Structure and decay width of the Θ+(1540) in a one-gluon exchange model

Abstract The mass and decay width of the Θ + ( 1540 ) with isospin 0 are calculated in a constituent quark model comprising u u d d s ¯ quarks. A correlated basis is used in a non-relativistic five-particle model, and the Θ + is identified with a resonance state described as a solution stable against changes in the basis. With the use of a one-gluon exchange quark–quark interaction, the mass is found to be larger than 2 GeV, in a sequence of spin-parity 1 2 − , 3 2 − , 1 2 + ( 3 2 + ) , and only the 3 2 − state has a small width to the n K ∗ + decay. By shifting the calculated mass to around 100 MeV above the N + K threshold, the level to be identified with the Θ + ( 1540 ) has spin-parity 1 2 + ( 3 2 + ) or 3 2 − , though in the latter case it cannot decay to the n K + channel. In addition it is conjectured that other pentaquark states with different spin-parities exist below the Θ + ( 1540 ) . The structure of the pentaquark states is discussed in terms of the densities and two-particle correlation functions of the quarks and in terms of the wave function decompositions into a baryon–meson model and into a diquark-pair model.