Spin asymmetries from16O(γ→,pπ−)nearΔresonance energies

Spin asymmetries for the ${}^{16}\mathrm{O}(\overrightarrow{\gamma },p{\pi }^{-})$ reaction are reported for incident photon energies of 293 $\pm$ 20 MeV, proton angles ranging from 28$°$ to 140$°$ (lab), and pion angles of 35$°$ to 115$°$. The data are compared with calculations in a quasifree plane-wave impulse approximation model. This model is in good agreement with the data at small momentum transfer $q$, but does not follow the trend of the data at large $q$. Sensitivity to the $\Delta$-nucleus potential and to modification of the $\Delta$ lifetime from nuclear medium effects are explored using a simple modification of the $\Delta$ propagator in the calculations.