论文标题
半抑制b衰变矩阵元素
Semileptonic B decays matrix elements
论文作者
论文摘要
我们介绍了基于单位性的分散矩阵（DM）方法的一些应用，以提取CKM矩阵元素$ | v_ {cb} | $从独家$ b _ {（s）} \ to D _ {（s）}}^{（s）}^{（*）}} {（*）}}} \ ell $ nc的实验数据中。 DM方法允许实现非扰动的，独立于模型的确定半抑制性形式因素的动量依赖性。从4个弹药转移的大值和实现非扰动统一界限的晶格结果开始，在其整个运动学范围内的形式因素的行为是在没有引入其动量依赖性的任何明确参数化的情况下获得的。首先，我们通过考虑半雌科$ b \rightarrowπ$衰减的情况来说明该方法的有效性，这是一个很好的基准，因为运动范围很大。然后，我们专注于四个独特的半蛋白质$ b _ {（s）} \ to d _ {（s）}^{（*）} \ellν_\ ell $衰变，我们从每个过渡的实验数据中提取$ | v_ {cb} | $。四个频道的平均值为$ | v_ {cb} | =（41.2 \ pm 0.8）\ cdot 10^{ - 3} $。我们首次找到一个独家值，它与最新的包含性确定$1σ$级别兼容。我们还通过计算每个通道分支分数的$τ/\ ell $比率的纯理论估计来解决Lepton风味普遍性的问题。如果是光观众夸克，我们获得了$ r（d^*）= 0.275（8）$和$ r（d）= 0.296（8）$，它们与$1.3σ$内的相应实验值兼容。对于一个奇怪的观众夸克，我们获得$ \ textit {r}（d_s^*）= 0.2497（60）$和$ \ textit {r}（d_s）= 0.298（5）$。
We present some applications of the unitarity-based Dispersion Matrix (DM) approach to the extraction of the CKM matrix element $|V_{cb}|$ from the experimental data on the exclusive $B_{(s)} \to D_{(s)}^{(*)} \ell ν_\ell$ decays. The DM method allows to achieve a non-perturbative, model-independent determination of the momentum dependence of the semileptonic form factors. Starting from lattice results available at large values of the 4-momentum transfer and implementing non-perturbative unitarity bounds, the behaviour of the form factors in their whole kinematical range is obtained without introducing any explicit parameterization of their momentum dependence. We firstly illustrate the effectiveness of the method by considering the case of the semileptonic $B \rightarrow π$ decay, which is a good benchmark since the kinematic range is large. Then, we focus on the four exclusive semileptonic $B_{(s)} \to D_{(s)}^{(*)} \ell ν_\ell$ decays and we extract $|V_{cb}|$ from the experimental data for each transition. The average over the four channels is $|V_{cb}| = (41.2 \pm 0.8) \cdot 10^{-3} $. We find, for the first time, an exclusive value which is compatible with the latest inclusive determination at $1σ$ level. We address also the issue of Lepton Flavour Universality by computing pure theoretical estimates of the $τ/\ell$ ratios of the branching fractions for each channel. In the case of a light spectator quark we obtain $R(D^*) = 0.275(8)$ and $R(D) = 0.296(8)$, which are compatible with the corresponding experimental values within $1.3σ$. In the case of a strange spectator quark we obtain $\textit{R}(D_s^*) =0.2497(60)$ and $\textit{R}(D_s) = 0.298(5)$.
