Interactions of antiprotons were studied at a momentum of 3.6 GeV/c in a hydrogen bubble chamber. Particular attention was paid to single and multiple pion production without annihilation. Cross sections for the various pion-production channels are given. The total cross section for pion production without annihilation and not including strange-particle production is ${18.6}_{-3.3\mathrm{}}^{+2.4\mathrm{}}$ mb. Single pion production is found to agree with the predictions of the one-pion-exchange model for small values of the four-momentum transfer. Double pion production in the reaction $\overline{p}p\to p\overline{p}{\pi }^{+}{\pi }^{-}$ agrees with the one-pion-exchange model for all values of the four-momentum transfer, if all possible diagrams are taken into account. The main contribution comes from events where a $\frac{3}{2}-\frac{3}{2}$ pion-nucleon isobar-anti-isobar pair is produced. For these events the Treiman-Yang angular distribution and the decay angular distributions of the isobars are also in agreement with the one-pion-exchange model.

• Received 12 June 1964

DOI:https://doi.org/10.1103/PhysRev.136.B843