MIXING ANGLES AND DECAY CONSTANTS IN THE SU(4) MIXING SCHEME OF ETA-ETA'-ETA(C)-IOTA

We extend the SU(3) mixing of isosinglet pseudoscalar mesons to the SU (4) level with eta, eta', eta(c) and iota. The quarkonium gluonium con tent of the physical states at the SU(4) level are being numerically e stimated. We derive a mass relation at the SU(4) level taking the dive rgence of vector current into account and solve for the SU(4) mixing a ngles and decay constants using the constraints obtained from anomalou s Ward identities, the mass relation, topological susceptibility, SU(4 ) transformation properties of pseudoscalar density, experimental data and other presently available constraints. The mixing has suggested t hat besides charm quark content, eta(c) meson has some percentage of n ormal and strange quarks along with gluonium as its constituents.