Nuclear medium effects on K and K interactions

Medium effects on the interaction of K and K mesons with nucleons are reviewed. Recent K⁺ nuclear data confirm that conventional multiple scattering models fail to describe the interaction of K mesons for incoming momenta p_L = 400 - 800 MeV/c, suggesting a particular form of density dependence for the K nuclear optical potential. K^- atom strong-interaction data, fitted using a density dependent nuclear optical potential which respects the low-density theorem, require an appreciably stronger attraction than that obtained using a V_opt = tp form, of order 180 ± 20 MeV at nuclear-matter density. The relationship of this result to the physics of the A(1405) KN unstable bound state is clarified, and the prospects of meeting the conditions for K^- condensation in high-density matter are discussed.