Multi-quark hadrons in the joined-spring quark model

The level structures of typical multi-quark exotic hadrons, (q2anti q2)-meson, (q4anti q)-baryon and (q6)-di-baryon with only nuclear quarks, are investigated systematically in the joined spring quark model, where hadron masses squared are described in terms of harmonic oscillators with various quanta. This model was proposed by us as a simple idealization of the string-junction model so as to make it possible a quantum mechanical treatment of constituent quarks. An interesting prediction of our model is that there exist orbital Regge trajectories with the steeper slope than the usual one for non-exotic hadrons. Somewhat strong experimental suggestions for existence of these trajectories are seen for all respective cases of exotic hadrons. (author)