Failed to reproduce pp > hh result of MG5 1405.0301 paper

Dear Tathagata,

The loop improved results can not be generated automatically by MG5_aMC so far since this is done
via a reweighting method. I put Eleni in charge to give you more details on how to apply this method and help you on this.
Note the following two detailed paper on that subject:
1408.6542 and 1401.7340

So I guess that you used the loop-induced module (1507.00020) which is LO compare to the loop-improved which is a method which approximates the NLO contributions. In that case, your difference is actually quite small.

Is this difference can be attributed to the usage of different PDF sets only?

Certainly, the PDF sets in itself should have small impact but the central value of alpha_s is decided by the PDF and this since those kind of process have a huge dependence in the strong coupling, this sounds possible.

If so then how can I implement MSTWnlo2008 in MG5?

1) install lhapdf on your machine
2) if you did not have it install in your $PATH then edit input/mg5_configuration.txt and edit the line
# lhapdf = lhapdf-config
to
lhapdf = PATH_TO_YOUR_lhapdf-config_SCRIPT
3) when using the run_card use as pdlabel:lhapdf and as lhaid the code correspond to MSTWnlo2008

Cheers,

Olivier

Thanks Olivier for all the information.

I got the LHAPDF installed and successfully implemented the MSTWnlo2008 PDF.

I'm awaiting eagerly for more information regarding the implementation of
loop improved results for the process in MG5.

Regards,
Tathagata

On Wed, Feb 3, 2016 at 9:32 PM, Olivier Mattelaer <
<email address hidden>> wrote:

> Your question #284537 on MadGraph5_aMC@NLO changed:
> https://answers.launchpad.net/mg5amcnlo/+question/284537
>
> Status: Open => Answered
>
> Olivier Mattelaer proposed the following answer:
> Dear Tathagata,
>
> The loop improved results can not be generated automatically by MG5_aMC so
> far since this is done
> via a reweighting method. I put Eleni in charge to give you more details
> on how to apply this method and help you on this.
> Note the following two detailed paper on that subject:
> 1408.6542 and 1401.7340
>
> So I guess that you used the loop-induced module (1507.00020) which is
> LO compare to the loop-improved which is a method which approximates the
> NLO contributions. In that case, your difference is actually quite
> small.
>
> Is this difference can be attributed to the usage of different PDF sets
> only?
>
> Certainly, the PDF sets in itself should have small impact but the
> central value of alpha_s is decided by the PDF and this since those kind
> of process have a huge dependence in the strong coupling, this sounds
> possible.
>
> If so then how can I implement MSTWnlo2008 in MG5?
>
> 1) install lhapdf on your machine
> 2) if you did not have it install in your $PATH then edit
> input/mg5_configuration.txt and edit the line
> # lhapdf = lhapdf-config
> to
> lhapdf = PATH_TO_YOUR_lhapdf-config_SCRIPT
> 3) when using the run_card use as pdlabel:lhapdf and as lhaid the code
> correspond to MSTWnlo2008
>
> Cheers,
>
> Olivier
>
> --
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>
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>
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> following page to enter your feedback:
> https://answers.launchpad.net/mg5amcnlo/+question/284537
>
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>

Hi Tathagata,

If you are interested in the NLO results, contact me by email to send you the special code we developed for this.

Best,

Eleni