On the role of hidden-colour states in 2q 2anti-q systems

We study a system of tw quarks and two antiquarks of equal masses in the framework of a nonrelativistic potential model with color confinement and hyperfine spin-spin interaction. We propose a simple variational solution and conclude that the hyperfine interaction is needed to bind the system in agreement with previous studies. Our results explicitly show the important role played by the hidden-color states in lowering the variational energy.