Relativistic corrections to radiative transitions and spectra of quarkonia

We calculate the energy spectrum and the one-photon E1 and M1 decays of charmonium and b-quarkonium including their first-order relativistic corrections, within the context of the Buchm̈ller-Tye potential. Results seem to suggest that the confining potential is predominantly scalar since this assumption gives good agreement for spectra and for E1 decay rates of cc and gives reasonable results for bb. For M1 decays discrepancies persist unless the quarks have large anomalous moments, but the resolution of such discrepancies can probably be achieved by other means. As an interesting by-product of our investigations we find that for the nonrelativistically inhibited E1 decay jb+ of the bb system, some rates are enhanced by a huge factor by first-order relativistic effects. When more data are available these decays should provide an additional testing ground for models of relativistic corrections.