Description of the (formula presented) Exotics States in a Quark Model Coupled Channel Calculation

Abstract

The nature of the (formula presented) and (formula presented) is analyzed in a coupled-channels calculation, including (formula presented), (formula presented) and (formula presented) channels, performed in the framework of a constituent quark model and the Resonating Group Method. The interactions among the different channels are dominated by the non-diagonal terms, which indicates the (formula presented) and the (formula presented) are unusual structures. The study of the analytic structure of the S-matrix on the complex energy plane leads us to conclude that the behaviour of the line shapes in the (formula presented) and the (formula presented) invariant mass distributions is due to the presence of virtual states.