Charge and isospin symmetry breaking via external (pi)0-eta meson mixing

A simple model of isospin and charge symmetry breaking due to external (pi)0-eta meson mixing is presented. It is based on amplitudes extracted from the available experimental data for pd --> 3He eta0, pd -->He eta and dd --> 4He eta reactions. Predictions of the strength of isospin symmetry breaking in pd --> 3H eta+/3He eta0 reactions are given. Within the same model, the cross section for the charge symmetry breaking dd --> 4He eta0 reaction is calculated.