MadGraph5_aMC@NLO

How to Display Feynman Diagrams from MadSpin Process

Asked by Braden Allmond

Hello,

What is the proper syntax to generate Feynman diagrams from a MadSpin process?

I’ve used these commands

#   import model loop_sm-no_b_mass
#   define p = p b b~
#   define j = j b b~
#   generate p p > h [QCD]
#   display diagrams ./

which generated two diagrams (gg->top-loop->Higgs).

Then, I decay the Higgs via madSPIN with a UFO model that allows for H -> tau+ tau- photon.
I would like to use Madgraph’s Feynman diagram generator to make the Feynman diagram for the H -> tau+ tau- photon process. Is this possible?

I have already tried generating 10 events with that process and simply using the command
display diagrams ./

which results in this error

MG5_aMC>display diagrams ./
Drawing Process: g g > h WEIGHTED<=4 [ noborn = QCD ]
Command "display diagrams ./" interrupted with error:
IndexError : list index out of range
Please report this bug on https://bugs.launchpad.net/mg5amcnlo
More information is found in 'MG5_debug'.
Please attach this file to your report.

I am 100% sure I am generating the process I expect, I just want consistent visual aid styling :)

Thanks in advance

-Braden

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Olivier Mattelaer (olivier-mattelaer) said : 		#1

Hi,

Since you are in madspin mode "none", we never generate the full matrix-element (we are actually not able to generate such diagram for the moment). And therefore since we can not generate it, we are not able to display it.

Cheers,

Olivier

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