1. Monte-Carlo Generators for CMS
CDF Run 2
CMS
Outline of Talk
Not favored at present!
Review briefly the CDF Run 1 and Run 2 PYTHIA 6.2 tunes.
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.
Introduce a new CTEQ6L tune Tune D6 and Tune D6T.
New CTEQ6L tune!
Discuss a few early measurements at CMS.
FNAL-CMS MC Generator Meeting June 7, 2007
Rick Field – Florida/CMS

2. CDF Run 1 PYTHIA Tune A PYTHIA 6.206 CTEQ5L
CDF Default!
PYTHIA CTEQ5L
Parameter
Tune B
Tune A
MSTP(81) 1
MSTP(82) 4
PARP(82)
1.9 GeV
2.0 GeV
PARP(83)
0.5
PARP(84)
0.4
PARP(85)
1.0
0.9
PARP(86)
0.95
PARP(89)
1.8 TeV
PARP(90)
0.25
PARP(67)
4.0
Run 1 Analysis
Plot shows the “transverse” charged particle density versus PT(chgjet#1) compared to the QCD hard scattering predictions of two tuned versions of PYTHIA (CTEQ5L, Set B (PARP(67)=1) and Set A (PARP(67)=4)).
Old PYTHIA default
(more initial-state radiation)
Old PYTHIA default
(more initial-state radiation)
New PYTHIA default
(less initial-state radiation)
New PYTHIA default
(less initial-state radiation)
FNAL-CMS MC Generator Meeting June 7, 2007
Rick Field – Florida/CMS

3. Rick Field – Florida/CMS
CDF Run 1 PT(Z)
PYTHIA 6.2 CTEQ5L
UE Parameters
Parameter
Tune A
Tune A25
Tune A50
MSTP(81) 1
MSTP(82) 4
PARP(82)
2.0 GeV
PARP(83)
0.5
PARP(84)
0.4
PARP(85)
0.9
PARP(86)
0.95
PARP(89)
1.8 TeV
PARP(90)
0.25
PARP(67)
4.0
MSTP(91)
PARP(91)
1.0
2.5
5.0
PARP(93)
15.0
25.0
ISR Parameter
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
Rick Field – Florida/CMS

4. CDF Run 1 PT(Z) PYTHIA 6.2 CTEQ5L
Tune used by the
CDF-EWK group!
PYTHIA 6.2 CTEQ5L
Parameter
Tune A
Tune AW
MSTP(81) 1
MSTP(82) 4
PARP(82)
2.0 GeV
PARP(83)
0.5
PARP(84)
0.4
PARP(85)
0.9
PARP(86)
0.95
PARP(89)
1.8 TeV
PARP(90)
0.25
PARP(62)
1.0
1.25
PARP(64)
0.2
PARP(67)
4.0
MSTP(91)
PARP(91)
2.1
PARP(93)
5.0
15.0
UE Parameters
ISR Parameters
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

5. CDF Run 1 PT(Z) PYTHIA 6.2 CTEQ5L
Tune used by the
CDF-EWK group!
PYTHIA 6.2 CTEQ5L
Parameter
Tune A
Tune AW
MSTP(81) 1
MSTP(82) 4
PARP(82)
2.0 GeV
PARP(83)
0.5
PARP(84)
0.4
PARP(85)
0.9
PARP(86)
0.95
PARP(89)
1.8 TeV
PARP(90)
0.25
PARP(62)
1.0
1.25
PARP(64)
0.2
PARP(67)
4.0
MSTP(91)
PARP(91)
2.1
PARP(93)
5.0
15.0
UE Parameters
Also fits the high pT tail!
ISR Parameters
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

6. Jet-Jet Correlations (DØ)
Df Jet#1-Jet#2
Jet#1-Jet#2 Df Distribution
MidPoint Cone Algorithm (R = 0.7, fmerge = 0.5)
L = 150 pb-1 (Phys. Rev. Lett (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

