MadGraph5_aMC@NLO

Discard some real emission diagrams

Asked by msadek

Hi,

I wan to discard some real emission Feynman diagrams, contributing at NLO order, just to make some tests.

So, is it possible to write a filter which discards some real emission graphs (as in the case of the loop diagrams)?

Thanks in advance,

Best regards,
Sadek

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marco zaro Edit question
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msadek
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marco zaro (marco-zaro) said : 		#1

Hi Sadek,
there is no analogous of filter for the real emissions.
One thing you can try is to remove diagrams by hand , setting the corresponding AMP(i) to zero inside the matrix_*.f files, which are the ones of the real emissions.
In order to know who is who, you can open the corresponding .ps files.

Please keep in mind that by doing so you might screw up things, starting from the IR behaviour of the real emissions...

Let me know

Cheers,

Marco

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msadek (msadek) said : 		#2

Hi Marco,

Thank you for your answer.

Yes, when I set one of the AMP(i) to zero inside matrix_*.f the IR behavior is screw up as expected. However, when I run the check pole test './check_poles' (inside SubProcesses/P0_*) all the point passed the test without any problem. As what I understand, this test compare only the IR divergent parts of the subtraction terms calculated à la FKS with the IR divergent part of the virtual contribution. Is that right?

Cheers,
Sadek

Revision history for this message
marco zaro (marco-zaro) said : 		#3

Hi Sadek,
check_poles computes the poles based on the born matrix element and on the identity of external particles. So changing the diagrams in the real emissions has no effect there (somehow it assumes that things are done correctly throughout the code…)

Best wishes,

Marco

> On 13 Feb 2021, at 10:50, msadek <email address hidden> wrote:
>
> Question #695484 on MadGraph5_aMC@NLO changed:
> https://answers.launchpad.net/mg5amcnlo/+question/695484
>
> Status: Answered => Open
>
> msadek is still having a problem:
> Hi Marco,
>
> Thank you for your answer.
>
> Yes, when I set one of the AMP(i) to zero inside matrix_*.f the IR
> behavior is screw up as expected. However, when I run the check pole
> test './check_poles' (inside SubProcesses/P0_*) all the point passed the
> test without any problem. As what I understand, this test compare only
> the IR divergent parts of the subtraction terms calculated à la FKS with
> the IR divergent part of the virtual contribution. Is that right?
>
> Cheers,
> Sadek
>
> --
> You received this question notification because you are assigned to this
> question.

Revision history for this message
msadek (msadek) said : 		#4

Thank you very much Marco.

Best regards,

Sadek