Münster 2002 – scientific programme
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HK: Physik der Hadronen und Kerne
HK 8: Plenary Session
HK 8.4: Plenary Talk
Tuesday, March 12, 2002, 10:00–10:30, Plenarsaal
Pionic 1s States in Heavy Atoms and the Pion-Nucleus Interaction — •Albrecht Gillitzer — IKP, Forschungszentrum Jülich
In the lowest energy levels negative pions bound to heavy nuclei form halo-like states whose size is given by nuclear dimensions. The 1s states are almost exclusively determined by the s-wave part of the interaction, which is therefore directly accessible by the measurement of pionic binding energies and widths. The deduced repulsive central potential is significantly larger than resulting from the free πN interaction which indicates the presence of nuclear medium effects.
Deeply bound pionic states in heavy atoms are inaccessible in electromagnetic cascades subsequent to the capture of stopped negative pions, and can only be populated in direct reactions. In a series of experiments at the GSI Fragment Separator these states were discovered in 207Pb and then more precisely studied in 205Pb. Very recently the formation of pionic 1s states in several Sn isotopes was studied in order to investigate the isotope dependence which would allow to separate the isoscalar and the isovector part of the interaction. First results of this new experiment will be presented.