MadGraph5_aMC@NLO

Definition of mixh in 2HDMtypeII model & alignment limit setup

Asked by Hui-Chi Lin on 2023-10-16

Dear Experts,

We are trying to generate ttH/A->tttt events with 2HDMtypeII model [1] at the alignment limit ( sin(beta-alpha)=1 ). We plan to fix tan(beta) to a certain value, and adjust "mixh" to achieve the alignment limit.

However, we are not sure the definition of the "mixh" parameter. Is that mixh=alpha?
We also wonder if there's any reference for this 2HDMtypeII model.

In addition, we are seeking recommendations of setting "dynamical_scale_choice" and "bwcutoff" in the 2HDMtypeII model.

Thank you very much!

Best regards,
Hui-Chi

[1] https://github.com/philippgadow/atlas-run3-multitops-bsm-joboptions/blob/main/models/2HDMtypeII/parameters.py

Question information

Language:: English Edit question

Status:: Answered

For:: MadGraph5_aMC@NLO Edit question

Assignee:: No assignee Edit question

Last query:: 2023-10-16

Last reply:: 2023-10-16

Link existing bug

Revision history for this message

Olivier Mattelaer (olivier-mattelaer) said on 2023-10-16:

Hi,

I'm not a 2HDM expert and I do not know that particular model implementation.
Do you have the arxiv number or web page documenting the model?

The only comment that I can do is that in your model mixh is a free parameter.

Concerning dynamical_scale_choice.
My typical advise is to use the default (so based on CKKW merging scale). This is typically providing suitable scale in most situation.
If it does not then this is likely very process specific and I certainly not have enough information to help.

For bwcutoff, this should be set such that narrow width approximation stay under control (and that gauge invariance is not too much broken by neglecting non resonant diagram). So this highly depend of the mass spectrum and of the width of each particle.
Our default is designed for the standard model (and already quite large to my point of view since this has to be reduced for ZZ/WW production for example to avoid issue with onshell Higgs). In general, keeping the default makes sense in general but obviously they are also cases where you have to reduce that value (like if the width is close or higher than M/bwcutoff).
Again difficult to be more precise.

Cheers,

Olivier

Revision history for this message

Hui-Chi Lin (huichilin) said on 2023-10-17:

Dear Olivier,

Thanks for your reply!

We also can't find the official documentation of this model, but only found a paper that mentions "mixh" (Table 3 in [1]).
We are not sure if the definition in this paper is consistent with this model.

Thank you!

Best,
Hui-Chi

[1] https://arxiv.org/pdf/1406.3030.pdf