π+Production in Al and C by 209-Mev Polarized Protons

The production of ${\pi }^{+}$ mesons by 209-Mev polarized protons incident on aluminum and carbon has been studied at production angles of 92° (for both elements) and 120° and 144° (for Al alone). Normalized right-left asymmetries of the order of -0.5 are observed at 92° in both elements and for mesons in the range 26-51 Mev. The asymmetry appears to decrease rapidly with increasing production angle. The absolute production cross sections are determined with statistical uncertainties of about 10%. The cross sections at 92° are approximately proportional to the atomic weights of the two target materials, and the angular distribution in Al is almost isotropic for all meson energies.