2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/186995We consider the existence of bound systems consisting of two quarks and two antiquarks ($q^2\bar q^2$) within the framework of a constituent quark model. The underlying quark dynamics is described by a linear confinement potential and an effective $q^2\bar q^2$ interaction which has its origin in instanton effects of QCD. We calculate the spectra and examine the internal structure of the states found.11 pages, needs epsf.styHigh Energy Physics - PhenomenologyNuclear Theorytext