The U-tilde(12)-classification scheme, static U(4)-spin symmetry for light-quarks and 'exotic' hadrons

Several years ago we have proposed a manifestly covariant U-tilde(12)SF-classification scheme of hadrons, which maintains the successful SU(6)SF x O(3)L framework in Non-Relativistic Quark Model and is also reconcilable with the mechanism of Spontaneously-Broken Chiral Symmetry in Relativistic Field Theoretical Models. The essential point here is to notice the overlooked freedom of the SU(2)ρ-spin for (confined) light quarks, which leads to existence of new type of 'exotic' hadrons, called 'chiralons' and to a selection rule, ρ3-line rule, on the spectator quark line. A series of puzzling new hadrons recently observed such as X(3872)-meson family and Θ(1540) and so on are possibly classified mostly as chiralons. (author)