Off-Mass-ShellKπScattering Phase Shifts

The final states $K^{-}{\pi }^{+}n$ and ${\overline{K}}^0{\pi }^{-}p$ were measured in a $K^{-}p$ experiment at $5.5 \frac{\mathrm{GeV}}{c}$. The data on the angular distribution of the outgoing $K$ meson in the $K\pi$ rest system at low momentum transfer were analyzed by a simple model including $I=\frac{3}{2}$ $s$-wave and $I=\frac{1}{2}$ $s$-, $p$-, and $d$-wave amplitudes. The results show that the phase shift for the $I=\frac{3}{2}$ $s$ wave is negative. The two solutions obtained for the $I=\frac{1}{2}$ $s$-wave off-mass-shell phase shift are consistent with an $s$-wave resonance at either ∼0.85 or ∼1.2 GeV.