Some experiments in elastic proton-antiproton scattering are suggested in order to test the $\mathrm{TCP}$ theorem, as well as the validities of the separate $T$, $C$, and $P$ invariances. Also, a theorem has been proved that the total scattering cross section of two particles is equal to that of antiparticles, provided that the $\mathrm{TCP}$ theorem is valid.

• Received 2 July 1962

DOI:https://doi.org/10.1103/PhysRev.128.1921