He3,4(p→,π+)Heg.s.4,5. reactions at 800 MeV

Angular distributions of the differential cross section and the analyzing power for ground state transitions in the ${}_{}{}^{3,4}{}_{}{}^{}\mathrm{He}(\overrightarrow{\mathrm{p}},{\pi }^{+}){}_{}{}^{4,5}{}_{}{}^{}\mathrm{He}$ reactions have been measured at 800 MeV using a polarized proton beam. The angular distributions of the analyzing power $A_y$ reveal a surprisingly strong spin dependence in these reactions. The analyzing power from the ${}_{}{}^3{}_{}{}^{}\mathrm{He}(\overrightarrow{\mathrm{p}},{\pi }^{+}){}_{}{}^4{}_{}{}^{}\mathrm{He}$ reaction is compared with $A_y$ data from elastic p-He scattering, the $\mathrm{pp}\to \mathrm{d}\pi$ reaction, and pion nucleon scattering, in order to find an indication of the origin to the spin dependence. Reasonably good agreement is obtained with the pion-nucleon $A_y$ data when momentum sharing is assumed between the nuclear vertices involved in a pion rescattering diagram of the ($\mathrm{p},\pi$) reaction.