Hermes Studies of the Nucleon Spin

The HERMES collaboration has measured double spin asymmetries using polarized deep inelastic scattering. The spin structure functions g₁ of the proton, the neutron, and the deuteron calculated from inclusive asymmetries are in agreement with world data. Quark polarizations were extracted from inclusive and semi-inclusive spin asymmetries. The polarization of the up quark is positive, the polarization of the down quark negative, and the sea polarization is consistent with zero. First measurements of hard exclusive electro-production of real photons (DVCS) can be interpreted in terms of the recently developed generalized parton distribution functions.