S-wave $K^-π+$ System in $D^+\to K^-π^+π^+$ Decays from Fermilab E791

Abstract

A new approach to the analysis of three body decays is presented. Model-independent results are obtained for the \swave $Kπ$ amplitude as a function of $Kπ$ invariant mass. These are compared with results from $\Km\pip$ elastic scattering, and the prediction of the Watson theorem, that the phase behavour be the same below $Kη^{\prime}$ threshold, is tested. Contributions from $I=\half$ and $I={3\over 2}$ are not resolved in this study. If $I=\half$ dominates, however, the Watson theorem does not describe these data well.}