MadGraph5_aMC@NLO

Contribution of individual diagrams

Asked by Daniel Schieber

Hello,

I am currently working on trilinear Higgs couplings. Therefore, I generate e+ e- > z h h, which gives me 4 diagrams, with one of them having the Higgs self coupling. Now I would like to know if I am launching for example 1000 Events, is there a way to find out, how much each diagram contributed? So the self coupling one was 200 events and so on.
Thank you very much.

Daniel

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Olivier Mattelaer (olivier-mattelaer) said : 		#1

Hi,

Such question can have multiple answer, depending on the exact definition that you take for "how much a diagram contributed".
One way is to generate only that diagram and then compare to the full cross-section.
Another is to generate everything but that diagram and compare to the full cross-section. (which then includes all the interference effect related to that diagram).

One way to have an estimator without having to have a dedicated run, is to use the detailed information about channel cross-section and use the following link to make the link between the reported cross-section and the "lead" Feynman diagram :
see https://answers.launchpad.net/mg5amcnlo/+question/187387

Obviously this will provide three different number, event if you do have (or assume) that you do not have gauge invariance issue when putting the diagram out.

Cheers,

Olivier

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