Abstract:
A partial analysis of one- and two-particle states is made on the basis of a complex vector
parametrization of the Larentz group. In the given approach the transformations of the littte
group are interpreted as rotations in a corresponding complex three-dimensional space of
parameters of this group; this interpretation makes it possible to construct conveniently the
states of a two-particle system with a definite value of the total angular momentum and its
projection. This construction is used to decompose the $S$ matrix with respect to partial
waves.