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 ${\eta }_{3\pi }$, ${\omega }_{2\pi }$, and ${\psi }^{\prime }\to \psi {\pi }^0$ 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.