| Summary: | We determine the strong coupling α s at NNLO in perturbative QCD using the global dataset input to the NNPDF2.1 NNLO parton fit: data from neutral and charged current deep-inelastic scattering, Drell-Yan, vector boson production and inclusive jets. We find α s(M Z)=0.1173±0.0007 stat, where the statistical uncertainty comes from the underlying data and uncertainties due to the analysis procedure are negligible. We show that the distribution of α s values preferred by different experiments in the global fit is statistically consistent, without need for rescaling uncertainties by a "tolerance" factor. We show that if deep-inelastic data only are used, the best-fit value of α s is somewhat lower, but consistent within one sigma with the global determination. We find that the shift between the NLO and NNLO values of α s is δαspert=0.0018, and we estimate the uncertainty from higher-order corrections to be δαsNNLO~0.0009. © 2011 Elsevier B.V.
|
|---|