Regenate weighted events

Asked by Kanhaiya Gupta

Dear Experts,

I am trying to generate weighted events using the command ./bin/mg5_aMC event_file.txt in MadGraph. Everything runs perfect but the lhe output seems to be unweighted. I have not generated weighted events before.

The contents inside the event_file.txt

generate p p > z WEIGHTED<=4
output test_Weight
launch
shower=Pythia8
reweight=ON
set nevents 2000
edit reweight_card --before_line='launch' change mode LO
edit reweight_card --before_line='launch' change output 2.0.
edit reweight_card --before_line='launch' change model loop_sm-no_b_mass
edit reweight_card --before_line='launch' change process u u~ > z [sqrvirt=QCD]
edit reweight_card --before_line='launch' change process d d~ > z [sqrvirt=QCD] --add
edit reweight_card --before_line='launch' change process c c~ > z [sqrvirt=QCD] --add
edit reweight_card --before_line='launch' change process s s~ > z [sqrvirt=QCD] --add
edit reweight_card --before_line='launch' change process b b~ > z [sqrvirt=QCD] --add
launch

Best
Kanhaiya Gupta

Question information

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Olivier Mattelaer (olivier-mattelaer) said :
#1

Well it should be no?
This is 2>1 process, so by symmetry this is the same as 1>2 body decay.
and due to lorentz invariance, those matrix-element are just constant.
So the generated events should indeed be unweighted.

Cheers,

Olivier

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