点形式相对论量子力学中的半轻子介子衰变：弱形状因子的明确提取
Semileptonic meson decays in point-form relativistic quantum mechanics: unambiguous extraction of weak form factors
摘要：
本文用点形式的Bakamjian-Thomas构造描述了介子的几种半轻子衰变。弱形状因子提取没有歧义的赝标量到赝标量以及赝标量到矢量的介子从最一般的协变分解的弱电流的过渡。与电磁情况下发生的情况相反，这种电流的结构没有以非物理贡献的形式出现集群可分性破坏的表现。此外，当我们从电流的最一般的协变分解中提取形状因子时，没有观察到帧依赖性，这与涉及矢量介子的类似的前形计算形成对比。本文给出了重轻介子衰变（$B\to D$）以及$B$和$D$介子衰变为$π$、$ρ$和$K^{(*)}$的结果，并与类似的前形方法进行了数值比较.出现了在$q\bar Q$ -系统的重夸克极限中看不到的点形式和前形式之间的差异。这些差异归因于非价贡献在描述每种形式的强子反应中所起的不同作用。有人认为如何从失踪的$Z$ -图的贡献可以估计。
英文摘要：
The point-form version of the Bakamjian-Thomas construction is applied to the description of several semileptonic decays of mesons. Weak form factors are extracted without ambiguity for pseudoscalar-to-pseudoscalar as well as for pseudoscalar-to-vector transitions of mesons from the most general covariant decomposition of the weak current. No manifestation of cluster-separability violation appears in the form of non-physical contributions to the structure of such a current, in contrast to what happens in the electromagnetic case. Moreover, no frame dependence is observed when we extract the form factors from the most general covariant decomposition of the current, which contrasts with analogous front-form calculations that involve vector mesons in the transition. We present our results for heavy-light meson decays, i.e. $B\to D$, as well as for $B$ and $D$ mesons decaying into $π$, $ρ$ and $K^{(*)}$ and perform a numerical comparison with the analogous front-form approach. Differences between point and front forms that are not seen in the heavy-quark limit of $q\bar Q$-systems appear. These differences are attributed to the different role that the non-valence contributions play in the description of hadronic reactions in each form. It is argued how contributions from missing $Z$-graphs can be estimated.
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