Diquark Structure of Pentaquark in the Quark Delocalization Colour Screening Model

In the framework of quark-delocalization, colour-screening model, the diquark structure of pentaquark θ⁺ is studied in detail under the adiabatic approximation. The calculation is carried out by using the fractional parentage expansion technique, which greatly simplify the calculation of the matrix elements of Hamiltonian. The results show that the ground state of the pentaquark has negative parity rather than positive parity, which was proposed by Jaffe--Wilczek. However the mass obtained is about 1651MeV which is still higher than the observed mass 1540MeV.