Five-flavor pentaquarks and other light- and heavy-flavor symmetry partners of the LHCb hidden-charm pentaquark

Abstract : The recent discovery of three pentaquark peaks --- the $P_c(4312)$, $P_c(4440)$ and $P_c(4457)$ --- by the LHCb collaboration has a series of interesting consequences for hadron spectroscopy. If these hidden-charm objects are indeed hadronic molecules, as suspected, they will be constrained by heavy-flavor and SU(3)-flavor symmetries. The combination of these two symmetries will imply the existence of a series of five-flavor pentaquarks with quark content $\bar{b} c s d u$ and $b \bar{c} s d u$, that is, pentaquarks that contain each of the five quark flavors that hadronize. In addition, from SU(3)-flavor symmetry alone we expect the existence of light-flavor partners of the three $P_c$'s pentaquarks with strangeness $S=-1$ and $S=-2$. The resulting structure for the molecular pentaquarks is analog to the light-baryon octet: we can denote the pentaquarks as $P_{Q' \bar{Q}}^N$, $P_{Q' \bar{Q}}^{\Lambda}$, $P_{Q' \bar{Q}}^{\Sigma}$, $P_{Q' \bar{Q}}^{\Xi}$ depending on the heavy- and light-quark content (with $N$, $\Lambda$, $\Sigma$, $\Xi$ the member of the light-baryon octet to which the light-quark structure resembles and $Q'$, $\bar Q$ the heavy quark-antiquark pair). In total we predict $45$ new pentaquarks, but there could be up to $109$ undiscovered states if we also consider heavy-quark spin symmetry. If an isoquartet ($I=\tfrac{3}{2}$) hidden-charm pentaquark is ever observed, this will in turn imply a second multiplet structure resembling the light-baryon decuplet: $P_{Q' \bar{Q}}^{\Delta}$, $P_{Q' \bar{Q}}^{\Sigma^*}$, $P_{Q' \bar{Q}}^{\Xi^*}$, $P_{Q' \bar{Q}}^{\Omega}$.
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https://hal.archives-ouvertes.fr/hal-02223021
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Submitted on : Thursday, August 1, 2019 - 2:15:14 AM
Last modification on : Wednesday, August 21, 2019 - 11:24:52 PM

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Fang-Zheng Peng, Ming-Zhu Liu, Ya-Wen Pan, Mario Sánchez Sánchez, Manuel Pavon Valderrama. Five-flavor pentaquarks and other light- and heavy-flavor symmetry partners of the LHCb hidden-charm pentaquark. 2019. ⟨hal-02223021⟩

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