AI 中文总结
本研究分析LHCb观测到的$B^0$衰变，通过振幅模型检验$η_c(6S,7S)$对$Λ_c^+\barΛ_c^-$谱4.63 GeV及更高质量区域的贡献，得到相关分支比乘积并指出需更精确数据。
AI 中文摘要
我们分析了LHCb合作组近期观测到的$B^0 \to K_S^0 Λ_c^+ \bar{\boldsymbol{\text{Λ}}}_c^-$衰变。$Λ_c^+\barΛ_c^-$不变质量谱在4.63 GeV附近呈现出一个积累结构，我们结合已知的$Ξ_c(2923)$和$Ξ_c(2939)$态所约束的伴随$Λ_c^+ K_S^0$谱，对该结构展开研究。我们的振幅模型包含非共振项、两个已确定的$Ξ_c$贡献，以及$Λ_c^+\barΛ_c^-$道中的高激发粲偶素态。在屏蔽Godfrey-Isgur模型和夸克对产生计算的指导下，我们用固定参数为$(4629.00, 24.20)$ MeV的$η_c(6S)$振幅检验4.63 GeV处的增强结构，该振幅提升了对4.63 GeV区域的描述；同时用固定参数为$(4718.84, 22.84)$ MeV的$η_c(7S)$贡献进行检验，该贡献提升了谱图更高质量区域的描述。我们还通过强子圈机制计算了$η_c(nS) \to Λ_c^+ \bar{\boldsymbol{\text{Λ}}}_c^-$的重子衰变，并利用朴素因子化估算了$B^0 \to K_S^0 η_c(nS)$的产生率。在窄宽度近似下，拟合得到$B^0\to K_S^0\boldsymbol{η}_c(6S)$的分支比与$η_c(6S)\toΛ_c^+\barΛ_c^-$的分支比之乘积约为$6.2 \times 10^{-6}$，而因子化和强子圈计算给出的速率比上述拟合比值低约1至3个数量级。这些结果表明，需要更精确的数据和完整的振幅分析来确定谱形并阐明高质量区域贡献的本质。
英文摘要
We analyze the $B^0 \to K_S^0 Λ_c^+ \barΛ_c^-$ decay recently observed by the LHCb Collaboration. The $Λ_c^+\barΛ_c^-$ invariant-mass spectrum exhibits an accumulation near 4.63~GeV, which we investigate together with the accompanying $Λ_c^+ K_S^0$ spectrum constrained by the known $Ξ_c(2923)$ and $Ξ_c(2939)$ states. Our amplitude model includes a nonresonant term, the two established $Ξ_c$ contributions, and high-lying charmonium states in the $Λ_c^+\barΛ_c^-$ channel. Guided by screened Godfrey--Isgur and quark-pair-creation calculations, we test the 4.63~GeV enhancement with a fixed $η_c(6S)$ amplitude at $(4629.00, 24.20)$~MeV, {which improves the description of the 4.63~GeV region}, and examine a fixed $η_c(7S)$ contribution at $(4718.84, 22.84)$~MeV, which improves the higher-mass region of the spectrum. We also evaluate the $η_c(nS) \to Λ_c^+ \barΛ_c^-$ baryonic decays via a hadron-loop mechanism and estimate the $B^0 \to K_S^0 η_c(nS)$ production in naive factorization. Within the narrow width approximation, the fit yields a $\mathcal B(B^0\to K_S^0η_c(6S)) \mathcal B(η_c(6S)\toΛ_c^+\barΛ_c^-)$ of about $6.2 \times 10^{-6}$, while the factorization and hadron-loop calculations give rates roughly one to three orders of magnitude lower than the above fitted ratio. These results highlight the need for more precise data and a full amplitude analysis to determine the line shapes and clarify the nature of the higher-mass contribution.
Comments12 pages, 4 figures and 3 tables
