Analysis for hypercharge-exchange reactions in terms of dispersion relations

An analysis of $\pi N\to K\Lambda$ and $\overline{K}N\to \pi \Lambda$ is presented in which the imaginary parts of the amplitudes are in approximate agreement with finite-energy sum rules and the real parts are calculated in terms of the imaginary parts via fixed-$t$ dispersion relations. The resulting differential cross sections and polarizations are in fair agreement with experiment. Certain features and implications of the amplitude structure are discussed.