Measurement of the pp. -->. pi. d spin correlation parameters A/sub SL/ and A/sub LL/ at energies between 500 and 800 MeV

Abstract

Angular distributions of the spin correlation parameters A/sub SL/ and A/sub LL/ for the inelastic reaction pp..--> pi..d have been measured at pion center-of-mass angles between 40 and 130/sup 0/, at energies of 500, 650, and 800 MeV. Additional measurements of A/sub LL/(THETA) were made at 600, 700, and 750 MeV. The reaction was studied using an incident beam of either longitudinally polarized protons. Both the final state pion and deuteron were detected in a two-armed detector system. The momenta of particles detected in the deuteron arm were analyzed with a magnetic spectrometer which allowed the deuterons to be distinguished from particles produced by quasi-free, three-body, or other background reactions. A/sub SL/ was found to be negative (approx. = -0.5) at 500 MeV. It became increasingly more negative as energy increased, going down to as low as -0.88 at forward angles at 800 MeV. A/sub SL/ showed only a slight angular dependence in the entire energy range. The angular distribution of A/sub LL/ was found to be almost flat at 500 (approx. = -0.5) and 600 MeV (approx. = -0.4). As energy increased A/sub LL/ became less negative and began to peak at theta/sub cm/ = 90/sup 0/. At 800 MeV A/sub LL/ was positive at almost all measured angles and had a well defined peak at theta/sub cm/ = 90/sup 0/ which reached a maximum of about +0.4. The data were compared to several partial wave analyses and to theoretical calculations based on unified theories of NN..-->..NN, ..pi..d..--> pi..d, and NN..--> pi..d reactions. In general these later calculations were found to be unsuccessful in fitting our data. Partial wave analyses, which included the present data, fitted the data reasonably well and did not indicate the need for any unusual (dibaryon like) structures in any of the partial waves. 52 references.