MadGraph5_aMC@NLO

anti top decay to muon and charm

Asked by Nitin Sethi

Hello all,

I am new to madgraph and I am trying to generate p p > t t~,(t > W+ b, W+ > l+ vl), (t~ > mu+ mu- c~).
I keep getting the error
No amplitudes generated from process Process: t~ > mu+ mu- c~ WEIGHTED=606. Please enter a valid process.

I am using the model SMEFTsim_top_MwScheme_PropCorr_UFO. I tried changing the SMEFT parameter in the param card but it is still no use.

Does anyone have any advice on what I can try?

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Olivier Mattelaer (olivier-mattelaer) said : 		#1

Hi,

I do not know that UFO model, so I can only help you on a quite generic level, I hope it will be usefull anyway.

Which Feynman diagram do you expect? (a four fermion vertex?)
Did you use the "display interactions mu+ mu- " to check the list of interactions with mu+ mu-.

The likely problem is that your model does not include the Feynman Diagram that you are looking for.
(and/or you use a restriction (can be the default one) which has remove that interactions from your model).

If this is a restriction you can try
import model SMEFTsim_top_MwScheme_PropCorr_UFO-full

If even that one does not work, then you should change the UFO model to use one that include the operator that you are looking for.

Cheers,

Olivier

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Nitin Sethi (nitin-1224) said : 		#2

Thanks @Oliver,

I checked interactions and I had several interactions with mu+ mu- c~ c. Does this mean that the diagram is present in the model ?
Please let me know

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Olivier Mattelaer (olivier-mattelaer) said : 		#3

You need to check the type of the interactions, if they are of type R2 (or any type of loop-counterterm) then it means that no you do not have that interaction at tree level.

Cheers,

Olivier

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