Mixing of meson, hybrid, and glueball states

An effective QCD Hamiltonian is constructed with the aid of the background perturbation theory and relativistic Feynman-Schwinger path integrals for Green's functions. The resulting spectrum displays mass gaps of about 1 GeV when an additional valence gluon is added to the bound state. The mixing of meson, hybrid, and glueball states is defined in two ways—through generalized Green's functions and through a modified Feynman diagram technique—giving similar answers. Results for mixing matrix elements are numerically not large (around 0.1 GeV) and agree with earlier analytic estimates and lattice simulations.