Evidence for Exotic Hadron Contributions to Λ0b → J/ψ p π− Decays

A full amplitude analysis of Λ0b → J/ψ p π− decays is performed with a data sample acquired with the LHCb detector from 7 and 8 TeV pp collisions, corresponding to an integrated luminosity of 3 fb^−1. A significantly better description of the data is achieved when, in addition to the previously observed nucleon excitations N → p π−, either the Pc(4380)+ and Pc(4450)+ → J/ψ p states, previously observed in Λ0b → J/ψ p K− decays, or the Zc(4200)− → J/ψ π− state, previously reported in B0 → J/ψ K+ π− decays, or all three, are included in the amplitude models. The data support a model containing all three exotic states, with a significance of more than three standard deviations. Within uncertainties, the data are consistent with the Pc(4380)+ and Pc(4450)+ production rates expected from their previous observation taking account of Cabibbo suppression.