Coulomb gauge approach to scalar hadrons
  The Coulomb gauge model, involving an effective QCD Hamiltonian in the Coulomb gauge, is applied to scalar hadrons. Mass predictions are presented for both conventional q-qbar meson and q-qbar-q-qbar tetra-quark states. Mixing matrix elements between these states were also computed and diagonalized to provide a reasonable description of the scalar spectrum below 2 GeV. 
Stephen R. Cotanch, Ignacio J. General, Ping Wang and Felipe J.   Llanes-Estrada