发表机构
University of Electronic Science and Technology of China; Institute of Theoretical Physics, Chinese Academy of Sciences; University of Chinese Academy of Sciences; Institute of Modern Physics, Chinese Academy of Sciences（电子科技大学; 中国科学院理论物理研究所; 中国科学院大学; 中国科学院近代物理研究所）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本文提出一种新颖的产生机制，仅用两个参数自然解释LHCb观测到的三个$P_c$态，并预言$\Sigma_c^*\bar{D}^{(*)}$态几乎不可见，给出可证伪的分支比预言。
AI 中文摘要
LHCb观测到的三个窄五夸克态$P_c(4312)$、$P_c(4440)$和$P_c(4457)$因其接近$\Sigma_c\bar{D}^{(*)}$阈值而被广泛解释为强子分子态。然而，重夸克自旋对称性预言了额外的伙伴态，但这些伙伴态尚未在实验中被观测到，这使得$\Lambda_b^0$衰变中的产生机制对于理解其本质尤为重要。我们提出了一种新颖的产生机制，该机制可以自然地解释为何只有这三个LHCb $P_c$态被清晰观测到。$P_c(4440)$和$P_c(4457)$通过$D_{s1}^*(2860)\Lambda_c(2595)\bar{D}\pi$箱图产生，该箱图导致$K^-\Sigma_c\bar{D}^{*}$，随后再散射为$K^- J/\psi p$。该箱图在$P_c(4457)$附近发展出箱奇异性，因为箱中的四个态都可以在壳上。$P_c$态本身通过$S$波$\Sigma_c\bar{D}^{(*)}$到$J/\psi p$的再散射动态产生。$P_c(4312)$则类似地通过$D_{s0}(2590)\Lambda_c(2595)\bar{D}^*\pi$箱图进行，但没有箱奇异性。$\Sigma_c^*\bar{D}^{(*)}$分子态的近乎不可见性归因于$\Lambda_b$弱衰变中$\Lambda_c(2625)$产生的抑制，这一点已由格点QCD计算所确立。该机制仅用两个产生参数即可自然重现数据，而此前的工作需要7个参数和精细调谐的背景，并为$\Sigma_c^*\bar{D}^{(*)}$态几乎不可见提供了自然解释。它产生了独特的、可证伪的预言：$\Gamma(\Lambda_b^0\to P_c(4440/4457) K\to J/\psi p K)/\Gamma(\Lambda_b^0\to\bar D_{s1}^*(2860)\Lambda_c(2595))\approx (0.2-0.4)\\%$，$\Gamma(\Lambda_b^0\to P_c(4312) K\to J/\psi p K)/\Gamma(\Lambda_b^0\to \bar D_{s0}(2590)\Lambda_c(2595))\approx (0.2-0.8)\\%$。
英文摘要
The three narrow pentaquarks $P_c(4312)$, $P_c(4440)$, and $P_c(4457)$ observed by LHCb are widely interpreted as hadronic molecules owing to their proximity to the $Σ_c\bar{D}^{(*)}$ thresholds. However, heavy-quark spin symmetry predicts additional partner states that have not been seen experimentally, making the production mechanism in $Λ_b^0$ decays particularly important in understanding their nature. We propose a novel production mechanism, which can naturally explain why only these three LHCb $P_c$ states have been clearly observed. The $P_c(4440)$ and $P_c(4457)$ are produced via the $D_{s1}^*(2860)Λ_c(2595)\bar{D}π$ box diagram leading to $K^-Σ_c\bar{D}^{*}$, followed by rescattering into $K^- J/ψp$. The box diagram develops a box singularity in the vicinity of the $P_c(4457)$, as all four states in the box can go on shell. The $P_c$ states themselves are dynamically generated through the rescattering of the $S$-wave $Σ_c\bar{D}^{(*)}$ to $J/ψp$. The $P_c(4312)$ proceeds analogously via the $D_{s0}(2590)Λ_c(2595)\bar{D}^*π$ box diagram but without a box singularity. The near-invisibility of the $Σ_c^*\bar{D}^{(*)}$ molecular states is attributed to the suppressed production of the $Λ_c(2625)$ in $Λ_b$ weak decays, as established by the lattice QCD calculations. This mechanism naturally reproduces the data with only two production parameters, whereas previous works required 7 parameters and a finely tuned background, and provides a natural explanation for why the $Σ_c^*\bar{D}^{(*)}$ states are barely visible. It yields unique, falsifiable predictions, $Γ(Λ_b^0\to P_c(4440/4457) K\to J/ψp K)/Γ(Λ_b^0\to\bar D_{s1}^*(2860)Λ_c(2595))\approx (0.2-0.4)\%$, $Γ(Λ_b^0\to P_c(4312) K\to J/ψp K)/Γ(Λ_b^0\to \bar D_{s0}(2590)Λ_c(2595))\approx (0.2-0.8)\%$.
Comments10 pages, 3 figures, 1 table
