The ~U(12)-Classification Scheme, Static U(4)-Spin Symmetry for Light-Quarks and "Exotic" Hadrons

Abstract

Several years ago we have proposed a manifestly covariant $\tilde{U}(12)_{SF}$-classification scheme of hadrons, which maintains the successful $SU(6)_{SF}\otimes O(3)_{L}$ 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, $ρ_{3}$-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.