Mixing of pentaquark and molecular states

There are experimental evidences for the existence of narrow states Θ ⁺ and Θ _c with the same quantum numbers of and pentaquarks and also NK ^(*) and ND ^(*) molecular states. Their masses deviate from many theoretical estimates of the pure pentaquark and molecular states. In this work we study the possibility that the observed Θ ⁺ and Θ _c are mixtures of pure pentaquark and molecular states. The mixing parameters are in general related to non-perturbative QCD which are not calculable at present. We determine them by fitting data from known states and then generalize the mechanism to Θ _b to predict its mass and width. The mixing mechanism can also naturally explain the narrow width for Θ ⁺ and Θ _c through destructive interferences, even if the pure pentaquark and molecular states have much larger decay widths. We also briefly discuss the properties of the partner eigenstates of Θ ⁺ and Θ _c and the possibility of experimentally observe them. Moreover, probable consequences of multi-state mixing are also addressed. Received: 6 March 2005, Revised: 29 July 2005, Published online: 27 September 2005 An erratum to this article is available at .