MadGraph5_aMC@NLO

Weights (scale, pdf) from lhe file to hepmc after showering

Asked by Zdenek Hubacek

Hi,
I'm trying to generate process p p > j j [QCD] in 2.6.3.2. I turn on the scale and PDF variations and I could see the weights in the lhe file (with correct names, etc), but after showering in Pythia8 these are not propagated to the hepmc output.
Is it possible to copy the weights by some switch?

The settings I have in the run_card.dat:
  lhapdf = pdlabel ! PDF set
  13100 = lhaid ! If pdlabel=lhapdf, this is the lhapdf number. Only
  PYTHIA8 = parton_shower
  1.0 = shower_scale_factor ! multiply default shower starting
  10 = dynamical_scale_choice ! Choose one (or more) of the predefined (my own)
#***********************************************************************
# Reweight variables for scale dependence and PDF uncertainty *
#***********************************************************************
  1.0, 2.0, 0.5 = rw_rscale ! muR factors to be included by reweighting
  1.0, 2.0, 0.5 = rw_fscale ! muF factors to be included by reweighting
  True = reweight_scale ! Reweight to get scale variation using the
            ! rw_rscale and rw_fscale factors. Should be a list of
            ! booleans of equal length to dynamical_scale_choice to
            ! specify for which choice to include scale dependence.
  True = reweight_pdf ! Reweight to get PDF uncertainty. Should be a
            ! list booleans of equal length to lhaid to specify for
            ! which PDF set to include the uncertainties.
#***********************************************************************
# Store reweight information in the LHE file for off-line model- *
# parameter reweighting at NLO+PS accuracy *
#***********************************************************************
  True = store_rwgt_info ! Store info for reweighting in LHE file
#***********************************************************************
  13101 = pdf_set_min # hidden_parameter
  13156 = pdf_set_max # hidden_parameter

Thank you,
Zdenek

Question information

Language:
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Status:
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For:
MadGraph5_aMC@NLO Edit question
Assignee:
Paolo Torrielli Edit question
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Last reply:
Revision history for this message
Zdenek Hubacek (zhubacek) said : 		#1

To add: the variations seem to work, in the summary, I get

   --------------------------------------------------------------
      Summary:
      Process p p > j j [QCD]
      Run at p-p collider (3500.0 + 3500.0 GeV)
      Number of events generated: 4000000
      Total cross section: 9.566e+05 +- 4.2e+03 pb
   --------------------------------------------------------------
      Scale variation (computed from LHE events):
          Dynamical_scale_choice 10 (envelope of 9 values):
              9.428e+05 pb +1.1% -5.1%
      PDF variation (computed from LHE events):
          CT14nlo (57 members; using hessian method):
              9.428e+05 pb +1.9% -3.1%
   --------------------------------------------------------------

The systematics module gives a different result:
INFO: #***************************************************************************
#
# original cross-section: 942520.219502
# scale variation: +-49.5% -52.6%
# central scheme variation: + 0% -54%
# PDF variation: + 0% -161%
#
# dynamical scheme # 1 : 433394 +4.53% -7.33% # \sum ET
# dynamical scheme # 2 : 433394 +4.53% -7.33% # \sum\sqrt{m^2+pt^2}
# dynamical scheme # 3 : 450057 +0.809% -4.27% # 0.5 \sum\sqrt{m^2+pt^2}
#***************************************************************************

But is it possible to have the weights for some differential cross section from the generated events?

Revision history for this message
Olivier Mattelaer (olivier-mattelaer) said : 		#2

Hi,

It is possible to make the plots on the flight without passing by the HepMC format.
See the end of the shower_card.

Cheers,

Olivier

> On 26 Sep 2018, at 21:02, Zdenek Hubacek <email address hidden> wrote:
>
> Question #674444 on MadGraph5_aMC@NLO changed:
> https://answers.launchpad.net/mg5amcnlo/+question/674444
>
> Zdenek Hubacek gave more information on the question:
> To add: the variations seem to work, in the summary, I get
>
> --------------------------------------------------------------
> Summary:
> Process p p > j j [QCD]
> Run at p-p collider (3500.0 + 3500.0 GeV)
> Number of events generated: 4000000
> Total cross section: 9.566e+05 +- 4.2e+03 pb
> --------------------------------------------------------------
> Scale variation (computed from LHE events):
> Dynamical_scale_choice 10 (envelope of 9 values):
> 9.428e+05 pb +1.1% -5.1%
> PDF variation (computed from LHE events):
> CT14nlo (57 members; using hessian method):
> 9.428e+05 pb +1.9% -3.1%
> --------------------------------------------------------------
>
> The systematics module gives a different result:
> INFO: #***************************************************************************
> #
> # original cross-section: 942520.219502
> # scale variation: +-49.5% -52.6%
> # central scheme variation: + 0% -54%
> # PDF variation: + 0% -161%
> #
> # dynamical scheme # 1 : 433394 +4.53% -7.33% # \sum ET
> # dynamical scheme # 2 : 433394 +4.53% -7.33% # \sum\sqrt{m^2+pt^2}
> # dynamical scheme # 3 : 450057 +0.809% -4.27% # 0.5 \sum\sqrt{m^2+pt^2}
> #***************************************************************************
>
> But is it possible to have the weights for some differential cross
> section from the generated events?
>
> --
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