发表机构
University of Chinese Academy of Sciences; Ningbo University; Institute of Modern Physics, Chinese Academy of Sciences; Tsinghua University（中国科学院大学; 宁波大学; 中国科学院近代物理研究所; 清华大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
在相对论三夸克模型中，无自由参数地计算了单粲重子半轻子衰变的分支比、形状因子和极化，结果与实验及格点QCD相符，并预言了Ω_c^0衰变的正纵向极化。
AI 中文摘要
我们在相对论三夸克模型中研究了单粲重子（$\Lambda_c^+$、$\Xi_c^{0,+}$ 和 $\Omega_c^0$）到轻子重子八重态的 spin-$1/2\to1/2$ 半轻子衰变。组分夸克质量和空间波函数由重子质量谱确定。对于物理的 $\Xi_c$ 态，轻夸克味 $\mathrm{SU}(3)$ 破缺（$m_s > m_{u,d}$）自然诱导了味反三重态与味六重态构型之间的相干混合，该混合完全由质量本征态固定。因此，在计算弱跃迁振幅时没有引入可调参数。利用这些波函数，我们通过 Bakamjian--Thomas boost 计算了 $c\to s,d$ 螺旋度振幅，包括空间雅可比行列式和组分夸克自旋的 Wigner 转动。由此获得了分支比、$q^2$ 分布、纵向极化和形状因子。对于 $\Lambda_c^+\to\Lambda\ell^+\nu_\ell$ 和 $\Lambda_c^+\to n\ell^+\nu_\ell$ 模式，我们的分支比和形状因子与实验数据和格点 QCD 结果吻合良好。对于 $\Xi_c^0\to\Xi^-e^+\nu_e$，我们得到分支比 $\mathcal B_{\ell} \simeq 4.0~\\%$，这与最近的格点 QCD 计算一致，但远高于当前实验平均值。澄清这一差异的起源需要实验和理论两方面的进一步专门努力。对于 $\Omega_c^0\to\Xi^-\ell^+\nu_\ell$ 衰变，自旋为 $1$ 的 $ss$ 旁观者产生了末态 $\Xi^-$ 的正纵向极化，这与主要反三重态衰变模式中的负极化形成对比。我们对 $q^2$ 谱、角不对称性和末态重子极化的预测可为未来单粲重子半轻子衰变的测量提供有用的参考。
英文摘要
We study the spin-$1/2\to1/2$ semileptonic decays of singly charmed baryons ($Λ_c^+$, $Ξ_c^{0,+}$, and $Ω_c^0$) into the light baryon octet within a relativistic three-quark model. The constituent quark masses and spatial wave functions are determined by the baryon mass spectrum. For the physical $Ξ_c$ states, the light flavor $\mathrm{SU}(3)$ breaking ($m_s > m_{u,d}$) naturally induces a coherent mixing between the flavor antitriplet and flavor sextet configurations, which is completely fixed by the mass eigenstates. Consequently, no adjustable parameters are introduced in calculating the weak transition amplitudes. Using these wave functions, we calculate the $c\to s,d$ helicity amplitudes with the Bakamjian--Thomas boost, including the spatial Jacobian and the Wigner rotations of the constituent spins. The branching fractions, $q^2$ distributions, longitudinal polarizations, and form factors are then obtained from these amplitudes. For the $Λ_c^+\toΛ\ell^+ν_\ell$ and $Λ_c^+\to n\ell^+ν_\ell$ modes, our branching fractions and form factors are in good agreement with the experimental data and Lattice QCD results. For $Ξ_c^0\toΞ^-e^+ν_e$, we obtain branch ratio $\mathcal B_{\ell} \simeq 4.0~\%$, which is consistent with recent Lattice QCD calculations but lies well above the current experimental average. Clarifying the origin of this discrepancy calls for further dedicated efforts from both experimental and theoretical sides. For the $Ω_c^0\toΞ^-\ell^+ν_\ell$ decay, the spin-$1$ $ss$ spectator yields a positive longitudinal polarization of the final $Ξ^-$, in contrast to the negative polarizations in the predominantly antitriplet decay modes. Our predictions for the $q^2$ spectra, angular asymmetries, and final baryon polarizations may provide useful references for future measurements of singly charmed baryon semileptonic decays.
Comments28 pages, 11 figures, 9 tables
