Conceptual

Heavy-Quark Contributions to the Bjorken Sum Rule in Analytic QCD

A calculation of the polarized Bjorken sum rule within analytic perturbation theory (analytic QCD), the framework whose coupling has no Landau singularity at low momentum transfer, extended to include heavy-quark contributions evaluated at two loops. Using derivative expansions of the analytic coupling and both leading-twist and twist-four terms, the result is compared with experimental Bjorken sum rule data down to very low Q^2 and the photoproduction limit, obtaining good agreement.