Resonant final-state interactions in exclusive hadronic D decays to eta ' or eta

For hadronic two-body decays of charmed mesons involving eta or eta', reson ance-induced final-state interactions (FSI) that mimic the W-exchange or th e W-annihilation topology can play an essential role. In particular, the de cays D-0 --> (K) over bar (0)eta' and D+ --> pi (+)eta, which are largely s uppressed in the absence of FSI, are enhanced dramatically by resonant FSI. It is stressed that the effect of resonant FSI is negligible for rho (+)(e ta,eta') final states because of the mismatch of the G parity of rho (+)(et a,eta') and the J = 0, I = 1 meson resonance. We argue that a possible gluo n-mediated process in which two gluons couple directly to the gluonic compo nent of the eta', e.g., the gluonium, rather than to the flavor-singlet eta (0), can enhance both modes D-s(+) --> rho (+)eta' and D-s(+) --> rho (+)e ta, especially the former; that is, this new mechanism can account for the unexpectedly large branching ratio of rho (+)eta' Without suppressing rho ( +)eta.