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How to reveal the exotic nature of the P_c(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 $χ_{c1} p$ to $J/ψp$: First, it is located exactly at the $χ_{c1} p$ 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 $χ_{c1} p$ threshold, and third, there is a narrow structure at the $χ_{c1}\,p$ threshold but not at the $χ_{c0} p$ and $χ_{c2} p$ thresholds. In order to check whether that structure corresponds to a real exotic resonance, one has to measure the process $Λ_b^0\to K^-χ_{c1} p$. If the $P_c(4450)$ structure exists in the $χ_{c1} p$ invariant mass distribution as well, then the structure cannot be just a kinematical effect but is a real resonance, otherwise, one cannot conclude the $P_c(4450)$ to be another exotic hadron. In addition, it is also worthwhile to measure the decay $Υ(1S)\to J/ψp \bar p$: a narrow structure at 4.45 GeV but not at the $χ_{c0} p$ and $χ_{c2} p$ thresholds would exclude the possibility of a pure kinematical effect.