Determination of $\alpha_{s}$ and the nucleon spin decomposition using recent polarized structure function data

New data on polarized \mu-p and e-p scattering permit a first determination of \alpha_s using the Bjorken sum rule, as well as higher precision in determining the nucleon spin decomposition. Using perturbative QCD calculations to O(\alpha_s^4) for the non-singlet combination of structure functions, we find \alpha_s(2.5 GeV^2) = 0.375^{+0.062}_{-0.081}, corresponding to \alpha_s(M_Z^2) =0.122^{+0.005}_{-0.009}, and using calculations to O(\alpha_s^3) for the singlet combination we find \Delta u = 0.83 \pm 0.03, \Delta d= -0.43 \pm 0.03, \Delta s =-0.10 \pm 0.03, \Delta \Sigma \equiv \Delta u + \Delta d + \Ds = 0.31 \pm 0.07, at a renormalization scale Q^2=10 GeV^2. Perturbative QCD corrections play an essential role in reconciling the interpretations of data taken using different targets. We discuss higher-twist uncertainties in these determinations. The \Delta q determinations are used to update predictions for the couplings of massive Cold Dark Matter particles and axions to nucleons.