A systematic study of QCD coupling constant from deep-inelastic measurements

Abstract

We reanalyze deep-inelastic scattering data of the BCDMS Collaboration by including proper cuts of ranges with large systematic errors. We also perform the fits of high-statistic deep-inelastic scattering data of the BCDMS, SLAC, NM, and BFP Collaborations taking the data separately and in a combined way and find good agreement between these analyses. We extract the values of both the QCD coupling constant α s(M Z 2 ) up to the NLO level and of the power corrections to the structure function F 2. The fits of the combined data for the nonsinglet part of the structure function F 2 predict the coupling constant value α s(M Z 2 ) = 0.1174 ± 0.0007 (stat.) ± 0.0019 (syst.) ± 0.0010 (norm.) (or QCD parameter $$\Lambda \tfrac{{(5)}}{{MS}} = 204 \pm 25$$ (total experimental error) MeV). The fits of the combined data for both the nonsinglet part and the singlet part lead to the values α s(M Z 2 ) = 0.1177 ± 0.0007 (stat.) ± 0.0021 (syst.) ± 0.0009 (norm.) (or QCD parameter $$\Lambda \tfrac{{(5)}}{{MS}}$$ =(208±27 (total experimental error)MeV). The above values are in very good agreement with each other. We estimate theoretical uncertainties for α s(M Z 2 ) at +0.0047 and −0.0057 from fits of the combined data when complete singlet and nonsinglet Q 2 evolution is taken into account.