Quark and Gluon Angular Momenta Contributions to Nucleon Spin

The nucleon spin structure has been a longstanding issue in hadronic physics, both experimentally and theoretically. From the polarized Deep Inelastic Scattering experiments and Lattice QCD calculations, it has been found that the contribution coming from the quark spin is rather small (~25%). Now, it is widely accepted that the rest of the nucleon spin should come from the gluon spin and the orbital angular momenta of quarks and gluons. In this talk, I will present a complete Lattice QCD calculation of the quark and glue angular momenta inside a proton. The calculation is carried out on a 16^3×24 quenched lattice using the standard Wilson action.