Molecular interpretation of the Pc (4440) and Pc (4457) states

Abstract

A molecular model of the Pc(4457) and Pc(4440) LHCb states is proposed. The model relies on channels coupled by long-range pion-exchange dynamics with features that depend crucially on the novel addition of the Λc(2595)D channel. A striking prediction of the model is the unusual combination of quantum numbers JP(4457)=1/2+ and JP(4440)=3/2-. Unlike in other models, a simultaneous description of both states is achieved without introducing additional short-range interactions. The model also gives a natural explanation for the relative widths of the states. We show that the usual molecular scenarios cannot explain the production rate of Pc states in Λb decays and that this can be resolved by including Λc(2595)D and related channels. Experimental tests and other states are discussed in the conclusions.