The LHCb Collaboration announced the observation of three narrow structures consistent with hidden-charm pentaquark states. They are candidates of hadronic molecules formed of a pair of a charmed baryon and an anticharmed meson. Among them, the $P_c(4457)$ mass is consistent with earlier predictions of a ${\mathrm{\Sigma }}_c{\overline{D}}^{*}$ molecule with $I=1/2$. We point out that if such a picture were true, one would have $\mathcal{B}(P_c(4457)\to J/\psi {\mathrm{\Delta }}^{+})/\mathcal{B}(P_c(4457)\to J/\psi p)$ at the level ranging from a few percent to about 30%. Such a large isospin breaking decay ratio is two to three orders of magnitude larger than that for normal hadron resonances. It is a unique feature of the ${\mathrm{\Sigma }}_c{\overline{D}}^{*}$ molecular model, and can be checked by LHCb.

• Received 29 March 2019

DOI:https://doi.org/10.1103/PhysRevD.99.091501

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Published by the American Physical Society