S wave Kπ scattering and effects of κ in

Kπ S wave scattering is studied using a chiral unitary approach (ChUT) taking into account coupled channels. With the amplitudes derived from the lowest order chiral Lagrangian as the kernel of a set of coupled channel Bathe–Salpeter equations, the I=1/2 S wave Kπ scattering phase shifts below 1.2 GeV can be fitted by one parameter, a subtraction constant, and a scalar resonance corresponding to the controversial κ () can be generated dynamically. A good description of the I=3/2 S wave Kπ scattering phase shifts below 1.2 GeV can also be obtained. An artificial singularity in the cut-off method of the 2-meson loop integral of the ChUT is found. The formalism is applied to deal with the S wave Kπ final state interaction (FSI) in the decay , and a qualitatively good fit to the data is achieved. The role of κ in the decay is discussed.