Existence of Parity Experiments in Multiparticle Reactions

We discuss a theorem of Csonka, Moravcsik, and Scadron on the nonexistence of purely kinematic parity experiments involving scattering processes with more than four particles. Such experiments can be carried out, even in the case of noncoplanar momenta in the center of mass frame, if the experimenter can construct coherent superpositions of some asymptotic states and their parity inverses, as one ideally supposes. If such information is not available, the result of Csonka, Moravcsik, and Scadron appears to stand. Work supported by the National Science Foundation. Copies of this document may be distributed without restriction as long as the content, including attributions, is unchanged. March 4, 2008: This LTEX version has only cosmetic changes from the original preprint. Csonka, Moravcsik, and Scadron [1], hereafter referred to as CMS, have proposed a theorem to the effect that the sign of the “process intrinsic parity” in a scattering reaction involving more than four particles, incoming plus outgoing, cannot be measured by kinematical means alone, unless no more than three of the particle four-momenta are linearly independent. Their theorem seems to contradict a result give by Stapp [2] in a rather thorough analysis of the concept of intrinsic parity for parity-invariant, Smatrix theories. The reason for the conflict is not far to seek; CMS have implicitly assumed that information coming from coherence among asymptotic states of different energy-momentum is unavailable, while Stapp makes the more conventional assumption that it is available. To make this clear, we show how the process intrinsic parities can be measured on the latter assumption, without any knowledge of dynamics. We assume that the transition probabilities