changing factorization scale

This is difficult to judge, at first sight this seems ok.
I would suggest that you generate a sample of events and then you check that all your event have the scale that you expect.

Cheers,

Olivier

On Jul 9, 2014, at 9:11 AM, karo <email address hidden> wrote:

> New question #251389 on MadGraph5_aMC@NLO:
> https://answers.launchpad.net/mg5amcnlo/+question/251389
>
> Hi MG team,
>
> I would like to use the factorization scale at the min(PT) of jets for VBF Zjj (z->vv) process. I have follow this web
> https://cp3.irmp.ucl.ac.be/projects/madgraph/wiki/FAQ-General-2. But I don't sure whether my new setscales file is right. Please help me check. My new setscales.f is like this:
>
> subroutine set_ren_scale(P,rscale)
> ......
> rscale=100000000d0
>
> do i=3,nexternal
> if(iabs(idup(i,1,1)).le.5.or.idup(i,1,1).eq.21.or.pmass(i).eq.0d0)then
> rscale=min(rscale,pt(p(0,i)))
> endif
> enddo
> return
> end
>
> subroutine set_fac_scale(P,q2fact)
> ......
> call set_ren_scale(P,q2fact(1))
>
> q2fact(1)=q2fact(1)**2
>
> q2fact(2)=q2fact(1)
> return
> end
>
> Thanks in advance
> Karo
>
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

But I don't know how to check the scale through a sample of events. I just see the four momentm in events.lhe. Where I could find the scale ?

Thanks,
Karo

Hi Olivier,

    I have checked the factorization scale through the events.lhe. The scale is not what I expect. I am not sure what I should do next, because I think I have followed the help web.

About the factorization scale, I also have some questions,
1. For vbf zjj (z->vv) process, what is the default factorization scale ?
2. For zjj process, what is the default factorization scale? I have checked it is not Sqrt[m_z^2+pt_z^2].

I am looking for your reply.

Thanks,
Karo

Hi,

The exact definition of the scale is:
All factorisation scales squared, and the renormalisation scale squared for the hard process (the process with
the zero-extra-parton multiplicity), are constructed by clustering back to the irreducible
2 → 2 system and by using the transverse mass in the resulting frame: μ2 = p2T + m2.

Otherwise, I will assign this to Marco since he plays with that option recently, he is currently in holliday, so you will need to be patient.

Cheers,

Olivier