separate off-shell and on-shell decay process

Asked by Murat on 2020-02-19

Does process

generate p p > t t~ > b b~ l+ l- vl vl~

can be divided into on-shell decay process

generate p p > t t~ , t > b l+ vl, t~ > b~ l- vl~

and off-shell decay process

generate p p > t t~ > b b~ l+ l- vl vl~ $ t
generate p p > t t~ > b b~ l+ l- vl vl~ $ t~
generate p p > t t~ > b b~ l+ l- vl vl~ $ t t~

I want to deal with the decay of the t and tbar separately.

Question information

Language:
English Edit question
Status:
Answered
For:
MadGraph5_aMC@NLO Edit question
Assignee:
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Last query:
2020-02-19
Last reply:
2020-02-19

Hi,

I'm feeling uncomfortabel to speak about the off-shell part of
> generate p p > t t~ > b b~ l+ l- vl vl~
since this syntax forces one top and one anti-top to be in s-channel.
If they are offshell what is the meaning to ask for that?

I would rather speak aboout
> generate p p > b b~ l+ l- vl vl~
which can be split to the onshell contribution
> generate p p > t t~ , t > b l+ vl, t~ > b~ l- vl~

and to the rest
> generate p p > b b~ l+ l- vl vl~ $ t t~

Note that for the last one using fix-width scheme for the propagator is not the most appropriate method (since it breaks gauge invariance and lorentz invariance) so in that case it is better to use complex mass scheme for the computation (set complex_mass True)

You can see this proceedings for more details: http://prometeo.sif.it/papers/?pid=ncc10760 <http://prometeo.sif.it/papers/?pid=ncc10760>

> and off-shell decay process

> generate p p > t t~ > b b~ l+ l- vl vl~ $ t t~

This would be the syntax that technically correspond to your request

Cheers,

Olivier

> On 19 Feb 2020, at 05:47, Murat <email address hidden> wrote:
>
> New question #688861 on MadGraph5_aMC@NLO:
> https://answers.launchpad.net/mg5amcnlo/+question/688861
>
> Does process
>
> generate p p > t t~ > b b~ l+ l- vl vl~
>
> can be divided into on-shell decay process
>
> generate p p > t t~ , t > b l+ vl, t~ > b~ l- vl~
>
> and off-shell decay process
>
> generate p p > t t~ > b b~ l+ l- vl vl~ $ t
> generate p p > t t~ > b b~ l+ l- vl vl~ $ t~
> generate p p > t t~ > b b~ l+ l- vl vl~ $ t t~
>
> I want to deal with the decay of the t and tbar separately.
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

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