regarding NLO matching in Madgraph

Asked by Disha Bhatia on 2018-08-01

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

Question information

Language:
English Edit question
Status:
Solved
For:
MadGraph5_aMC@NLO Edit question
Assignee:
No assignee Edit question
Solved by:
Olivier Mattelaer
Solved:
2018-08-02
Last query:
2018-08-02
Last reply:
2018-08-01

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.

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.

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.

Disha Bhatia (dishabhatia1989) said : #4

Thanks Olivier, this solves my problem.