Masses of di-mesonic molecular states

The forces binding the quarks into mesons and baryons are described by Quantum Chromodynamics (QCD). But certain states like molecular states, tetraquark and hybrid mesons do not fit with such classifications of hadrons are been studied under framework of Bag Model and non-relativistic potential models. The non-relativistic potential models are successful at the heavy flavor sectors, while nonrelativistic harmonic oscillator potentials and Bethe-Salpeter approach under harmonic confinement are successful at low flavor sectors for their mass predictions