MadGraph5_aMC@NLO

Renormalization/Factorization scales in VBS

Asked by Philipp Pigard

Dear MadGraph Team,

in order to compare the cross-section results from MG and other generators, I need to know which renormalization/factorization scales are used. I am aware of the FAQ-page on the topic, but I cannot make sense of the information given there and which case is relevant to my process.

The process in question in ZZjj VBS :
generate p p > z z j j QED=4 QCD=0, z > l+ l- and also
generate p p > z z j j QED=2 QCD=99, z > l+ l-

My questions are :
A) What is the scale choice for these processes? (Do they differ depending on restrictions on the vertices?)
B) Does it make a difference if one uses the decay-chain syntax or not, e.g. p p > l+ l- l+ l- j j QED=2 QCD=99 ?

Cheers
Philipp

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Olivier Mattelaer (olivier-mattelaer) said : 		#1

Dear Philipp,

If you want to compare with various code, then the easiest is to use an analytical formula and not our default based on a clustering.
For this you can use the option “dynamical_scale_choice” to select the scale that you want.
Using our default (ckkw like) for comparison requires that you re-inplement the same algorithm in all code which is a lot of work.

Cheers,

Olivier

> On Dec 3, 2015, at 13:13, Philipp Pigard <email address hidden> wrote:
>
> New question #276606 on MadGraph5_aMC@NLO:
> https://answers.launchpad.net/mg5amcnlo/+question/276606
>
> Dear MadGraph Team,
>
> in order to compare the cross-section results from MG and other generators, I need to know which renormalization/factorization scales are used. I am aware of the FAQ-page on the topic, but I cannot make sense of the information given there and which case is relevant to my process.
>
> The process in question in ZZjj VBS :
> generate p p > z z j j QED=4 QCD=0, z > l+ l- and also
> generate p p > z z j j QED=2 QCD=99, z > l+ l-
>
> My questions are :
> A) What is the scale choice for these processes? (Do they differ depending on restrictions on the vertices?)
> B) Does it make a difference if one uses the decay-chain syntax or not, e.g. p p > l+ l- l+ l- j j QED=2 QCD=99 ?
>
>
> Cheers
> Philipp
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

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