MadGraph5_aMC@NLO

Navigating particles for setting dynamic scale

Asked by Josh McFayden

Hi,

I'd like to set the dynamic scale of some Z(->ll)+jets events to m(ll).
From (https://answers.launchpad.net/mg5amcnlo/+question/204751) I understand that I have to change SubProcesses/setscale.f to use something like this:

      rscale=dsqrt(SumDot(P(0,3),P(0,4),1d0))

and

      call set_ren_scale(P,q2fact(1))
      q2fact(1)=q2fact(1)**2
      q2fact(2)=q2fact(1) !factorization scale**2 for pdf2

But I want to know whether the leptons are always in position 3 and 4 in the event record. How do I check e.g. the pdg ID of the particles?

Thanks in advance,

Josh.

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

Hi Josh,

Do you want to do that @leading order or at NLO?

At leading order the order is always the one set by the process definition, and can be check in any of the Feynman Diagram in case of doubt.
If it is at NLO, this is more complicated and I should ask Marco to answer this.

Olivier

On Jun 4, 2014, at 12:32 PM, Josh McFayden <email address hidden> wrote:

> New question #249754 on MadGraph5_aMC@NLO:
> https://answers.launchpad.net/mg5amcnlo/+question/249754
>
> Hi,
>
> I'd like to set the dynamic scale of some Z(->ll)+jets events to m(ll).
>> From (https://answers.launchpad.net/mg5amcnlo/+question/204751) I understand that I have to change SubProcesses/setscale.f to use something like this:
>
> rscale=dsqrt(SumDot(P(0,3),P(0,4),1d0))
>
> and
>
> call set_ren_scale(P,q2fact(1))
> q2fact(1)=q2fact(1)**2
> q2fact(2)=q2fact(1) !factorization scale**2 for pdf2
>
> But I want to know whether the leptons are always in position 3 and 4 in the event record. How do I check e.g. the pdg ID of the particles?
>
> Thanks in advance,
>
> Josh.
>
>
>
>
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

Revision history for this message
Josh McFayden (mcfayden) said : 		#2

Hi Olivier,

I am only interested in LO for now so that is fine.

Can you just confirm that the code snippet I pasted above is the correct one?

Thanks a lot!

Josh.

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

Yes it sounds correct.

Olivier
On Jun 4, 2014, at 4:51 PM, Josh McFayden <email address hidden> wrote:

> Question #249754 on MadGraph5_aMC@NLO changed:
> https://answers.launchpad.net/mg5amcnlo/+question/249754
>
> Status: Answered => Open
>
> Josh McFayden is still having a problem:
> Hi Olivier,
>
> I am only interested in LO for now so that is fine.
>
> Can you just confirm that the code snippet I pasted above is the correct
> one?
>
> Thanks a lot!
>
> Josh.
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

Revision history for this message
Josh McFayden (mcfayden) said : 		#4

Thanks a lot Olivier.

Josh.

Revision history for this message
Josh McFayden (mcfayden) said : 		#5

Thanks Olivier Mattelaer, that solved my question.