7. CDF Run 1 PT(Z) PYTHIA 6.2 CTEQ5L
Parameter
Tune DW
Tune AW
MSTP(81) 1
MSTP(82) 4
PARP(82)
1.9 GeV
2.0 GeV
PARP(83)
0.5
PARP(84)
0.4
PARP(85)
1.0
0.9
PARP(86)
0.95
PARP(89)
1.8 TeV
PARP(90)
0.25
PARP(62)
1.25
PARP(64)
0.2
PARP(67)
2.5
4.0
MSTP(91)
PARP(91)
2.1
PARP(93)
15.0
UE Parameters
ISR Parameters
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

8. “Transverse” Nchg Density
PYTHIA 6.2 CTEQ5L
Three different amounts of MPI!
UE Parameters
Parameter
Tune AW
Tune DW
Tune BW
MSTP(81) 1
MSTP(82) 4
PARP(82)
2.0 GeV
1.9 GeV
1.8 GeV
PARP(83)
0.5
PARP(84)
0.4
PARP(85)
0.9
1.0
PARP(86)
0.95
PARP(89)
1.8 TeV
PARP(90)
0.25
PARP(62)
1.25
PARP(64)
0.2
PARP(67)
4.0
2.5
MSTP(91)
PARP(91)
2/5
PARP(93)
15.0
ISR Parameter
Shows the “transverse” charged particle density, dN/dhdf, 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!
Intrensic KT
FNAL-CMS MC Generator Meeting June 7, 2007
Rick Field – Florida/CMS

9. NLO Structure Function! Tune A energy dependence!
New PYTHIA 6.2 Tunes
Use LO as
with L = 192 MeV!
Parameter
Tune DW
Tune D6
Tune QW
Tune QK
PDF
CTEQ5L
CTEQ6L
CTEQ6.1
MSTP(2) 1
MSTP(33)
PARP(31)
1.0
1.8
MSTP(81)
MSTP(82) 4
PARP(82)
1.9 GeV
1.8 GeV
1.1 GeV
PARP(83)
0.5
PARP(84)
0.4
PARP(85)
PARP(86)
PARP(89)
1.8 TeV
PARP(90)
0.25
PARP(62)
1.25
PARP(64)
0.2
PARP(67)
2.5
MSTP(91)
PARP(91)
2.1
PARP(93)
15.0
NLO Structure Function!
K-factor
(T. Sjostrand)
UE Parameters
Tune A energy dependence!
ISR Parameter
Intrinsic KT
FNAL-CMS MC Generator Meeting June 7, 2007
Rick Field – Florida/CMS

10. NLO Structure Function! ATLAS energy dependence!
New PYTHIA 6.2 Tunes
Use LO as
with L = 192 MeV!
NLO Structure Function!
Parameter
Tune DWT
ATLAS
Tune D6T
Tune QWT
Tune QKT
PDF
CTEQ5L
CTEQ6L
CTEQ6.1
MSTP(2) 1
MSTP(33)
PARP(31)
1.0
1.8
MSTP(81)
MSTP(82) 4
PARP(82)
GeV
1.8 GeV
GeV
GeV
PARP(83)
0.5
PARP(84)
0.4
PARP(85)
0.33
PARP(86)
0.66
PARP(89)
1.96 TeV
1.0 TeV
PARP(90)
0.16
PARP(62)
1.25
PARP(64)
0.2
PARP(67)
2.5
MSTP(91)
PARP(91)
2.1
PARP(93)
15.0
5.0
K-factor
(T. Sjostrand)
UE Parameters
ATLAS energy dependence!
ISR Parameter
Intrinsic KT
FNAL-CMS MC Generator Meeting June 7, 2007
Rick Field – Florida/CMS

11. Rick Field – Florida/CMS
New PYTHIA 6.2 Tunes
1.96 TeV
14 TeV
PT0(MPI) GeV
s(MPI) mb
Tune DW
1.9409
351.7
3.1730
549.2
Tune DWT
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
2.5184
786.5
Tune QK
259.5
422.0
Tune QKT
588.0
Average charged particle density and PTsum density in the “transverse” region (pT > 0.5 GeV/c, |h| < 1) versus PT(jet#1) at 1.96 TeV for PY Tune DW, Tune D6, and Tune QK.
FNAL-CMS MC Generator Meeting June 7, 2007
Rick Field – Florida/CMS

