Kaonic atoms and in-medium K−N amplitudes

Recent work on the connection between in-medium subthreshold K−N amplitudes and kaonic atom potentials is updated by using a next to leading order chirally motivated coupled channel separable interaction model that reproduces observables at low energies, including the very recent SIDDHARTA results for the atomic K−-hydrogen 1s level shift and width. The corresponding K−-nucleus potential is evaluated self-consistently within a single-nucleon approach and is critically reviewed with respect to empirical features of phenomenological optical potentials. The need to supplement the single-nucleon based approach with multi-nucleon interactions is demonstrated by showing that additional empirical absorptive and dispersive terms, beyond the reach of chirally motivated K−-nucleus potentials, are required in order to achieve good agreement with the bulk of the data on kaonic atoms.