The tests of CP symmetry described in the Letter are only valid for an unpolarized e + e ~ (or pp) initial state, or one where the spin-density matrix describing the initial state is symmetric under the interchange of the spins of the particle and antiparticle. This is required so that the initial-state probability, X p s s + _: s s t\e + (p + ,s + )e'(p-,s-)) s -,sL x{e+(p+ 9 s'+)e~(p-,s'-)\,where p^*'** is the initial-state spin-density matrix, transforms into itself in the center of mass under the operations of CP. In Eq. (5), the symbol b is meant as a constant with no further kinematic dependence on momenta.We also note that related tests of CP symmetry at high energy can be found in recent work by S. L. Adler (to appear in the 1986 Snowmass workshop proceedings).
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