标题： 在低$q^2$时$B\to K^{(*)} \ell\ell$中 charm 环效应的微小性：轻介子分布幅度分析 显示英文标题

标题： On the smallness of charm loop effects in $B\to K^{(*)} \ell\ell$ at low $q^2$: light meson Distribution Amplitude analysis

摘要： 来自 $B\to K \ell\ell$ 中轻子不变质量小于底夸克环的奇夸克阈值的非局部效应，是通过轻介子分布幅度进行评估的。 修正后的估计，在光锥求和规则方法中使用 B 介子分布幅度，得出的结果比原始计算小约三个数量级。 鉴于这些不可分解的软胶子效应在概念上和现象学上的重要性，进行独立评估是必要的。 发现当采用 K 介子分布幅度进行评估时，这些软胶子效应在扭曲-4 精度下消失。 对于 $B\to K^* \ell\ell$ 到主导扭曲的情况，结果类似。 这消除了潜在不确定性的一个主要来源，通常使得在数据表现出与标准模型偏差时，难以明确判断新物理现象。 显示英文摘要

摘要： The non-local effects originating from the charm quark loops at dilepton invariant masses smaller than the charmonium threshold in $B\to K \ell\ell$ are evaluated with light meson distribution amplitudes. The revised estimates with B-meson distribution amplitude within a Light Cone Sum Rule approach yielded results about three orders smaller than the original computation. In view of the importance of these non-factorizable soft gluon effects, both conceptually and phenomenologically, an independent evaluation is necessary. It is found that to twist-4 accuracy, these soft gluon effects vanish when evaluated employing the kaon distribution amplitude. Similar results hold for $B\to K^* \ell\ell$ to the leading twist. This eliminates one of the major sources of potential uncertainty which usually makes it difficult for a clear case of new physics, should the data show deviations from the standard model.