Spinning particles on spacelike hypersurfaces and their rest frame description

A new spinning particle with a definite sign of the energy is defined on sp acelike hypersurfaces after a critical discussion of the standard spinning particles. It is the pseudoclassical basis of the positive energy (1/2,0) [ or negative energy (0, 1/2)] part of the (1/2, 1/2) solutions of the Dirac equation. The study of the isolated system of N such spinning charged parti cles plus the electromagnetic held leads to their description in the rest f rame Wigner-covariant instant form of dynamics on the Wigner hyperplanes or thogonal to the total four-momentum of the isolated system (when it is time like). We find that on such hyperplanes these spinning particles have a non minimal coupling only of the type "spin-magnetic field," like the nonrelati vistic Pauli particles to which they tend in the nonrelativistic limit. The Lienard-Wiechert potentials associated with these charged spinning particl es are found. Then, a comment is made on how to quantize the spinning parti cles respecting their fibered structure describing the spin structure.