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arXiv 1901.09052hep-lat
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强子真空极化对μ g-2贡献的格点量子色动力学研究

Review of Lattice QCD Studies of Hadronic Vacuum Polarization Contribution to Muon g-2

Kohtaroh Miura

摘要:

综述了格点量子色动力学(LQCD)对强子真空极化(HVP)及其对μ子反常磁矩(μ子g-2)的贡献的研究.目前存在超过3-sigma的偏差μ子g-2之间的BNL实验与0.5 ppm的精度和标准模型(SM)的预测,后者依赖于QCD色散关系的HVP。LQCD提供了一个独立的交叉检查的分散的方法和重要的指标,用于评估SM预测与测量正在进行/即将进行的实验在费米实验室/J-PARC(0.14/0.1 ppm精度)。LQCD在长距离和有限体积控制、连续外推、QED和强同位旋破缺(SIB)修正等方面取得了显著的进展。在最近发表的论文中,两个LQCD估计HVP μ介子g-2是一致的,而其他三个不符合。这种张力仅起源于光夸克相关的贡献,并表明大距离控制中的一些被低估的系统性。所有LQCD群的奇异和魅力连通贡献以及不连通贡献是一致的,并且是精确确定的。总误差在百分之几的水平。用LQCD来证实或削弱实验与SM预言之间的偏差还为时过早。如果LQCD与色散方法相结合,HVP μ on g-2的预测具有0.4%的不确定度,这是接近的费米实验室/J-PARC实验所要求的目标精度。持续和显著的改进正在进行中,并且有良好的前景,目标精度将在未来几年内实现。

英文摘要:

Lattice QCD (LQCD) studies for the hadron vacuum polarization (HVP) and its contribution to the muon anomalous magnetic moment (muon g-2) are reviewed. There currently exists more than 3-sigma deviations in the muon g-2 between the BNL experiment with 0.5 ppm precision and the Standard Model (SM) predictions, where the latter relies on the QCD dispersion relation for the HVP. The LQCD provides an independent crosscheck of the dispersive approaches and important indications for assessing the SM prediction with measurements at ongoing/forthcoming experiments at Fermilab/J-PARC (0.14/0.1 ppm precision). The LQCD has made significant progress, in particular, in the long distance and finite volume control, continuum extrapolations, and QED and strong isospin breaking (SIB) corrections. In the recently published papers, two LQCD estimates for the HVP muon g-2 are consistent with No New Physics while the other three are not. The tension solely originates to the light-quark connected contributions and indicates some under-estimated systematics in the large distance control. The strange and charm connected contributions as well as the disconnected contributions are consistent among all LQCD groups and determined precisely. The total error is at a few percent level. It is still premature by the LQCD to confirm or infirm the deviation between the experiments and the SM predictions. If the LQCD is combined with the dispersive method, the HVP muon g-2 is predicted with 0.4% uncertainty, which is close upon the target precision required by the Fermilab/J-PARC experiments. Continuous and considerable improvements are work in progress, and there are good prospects that the target precision will get achieved within the next few years.

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