Two examples of antiproton annihilation have been observed in an emulsion stack exposed at the Bevatron. The experimental arrangement was designed to affect a partial separation of antiproton and pion fluxes. From the yield of antiprotons, we estimate the total cross section for antiprotons in beryllium to be ($1_{-0.1\mathrm{}}^{+0.2\mathrm{}}$) barn. The average energy of the antiprotons in the beryllium was 315 Mev.

• Received 8 October 1956

DOI:https://doi.org/10.1103/PhysRev.105.729