论文标题
使用晶格QCD模拟的中子电偶极矩
Neutron electric dipole moment using lattice QCD simulations at the physical point
论文作者
论文摘要
我们在晶格QCD形式主义中提取中子电动偶极矩$ \ vert \ vec {d} _n \ vert $。我们分析了一个$ n_f = 2+1+1 $扭曲的质量三叶草改良的费米子的合奏，并用$ a \ simeq 0.08 \ {\ rm fm fm} $的晶格间距以及对应于Quark Masse的物理值，与Pion Mass $m_π\ simeq 139 \ simeq 139 \ \ rm mev {中子电偶极力矩是通过计算$ CP $ -ODD电磁形式$ f_3（q^2 \ to 0）$通过小$θ$ - 动作的表达来提取的。这种方法需要计算我们通过光谱投影仪采用费米定义的拓扑费用，同时我们还提供了与gluonic定义以及伴随梯度流量的比较。我们表明，使用光谱投影仪的拓扑电荷导致绝对误差的绝对误差，其比采用字段理论定义时提供的倍数高两倍以上。我们找到$ \ vert \ vec {d} _n \ vert = 0.0009（24）\θ\ e \ cdot {\ rm fm} $的值，当使用fermionic定义时，该定义在统计上与零一致。
We extract the neutron electric dipole moment $\vert \vec{d}_N\vert$ within the lattice QCD formalism. We analyse one ensemble of $N_f=2+1+1$ twisted mass clover-improved fermions with lattice spacing of $a \simeq 0.08 \ {\rm fm}$ and physical values of the quark masses corresponding to a pion mass $m_π \simeq 139 \ {\rm MeV}$. The neutron electric dipole moment is extracted by computing the $CP$-odd electromagnetic form factor $F_3(Q^2 \to 0)$ through small $θ$-expansion of the action. This approach requires the calculation of the topological charge for which we employ a fermionic definition by means of spectral projectors while we also provide a comparison with the gluonic definition accompanied by the gradient flow. We show that using the topological charge from spectral projectors leads to absolute errors that are more than two times smaller than those provided when the field theoretic definition is employed. We find a value of $\vert \vec{d}_N\vert = 0.0009(24) \ θ\ e \cdot {\rm fm}$ when using the fermionic definition, which is statistically consistent with zero.
