Quark-based phenomenology of strong and electromagnetic particle mixing

Isoscalar quark-annihilation diagrams mediated by gluon exchanges are assumed to be the origin of particle mixing. Without specifying the detailed dynamics, the 0^-, 0⁺, 1^-, 1⁺, and 2⁺ meson U(3) nonets are systematically diagonalized and compared with quadratic mixing-angle and meson-decay predictions at the semistrong level. The scheme is then extended to higher U(3) nonets, to the charmed sector, and to electromagnetic quark-annihilation diagrams in conjunction with SU(2) meson mass splittings and nonphotonic η_3π, ω_2π, and ψ^'→ψπ⁰ meson decays. Finally, the phenomenologically deduced quark-annihilation strengths are classified in quark-model language and used to qualitatively justify the gluon-exchange QCD picture.