The hadronic shift in pionic hydrogen has been redetermined to be $epsilon_{1s}=7.086,pm,0.007(stat),pm,0.006(sys)$,eV by X-ray spectroscopy of ground state transitions applying various energy calibration schemes. The experiment was performed at the
high-intensity low-energy pion beam of the Paul Scherrer Institut by using the cyclotron trap and an ultimate-resolution Bragg spectrometer with bent crystals.
The strong interaction shift $epsilon$ and broadening {Gamma} in pionic deuterium have been determined in a high statistics study of the {pi}D(3p - 1s) X-ray transition using a high-resolution crystal spectrometer. The pionic deuterium shift will pro
vide constraints for the pion-nucleon isospin scattering lengths extracted from measurements of shift and broadening in pionic hydrogen. The hadronic broadening is related to pion absorption and production at threshold. The results are epsilon = (-2356 {pm} 31)meV (repulsive) and {Gamma}1s = (1171+23/-49) meV yielding for the complex {pi}D scattering length a = [-(24.99 {pm} 0.33) + i (6.22+0.12/-0.26)]x10-3/m{pi}. From the imaginary part, the threshold parameter for pion production is obtained to be {alpha} = (251 +5/-11) {mu}b. This allows, in addition, and by using results from pion absorption in 3He at threshold, the determination of the effective couplings g0 and g1 for s-wave pion absorption on isoscalar and isovector NN pairs.
An unusual but effective way to determine at threshold the dpi -> NN transition strength is to exploit the hadronic ground-state broadening in pionic deuterium, accessible by x-ray spectroscopy. The broadening is dominated by the true absorption chan
nel dpi- -> nn, which is related to s-wave pion production pp -> dpi+ by charge symmetry and detailed balance. Using the exotic atom circumvents the problem of Coulomb corrections to the cross section as necessary in the production experiments. Our dedicated measurement finds (1171+23/-49) meV for the broadening yielding (252+5/-11) mub.
The strong interaction shift and broadening in pionic deuterium have been remeasured with high statistics by means of the (3p-1s) X-ray transition using the cyclotron trap and a high-resolution crystal spectrometer. Preliminary results are (-2325+/-3
1) meV (repulsive) for the shift and (1171+23/-49} meV for the width, which yields precise values for the pion-deuteron scattering length and the threshold parameter for pion production.
The onset of antiprotonic X-ray transitions at high principal quantum numbers and the occurence of electronic X-rays in antiprotonic argon, krypton, and xenon has been analyzed with the help of Multiconfiguration Dirac-Fock calculations. The shell-by
-shell ionisation by Auger electron emission, characterised by appearance and disappearance of X-ray lines, is followed through the antiprotonic cascade by considering transition and binding energies of both the antiproton and the remaining electrons. Electronic lines could be attributed partly to specific states of the antiprotonic atom de-excitation.
