Particle physics aspects in hadronic atoms

From the study of hadronic atoms one can obtain information about the two components of the system, the nucleus and the orbiting particle and about the interaction between them. Observing transitions between highly excited states of the hadronic atoms one is outside the range of the strong interaction. Under these conditions the energies of the levels can be calculated precisely, taking into account all electromagnetic effects, particularly the vacuum polarization. Thus the value of the mass of the orbiting particle can be derived. The best values so far of the masses of the antiproton could be obtained and are presented for the K/sup -/ meson. The magnetic moment of the particle will cause a fine structure splitting indications of which may be seen. The strong electrical fields may cause a polarization of the nucleus and of the orbiting particle itself resulting in an increase of the level energies. The limits which can be set experimentally, to those effects at present, are discussed. The lower lying levels are affected by the strong interaction between the orbiting particle and the nucleus. As a consequence, the atomic cascade of the particle stops at a certain level, since nuclear capture dominates. Due to the nuclear absorption the last X-ray transition observable has a reduced intensity and the lower level is broadened. (1 refs).