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Monte-Carlo Generators for CMS. Discuss four NLO structure function CTEQ6.1M PYTHIA 6.2 tunes, Tune QK and Tune QKT , Tune QW and Tune QWT . . CDF Run 2. CMS . Outline of Talk. Not favored at present!. Review briefly the CDF Run 1 and Run 2 PYTHIA 6.2 tunes. UE&[email protected]

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monte carlo generators for cms
Monte-Carlo Generators for CMS
  • Discuss four NLO structure function CTEQ6.1M PYTHIA 6.2 tunes, Tune QK and Tune QKT, Tune QW and Tune QWT.

CDF Run 2

CMS

Outline of Talk

Not favored at present!

  • Review briefly the CDF Run 1 and Run 2 PYTHIA 6.2 tunes.

UE&[email protected]

Perugia, Florida, Hamburg, Trieste

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

New CTEQ6L tune!

  • Discuss a few early measurements at CMS.

Rick Field – Florida/CMS

cdf run 1 pythia tune a
CDF Run 1 PYTHIA Tune A

CDF Default!

  • 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)andSet A(PARP(67)=4)).

PYTHIA 6.206 CTEQ5L

Run 1 Analysis

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)

Rick Field – Florida/CMS

cdf run 1 p t z
CDF Run 1 PT(Z)

PYTHIA 6.2 CTEQ5L

  • 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).

UE Parameters

ISR Parameter

Vary the intrensic KT!

Intrensic KT

Rick Field – Florida/CMS

cdf run 1 p t z1
CDF Run 1 PT(Z)

Tune used by the

CDF-EWK group!

PYTHIA 6.2 CTEQ5L

  • 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).

UE Parameters

ISR Parameters

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)!

Rick Field – Florida/CMS

cdf run 1 p t z2
CDF Run 1 PT(Z)

Tune used by the

CDF-EWK group!

PYTHIA 6.2 CTEQ5L

  • 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).

UE Parameters

Also fits the high pT tail!

ISR Parameters

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)!

Rick Field – Florida/CMS

jet jet correlations d

Df Jet#1-Jet#2

Jet#1-Jet#2 Df Distribution

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).

Rick Field – Florida/CMS

cdf run 1 p t z3
CDF Run 1 PT(Z)

PYTHIA 6.2 CTEQ5L

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

UE Parameters

ISR Parameters

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!

Rick Field – Florida/CMS

transverse nchg density
“Transverse” Nchg Density

Three different amounts of MPI!

PYTHIA 6.2 CTEQ5L

  • 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).

UE Parameters

ISR Parameter

Three different amounts of ISR!

Intrensic KT

Rick Field – Florida/CMS

new pythia 6 2 tunes
New PYTHIA 6.2 Tunes

Use LO as

with L = 192 MeV!

NLO Structure Function!

K-factor

(T. Sjostrand)

UE Parameters

Tune A energy dependence!

ISR Parameter

Intrinsic KT

Rick Field – Florida/CMS

new pythia 6 2 tunes1
New PYTHIA 6.2 Tunes

Use LO as

with L = 192 MeV!

NLO Structure Function!

K-factor

(T. Sjostrand)

UE Parameters

ATLAS energy dependence!

ISR Parameter

Intrinsic KT

Rick Field – Florida/CMS

new pythia 6 2 tunes2
New PYTHIA 6.2 Tunes
  • 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.

Rick Field – Florida/CMS

new pythia 6 2 tunes3
New PYTHIA 6.2 Tunes
  • 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.

Rick Field – Florida/CMS

pythia 6 2 tunes lhc min bias predictions
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.

Rick Field – Florida/CMS

pythia 6 2 tunes lhc min bias predictions1
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| < 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)!

Rick Field – Florida/CMS

new pythia 6 2 tunes4
New PYTHIA 6.2 Tunes

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 = 10100 or 10150 which are the same).

Rick Field – Florida/CMS

the evolution of charged jets and the underlying event
The Evolution of Charged Jetsand the “Underlying Event”
  • 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.

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

Rick Field – Florida/CMS

cdf run 2 min bias associated charged particle density
CDF Run 2 Min-Bias “Associated”Charged 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 > 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.

Rick Field – Florida/CMS

cdf run 2 min bias associated charged particle density1
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” eventswith 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!).

Rick Field – Florida/CMS

cdf run 2 min bias associated charged particle density2
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” eventswith 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”).

Rick Field – Florida/CMS

tune summary

Tevatron LHC

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!

Rick Field – Florida/CMS

next round of tunes

Tevatron LHC

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!

Rick Field – Florida/CMS

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