changing coupling

You can change the value of the param_card, which should impact the value of the coupling(s).

Cheers,

Olivier

I did, I used the same benchmark points in the paper, but I did not get the same results.

so cannot I change the couplings?

You can hack the MODEL directory if you want to, but then you need to be careful (especially at NLO) that you edit the coupling value in a consistent way. (especially at NLO, you need to be carefull about all counterterm, finite piece of the loop, ...)

Cheers,

Olivier

Thank you Olivier

Good morning
I have a question related to this point.

I am working on 2HDMtII_NLO model, studying the decay h3 > h1 z
( h3 = A Higgs boson, h1 = the SM Higgs)

in the coupling.py file of the model there are many couplings their values are functions. For example
GC_140 = Coupling(name = 'GC_140',
                  value = '-(cw*g1*TH2x1*TH3x3)/2. + (gw*sw*TH2x1*TH3x3)/2.',
                  order = {'QED':1})

Can I change the value to a number? I mean like this
Coupling(name = 'GC_140',
                  value = '1.36074468e-01',
                  order = {'QED':1})
or Madgraph will calculate them while it is running the process?

I will calculate the coupling values in 2HDMC code.

best regards

Hi,

> Can I change the value to a number? I mean like this
> Coupling(name = 'GC_140',
> value = '1.36074468e-01',
> order = {'QED':1})

This is a valid UFO syntax so you can do that.

Now It is likely not a smart thing to do
1) It is not clear to me that the value that you have to put here match the one of the 2HDMC code.
it is highly possible that the internal of the UFO model does not follow the convention of 2HDMC.
espeically since the splitting of an interaction into three piece (coupling, lorentz,color) is not unique
and you can easily move factor from one to the other.

2) you are using a NLO model, then a lot of those formula are correlated to each other. Just changing one coupling might break gauge invariance, nlo accuracy, lorentz invariance, .... (the same issue can also occur at LO but their the relation are simpler and the risk is less critical in general)

Cheers,

Olivier

PS: Obviously this will force you to regenerate the code since you change the UFO model.

> On 11 Nov 2021, at 10:30, Sarah <email address hidden> wrote:
>
> Question #699394 on MadGraph5_aMC@NLO changed:
> https://answers.launchpad.net/mg5amcnlo/+question/699394
>
> Sarah posted a new comment:
> Good morning
> I have a question related to this point.
>
> I am working on 2HDMtII_NLO model, studying the decay h3 > h1 z
> ( h3 = A Higgs boson, h1 = the SM Higgs)
>
> in the coupling.py file of the model there are many couplings their values are functions. For example
> GC_140 = Coupling(name = 'GC_140',
> value = '-(cw*g1*TH2x1*TH3x3)/2. + (gw*sw*TH2x1*TH3x3)/2.',
> order = {'QED':1})
>
> Can I change the value to a number? I mean like this
> Coupling(name = 'GC_140',
> value = '1.36074468e-01',
> order = {'QED':1})
> or Madgraph will calculate them while it is running the process?
>
> I will calculate the coupling values in 2HDMC code.
>
>
> best regards
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

thank you
sorry I made a mistake, the value 1.36074468e-01 is the coupling of h3 h1 z in 2HDMC for CG_138 not for GC_140'