The importance of the isospin symmetry breaking in extracting various particle physics parameters is discussed. In particular the measurement of isospin symmetry breaking in the reaction pd→³Hπ⁺/³Heπ⁰ is presented. The energy dependence of the measured cross sections ratio indicate isospin symmetry breaking effects. Within a simple model based on π⁰ −η meson mixing the mixing angle of these mesons is extracted.