AI 中文总结
研究通过格点量子色动力学+量子电动力学计算轻介子轻子衰变中轻子味普适性比率$R_{e/\mu}$的结构依赖辐射修正，采用无限体积重构方法降低误差，给出高精度标准模型预测值，为LFU高精度测试建立基准。
AI 中文摘要
轻介子π和K的电子与缪子轻子衰变宽度之比$R_{e/\mu}$，是轻子味普适性（LFU）的清晰测试及超出标准模型物理的灵敏探针。其标准模型预测精度极高，主要不确定性源于结构依赖的（SD）辐射修正$O(0.1\%)$。随着PIONEER和NA62等实验追求前所未有的精度，此SD修正成为精密实验与理论比较的关键因素。我们首次在物理π介子质量和连续极限下进行了格点量子色动力学+量子电动力学对该SD修正的计算。采用带库仑规范光子的无限体积重构（IVR）方法，显著降低了统计误差和有限体积效应。我们得到了标准模型预测值，π介子的$R_{e/\mu}=1.23501(10)\times10^{-4}$，K介子的$R_{e/\mu}=2.47653(34)\times10^{-5}$。我们的结果降低了$R_{e/\mu}$中的强子不确定性，提供了迄今为止最精确的标准模型预测，并为未来LFU的高精度测试建立了第一性原理基准。
英文摘要
The ratio of electronic to muonic leptonic decay widths, $R_{e/μ}$, for the light mesons $π$ and $K$, provides a clean test of lepton flavor universality (LFU) and a sensitive probe of physics beyond the Standard Model. Its Standard-Model prediction is exceptionally precise, with the leading uncertainty associated with the structure-dependent (SD) radiative correction of $O(0.1\%)$. As experiments such as PIONEER and NA62 aim for unprecedented precision, this SD correction has become an essential ingredient in precision experiment--theory comparisons. We present the first lattice QCD$+$QED calculation of this SD correction at the physical pion mass and in the continuum limit. We employ the infinite-volume reconstruction (IVR) method with Coulomb-gauge photons, significantly reducing both statistical errors and finite-volume effects. We obtain the Standard-Model predictions, $R_{e/μ}=1.23501(10)\times10^{-4}$ for $π$ and $R_{e/μ}=2.47653(34)\times10^{-5}$ for $K$. Our results reduce the hadronic uncertainty in $R_{e/μ}$, provide the most precise Standard-Model predictions to date, and establish first-principles benchmarks for future high-precision tests of LFU.
Comments18 pages, 7 figures
