  In a previous work, we have reanalyzed the I=0 S-wave \pi\pi-scattering
phase-shift through a new method of Interfering Breit-Wigner amplitudes, and
have shown the existence of a light scalar, \sigma particle, accompanied by a
negative "repulsive core"-type background phase-shift, whose origin may have
some correspondence to a ``compensating'' \pi\pi contact interaction. In this
work we make further analysis on the phase shift under KKbar threshold from the
same standpoint, to determine precise values of \sigma mass and width, so far
as present experimental data are concerned.
