从格点量子色动力学（Lattice QCD）计算中子电偶极矩
Calculation of neutron electric dipole moment from Lattice QCD
中文总结 AI 辅助
本研究通过格点QCD结合费曼-赫尔曼定理与变分分析，从2+1味动力学畴壁费米子格点计算中子电偶极矩，外推后获dn=-0.0050(4)(8)θ̄ e·fm，证实强CP问题存在，可扩展至其他CP破坏相互作用。
中文摘要 AI 辅助
实验对中子电偶极矩（nEDM）的约束可能意味着量子色动力学（QCD）中存在强CP问题，或者QCDθ角的非自然小量。本研究中，我们在带有背景电场的格点上，通过非微扰QCD确定中子电偶极矩（nEDM）dn对θ项的灵敏度。利用费曼-赫尔曼定理，我们从受电场空间极化的核子基态之间的局域拓扑荷密度矩阵元计算nEDM，这些态具有混合空间宇称，我们通过变分分析构建这些态。我们从对应π介子质量为340、420和576 MeV、格点间距a≈0.11 fm的2+1味动力学畴壁费米子格点中，获得了θ诱导nEDM的统计显著信号。外推至物理点后，我们得到dn=-0.0050(4)(8)θ̄ e·fm。与当前nEDM实验边界的比较意味着约束|θ̄|≲10⁻¹¹，这证实了QCD中强CP问题的存在。我们的开创性工作表明，中子EDM可通过局域拓扑荷密度可靠确定，且能稳健控制系统效应，还可直接扩展至其他CP破坏相互作用。
英文摘要
Experimental constraints on the neutron electric dipole moment (nEDM) may imply strong-CP problem in QCD, or unnatural smallness of the QCD theta angle. In this work, we present a novel determination of the neutron electric dipole moment (nEDM) $d_n$ sensitivity to theta term from nonperturbative QCD on a lattice with background electric field. Using Feynman-Hellmann theorem, we compute nEDM from the matrix element of local topological charge density between nucleon ground states spatially polarized by an electric field. These states have mixed spatial parity, and we construct them using variational analysis. We obtain statistically significant signal for the theta induced nEDM from lattices with 2+1 dynamical domain wall fermions corresponding to pion masses of 340, 420, and 576 MeV and lattice spacing $a\approx 0.11~\text{fm}$. After extrapolating to the physical point, we obtain $d_n=-0.0050(4)(8)\barθ$ e$\cdot$fm. Comparison with the current experimental bound on nEDM implies constraint $|\barθ|\lesssim 10^{-11}$, which confirms existence of the strong-CP problem in QCD. Our pioneering work demonstrates that neutron EDM can be reliably determined from the local density of topological charge with robust control of systematic effects, and can be directly extended to other CP-violating interactions.
