2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/41943We discuss the partial width of the pseudoscalar charmonium state eta_c and bottomonium state eta_b into two photons. Predictions from potential models are examined and compared with experimental values for the eta_c case. Through the NRQCD factorisation procedure results for eta_c are also compared with those from J/psi data, and results for eta_b to the Upsilon decay data.To appear in the proceedings of ``First international Workshop on Frontier Science, October 6-11, 2002 INFN Laboratory, Frascati, Italy''. 2 pages, uses frascatiphys_SP.styHigh Energy Physics - Phenomenologytext