MASS EFFECTS IN THE QUARK-GLUON DECAYS OF HEAVY PARAQUARKONIA

Quark-gluon decays of heavy paraquarkonia S-1(0)((Q) over bar Q) --> ( q) over bar qg are investigated with account of the masses of final qu arks. The decay widths and the energy distributions of the final quark s and gluons are calculated in dependence on the relative quark masses . The strong collinear enhancement of the gluon energy distribution at the end of the spectrum is shown to take place in all such decays of eta(c) and eta(b) mesons except the decay eta(b) --> (c) over bar cg. The total decay width is shown to have an essential dependence on the final quark masses. The corresponding branching ratios of eta(c) and e ta(b) mesons are numerically estimated with a good agreement of Br(eta (c) --> (s) over bar sg) with experimental data on eta(c) decays.