Proton-Proton Interactions at 2.75 Bev

212 interactions of 2.75-Bev protons have been observed in a hydrogen-filled diffusion cloud chamber. The data indicate an elastic cross section of 15 millibarns, with about 9 millibarns cross section for single pion production, 13 millibarns for double, and 4 for triple. There is one example of quadruple pion production. One definite example of the production of heavy unstable particles was observed, and two doubtful cases. The median elastic scattering angle was 19\ifmmode^\circ\else\textdegree\fi{} in the c.m. system. Angle and momentum distributions for inelastic events are consistent with those observed at lower energies.