ExclusiveO16(γ,π−p) reaction in the Δ resonance region

We report the first exclusive (γ,${\mathrm{\pi }}^{\mathrm{-}}$p) measurements on a complex nucleus. The ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$(γ,${\mathrm{\pi }}^{\mathrm{-}}$p) reaction was measured at pion laboratory angles of 64° and 120°. Coincident protons were detected over the quasifree angular correlation range using a vertical array of seven plastic scintillator detectors spanning ±33° about the scattering plane. The cross sections are compared to factorized distorted-wave impulse approximation calculations; these provide a good description of the backward angle data, but are in serious disagreement with the forward angle data.