Interference Effects inO16(π±,π±p)N15andΔ-Nucleus Interactions

First results for ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}({\pi }^{\pm },{\pi }^{\pm }p){}_{}{}^{15}{}_{}{}^{}\mathrm{N}_{\mathrm{g}.\mathrm{s}.\mathrm{}}^{}{}_{}{}^{}$ at 240 MeV for ${\theta }_{\pi }=35\mathrm{}°, 60°, \mathrm{and} 130°$ in quasifree kinematics are reported. $\frac{{\pi }^{+}}{{\pi }^{-}}$ cross-section ratios much greater than for scattering by free protons are interpreted as due to a $\Delta -N$ interaction interfering with the quasifree process.