Phenomenology of Κ^- atoms and other strange hadronic atoms

Recent optical-potential studies of the phenomenology of Κ^- atoms are reviewed. It is shown that the data can be fitted by a complex optical potential with either a relatively shallow attractive component (∼ -50 MeV at ρ₀), as suggested by a self consistent application of chirally motivated coupled-channels models, or a relatively deep attractive component (∼ -180 MeV at ρ₀) as suggested by a mean-field extrapolation of a phenomenological low-density expansion. Both classes of these optical potentials, due to their strongly absorptive component, predict similarly structured relatively narrow 'deeply bound' Κ^- atomic states with widths saturating at about 2 MeV. Possible formation reactions are briefly discussed. The more speculative case for relatively narrow deeply bound Κ^- nuclear states is briefly mentioned. Recent works on other strange hadronic atom systems, for the Σ^- and Ξ^- hyperons, are also discussed.