We present the first lattice QCD calculation of the charm quark contribution to the nucleon electromagnetic form factors $G^c_{E,M}(Q^2)$ in the momentum transfer range $0\leq Q^2 \leq 1.4$ $\rm GeV^2$. The quark mass dependence, finite lattice spacing and volume corrections are taken into account simultaneously based on the calculation on three gauge ensembles including one at the physical pion mass. The nonzero value of the charm magnetic moment $\mu^c_M=-0.00127(38)_{\rm stat}(5)_{\rm sys}$, as well as the Pauli form factor, reflects a nontrivial role of the charm sea in the nucleon spin structure. The nonzero $G^c_{E}(Q^2)$ indicates the existence of a nonvanishing asymmetric charm-anticharm sea in the nucleon. Performing a nonperturbative analysis based on holographic QCD and the generalized Veneziano model, we study the constraints on the $[c(x)-\bar{c}(x)]$ distribution from the lattice QCD results presented here. Our results provide complementary information and motivation for more detailed studies of physical observables that are sensitive to intrinsic charm and for future global analyses of parton distributions including asymmetric charm-anticharm distribution.

中文翻译：

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来自晶格 QCD 的核子中魅力-反魅力不对称性的约束

我们在动量传递范围 $0\leq Q^2 \leq 1.4$ $\ 中提出了魅力夸克对核子电磁形状因子 $G^c_{E,M}(Q^2)$ 的贡献的第一个晶格 QCD 计算rm GeV^2$。夸克质量相关性、有限晶格间距和体积校正是基于对三个规范集合的计算同时考虑在内的，其中一个集合是物理π质量。魅力磁矩的非零值 $\mu^c_M=-0.00127(38)_{\rm stat}(5)_{\rm sys}$ 以及泡利形状因子，反映了魅力海中的核子自旋结构。非零 $G^c_{E}(Q^2)$ 表示核子中存在一个不消失的不对称魅力-反魅力海。执行基于全息 QCD 和广义 Veneziano 模型的非微扰分析，我们从这里呈现的格子 QCD 结果研究 $[c(x)-\bar{c}(x)]$ 分布的约束。我们的结果为更详细地研究对内在魅力敏感的物理可观察量以及未来对部分分布（包括不对称魅力-反魅力分布）的全局分析提供了补充信息和动机。