Effective Kbar N interaction with strong pi Sigma dynamics constrained by chiral SU(3) symmetry

We derive a single-channel effective Kbar N interaction from chiral SU(3) coupled-channel dynamics, emphasizing the important role of the pi Sigma channel and the structure of the Lambda(1405) resonance. The chiral low energy theorem requires strongly attractive interaction not only in the Kbar N channel but also in the pi Sigma channel. As a consequence of the strong pi Sigma dynamics, the equivalent potential in single Kbar N channel turns out to be less attractive than the one used in a purely phenomenological approach.