Production of Pc states in Λb decays

We develop a model for the production of the Pc states observed at LHCb in Ab -> J=psi pK- decays. With fewer parameters than other approaches, we obtain excellent fits to the J=psi p invariant mass spectrum, capturing both the prominent peaks, and broader features over the full range of invariant mass. A distinguishing feature of our model is that whereas Pc(4312), Pc(4380), and Pc(4440) are resonances with E(*) c over bar D(*) constituents, the nature of Pc(4457) is quite different, and can be understood either as a Ec over bar D* threshold cusp, a Ac(2595)D over bar enhancement due to the triangle singularity, or a Ac(2595)D over bar resonance. We propose experimental measurements that can discriminate among these possibilities. Unlike in other models, our production mechanism respects isospin symmetry and the empirical dominance of color -enhanced processes in weak decays, and additionally gives a natural explanation for the overall shape of the data. Our model is consistent with experimental constraints from photoproduction and Ab -> Ac decays and it does not imply the existence of partner states whose apparent absence in experiments is unexplained in other models. over bar D(*)0K-

Automated summary

This paper presents a model to explain the observed Pc states in Ab -> J/Ψ pK- decays at LHCb. The model has fewer parameters compared to other approaches, yet it provides excellent fits to the experimental data and offers a natural explanation for the overall shape of the data. In addition, the model is consistent with experimental constraints and does not imply the existence of unexplained partner states.