Quasifreeπ+production studied using theC12(γ, π+n)B11reaction in theΔ(1232)resonance region

Results are presented from a coincidence study of the ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}(\gamma , {\pi }^{+}n){}_{}{}^{11}{}_{}{}^{}\mathrm{B}$ quasifree pion production reaction made in the $\Delta$-resonance region using tagged photons. Cross sections for reactions originating on $1p$-shell protons are found to be significantly larger than predicted by calculations based on quasifree pion production. It is suggested that more sophisticated calculations, perhaps including medium effects, may be required to reproduce the data.