Five-body calculation of resonance and scattering states of pentaquark system

Scattering problem of the uudds system in the standard nonrelativistic quark model of Isgur-Karl is solved for the first time, by treating the large five-body model space including the NK scattering channel accurately with the Gaussian expansion method and the Kohn-type coupled-channel variational method. The two-body interaction that reproduces observed properties of ordinary baryons and mesons is applied to the pentaquark system with no additional adjustable parameter. The resulting five-body wave function has the correct asymptotic form in its scattering-channel component and describes qq and qq correlations properly. The NK scattering phase shift shows no resonance in the energy region of the reported pentaquark Theta(+) (1540), that is, at 0-500 MeV above the NK threshold (1.4-1.9 GeV in mass). Instead, the phase shift does show two resonances just above 500 MeV: a broad 1/2(+) resonance with a width of Gamma similar to 110 MeV located at similar to 520 MeV (similar to 2.0 GeV in mass) and a sharp 1/2(-) resonance with Gamma = 0.12 MeV at 540 MeV. Properties of these states are discussed. (c) 2005 Elsevier B.V. All rights reserved.