Direct extraction of QCD LambdaMSbar from moments of structure functions in neutrino-nucleon scattering, using the CORGI approach

We use recently calculated next-to-next-to-leading (NNLO) anomalous dimension coefficients for the n=1,3,5,...,13 moments of the xF3 structure function in nuN scattering, together with the corresponding three-loop Wilson coefficients, to obtain improved QCD predictions for the moments. The Complete Renormalization Group Improvement (CORGI) approach is used, in which all dependence on renormalization or factorization scales is avoided by a complete resummation of ultraviolet logarithms. The Bernstein Polynomial method is used to compare these QCD predictions to the xF3 data of the CCFR collaboration. Direct fits for LambdaMSbar(5), with Nf=5 effective quark flavours, over the range 20<Q^2<125.9 GeV^2 were performed. We obtain LambdaMSbar(5)=202+54/-45 MeV, corresponding to the three-loop running coupling alphas(MZ)=0.1174+0.0043-0.0043. Including target mass corrections as well we obtain LambdaMSbar(5)=228+35/-36 MeV, corresponding to alphas(MZ)=0.1196+0.0027-0.0031.