Antiprotonic atoms at Lear: achievements and perspectives

The outcome of the experimental study of the X-and gamma-ray spectra from antiprotonic atoms of Experiment PS176 is presented. First tentative results on the measurement of strong interaction effects in light antip atoms are given. Isotope effects caused by strong interaction have been observed. From these data, information about the real to imaginary part of the antipn forward scattering amplitude at zero energy was derived. An attempt was made to determine L-S dependence in the antiNN force. Gamma spectra from nuclear fragments left over after antip absorption were measured, and information about the frequency of antipp to antipn annihilation and single-nucleon removal was obtained. For the first time the spectra of neutrons emitted from residual nuclei were also observed. The fine-structure splitting of atomic levels was measured with high precision in order to determine the magnetic moment of the antiproton with greater accuracy. The high-energy gamma spectra associated with antip annihilation was measured in order to search for antip-nuclear and antip-nucleon states. Moreover, a wealth of information on the antiprotonic atomic cascade was obtained. 25 refs