Proton-Proton Interactions at 1.5 Bev

152 interactions of 1.5-Bev protons have been observed in a hydrogen-filled diffusion cloud chamber. The data indicate an elastic cross section of 20 millibarns, with about 22 millibarns cross section for single pion production and 5 millibarns for double pion production Most single pion production cases are $p+p\to p+n+{\pi }^{+}$; no $\mathrm{definite}\mathrm{case}\mathrm{of}\to d+{\pi }^{+} or\to p+p+{\pi }^0$ were observed. The median elastic scattering angle is 24° in the c.m. system. Inelastic events have pions emitted isotropically with low momenta, nucleons emitted near 0° and 180° with high momenta. The average relative energy ($Q$ value) for the $p$, ${\pi }^{+}$ pair is 154 Mev.