Low energy KN interaction in nuclear matter

We investigate the low-energy KN interaction in nuclear matter including Pauli blocking, Fermi motion and binding effects. We use a coupled-channel approach based on the Chiral SU(3) Effective Lagrangian which describes all available low energy data of the coupled KN, πΣ, πΛ system. Due to the dynamics of the Λ (1405) resonance we find a strong non-linear density dependence of the K−p scattering amplitude in nuclear matter. The real part of the K−p scattering length changes sign already at a small fraction of nuclear matter density, less than 0.2 po. This may explain the striking behaviour of the K− -nuclear optical potential found in the analysis of kaonic atom data.