Can't find diagrams for a Top decay process

Depending of your model

1) b quark can be part of the proton definition or not (they are if they are consider massless)
(In your case they are massive and not include in the proton definiton)

2) The CKM can be diagonal (or not). For pheno study it makes a lot of sense to put those diagonal to fasten the computation. (In your case it seems to be diagonal)

Cheers,

Olivier

> On 20 Oct 2018, at 23:52, Mario Alberto Werle Barela <email address hidden> wrote:
>
> New question #675412 on MadGraph5_aMC@NLO:
> https://answers.launchpad.net/mg5amcnlo/+question/675412
>
> I'm new to MadGraph (and to Particle Physics, for that matter) so sorry if it is a stupid question.
>
> I'm trying to generate the process
>
> generate t > p l+ vl
>
> and am getting the error
>
> Command "generate t > p l+ vl QCD^2=2" interrupted with error:
> NoDiagramException : No amplitudes generated from process Process: t > g/u/c/d/s/u~/c~/d~/s~ e+/mu+ ve/vm/vt QCD=2 QCD^2<=2 @1. Please enter a valid process
>
> What is the problem?
>
> Thank you very much!
>
> Regards,
> Mario Barela
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

Adding the bottom to a multiparticle call solved my problem!

Now, another question that may be far too broad (and probably innapropriate to be posted here): when would I want to use MadSpin?