X-ray spectroscopy of light hadronic atoms

Abstract

A series of measurements on light exotic atoms has been performed over the last 15 years at the pion factory of the Paul Scherrer Institut and at CERN's antiproton facility LEAR using the cyclotron trap and a focusing Bragg crystal spectrometer. The experiments with pions reached already an accuracy close to the presently achievable technical limits. The information on antiprotons remains unsatisfactory because the studies were terminated with the shut down of LEAR. Some aspects of high resolution X-ray spectroscopy are discussed as well as relations between the elementary processes of absorption and annihilation to observables in light nuclei.