On the Possible Trajectories of Particles with Spin. II. Particles in   the Stationary Homogeneous Magnetic Field
  The behavior of spinning particles in the stationary homogeneous magnetic field is considered and all types of trajectories for massive and massless particles are found. It is shown that spin of particles in a magnetic field is always arranged parallel or antiparallel to the field. Helicity $e$ plays a role of electric charge. The oscillation frequency of massless particle in a magnetic field increases. 
Alexander N. Tarakanov
physics.class-ph