Plane waves for kaon-nucleus reactions

The plane wave impulse approximation (PWIA) is assessed for $K^{+}$ meson inelastic scattering from ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ by comparison with distorted wave impulse approximation (DWIA) calculations. The $K^{+}$-nucleus distortions are directly determined from phenomenological $K^{+}$-nucleon amplitudes. For $E_{\mathrm{lab}}\ge 50$ MeV, use of plane waves enhances the DWIA cross section less than 50%, an effect size comparable to distorted wave calculations with different sets of $K^{+}$-nucleon amplitudes.