Strong interaction physics from hadronic atoms

Hadronic atoms provide a unique laboratory for studying strong interactions and nuclear medium effects at zero kinetic energy. Previous results from analyses of strong-interaction data consisting of level shifts, widths and yields in pi(-), K-, (p) over bar and Sigma(-) atoms are reviewed. Recent results from fits to comprehensive sets of data in terms of density-dependent optical potentials that respect the low-density limit. where the interaction tends to the free hadron nucleon value, are discussed. The importance of using realistic nuclear density distributions is highlighted. The introduction of density dependence in most cases significantly improves the fit to the data and leads to some novel results. For K- atoms, a substantial attraction of order 200 MeV in nuclear matter is suggested, with interesting repercussions for (K) over bar condensation and the evoIution of strangeness in high-density stars. For (p) over bar atoms it is found that a reasonable p-wave strength can be accommodated in the fitted optical potential, in agreement with the energy dependence observed for some low-energy (p) over bar N reactions. For Sigma(-) atoms, the fitted potential becomes repulsive inside the nucleus, implying that Sigma hyperons generally do not bind in nuclei in agreement with recent measurements. This repulsion significantly affects calculated masses of neutron stars.