Chao En-Hung, Hudspith Renwick J, Gérardin Antoine, Green Jeremy R, Meyer Harvey B
PRISMA+ Cluster of Excellence, Institut für Kernphysik, Johannes Gutenberg-Universität Mainz, 55099 Mainz, Germany.
Aix Marseille Univ, Université de Toulon, CNRS, CPT, Marseille, France.
Eur Phys J C Part Fields. 2022;82(8):664. doi: 10.1140/epjc/s10052-022-10589-2. Epub 2022 Aug 2.
We compute the hadronic light-by-light scattering contribution to the muon from the charm quark using lattice QCD. The calculation is performed on ensembles generated with dynamical (, , ) quarks at the SU(3) symmetric point with degenerate pion and kaon masses of around 415 MeV. It includes the connected charm contribution, as well as the leading disconnected Wick contraction, involving the correlation between a charm and a light-quark loop. Cutoff effects turn out to be sizeable, which leads us to use lighter-than-physical charm masses, to employ a broad range of lattice spacings reaching down to 0.039 fm and to perform a combined charm-mass and continuum extrapolation. We use the meson to define the physical charm-mass point and obtain a final value of , whose uncertainty is dominated by the systematics of the extrapolation. Our result is consistent with the estimate based on a simple charm-quark loop, whilst being free of any perturbative scheme dependence on the charm mass. The mixed charm-light disconnected contraction contributes a small negative amount to the final value.
我们使用格点量子色动力学（lattice QCD）计算了粲夸克对μ子的强子光致光散射贡献。该计算是在具有动力学（，，）夸克的系综上进行的，处于SU(3)对称点，π介子和K介子质量简并，约为415 MeV。它包括连通的粲贡献，以及主导的非连通维克收缩（Wick contraction），涉及一个粲夸克圈和一个轻夸克圈之间的关联。结果表明截断效应相当大，这促使我们使用比实际物理值更轻的粲夸克质量，采用范围广泛的格点间距直至0.039 fm，并进行粲夸克质量和连续统外推的联合操作。我们使用介子来定义物理粲夸克质量点，并得到的最终值，其不确定性主要由外推的系统误差主导。我们的结果与基于简单粲夸克圈的估计一致，同时不存在任何对粲夸克质量的微扰方案依赖性。混合的粲-轻非连通收缩对最终值贡献了一个小的负值。