12. Rick Field – Florida/CMS
New PYTHIA 6.2 Tunes
1.96 TeV
14 TeV
PT0(MPI) GeV
s(MPI) mb
Tune DW
1.9409
351.7
3.1730
549.2
Tune DWT
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
2.5184
786.5
Tune QK
259.5
422.0
Tune QKT
588.0
Average charged particle density and PTsum density in the “transverse” region (pT > 0.5 GeV/c, |h| < 1) versus PT(jet#1) at 14 TeV for PY Tune DWT, Tune D6T, and Tune QKT.
FNAL-CMS MC Generator Meeting June 7, 2007
Rick Field – Florida/CMS

13. PYTHIA 6.2 Tunes LHC Min-Bias Predictions
Shows the predictions of PYTHIA Tune A, Tune DW, Tune DWT, and the ATLAS tune for the charged particle density dN/dh and dN/dY at 14 TeV (all pT).
PYTHIA Tune A and Tune DW predict about 6 charged particles per unit h at h = 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

14. PYTHIA 6.2 Tunes LHC Min-Bias Predictions
Shows the predictions of PYTHIA Tune A, Tune DW, Tune DWT, and the ATLAS tune for the charged particle pT distribution at 14 TeV (|h| < 1) and the average number of charged particles with pT > pTmin (|h| < 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

15. New PYTHIA 6.2 Tunes We now have CTEQ6L Tune D6T!
14 TeV (pT > 0.5 GeV/c, |h| < 1)
<Nchg>
<PTsum>
(GeV/c)
<PT>
Tune DWT
6.268
7.091
1.131
Tune D6T
5.743
6.467
1.126
Tune QKT
5.361
6.115
0.982
Numbers for pT > 0.5 GeV/c, |h| < 1.
We now have CTEQ6L
Tune D6T!
PseudoRapidity distribution, dN/dh, 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 = or which are the same).
FNAL-CMS MC Generator Meeting June 7, 2007
Rick Field – Florida/CMS

16. The Evolution of Charged Jets and the “Underlying Event”
Charged Particle Df Correlations PT > 0.5 GeV/c |h| < 1
Look at the charged particle density in the “transverse” region!
“Transverse” region very sensitive to the “underlying event”!
CDF Run 1 Analysis
Look at charged particle correlations in the azimuthal angle Df relative to the leading charged particle jet.
Define |Df| < 60o as “Toward”, 60o < |Df| < 120o as “Transverse”, and |Df| > 120o as “Away”.
All three regions have the same size in h-f space, DhxDf = 2x120o = 4p/3.
FNAL-CMS MC Generator Meeting June 7, 2007
Rick Field – Florida/CMS

17. CDF Run 2 Min-Bias “Associated” Charged Particle Density
Highest pT charged particle!
“Associated” densities do not include PTmax!
Use the maximum pT charged particle in the event, PTmax, to define a direction and look at the the “associated” density, dNchg/dhdf, in “min-bias” collisions (pT > 0.5 GeV/c, |h| < 1).
It is more probable to find a particle accompanying PTmax than it is to find a particle in the central region!
Shows the data on the Df dependence of the “associated” charged particle density, dNchg/dhdf, 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/dhdf, for “min-bias” events.
FNAL-CMS MC Generator Meeting June 7, 2007
Rick Field – Florida/CMS

18. CDF Run 2 Min-Bias “Associated” Charged Particle Density
Rapid rise in the particle density in the “transverse” region as PTmax increases!
PTmax > 2.0 GeV/c
Transverse Region
Transverse Region
Ave Min-Bias
0.25 per unit h-f
PTmax > 0.5 GeV/c
Shows the data on the Df dependence of the “associated” charged particle density, dNchg/dhdf, 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!).
FNAL-CMS MC Generator Meeting June 7, 2007
Rick Field – Florida/CMS

19. CDF Run 2 Min-Bias “Associated” Charged Particle Density
PY Tune A
PTmax > 2.0 GeV/c
Transverse Region
Transverse Region
PTmax > 0.5 GeV/c
Shows the data on the Df dependence of the “associated” charged particle density, dNchg/dhdf, 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 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

20. Rick Field – Florida/CMS
Tune Summary
Tevatron LHC
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 Df 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 = or 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

21. I hope Steve Mrenna will take
Next Round of Tunes?
Tevatron LHC
Torbjorn has made comparing tunes easy!
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