About 10 000 two-prong events of 8.1 GeV/ c proton-proton interactions in the CERN 2 m. bubble chamber have been analyzed. We study elastic scattering and single-pion production reactions. We give cross sections for isobar production. We attempt to interpret the general features of the pp→pn π + reaction by the Deck mechanism. We compare the production and the decay of δ ++ (1236) with absorption or π Regge trajectory exchange models.
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We measured dσdt for p↑+p↑→p+p from P⊥2=4.50 to 5.09 (GeV/c)2 at 11.75 GeV/c. We used a 59%-polarized proton beam and a 71%-polarized proton target with both spins oriented perpendicular to the scattering plane. In these large-P⊥2 hard-scattering events, spin effects are very large and the ratio (dσdt)↑↑:(dσdt)↑↓ grows rapidly with increasing P⊥2, reaching a value of 4 at 90° (c.m.). Thus, hard elastic scattering, which is presumably due to the direct scattering of the protons' constituents, may only occur when the two incident protons' spins are parallel.
THE ERRORS INCLUDE STATISTICAL AND SYSTEMATIC ERRORS ADDED IN QUADRATURE. THE PARALLEL/ANTIPARALLEL SPIN CROSS SECTION RATIO IS (1+CNN)/(1-CNN).