Magnetic moment operator of non-Dirac particles and some elements of   polarization $ep$-experiments
  An explicit form of the magnetic moment tensor operator for non-Dirac particles with rest spin 1/2 and its essential difference from the spin operator are established. Possible consequences of the last fact for the description of the spin rotation in the magnetic field and for the values of magnetic moments of some nuclei, as well as the impact of this and other facts on the validity of modelling the azimuthal asymmetry of the secondary-scattered protons in $ep$-experiments are noted. 
L.M. Slad
hep-ph nucl-th