Determination of the lightest strange resonance $K_0^{\ast }(700)$ or $\hat{I}º$, from a dispersive data analysis

Abstract

In this work we present a precise and model-independent dispersive determination from data of the existence and parameters of the lightest strange resonance $\hat{I}º/K_0^{\ast }(700)$. We use both subtracted and unsubtracted partial-wave hyperbolic and fixed-$t$ dispersion relations as constraints on combined fits to $\ddot{I}€K\to \ddot{I}€K$ and $\ddot{I}€\ddot{I}€\to K\bar{K}$ data. We then use the hyperbolic equations for the analytic continuation of the isospin $I=1/2$ scalar partial wave to the complex plane, in order to determine the $\hat{I}º/K_0^{\ast }(700)$ and $K^{\ast }(892)$ associated pole parameters and residues.

6 pages, 3 figures, 2 tables. References, comments, clarifications and 1 table added. Minor typos corrected. Version to appear on Phys.Rev.Lett