The Spin Structure of the Nucleon

This article reviews recent results on the spin structure of the nucleon from polarized deep inelastic lepton-nucleon scattering and polarized proton-proton scattering. For a description of the nucleon in terms of parton distribution functions (pdf) the knowledge of three basic distributions is needed: The relatively well known unpolarized pdfs, the helicity distributions and the transversity distributions. The latter two play an essential role in understanding the spin structure of the nucleon. New results on the gluon helicity distribution $\Delta G(x)$ and the helicity distributions for strange and valence quarks are discussed. A first determination of the up to now unknown transversity distributions $\Delta_{T}q(x)$ is presented. Finally results from deep virtual Compton scattering, giving access to the orbital angular momentum contribution of quarks to the nucleon spin, are discussed.