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arXiv 1806.09006hep-lat
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2+1+1味格点量子色动力学中核子的等矢荷

Isovector Charges of the Nucleon from 2+1+1-flavor Lattice QCD

Rajan Gupta, Yong-Chull Jang, Boram Yoon, Huey-Wen Lin, Vincenzo Cirigliano, Tanmoy Bhattacharya

备注：
Final published version with 35 pages and 17 figures. arXiv admin note: text overlap with arXiv:1606.07049
发表信息：
Phys. Rev. D 98, 034503 (2018)
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摘要：

我们给出了核子的等矢量电荷$g^{u-d}_A$、$g^{u-d}_S$和$g^{u-d}_T$的高统计结果。计算了MILC合作产生的11个规范位形系综，使用具有2+1+1动力学味的高度改进的交错夸克（HISQ）作用量。这些系综跨越四个晶格间距$a \approx$ 0.06，0.09，0.12和0.15 fm和轻夸克质量对应于$M_π\approx$ 135，225和315 MeV。激发态污染的核子3点相关函数的控制，包括三个国家的光谱分解。剩余的系统不确定性与晶格离散化，晶格体积和轻夸克质量控制使用同时适合这三个变量。在2 GeV的$\overline{\text{MS}}$方案中，我们对等矢量电荷的最终估计是$g_A^{u-d} = 1.218(25)(30)$、$g_S^{u-d} = 1.022(80)(60) $和$g_T^{u-d} = 0.989(32)(10)$。第一个误差包括统计和所有系统的不确定性，除了由于外推的不确定性，这是由第二个误差估计。我们提供了一个详细的比较最近的结果$g_A^{u-d} = 1.271(13)$的CalLat合作，并认为我们的误差估计是更现实的。结合我们对$g_S^{u-d}$的估计和MILC/Fermilab/TUMQCD合作组给出的2+1+1-味理论下轻夸克质量的差$(m_d-m_u)^{\rm QCD}=2.572(66)$ MeV，我们得到了$(M_N-M_P)^{\rm QCD} = 2.63(27)$ MeV.我们更新的低能量约束新的标量和张量相互作用，$ε_{S}$和$ε_{T}$，在TeV尺度结合我们的新估计$g^{u-d}_S$和$g^{u-d}_T$与精确的低能量核实验，并发现它们可比的ATLAS和CMS实验在大型强子对撞机。

英文摘要：

We present high statistics results for the isovector charges $g^{u-d}_A$, $g^{u-d}_S$ and $g^{u-d}_T$ of the nucleon. Calculations were carried out on eleven ensembles of gauge configurations generated by the MILC collaboration using highly improved staggered quarks (HISQ) action with 2+1+1 dynamical flavors. These ensembles span four lattice spacings $a \approx$ 0.06, 0.09, 0.12 and 0.15 fm and light-quark masses corresponding to $M_π\approx$ 135, 225 and 315 MeV. Excited-state contamination in the nucleon 3-point correlation functions is controlled by including up to three-states in the spectral decomposition. Remaining systematic uncertainties associated with lattice discretization, lattice volume and light-quark masses are controlled using a simultaneous fit in these three variables. Our final estimates of the isovector charges in the $\overline{\text{MS}}$ scheme at 2 GeV are $g_A^{u-d} = 1.218(25)(30)$, $g_S^{u-d} = 1.022(80)(60) $ and $g_T^{u-d} = 0.989(32)(10)$. The first error includes statistical and all systematic uncertainties except that due to the extrapolation ansatz, which is given by the second error estimate. We provide a detailed comparison with the recent result of $g_A^{u-d} = 1.271(13)$ by the CalLat collaboration and argue that our error estimate is more realistic. Combining our estimate for $g_S^{u-d}$ with the difference of light quarks masses $(m_d-m_u)^{\rm QCD}=2.572(66)$ MeV given by the MILC/Fermilab/TUMQCD collaboration for 2+1+1-flavor theory, we obtain $(M_N-M_P)^{\rm QCD} = 2.63(27)$ MeV. We update the low-energy constraints on novel scalar and tensor interactions, $ε_{S}$ and $ε_{T}$, at the TeV scale by combining our new estimates for $g^{u-d}_S$ and $g^{u-d}_T$ with precision low-energy nuclear experiments, and find them comparable to those from the ATLAS and the CMS experiments at the LHC.

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