MadGraph5_aMC@NLO

bilinear interactions

Asked by Giacomo

I'd like to model the interaction of a vector meson with a photon, say. I'm doing this by implementing a bilinear term in the UFO file that involves the photon and meson. When I then try to look at a decay of the meson to an electron-positron pair mediated by the photon, I am told 'No amplitudes generated from process'. Does MadGraph accept such bilinear interactions in a UFO file, or will I have to rediagonalise everything to get rid of them?

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Olivier Mattelaer
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Olivier Mattelaer (olivier-mattelaer) said : 		#1

Is it a 2 point interaction?

> On 16 Oct 2020, at 19:00, Giacomo <email address hidden> wrote:
>
> New question #693491 on MadGraph5_aMC@NLO:
> https://answers.launchpad.net/mg5amcnlo/+question/693491
>
> I'd like to model the interaction of a vector meson with a photon, say. I'm doing this by implementing a bilinear term in the UFO file that involves the photon and meson. When I then try to look at a decay of the meson to an electron-positron pair through mediated by the photon, I am told 'No amplitudes generated from process'. Does MadGraph accept such bilinear interactions in a UFO file, or will I have to rediagonalise everything to get rid of them?
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

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Giacomo (gmarocco) said : 		#2

Yes it is.

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Best Olivier Mattelaer (olivier-mattelaer) said : 		#3

Then indeed 2 point interaction are not supported in mG5aMC.

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Giacomo (gmarocco) said : 		#4

Ok, thank you Olivier.

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Giacomo (gmarocco) said : 		#5

Thanks Olivier Mattelaer, that solved my question.