The analyzing-power behavior and the isospin dependence of the cross sections for near-threshold reactions ${}_{}{}^{13}{}_{}{}^{}$C(p,${\pi }^{\pm }$) and ${}_{}{}^{12}{}_{}{}^{}$C(p,${\pi }^{+}$) are compared with expectations from pion production measurements in free two-nucleon collisions. The general agreement for ($p_{\mathrm{pol}}$,${\pi }^{+}$) suggests that the stable analyzing-power pattern observed for ($p_{\mathrm{pol}}$,${\pi }^{\mathrm{-}}$) continuum transitions may reflect the as yet unmeasured free $p_{\mathrm{pol}\mathrm{n}\to \mathrm{pp}{\pi }^{\mathrm{-}}}$ behavior. We also discuss constraints imposed by quasifree ${\mathrm{NN}}_{\mathrm{pol}\to \mathrm{NN}\mathrm{\pi }}$ expectations on the interpretation of anomalous ($p_{\mathrm{pol}}$,${\pi }^{+}$) results for two strongly populated states at high excitation in ${}_{}{}^{13}{}_{}{}^{}$,14C.

• Received 11 July 1986

DOI:https://doi.org/10.1103/PhysRevLett.58.104