Why there is no renormalization uncertainty in EW processes?

Asked by Yannis Maznas

Dear MG experts,

I have produced two different VBS ZZjj samples, decayed with Madspin to 4 leptons.
One for purely EW processes (QCD==0) and one with QCD vertices (QCD==2)

In both cases I configured the run_card so as to get weights for theoretical variations (PDF,μR,μF)
For the case of QCD the scale variations appear to be as expected http://prntscr.com/1zo1bv9

On the other hand for the EW sample, renormalization scales do not seem to have any effect on the weight.
i.e. (μR, μF) : (1,1) (2,1) and (0.5,1) have exactly the same weight. http://prntscr.com/1zo18qm
I'm not really familiar with the theoretical background of these scales in terms of mathematical formulas but I had the impression that renormalization scales affect also the EW interactions.

Could you enlighten me a bit on this?

Thanks in advance!

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Olivier Mattelaer (olivier-mattelaer) said :
#1

since mu_r is the running of alpha_s and the your process does not depend of alpha_s, the dependence in the renormalization scale is indeed 0 (at LO)

Cheers,

Olivier

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