标题： 新的BaBar对高阶辐射的研究以及数据驱动的μ子g-2 HVP预测的新格局 显示英文标题

标题： New BaBar studies of high-order radiation and the new landscape of data-driven HVP predictions of the muon g-2

摘要： 对使用完整$BaBar$数据样本的$e^+e^- \to \mu^+\mu^- \gamma$和$e^+e^- \to \pi^+\pi^- \gamma$初始态辐射事件中额外辐射的测量进行了介绍。 首次在次领头阶和次次领头阶给出了结果，分别对应于初始态和末态辐射的一个和两个额外光子。 与 Phokhara 和 AfkQed 生成器的预测相比，前者在单光子速率和角度分布上存在差异。 尽管这种不一致对$BaBar$测量的$e^+e^- \to \pi^+\pi^- (\gamma)$截面影响可以忽略，但对 KLOE 和 BESIII 测量的影响进行了估计，并发现其表明存在显著的系统效应。 这些发现为缪子$g-2$测量、使用数据驱动的色散方法计算强子真空极化（HVP）的标准模型预测，以及与格点 QCD 计算的比较之间长期存在的偏差提供了新的见解。 显示英文摘要

摘要： A measurement of additional radiation in $e^+e^- \to \mu^+\mu^- \gamma$ and $e^+e^- \to \pi^+\pi^- \gamma$ initial-state-radiation events is presented using the full $BaBar$ data sample. For the first time results are presented at next-to- and next-to-next-to-leading order, with one and two additional photons, respectively, for radiation from the initial and final states. The comparison with the predictions from Phokhara and AfkQed generators reveals discrepancies for the former in the one-photon rates and angular distributions. While this disagreement has a negligible effect on the $e^+e^- \to \pi^+\pi^- (\gamma)$ cross section measured by $BaBar$, the impact on the KLOE and BESIII measurements is estimated and found to be indicative of significant systematic effects. The findings shed a new light on the longstanding deviation among the muon $g-2$ measurement, the Standard Model prediction using the data-driven dispersive approach for calculation of the hadronic vacuum polarization (HVP), and the comparison with lattice QCD calculations.