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v3.3.2-pre
Nansi showed that the difference between the central value in CTEQ6.6 and MSTW2008 is of the order of 3 MeV (smaller than the 6 MeV quoted in the Tevatron paper which was taken as an average value of the electron 8 MeV and muon 4 MeV channels and has a couple of MeV stat uncertainties). The factor of 2.15 between the scaling from 90 to 68%CL was found back for the pp-bar 2 TeV sample. A smaller (but consistent) factor of 2 was found for the 7 TeV sample. It was noted that the events used to estimate the shifts/uncertainties on CT10 and CTEQ6.6 are not the same as the ones used for MSTW2008 (different samples) therefore decorrelation of the stat uncertainties is expected. TO DO: to check the stat uncertainty on these numbers.
The PDF uncertainties for the 7 TeV case using MSTW2008 are 1.7 times smaller than CT10 and show a very small correlation with 2 TeV for W+ case (4 to 8% compared to 30% in CT10 and to 35% in CTEQ6.6). It was also noted that the correlation between 2TeV and 7TeV W- is larger than with W+ for both CT10 and CTEQ6.6 which could be due to the x-dependency of the valence quarks..
TO DO: update the stat correlation between pT and mT for 2TeV, add the pTZ constraint on the ATLAS results, improve the 7 TeV smearing, evaluate the uncertainties using different PDF sets.
TO DO CDF: update Tevatron parameterisation functions to git.