# Scale uncertainty in a a > X processes

Asked by
Kristin Lohwasser
on 2020-07-21

Dear all,

I am wondering about the scale uncertainties in processes like a a > ll or a a > W W.

I see large scale variations (order ~10%) as well as large PDF uncertainties (150% for CT14qed but it seems to be independent from the beam, i.e. is the same for using the EPA approximation with photon beams) for the total cross section and I would like to investigate/check that everything is properly implemented and what is taken as actual scale uncertainties here (presumably this comes from the factorization scale only?

I would like to understand, if these large numbers are to be trusted?

Thanks & Best

Kristin

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