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We calculate the two-loop QCD corrections to paracharmonium decays $eta_{c}rightarrow gamma gamma$ and $eta_{c} rightarrow g g$ involving light-by-lightscattering diagrams with light quark loops. Artificial large mass expansion andconvergence improvement techniques are used to evaluate these corrections. Theobtained corrections to the decays $eta_{c} rightarrow gamma gamma$ and$eta_{c} rightarrow g g$ account for $-1.25 %$ and $ -0.73 %$ of the leadingorder contribution, respectively.Comment: 24 pages, 10 figures; REVTeX version; Version to appear in Phys. Rev.  D, 9 pages, 4 figure

Large mass expansion in two-loop QCD corrections of paracharmonium decay