An improved study of the kappa resonance and the non-exotic $s$ wave $\pi K$ scatterings up to $\sqrt{s}=2.1$GeV of LASS data

Abstract

We point out that the dispersion relation for the left hand cut integral presented in one of our previous paper (Nucl. Phys. {\bf A}733(2004)235) is actually free of subtraction constant, even for unequal mass elastic scatterings. A new fit to the LASS data~\cite{Aston} is performed and firm evidence for the existence of $\kappa$ pole is found. The correct use of analyticity also put strong constraints on threshold parameters -- which are found to be in good agreement with those obtained from chiral theories. We also determined the pole parameters of $K_0^{\ast }(1430)$ on the second sheet, and reconfirm the existence of $K_0^{\ast }(1950)$ on the third sheet. We stress that the LASS data do not require them to have the twin pole structure of a typical Breit--Wigner resonance.

Comments: 14 pages + 4 postscript figures; discussions largely expanded; references added; version to appear in NPA; title changed in the journal