Abstract: | Developing some earlier work for spin-zerosystems found in the literature, we use some recentlyobtained generalized systems of covariance for thePoincare group to suggest a method for definingcovariant localization operators on phase space formassive relativistic particles with arbitrary integralor half-integral spins. These operators lead tooperationally defined position operators on spacelikehyperplanes, which turn out to be the Newton-Wigneroperators, and, as in the earlier results on spin-zerosystems, admit a consistent probability interpretationwith conserved currents. |