How to reveal the exotic nature of the Pc(4450).

The LHCb Collaboration announced two pentaquark-like structures in the J/ψp invariant mass distribution. We show that the current information on the narrow structure at 4.45 GeV is compatible with kinematical effects of the rescattering from χc1p to J/ψp: First, it is located exactly at the χc1p threshold. Second, the mass of the four-star well-established Λ(1890) is such that a leading Landau singularity from a triangle diagram can coincidentally appear at the χc1p threshold, and third, there is a narrow structure at the χc1p threshold but not at the χc0p and χc2p thresholds. In order to check whether that structure corresponds to a real exotic resonance, one can measure the process Λ0b→K-χc1p. If the Pc(4450) structure exists in the χc1p invariant mass distribution as well, then the structure cannot be just a kinematical effect but is a real resonance; otherwise, one cannot conclude that Pc(4450) is another exotic hadron. In addition, it is also worthwhile to measure the decay Υ(1S)→J/ψpp¯: a narrow structure at 4.45 GeV but not at the χc0p and χc2p thresholds would exclude the possibility of a pure kinematical effect. [ABSTRACT FROM AUTHOR]