Contribution of higher meson resonances to the electromagnetic π-meson mass difference

Modifications of the DGMLY relation for calculation of electromagnetic π-meson mass difference based on the Chiral Symmetry Restoration phenomenon at high energies as well as the Operator Product Expansion of quark densities for vector (ρ) and axial-vector (a1) meson fields difference are proposed. In the calculations higher meson resonances in vector and axial-vector channels are taken into account. It is shown that the inclusion of the first ρ and a1 radial excitations improves the results for electromagnetic π-meson mass difference as compared with the previous ones. Estimations on the electromagnetic ρ and a1-meson decay constants and the constant L10 of effective chiral Lagrangian are obtained from the generalized Weinberg sum rules.