Higher η c( nS) and η b( nS) mesons.

The hyperfine splittings in heavy quarkonia are studied in a model-independent way using experimental data on dielectron widths. Relativistic correlations are taken into account together with the smearing of spin-spin interaction. The radius of smearing is fixed by known G/ ψ−η _c(1 S), ψ(2 S)− η _c′(2 S) splittings, which appears to be small, r _ss ≅ 0.06 fm. Nevertheless, even with such a small radius, substantial suppression of hyperfine splittings (∼50%) is observed in bottomonium. For nS b $$\bar b$$ states ( n = 1, 2, ..., 6), our predicted splittings (in MeV) are 28, 12, 10, 5, 6, 3. For the 3 S and 4 S charmonium states, the splittings 16(2) and 12(4) MeV are obtained. [ABSTRACT FROM AUTHOR]