune A 1.96 TeV
Transverse
Region
0.4
0.2
PTmax
PTmax not included
(||<1.0, PT>0.5 GeV/c)
0.0
0
30
60
90
120
PTmax > 0.5 GeV/c
150
180
210
240
270
300
330
360
D (degrees)
 Shows the data on the D dependence of the “associated” charged particle density,
dNchg/dd, for charged particles (pT > 0.5 GeV/c, || < 1, not including PTmax) relative
to PTmax (rotated to 180o) for “min-bias” events with PTmax > 0.5 GeV/c and PTmax >
2.0 GeV/c compared with PYTHIA Tune A (after CDFSIM).
 PYTHIA Tune A predicts a larger correlation than is seen in the “min-bias” data (i.e.
Tune A “min-bias” is a bit too “jetty”).
FNAL-CMS MC Generator Meeting
June 7, 2007
Rick Field – Florida/CMS
Page 19
Tune Summary
Outgoing Parton
“Minumum Bias” Collisions
Tevatron
LHC
PT(hard)
Initial-State Radiation
Proton
AntiProton
Proton
AntiProton
Underlying Event
Outgoing Parton
Underlying Event
Final-State
Radiation
 PYTHIA Tune DW is very similar to Tune A except that it fits the CDF PT(Z) distribution
and it uses the DØ prefered value of PARP(67) = 2.5 (determined from the dijet D
distribution).
 PYTHIA Tune DWT is identical to Tune DW at 1.96 TeV but uses the ATLAS energy
extrapolation to the LHC (i.e. PARP(90) = 0.16).
 PYTHIA Tune D6 and D6T are similar to Tune DW and DWT, respectively, but use
CTEQ6L (i.e. LHAPDF = 10042).
 PYTHIA Tune QK and QKT uses the NLO PDF CTEQ6.1M (i.e. LHAPDF = 10100 or
10150 which are the same) and use the “K-factor” to get the right amount of MPI.
Not favored at present!
FNAL-CMS MC Generator Meeting
June 7, 2007
Rick Field – Florida/CMS
Page 20
Next Round of Tunes?
Outgoing Parton
Torbjorn
“Minumum Bias” Collisions
has
made comparingLHC
tunes easy!
Tevatron
PT(hard)
Initial-State Radiation
Proton
AntiProton
Proton
AntiProton
Underlying Event
Outgoing Parton
Underlying Event
Final-State
Radiation
 I do not believe that we should continue to produce PYTHIA 6.2 tunes!
 We need one good PYTHIA 6.2 tune as a “reference tune” for the LHC (like
tune DWT) to compare with early CMS data.
 Depending on what we see early on at CMS, we might make one new PYTHIA
6.2 tune, BUT we need to start tuning the new Monde-Carlo generators
(PYTHIA 6.4, PYTHIA 8.0, Sherpa, HERWIG + JIMMY, etc.)
 We need to be able to easily validate the tunes within the CMS software
framework.
I hope Steve Mrenna will take
charge of this effort!
FNAL-CMS MC Generator Meeting
June 7, 2007
Rick Field – Florida/CMS
Page 21