THE RELATIVISTIC THEORY OF REACTIONS INVOLVING POLARIZED PARTICLES

It is shown that, in the rest system, the relativistic formulas for the angular distribution and the polarization vectors and tensors for a reaction of the type a + b → c + d are essentially the same as the nonrelativistic formulas, if the spin of a particle is defined as its internal angular momentum around its center of mass. The square of this internal angular momentum is Lorentz invariant. The spins of the particles are arbitrary, and their rest masses are nonvanishing.

The main difference from the nonrelativistic case is that the description of the spin state is not the same in different Lorentz reference systems. Therefore for cascades of reactions (for example, for experiments on double scattering) corrections must be applied to the non-relativistic formal theory. The relativistic changes in the angular correlations are indicated for successive reactions of the type π + p → Y + K, Y → N + π.