Penta-quark states with hidden charm and beauty
  More and more hadron states are found to be difficult to be accommodated by the quenched quark models which describe baryons as 3-quark states and mesons as antiquark-quark states. Dragging out an antiquark-quark pair from the gluon field in hadrons should be an important excitation mechanism for hadron spectroscopy. Our recent progress on the penta-quark states with hidden charm and beauty is reviewed. 
Bing-Song Zou
hep-ph nucl-th