How to change the trilinear higgs coupling in madgraph?

Hi,

It might depend of the model that you are going to use sm? heft? loop_sm? something else?
In most case, the trilinear would not be a free parameter of your model and therefore nothing will be prepared to modify it.

However it should be easy to modify the UFO format in order to add one parameter to the model and change the tri-linear coupling definition to multiply it by that additional parameter. You should have all the information on how to do from the starting model of your choice in the following paper: arXiv:1108.2040

Cheers,

Olivier

PS: Note if a file decays.py exists in your UFO model, it is better to remove it to be sure that it is not used anymore (a simple rm decay.py is enough)

Hii,

Thank you for your reply,

The model I'm using is heft.
I took a look at the paper but I don't seem to see an answer in it.

What I tried to do so far is:

 - When I did the (pp>hh) process, I looked at the coupling.py file and there was a list of couplings all named as GC_#(number).
   Is there a coupling among these which corresponds to trilinear higgs boson ?

 - I downloaded from the internet some codes such as the one in this link:

                                       https://cp3.irmp.ucl.ac.be/projects/madgraph/wiki/HiggsPairProduction

    this link shows four examples. The param_card of the 2nd and the 3rd examples include BSM blocks like: ("Block bsminputs" "Block bsm ") where we are able to modify the values of the couplings.

 So, what should I do to make include these blocks in my process ? is there any other type of model that have to include ?

THANKS IN ADVANCE

Hi,

I'm a bit surprised by the model choice.
This model is known to not be correct (since 2*m_h > mt)
But this is up to you.

> I took a look at the paper but I don't seem to see an answer in it.

This model is just describing the content of all the .py files present in the model.
Such that you will be able to modify those to your need.

So to be more explicit you need
1) to find which GC_XX couplings is the one you are looking for.
   a. for this you have to look inside vertices.py to which vertex is the three higgs one
   b. find which coupling(s) is associated to that coupling
2) define a new external parameter in parameters.py
   a. this is here that you can define a new block BSM (or the name that you want)
3) change the expression of the coupling that you found in 1 (or all of them if more than one) and each time multiply the full expression by the name of your new parameter.
4) remove the decays.py if that file exists.

For any doubt on (any) convention refer to the paper above.

Cheers,

Olivier

> On 7 Feb 2019, at 22:02, TAIL Saad <email address hidden> wrote:
>
> Question #678406 on MadGraph5_aMC@NLO changed:
> https://answers.launchpad.net/mg5amcnlo/+question/678406
>
> Status: Answered => Open
>
> TAIL Saad is still having a problem:
> Hii,
>
> Thank you for your reply,
>
> The model I'm using is heft.
> I took a look at the paper but I don't seem to see an answer in it.
>
> What I tried to do so far is:
>
> - When I did the (pp>hh) process, I looked at the coupling.py file and there was a list of couplings all named as GC_#(number).
> Is there a coupling among these which corresponds to trilinear higgs boson ?
>
> - I downloaded from the internet some codes such as the one in this
> link:
>
> https://cp3.irmp.ucl.ac.be/projects/madgraph/wiki/HiggsPairProduction
>
> this link shows four examples. The param_card of the 2nd and the 3rd examples include BSM blocks like: ("Block bsminputs" "Block bsm ") where we are able to modify the values of the couplings.
>
> So, what should I do to make include these blocks in my process ? is there any other type of model that have to include ?
>
> THANKS IN ADVANCE
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

Hello,

thank you again for your answers.

I did what you have listed but I still don't get a block in my param_card
where I can change the added parameter (in fact, it doesn't even show it).
I think the problem is in the model (heft doesn't include
higgs self-coupling). What model do you suggest me to use?

Regards.

Le jeu. 7 févr. 2019 à 22:17, Olivier Mattelaer <
<email address hidden>> a écrit :

> Your question #678406 on MadGraph5_aMC@NLO changed:
> https://answers.launchpad.net/mg5amcnlo/+question/678406
>
> Status: Open => Answered
>
> Olivier Mattelaer proposed the following answer:
> Hi,
>
> I'm a bit surprised by the model choice.
> This model is known to not be correct (since 2*m_h > mt)
> But this is up to you.
>
> > I took a look at the paper but I don't seem to see an answer in it.
>
> This model is just describing the content of all the .py files present in
> the model.
> Such that you will be able to modify those to your need.
>
> So to be more explicit you need
> 1) to find which GC_XX couplings is the one you are looking for.
> a. for this you have to look inside vertices.py to which vertex is the
> three higgs one
> b. find which coupling(s) is associated to that coupling
> 2) define a new external parameter in parameters.py
> a. this is here that you can define a new block BSM (or the name that
> you want)
> 3) change the expression of the coupling that you found in 1 (or all of
> them if more than one) and each time multiply the full expression by the
> name of your new parameter.
> 4) remove the decays.py if that file exists.
>
> For any doubt on (any) convention refer to the paper above.
>
> Cheers,
>
> Olivier
>
>
> > On 7 Feb 2019, at 22:02, TAIL Saad <email address hidden>
> wrote:
> >
> > Question #678406 on MadGraph5_aMC@NLO changed:
> > https://answers.launchpad.net/mg5amcnlo/+question/678406
> >
> > Status: Answered => Open
> >
> > TAIL Saad is still having a problem:
> > Hii,
> >
> > Thank you for your reply,
> >
> > The model I'm using is heft.
> > I took a look at the paper but I don't seem to see an answer in it.
> >
> > What I tried to do so far is:
> >
> > - When I did the (pp>hh) process, I looked at the coupling.py file and
> there was a list of couplings all named as GC_#(number).
> > Is there a coupling among these which corresponds to trilinear higgs
> boson ?
> >
> > - I downloaded from the internet some codes such as the one in this
> > link:
> >
> > https://cp3.irmp.ucl.ac.be/projects/madgraph/wiki/HiggsPairProduction
> >
> > this link shows four examples. The param_card of the 2nd and the 3rd
> examples include BSM blocks like: ("Block bsminputs" "Block bsm ") where we
> are able to modify the values of the couplings.
> >
> > So, what should I do to make include these blocks in my process ? is
> there any other type of model that have to include ?
> >
> > THANKS IN ADVANCE
> >
> > --
> > You received this question notification because you are an answer
> > contact for MadGraph5_aMC@NLO.
>
> --
> If this answers your question, please go to the following page to let us
> know that it is solved:
>
> https://answers.launchpad.net/mg5amcnlo/+question/678406/+confirm?answer_id=2
>
> If you still need help, you can reply to this email or go to the
> following page to enter your feedback:
> https://answers.launchpad.net/mg5amcnlo/+question/678406
>
> You received this question notification because you asked the question.
>

Hi,

Did you follow correctly the UFO convention for the parameters?
If it does not appear in the param_card, it might be that you did not define it correctly.

One other potential problem is if your model has some restrict_XXXX.dat in the UFO model.
Those file are MG5aMC specifc (as far as I know) and you might want to remove those (as well as the default_XXXX.dat if any)

> (heft doesn't include higgs self-coupling).

If I load the heft model and then ask madgraph to print me all interactions with at least three higgs. I have it.
MG5_aMC>display interactions h h h
1 : h h h h
2 : h h h

For the model, I would actually use either the loop_sm (and use the loop_induced mode)
or use the equivalent of heft at NLO accuracy and then use re-weighting approach to correct for the mistake due to the approximation in that model.

Cheers,

Olivier

Hii,

I finally did it by changing the values inside the file of the heft model.

Thank you, Olivier, you are so helpful.