Top-quark loop in Higgs pair production

Hi,

I'm actually surprised that you have ANY diagram.
When I run the following command
import model sm
generate p p > h h

It crashes with NoDiagramException (as it should since the above syntax is tree-level only).
So which model did you use.
I would have guess that the correct syntax would have been
generate g g > h h [QCD] but this only works for a couple of model (basically the sm ones and that's it).

So I do not have enough information to answer your question.

Cheers,

Olivier

Hii

I'm using heft model
I'm looking to have all the possible processes (and Feynman diagrams) that
will lead to "hh" final state.

Now when I make : generate pp --hh I get only one diagram where actually
their are others. So I would like these other diagrams to be included.

Thank you

Le lun. 11 févr. 2019 20:12, Olivier Mattelaer <
<email address hidden>> a écrit :

> Your question #678484 on MadGraph5_aMC@NLO changed:
> https://answers.launchpad.net/mg5amcnlo/+question/678484
>
> Status: Open => Answered
>
> Olivier Mattelaer proposed the following answer:
> Hi,
>
> I'm actually surprised that you have ANY diagram.
> When I run the following command
> import model sm
> generate p p > h h
>
> It crashes with NoDiagramException (as it should since the above syntax is
> tree-level only).
> So which model did you use.
> I would have guess that the correct syntax would have been
> generate g g > h h [QCD] but this only works for a couple of model
> (basically the sm ones and that's it).
>
> So I do not have enough information to answer your question.
>
> Cheers,
>
> Olivier
>
> --
> 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/678484/+confirm?answer_id=0
>
> 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/678484
>
> You received this question notification because you asked the question.
>

Hi,

That model does not have it.
The heft model is based on an approximation of the top quark loop in effective operator.
This correspond to an expansion into E/m_t, for single Higgs production, it works since in that case E=m_h.
If you have two Higgs production, then you would have 2*m_h/M_t which is bigger than one,. showing that the heft model is not working in that case.

Note that the same is True if you try to generate with the heft model, Higgs plus one jet for high energetic jet,...

So I would recommend to use the loop-induced mode within the standard model (which is obviously much slower but Leading Order accurate). If you need higher accuracy (approximate NLO) this is also possible.
But this is much more complex.

Cheers,

Olivier

> On 11 Feb 2019, at 20:27, TAIL Saad <email address hidden> wrote:
>
> Question #678484 on MadGraph5_aMC@NLO changed:
> https://answers.launchpad.net/mg5amcnlo/+question/678484
>
> Status: Answered => Open
>
> TAIL Saad is still having a problem:
> Hii
>
> I'm using heft model
> I'm looking to have all the possible processes (and Feynman diagrams) that
> will lead to "hh" final state.
>
> Now when I make : generate pp --hh I get only one diagram where actually
> their are others. So I would like these other diagrams to be included.
>
>
> Thank you
>
> Le lun. 11 févr. 2019 20:12, Olivier Mattelaer <
> <email address hidden>> a écrit :
>
>> Your question #678484 on MadGraph5_aMC@NLO changed:
>> https://answers.launchpad.net/mg5amcnlo/+question/678484
>>
>> Status: Open => Answered
>>
>> Olivier Mattelaer proposed the following answer:
>> Hi,
>>
>> I'm actually surprised that you have ANY diagram.
>> When I run the following command
>> import model sm
>> generate p p > h h
>>
>> It crashes with NoDiagramException (as it should since the above syntax is
>> tree-level only).
>> So which model did you use.
>> I would have guess that the correct syntax would have been
>> generate g g > h h [QCD] but this only works for a couple of model
>> (basically the sm ones and that's it).
>>
>> So I do not have enough information to answer your question.
>>
>> Cheers,
>>
>> Olivier
>>
>> --
>> 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/678484/+confirm?answer_id=0
>>
>> 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/678484
>>
>> You received this question notification because you asked the question.
>>
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

Hii,

p p > h h [QCD] solves the problem.

Thank you, Olivier, you're so helpful.