How does Madgraph/Delphes calculate final particles

> By specifying the above it seems that we only have S4 in the final state together with SM particles , but no decays of S4

That’s correct. (you can also ask the decay inside MG in order to have the decay at that level)

If the decay is not done internally to MG (like in your syntax) pythia is going to decay those.
For that you need to run with a param_card containing the Branching ratio table. If you put the width to “Auto” then this table is created automatically
(See arXiv:1402.1178)

Delphes is not going to perform any decay. For more detail on Delphes, I would suggest that you contact Delphes author:
https://cp3.irmp.ucl.ac.be/projects/delphes/report/1

Cheers,

Olivier

On 16 Jun 2015, at 10:01, guy pitman <email address hidden> wrote:

> New question #268199 on MadGraph5_aMC@NLO:
> https://answers.launchpad.net/mg5amcnlo/+question/268199
>
> I have a process
> generate p p > S4
> add process p p > S4 j
> add process p p > S4 j j
>
> where S4 is a majorana Fermion which can decay to SM fermions and DM
>
> By specifying the above it seems that we only have S4 in the final state together with SM particles , but no decays of S4
>
> We then use Pythia with jet matching , running into Delphes. The final particles will include S4 in each case - but in the Delphes simulation would the S4 Fermions be removed from the output where they would have decayed? Ie if we add processes with S4 decaying , these would include the above, and the output would bot have these final state S4s in the output?
>
> Thank you
>
> --
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> contact for MadGraph5_aMC@NLO.

Thank you - this answered my question