Four Quark cn - nbar cbar States in U(12)-Scheme and X(3872)/Y(3940)
  The properties of four quark cn - nbar cbar states are investigated as cn di-quark and nbar cbar di-antiquark system in U(12)-classification scheme of hadrons, recently proposed by us. We consider the negative-parity di-quark and di-antiquark in ground states, which form with the ordinary positive-parity ones the respective linear representations of chiral symmetry. The masses and widths of ground-states are predicted by using Joint Spring Quark Model, and the observed properties of X(3872) and Y(3940) are consistent, respectively, with those of the JPC=1++ and 2++ states from the negative-parity di-quark and di-antiquark. Their narrow-widths are explained from an orthogonality of spinor wave functions. The properties of ground-state cs - sbar cbar system are also predicted in this scheme. 
Muneyuki Ishida (Meisei univ.), Shin Ishida (Nihon univ.) and Tomohito   Maeda (Nihon univ.)