Generate p p > h h [QCD] in Fixed-Order model with amcfast

Hi,

p p > h h does not exists at tree level.
Therefore this is a completly different type of computation (LO computation) than
> p p > w+ [QCD],

Which is a NLO computation.

LO computation are fixed order but you will only have the possibility to generate events for LO computation.
We do not have an equivalent to aMCfast-APPLgrid for LO computation so I do not have a good way for you to more forward here.

Sorry,

Olivier

> On 6 Mar 2021, at 07:50, dianyu liu <email address hidden> wrote:
>
> New question #695882 on MadGraph5_aMC@NLO:
> https://answers.launchpad.net/mg5amcnlo/+question/695882
>
> Hi,
>
> I was trying to generate p p > h h through the chain MG5-aMCfast-APPLgrid. The aMCfast work only when running MadGraph5_aMC@NLO in the Fixed-Order (FO) mode. But the p p > h h [QCD] cannot enter the Fixed-Order mode.
>
> I run the command:
> MG5_aMC>generate g g > h h [QCD]
> It cannot enter the Fixed-Order mode.
>
> It shows
> The following switches determine which programs are run:
> 1 Run the pythia shower/hadronization: pythia=NOT INSTALLED
> 2 Run PGS as detector simulator: pgs=NOT INSTALLED
> 3 Run Delphes as detector simulator: delphes=NOT INSTALLED
> 4 Decay particles with the MadSpin module: madspin=OFF
> 5 Add weights to the events based on changing model parameters: reweight=Not available (requires NumPy)
>
> However, for other processes, for exanple g g > w+ [QCD], can enter the Fixed-Order mode.
>
> Cannpt p p > h h enter Fixed-Order mode?
>
> It will be helpful if I can get any suggestions from your side. Thank you very much.
>
> regards,
> Dianyu
>
>
>
> --
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> contact for MadGraph5_aMC@NLO.

Hello Olivier,

Thanks for your help.

Is there any way to force into Fixed-Order mode? Or do you know any other way to generate the p p > h h process for the Applgrid?

Can you give me some advice about that?

Many thanks
Dianyu

Dear Dianyu,

I'm a bit confused what your goal is here. ApplGrid is meant for PDF fitting -- in particular at NLO. Is your goal to include the leading order double Higgs production in PDF fits? If this is the case, then note that the PDF (and factorisation scale) dependence in LO processes is trivial -- so, it should be straight-forward to create/setup your own "grids" to do this. It's probably easiest to simply start from the generated events and use the kinematics of the events to determine the values of the PDF (and factorisation scale) used.

Or is there another reason why you wish to use applgrid?

Best,
Rikkert