The exciting discovery by LHCb of the $P_c(4312)^+$ and $P_c(4450)^+$ pentaquarks, or the suggestion of a tetraquark nature for the $Z_c(3900)$ state seen at BESIII and Belle, have triggered a lot of activity in the field of hadron physics, with new experiments planned for searching other exotic mesons and baryons, and many theoretical developments trying to disentangle the true multiquark nature from their possible molecular origin. After a brief review of the present status of these searches, this paper focusses on recently seen or yet to be discovered exotic heavy baryons that may emerge from a conveniently unitarized meson-baryon interaction model in coupled channels. In particular, we will show how interferences between the different coupled-channel amplitudes of the model may reveal the existence of a $N^*$ resonance around 2 GeV having a meson-baryon quasi-bound state nature. We also discuss the possible interpretation of some of the $\Omega_c$ states recently discovered at LHCb as being hadron molecules. The model also predicts the existence of doubly-charmed quasibound meson-baryon $\Xi_{cc}$ states, which would be excited states of the ground-state $\Xi_{cc}(3621)$ MeV, whose mass has only been recently established. Extensions of these results to the bottom sector will also be presented.

中文翻译：

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一些奇异强子的分子性质

LHCb 对 $P_c(4312)^+$ 和 $P_c(4450)^+$ 五夸克的激动人心的发现，或者在 BESIII 和 Belle 上看到的 $Z_c(3900)$ 状态的四夸克性质的建议，已经触发强子物理学领域的许多活动，计划进行新的实验以寻找其他奇异的介子和重子，以及许多试图将真正的多夸克性质与其可能的分子起源分开的理论发展。在简要回顾了这些搜索的现状后，本文重点介绍了最近看到或尚未发现的奇异重重子，这些重重子可能来自耦合通道中方便的统一介子-重子相互作用模型。特别是，我们将展示模型的不同耦合通道振幅之间的干扰如何揭示在 2 GeV 附近存在 $N^*$ 共振，具有介子重子准束缚态性质。我们还讨论了最近在 LHCb 上发现的一些 $\Omega_c$ 状态是强子分子的可能解释。该模型还预测了双重魅力准束缚介子重子 $\Xi_{cc}$ 状态的存在，这将是基态 $\Xi_{cc}(3621)$ MeV 的激发态，其质量仅为最近成立。还将介绍这些结果对底部扇区的扩展。该模型还预测了双吸引准束缚介子重子 $\Xi_{cc}$ 状态的存在，这将是基态 $\Xi_{cc}(3621)$ MeV 的激发态，其质量仅为最近成立。还将介绍这些结果对底部扇区的扩展。该模型还预测了双吸引准束缚介子重子 $\Xi_{cc}$ 状态的存在，这将是基态 $\Xi_{cc}(3621)$ MeV 的激发态，其质量仅为最近成立。还将介绍这些结果对底部扇区的扩展。