Energy dependence of the analyzing power for theC12(p→,π+)C13reaction with polarized protons of 200 to 250 MeV

The analyzing power angular distributions $A_y\left(\theta \right)$ for the ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}_{\mathrm{g}.\mathrm{s}.\mathrm{}}^{}{}_{}{}^{}$ as well as for several ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$* excited state transitions from the ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$($\overrightarrow{p}$, ${\pi }^{+}$)${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$ reaction are reported as a function of incident proton energy from 200 to 250 MeV. For the first time in reactions of the type $A(\overrightarrow{p},{\pi }^{+})A+1\mathrm{}$, a dramatic energy dependence is observed for the analyzing power. A dependence of the shape of the analyzing power on the nature of the excited nuclear state is also observed. The cross section for the ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}_{\mathrm{g}.\mathrm{s}.\mathrm{}}^{}{}_{}{}^{}$ transition shows indication of backward peaking not observed at energies below 225 MeV.