QCD Analysis of the Polarized World Data

The results of a recent next-to-leading order QCD analysis of the world data on polarized deep inelastic scattering are reported. New parameterizations are derived for the quark and gluon distributions and the value of ${\alpha }_s(M_z^2)$ is determined. We obtain $\alpha_s^{\rm NLO}(M_Z^2)= 0.1132~~\begin{array}{l} + 0.0056 \ -0.0095 \end{array}$. Potential higher twist contributions to the structure function $g_1(x,Q^2)$ are considered.