MadGraph5_aMC@NLO

regarding NLO matching in Madgraph

Asked by Disha Bhatia

Hi,

I wanted to confirm one thing:
I am required to compute QCD corrections to the process p p > e+ ve a ..
While I madgraph when I do NLO, it also computes p p > e+ ve a j.

So does the pythia interface in madgraph automatically merges the parton showers with hard jet emissions
if I set ickkw = 3? Or I need to take the lhe file separately in pythia and then perform merging?

Thanks,
Disha

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Olivier Mattelaer
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Olivier Mattelaer (olivier-mattelaer) said : 		#1

Hi,

If you do
> generate p p > e+ ve a [QCD]

Then you do not need merging methods and you can keep ickkw =0
The matching procedure of the MC@NLO algorithm takes care of the double counting.

Cheers,

Olivier

> On 1 Aug 2018, at 12:37, Disha Bhatia <email address hidden> wrote:
>
> New question #671276 on MadGraph5_aMC@NLO:
> https://answers.launchpad.net/mg5amcnlo/+question/671276
>
> Hi,
>
> I wanted to confirm one thing:
> I am required to compute QCD corrections to the process p p > e+ ve a ..
> While I madgraph when I do NLO, it also computes p p > e+ ve a j.
>
> So does the pythia interface in madgraph automatically merges the parton showers with hard jet emissions
> if I set ickkw = 3? Or I need to take the lhe file separately in pythia and then perform merging?
>
> Thanks,
> Disha
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

Revision history for this message
Disha Bhatia (dishabhatia1989) said : 		#2

Ok,

sorry, I need to ask one more thing for the clarification. There are no matching parameters given in the NLO run card.
Do I need to do a separate matching in pythia or running pythia interface in madgraph to give .hepmc files will be enough.

Revision history for this message
Best Olivier Mattelaer (olivier-mattelaer) said : 		#3

Hi,

You do not have any free parameter for such matching.
Running pythia (whitin or outside the interface) would be enough.

Cheers,

Olivier

> On 1 Aug 2018, at 13:38, Disha Bhatia <email address hidden> wrote:
>
> Question #671276 on MadGraph5_aMC@NLO changed:
> https://answers.launchpad.net/mg5amcnlo/+question/671276
>
> Disha Bhatia posted a new comment:
> Ok,
>
> sorry, I need to ask one more thing for the clarification. There are no matching parameters given in the NLO run card.
> Do I need to do a separate matching in pythia or running pythia interface in madgraph to give .hepmc files will be enough.
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

Revision history for this message
Disha Bhatia (dishabhatia1989) said : 		#4

Thanks Olivier, this solves my problem.