标题： 核子轴向、张量和标量电荷以及格点QCD中的$σ$项 显示英文标题

标题： Nucleon axial, tensor and scalar charges and $σ$-terms in lattice QCD

摘要： 我们确定了核子的轴矢电荷、标量电荷和张量电荷，包括来自价夸克和海夸克的所有贡献。我们分析了在扭曲质量公式中模拟的三个规范系综，其介子质量接近物理值。这三个系综中的两个使用了两个动态轻夸克和格点间距$a=0.094$~fm，第三个使用了$a=0.08$~fm，并且额外包含了海中的奇异夸克和魅夸克。在比较这三个系综的结果后，我们引用了使用最后一个系综进行的最准确分析作为最终结果。对于核子等距轴矢电荷，我们发现$1.286(23)$，与实验值一致。 我们提供了核子中由夸克携带的内在自旋$\frac{1}{2}\Delta\Sigma^q$的味分解，分别得到上夸克、下夸克、奇夸克和魅夸克的$\frac{1}{2}\Delta\Sigma^{u}=0.431(8)$、$\frac{1}{2}\Delta\Sigma^{d}=-0.212(8)$、$\frac{1}{2}\Delta\Sigma^{s}=-0.023(4)$和$\frac{1}{2}\Delta\Sigma^{c}=-0.005(2)$。 每种夸克味的张量电荷和标量电荷的相应值也进行了评估，为寻找标准模型以外的物理现象的实验提供了有价值的信息。 此外，我们提取了核子的$\sigma$-项，并发现轻夸克成分$\sigma_{\pi N}=41.6(3.8)$~MeV 和奇异的$\sigma_{s}=45.6(6.2)$~MeV。 在现象学研究中使用的 y-参数我们发现是$y=0.078(7)$。 显示英文摘要

摘要： We determine the nucleon axial, scalar and tensor charges within lattice Quantum Chromodynamics including all contributions from valence and sea quarks. We analyze three gauge ensembles simulated within the twisted mass formulation at approximately physical value of the pion mass. Two of these ensembles are simulated with two dynamical light quarks and lattice spacing $a=0.094$~fm and the third with $a=0.08$~fm includes in addition the strange and charm quarks in the sea. After comparing the results among these three ensembles, we quote as final values our most accurate analysis using the latter ensemble. For the nucleon isovector axial charge we find $1.286(23)$ in agreement with the experimental value. We provide the flavor decomposition of the intrinsic spin $\frac{1}{2}\Delta\Sigma^q$ carried by quarks in the nucleon obtaining for the up, down, strange and charm quarks $\frac{1}{2}\Delta\Sigma^{u}=0.431(8)$, $\frac{1}{2}\Delta\Sigma^{d}=-0.212(8)$, $\frac{1}{2}\Delta\Sigma^{s}=-0.023(4)$ and $\frac{1}{2}\Delta\Sigma^{c}=-0.005(2)$, respectively. The corresponding values of the tensor and scalar charges for each quark flavor are also evaluated providing valuable input for experimental searches for beyond the standard model physics. In addition, we extract the nucleon $\sigma$-terms and find for the light quark content $\sigma_{\pi N}=41.6(3.8)$~MeV and for the strange $\sigma_{s}=45.6(6.2)$~MeV. The y-parameter that is used in phenomenological studies we find $y=0.078(7)$.