Narrow Pentaquark States in a Quark Model with Antisymmetrized Molecular Dynamics

The exotic baryon Θ ^ + ( {uuddbar s} ; ) is studied with microscopic calculations in a quark model by using a method of antisymmetrized molecular dynamics(AMD). We predict narrow states, J^π = 1/2⁺(I = 0), J^π = 3/2⁺(I = 0), and J^π = 3/2^- (I = 1), which nearly degenerate in a low-energy region of the uuddbar s system. We discuss N K decay widths and estimate them to be Γ < 7 for the J^π = {1/2⁺, 3/2⁺}, and Γ < 1 MeV for the J^π = 3/2^- state.