MadGraph5_aMC@NLO

Comparing Parton-Level Information from ROOT Files with MadAnalysis Plots

Asked by Gabriel Vian

ROOT files generated by MadGraph, after passing through Pythia 8 and Delphes, still contain parton-level information about the process, right? i.e. can I still plot variables (PT, Eta, Phi) from the .root file for partons?

So why do plots made by MadAnalysis give different average values than those generated by the .root file?

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Olivier Mattelaer (olivier-mattelaer) said : 		#1

parton-level information from the output of pythia8 (so the hepmc file) are not identical to the parton-level information from the input of pythia8 (so the lhe file).

This is because pythia is doing reshuffling of the momenta to put them off shell and/or ...
So yes it make sense that some plot are not the same.

Cheers,

Olivier

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Gabriel Vian (gabriel-vian-24) said : 		#2

But can I relly on the .root archive for the parton-level analysis?

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Olivier Mattelaer (olivier-mattelaer) said : 		#3

I guess it depends of the accuracy that you claim and the conclusion that you are doing/planning to do.
But those information are physical and can be plotted in a meaningful way (even if some can be quite different from the information from the lhe file).

Cheers,

Olivier

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Gabriel Vian (gabriel-vian-24) said : 		#4

So, what you mean is that I should trust more on the hepmc results, is that?

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Olivier Mattelaer (olivier-mattelaer) said : 		#5

No,

I say that both information are physical but they are not the same information, does not contain the same physics,...
Personally, I never use the information from the hepmc, but that does not mean that this should not be done.

Cheers,

Olivier

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