Monte-Carlo Generators for CMS

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.

UEMB_at_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.

• Introduce a new CTEQ6L tune Tune D6 and Tune D6T.

New CTEQ6L tune!

• Discuss a few early measurements at CMS.

2
CDF Run 1 PYTHIA Tune A
CDF Default!
PYTHIA 6.206 CTEQ5L
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
Run 1 Analysis

• Plot shows the transverse charged particle
  density versus PT(chgjet1) 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)
Old PYTHIA default (more initial-state radiation)
New PYTHIA default (less initial-state radiation)
New PYTHIA default (less initial-state radiation)
3
CDF Run 1 PT(Z)
PYTHIA 6.2 CTEQ5L
UE Parameters
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
PARP(89) 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

• Shows the Run 1 Z-boson pT distribution (ltpT(Z)gt
  11.5 GeV/c) compared with PYTHIA Tune A
  (ltpT(Z)gt 9.7 GeV/c), Tune A25 (ltpT(Z)gt
  10.1 GeV/c), and Tune A50 (ltpT(Z)gt 11.2
  GeV/c).

Vary the intrensic KT!
Intrensic KT
4
CDF Run 1 PT(Z)
Tune used by the CDF-EWK group!
PYTHIA 6.2 CTEQ5L
Parameter Tune A Tune AW
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
UE Parameters
ISR Parameters

• Shows the Run 1 Z-boson pT distribution (ltpT(Z)gt
  11.5 GeV/c) compared with PYTHIA Tune A
  (ltpT(Z)gt 9.7 GeV/c), and PYTHIA Tune AW
  (ltpT(Z)gt 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)!
5
CDF Run 1 PT(Z)
Tune used by the CDF-EWK group!
PYTHIA 6.2 CTEQ5L
Parameter Tune A Tune AW
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
UE Parameters
Also fits the high pT tail!
ISR Parameters

• Shows the Run 1 Z-boson pT distribution (ltpT(Z)gt
  11.5 GeV/c) compared with PYTHIA Tune A
  (ltpT(Z)gt 9.7 GeV/c), and PYTHIA Tune AW
  (ltpT(Z)gt 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)!
6
Jet-Jet Correlations (DØ)

• 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).

7
CDF Run 1 PT(Z)
PYTHIA 6.2 CTEQ5L
Parameter Tune DW Tune AW
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
UE Parameters
ISR Parameters

• Shows the Run 1 Z-boson pT distribution (ltpT(Z)gt
  11.5 GeV/c) compared with PYTHIA Tune DW, and
  HERWIG.

Tune DW uses D0s perfered value of PARP(67)!
Intrensic KT
Tune DW has a lower value of PARP(67) and
slightly more MPI!
8
Transverse Nchg Density
Three different amounts of MPI!
PYTHIA 6.2 CTEQ5L
UE Parameters
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
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 1.0
MSTP(91) 1 1 1
PARP(91) 2.5 2.5 2/5
PARP(93) 15.0 15.0 15.0
ISR Parameter

• Shows the transverse charged particle density,
  dN/dhdf, versus PT(jet1) 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
9
New PYTHIA 6.2 Tunes
Use LO as with L 192 MeV!
NLO Structure Function!
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
K-factor (T. Sjostrand)
UE Parameters
Tune A energy dependence!
ISR Parameter
Intrinsic KT
10
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 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
K-factor (T. Sjostrand)
UE Parameters
ATLAS energy dependence!
ISR Parameter
Intrinsic KT
11
New PYTHIA 6.2 Tunes
1.96 TeV 1.96 TeV 14 TeV 14 TeV
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

• Average charged particle density and PTsum
  density in the transverse region (pT gt 0.5
  GeV/c, h lt 1) versus PT(jet1) at 1.96 TeV for
  PY Tune DW, Tune D6, and Tune QK.

12
New PYTHIA 6.2 Tunes
1.96 TeV 1.96 TeV 14 TeV 14 TeV
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

• Average charged particle density and PTsum
  density in the transverse region (pT gt 0.5
  GeV/c, h lt 1) versus PT(jet1) at 14 TeV for PY
  Tune DWT, Tune D6T, and Tune QKT.

13
PYTHIA 6.2 TunesLHC 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.

14
PYTHIA 6.2 TunesLHC 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 lt 1) and
  the average number of charged particles with pT gt
  pTmin (h lt 1).

• The ATLAS tune has many more soft particles
  than does any of the CDF Tunes. The ATLAS tune
  has ltpTgt 548 MeV/c while Tune A has ltpTgt 641
  MeV/c (100 MeV/c more per particle)!

15
New PYTHIA 6.2 Tunes
14 TeV (pT gt 0.5 GeV/c, h lt 1) 14 TeV (pT gt 0.5 GeV/c, h lt 1) 14 TeV (pT gt 0.5 GeV/c, h lt 1)
ltNchggt ltPTsumgt (GeV/c) ltPTgt (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
Numbers for pT gt 0.5 GeV/c, h lt 1.
We now have CTEQ6L Tune D6T!

• PseudoRapidity distribution, dN/dh, for charged
  particles with pT gt 0.5 GeV/c at 14 TeV for PY
  Tune DWT, Tune D6T, and Tune QKT. Note this is
  hard core (i.e. MSEL1, 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).

16
The Evolution of Charged Jetsand the Underlying
Event
Charged Particle Df Correlations PT gt 0.5 GeV/c
h lt 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 lt 60o as Toward, 60o lt Df lt 120o
  as Transverse, and Df gt 120o as Away.
• All three regions have the same size in h-f
  space, DhxDf 2x120o 4p/3.

17
CDF Run 2 Min-Bias AssociatedCharged Particle
Density
Associated densities do not include PTmax!
Highest pT charged particle!

• 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 gt 0.5 GeV/c, h lt 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 gt 0.5
  GeV/c, h lt 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.

18
CDF Run 2 Min-Bias AssociatedCharged Particle
Density
Rapid rise in the particle density in the
transverse region as PTmax increases!
PTmax gt 2.0 GeV/c
Transverse Region
Transverse Region
Ave Min-Bias 0.25 per unit h-f
PTmax gt 0.5 GeV/c

• Shows the data on the Df dependence of the
  associated charged particle density,
  dNchg/dhdf, for charged particles (pT gt 0.5
  GeV/c, h lt 1, not including PTmax) relative to
  PTmax (rotated to 180o) for min-bias events
  with PTmax gt 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!).

19
CDF Run 2 Min-Bias AssociatedCharged Particle
Density
PY Tune A
PTmax gt 2.0 GeV/c
Transverse Region
Transverse Region
PTmax gt 0.5 GeV/c

• Shows the data on the Df dependence of the
  associated charged particle density,
  dNchg/dhdf, for charged particles (pT gt 0.5
  GeV/c, h lt 1, not including PTmax) relative to
  PTmax (rotated to 180o) for min-bias events
  with PTmax gt 0.5 GeV/c and PTmax gt 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).

20
Tune Summary

• 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 10100 or 10150 which are the same)
  and use the K-factor to get the right amount of
  MPI.

Not favored at present!
21
Next Round of Tunes?
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!