标题： 格点QCD中的$Λ_b \to Λ_c^*(2595,2625)\ell^-\barν$形因子 显示英文标题

标题： $Λ_b \to Λ_c^*(2595,2625)\ell^-\barν$ form factors from lattice QCD

摘要： 我们给出了描述半轻子衰变$\Lambda_b \to \Lambda_c^*(2595)\ell^-\bar{\nu}$和$\Lambda_b \to \Lambda_c^*(2625)\ell^-\bar{\nu}$的形式因子的第一个格点QCD确定，其中$\Lambda_c^*(2595)$和$\Lambda_c^*(2625)$是带有$J^P=\frac12^-$和$J^P=\frac32^-$的最轻的粲重子。这些衰变模式提供了检验轻子味普适性的新机会，也在$b\to c$半轻子衰变的强相互作用全局分析中扮演了重要角色。我们确定了这两种衰变的全部矢量、轴矢量和张量形式因子，但仅限于接近零反冲点的小动量转移平方区域。 晶格计算使用了三种不同的规范场构型 ensemble，其中包含 $2+1$ 味域墙费米子，并且我们对形式因子进行了从格点间距到连续极限以及物理 pion 质量的外推。 我们给出了标准模型下微分衰变率和角可观测量的预测。 在所考虑的动力学区域内，发现 $\frac12^-$ 最终态的微分衰变率大约比 $\frac32^-$ 最终态的衰变率大 2.5 倍。 我们还检验了我们的形式因子结果与零反冲求和规则的一致性。 显示英文摘要

摘要： We present the first lattice-QCD determination of the form factors describing the semileptonic decays $\Lambda_b \to \Lambda_c^*(2595)\ell^-\bar{\nu}$ and $\Lambda_b \to \Lambda_c^*(2625)\ell^-\bar{\nu}$, where the $\Lambda_c^*(2595)$ and $\Lambda_c^*(2625)$ are the lightest charm baryons with $J^P=\frac12^-$ and $J^P=\frac32^-$, respectively. These decay modes provide new opportunities to test lepton flavor universality and also play an important role in global analyses of the strong interactions in $b\to c$ semileptonic decays. We determine the full set of vector, axial vector, and tensor form factors for both decays, but only in a small kinematic region near the zero-recoil point. The lattice calculation uses three different ensembles of gauge-field configurations with $2+1$ flavors of domain-wall fermions, and we perform extrapolations of the form factors to the continuum limit and physical pion mass. We present Standard-Model predictions for the differential decay rates and angular observables. In the kinematic region considered, the differential decay rate for the $\frac12^-$ final state is found to be approximately 2.5 times larger than the rate for the $\frac32^-$ final state. We also test the compatibility of our form-factor results with zero-recoil sum rules.