MadGraph5_aMC@NLO

InertDoublet model with complex mass scheme

Asked by Halley_X

Hi,

I generate a process with InertDoublet_UFO model, and I prepare to use complex mass scheme because there are unstable particles in my process. But when I set cms true, the decay width in param_card.dat is zero and cannot be changed. So I would like to know how can I change decay width in this situation. Thanks.

Sincerely,
Halley

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Olivier Mattelaer (olivier-mattelaer) said : 		#1

Hi,

I guess that you are using an old version of the code that is not supported since I do not have the same behavior than you with the two supported version (the Long term stable 2.9.12 or the latest feature release version 3.4.1).

Actually in both case, that particular model fails to be in the complex mass scheme. I'm going to investigate and see why this is the case, but not all model are compatible with the complex mass scheme so it might be that such model is not compatible with such mode (will see if this is the case or not).

Cheers,

Olivier

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Olivier Mattelaer (olivier-mattelaer) said : 		#2

Ok fix the "bug" in those two versions: https://github.com/mg5amcnlo/mg5amcnlo/commit/5c573f1ebd348cdb3e033f39d0593ad4efa49b34

But indeed that model does not follow any standard convention and therefore they are no way for such model that the command
set complex_mass_scheme T can achieve anything meaningful for such model.

Cheers,

Olivier

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Halley_X (neuromance) said : 		#3

Thanks. But if I don't use cms, I can see the decay width in param_card. In the idm model, if it use a default scheme like fixed width scheme when there are unstable particles in the process?

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Olivier Mattelaer (olivier-mattelaer) said : 		#4

Yes that fix width scheme i the only scheme supported by that UFO model

Cheers,

Olivier

> On 27 Oct 2022, at 12:20, Halley_X <email address hidden> wrote:
>
> Question #703605 on MadGraph5_aMC@NLO changed:
> https://answers.launchpad.net/mg5amcnlo/+question/703605
>
> Status: Answered => Open
>
> Halley_X is still having a problem:
> Thanks. But if I don't use cms, I can see the decay width in param_card.
> In the idm model, if it use a default scheme like fixed width scheme
> when there are unstable particles in the process?
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

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Halley_X (neuromance) said : 		#5

Understood. Thanks, Olivier.

Halley