Reactionp+p→π++din the 425-Mev Energy Region

The 437-Mev external proton beam of the Carnegie Institute of Technology synchrocyclotron has been used to measure the angular distribution and total cross section of the reaction $p+p\to {\pi }^{+}+d$. The proton beam impinged upon liquid hydrogen, and the resulting positive pions were detected in fast coincidence with their associated deuterons. The differential cross section was measured at seven pion center-of-mass angles in the range from 30° to 130°. Several corrections were applied to the observed counting rates, including a downward correction of about 7% to compensate for coincidence counts which arose from the reaction $p+p\to {\pi }^{+}+p+n$. The corrected total cross section for the reaction $p+p\to {\pi }^{+}+d$ is 1.23±0.07 mb, with a center-of-mass angular distribution proportional to $(0.23\mathrm{}\pm 0.02)+{cos}^2\theta$. In addition, a 53% polarized proton beam of energy about 415 Mev was used to measure azimuthal asymmetries in the $p+p\to {\pi }^{+}+d$ reaction. The experimental technique was very similar to that used for the production cross-section measurements. The asymmetry $\epsilon$, defined as the difference divided by the sum of the pion intensities on the right and left, was measured at pion center-of-mass angles of 90° and 50°. The magnitudes of the measured asymmetries were $\epsilon \left(90\mathrm{}°\right)=0.20\mathrm{}\pm 0.03$ and $\epsilon \left(50\mathrm{}°\right)=0.023\mathrm{}\pm 0.015$ in such a sense that the greatest meson intensity was on the left when the polarized beam originated in a scattering to the right. The results of the cross-section and asymmetry measurements are discussed in relation to phenomenological analyses of the threshold behavior of the $p+p\to {\pi }^{+}+d$ reaction.