Kinetic equation, spin hydrodynamics and collisional depolarization rate in a spin-polarized plasma

On the basis of our previous work, a rigorous kinetic equation for a spin-polarized plasma is derived in the weak-coupling quasi-classical limit. The macroscopic polarization vector is defined in a unified form for spin-½ and spin-1 particles. Using the kinetic equation, an equation for the macroscopic polarization density is derived in the form of a ‘spin-hydrodynamical equation’. The depolarization rate for the spin–orbit interaction and the spin–spin interaction is estimated. Some difficulties for the spin–spin interaction are displayed and discussed.