发表机构
Hunan Normal University; Hangzhou Institute for Advanced Study, UCAS; Institute of Theoretical Physics, UCAS; University of Chinese Academy of Sciences（湖南师范大学; 杭州高等研究院，中国科学院大学; 理论物理研究所，中国科学院大学; 中国科学院大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本文利用光前夸克模型和Bethe-Salpeter形式，计算了$\Lambda_b$重子半轻子及非轻子弱衰变的分支比和前后不对称性，结果与实验一致，并发现非价贡献对不对称性影响可忽略。
AI 中文摘要
我们在标准模型框架内，利用光前夸克模型研究了唯象的半轻子及非轻子 $\Lambda_{b} \to \Lambda_{c}(p)$ 衰变。为确定 $\Lambda_{b} \to \Lambda_{c}(p)$ 跃迁形状因子的行为，我们在类时区域采用 Bethe-Salpeter 形式，有效计及了价贡献与非价贡献。利用这些包含非价贡献的形状因子，我们得到 $\Lambda_b \to \Lambda_c\\,\ell\\,\bar{\nu}_{\ell}$、$\Lambda_b \to \Lambda_c\\,\tau\\,\bar{\nu}_{\tau}$、$\Lambda_b \to p\\,\ell\\,\bar{\nu}_{\ell}$ 和 $\Lambda_b \to p\\,\tau\\,\bar{\nu}_{\tau}$（其中 $\ell=e$ 或 $\mu$）的分支比分别约为 $5.39\\%$、$1.41\\%$、$3.33\times 10^{-4}$ 和 $2.08\times 10^{-4}$，这些结果与实验测量一致。比值 $R^{\ell\tau}(\Lambda_{c})=\frac{{\cal B}({\Lambda_b}\to {\Lambda_c}\\,\tau\\,\bar{\nu}_\tau)} {{\cal B}({\Lambda_b}\to {\Lambda_c}\\,\ell\\,\bar{\nu}_l)}$ 和 $R^{\ell\tau}(p)=\frac{{\cal B}({\Lambda_b}\to p\\,\tau\\,\bar{\nu}_\tau)} {{\cal B}({\Lambda_b}\to p\\,\ell\\,\bar{\nu}_l)}$ 分别给出为 $0.261^{+0.097}_{-0.117}$ 和 $0.624^{+0.119}_{-0.129}$。我们还考察了上述半轻子衰变中的前后不对称性。我们的结果表明，在光前框架内，非价贡献对这些不对称性的影响相对于 $\beta$ 引起的不确定性而言可忽略不计。此外，我们计算了非轻子衰变 $\Lambda_{b}\to \Lambda_{c}(p)\\,M$ 的分支比，其中 $M$ 为赝标量介子和矢量介子，所得结果与当前实验数据一致。
英文摘要
We investigate the exclusive semileptonic and nonleptonic $Λ_{b} \to Λ_{c}(p)$ decays within the Standard Model by using the light-front quark model. To determine the behavior of the $Λ_{b} \to Λ_{c}(p)$ transition form factors, we employ the Bethe-Salpeter formalism in the timelike region, effectively accounting for both valence and nonvalence contributions. Using these form factors, including nonvalence contributions, we obtain branching fractions of $Λ_b \to Λ_c\,\ell\,\barν_{\ell}$, $Λ_b \to Λ_c\,τ\,\barν_τ$, $Λ_b \to p\,\ell\,\barν_{\ell}$ and $Λ_b \to p\,τ\,\barν_τ$~($\ell=e$ or $μ$) are found to be around $5.39\%$, $1.41\%$, $3.33\times 10^{-4}$ and $2.08\times 10^{-4}$, respectively, which are consistent with the experimental measurements. The ratios of $R^{\ellτ}(Λ_{c})=\frac{{\cal B}({Λ_b}\to {Λ_c}\,τ\,\barν_τ)} {{\cal B}({Λ_b}\to {Λ_c}\,\ell\,\barν_l)}$ and $R^{\ellτ}(p)=\frac{{\cal B}({Λ_b}\to p\,τ\,\barν_τ)} {{\cal B}({Λ_b}\to p\,\ell\,\barν_l)}$, are given by $0.261^{+0.097}_{-0.117}$ and $0.624^{+0.119}_{-0.129}$, respectively. The forward-backward asymmetries in the above semilepton decays are also examined. Our results indicate that, within the light-front framework, the nonvalence contributions to the asymmetries are negligible compared to the $β$-induced uncertainties. In addition, we calculate the branching ratios for the nonleptonic decays of $Λ_{b}\to Λ_{c}(p)\,M$ with $M$ being the pseudo scalar and vector mesons with the results found to be consistent with the current experimental data.
Comments23 pages, 3 figures and 6 Tables
