Structure and decay width of Θ^+ in a one-gluon exchange model

Abstract

The mass and decay width of the $Θ^+(1540)$ with isospin 0 are investigated in a constituent quark model comprising $uudd\bar{s}$ quarks. The resonance state for the $Θ^+$ is identified as a stable solution in correlated basis calculations. With the use of a one-gluon exchange quark-quark interaction, the mass is calculated to be larger than 2 GeV, increasing in order of the spin-parity, ${1/2}^-, {3/2}^-$ and ${1/2}^+ ({3/2}^+)$, and only the ${3/2}^-$ state has a small width to the $nK^{*+}$ decay. If the calculated mass is shifted to around 100 MeV above the $N+K$ threshold, the $Θ^+(1540)$ is possibly ${1/2}^+ ({3/2}^+)$ or ${3/2}^-$, though in the latter case it cannot decay to the $nK^{+}$ channel. In addition it is conjectured that other pentaquark state with different spin-parity exists below the $Θ^+(1540)$. The structure of the $Θ^+$ is discussed through the densities and two-particle correlation functions of the quarks and through the wave function decomposition to a baryon-meson model and a diquark-pair model.