Positive Pion Production inp−pCollisions at 420 Mev with Polarized Protons

The asymmetry in the production of positive $\pi$ mesons in $p-p$ collisions has been studied, using a 420-Mev, 62% polarized proton beam from the Chicago synchrocyclotron, with nuclear emulsions as the pion detector. The asymmetry at 65° in the laboratory for the entire spectrum above 20 Mev in the center-of-mass system is found to be 0.151±0.021, in the direction opposite the elastic scattering that produced the polarized beam. In the region of the spectrum above 40 Mev, results are consistent with those found by other authors for the reaction $p+p\to {\pi }^{+}+d$; at lower energies where pions associated with final nucleon $p$ states become predominant, the asymmetry decreases rapidly and may possibly reverse.