ETA AND ETA' IN A COUPLED SCHWINGER-DYSON AND BETHE-SALPETER APPROACH- ART. NO. 096003

Extending our earlier treatments of pi(0), eta(c), and eta(b), we stud y the eta-eta' system and its gamma gamma decays using a model which i s a leading version of the consistently coupled Schwinger-Dyson (SD) a nd Bethe-Salpeter (BS) approaches. The electromagnetic interactions an incorporated through a (generalized) impulse approximation consistent with this bound-state approach, so that the Ward-Takahashi identities of QED are preserved when quarks are dynamically dressed. To overcome some of the limitations due to the ladder approximation, we introduce a minimal extension to the bound-state approach employed, so that the U-A(1) problem is avoided. Pointing out which of our predictions hold in the coupled SD-BS approach in general, and which are the consequen ces of the specific, chosen model, we present the results for the axia l-current decay constants of eta(8), eta(0), and of their physical com binations eta and eta', the results for the gamma gamma-decay constant s of eta(0) and eta(8), for the two-photon decay widths of eta and eta ', and for the mixing-independent R ratio constructed from them. [S055 6-2821(98)03217-2]