SU3Invariance in Nucleon-Antinucleon Annihilation

The relations among the amplitudes for nucleon-antinucleon annihilation into two mesons, and also those for annihilation into a baryon-antibaryon pair and a decuplet-antidecuplet pair, are obtained on the basis of S${\mathrm{U}}_3$ invariance. The dynamical assumptions made are that for the two-meson case the 8 representations dominate the direct channel and that for the baryon-antibaryon pair case, the 8a and 27 representations dominate the crossed channel. The relations are compared with experiments, and some resulting tests of S${\mathrm{U}}_3$ invariance are suggested.