Pionic deuterium

Data taking of the project PIONIC HYDROGEN has been completed with a high statistics study of the strong-interaction effects by measuring the Kβ X-radiation in πD. The πD hadronic shift will provide a constraint for πN isospin scattering lengths extracted from the πH measurement. In addition, as an outstanding case in charged pion-nucleon interactions the shift is very sensitive to isospin-breaking corrections owing to the almost complete cancellation of the pion-proton and pion-neutron scattering lengths. Secondly, the hadronic width is directly related to pion production processes at threshold, which is subject of continuing theoretical efforts within the framework of chiral perturbation theory. The measurement was performed at the Paul Scherrer Institut, Switzerland, using the cyclotron trap and a high-resolution Bragg crystal spectrometer. By measuring the density dependence cascade effects can be identified and corrected in order to allow an unambiguous determination of the strong-interaction effects. First results of the new πD experiments will be discussed. (orig.)