Leading hadronic contribution to the muon magnetic moment from lattice QCD
Leading hadronic contribution to the muon magnetic moment from lattice QCD
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DOI：
10.1038/s41586-021-03418-1
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发表时间：
2021-04-07
期刊：
影响因子：
64.8
通讯作者：
Varnhorst, L.
中科院分区：
文献类型：
--
作者：
Borsanyi, Sz.;Fodor, Z.;Varnhorst, L.
粒子物理学的标准模型描述了涉及基本粒子的绝大多数实验和观察。任何与其预测的偏差都将是新的基础物理学的标志。一个长期存在的差异涉及μ子的反常磁矩，这是对该粒子周围磁场的一种测量。标准模型预测 (1) 与测量值 (2) 存在不一致，测量值紧密分散在 3.7 个标准差附近。如今，理论误差和测量误差具有可比性。然而，正在进行和计划中的实验旨在将测量误差减少四倍。理论上，误差的主要来源是主阶强子真空极化 (LO-HVP) 的贡献。对于即将到来的测量，必须使用独立的方法评估这种贡献的预测并减少其不确定性。迄今为止，最精确、与模型无关的测定依赖于色散技术，并结合正负电子湮灭成强子的横截面的测量(3-6)。为了消除对这些实验的依赖，我们在这里使用从头算量子色动力学 (QCD) 和量子电动力学模拟来计算 LO-HVP 贡献。我们达到了足够的精度来区分 μ 子反常磁矩的测量和色散方法的预测。我们的结果比使用色散关系获得的结果更有利于实验测量值。此外，随着更强大的计算机的出现，这项工作中使用和开发的方法将进一步提高精度。
The standard model of particle physics describes the vast majority of experiments and observations involving elementary particles. Any deviation from its predictions would be a sign of new, fundamental physics. One long-standing discrepancy concerns the anomalous magnetic moment of the muon, a measure of the magnetic field surrounding that particle. Standard-model predictions(1) exhibit disagreement with measurements(2) that is tightly scattered around 3.7 standard deviations. Today, theoretical and measurement errors are comparable; however, ongoing and planned experiments aim to reduce the measurement error by a factor of four. Theoretically, the dominant source of error is the leading-order hadronic vacuum polarization (LO-HVP) contribution. For the upcoming measurements, it is essential to evaluate the prediction for this contribution with independent methods and to reduce its uncertainties. The most precise, model-independent determinations so far rely on dispersive techniques, combined with measurements of the cross-section of electron-positron annihilation into hadrons(3-6). To eliminate our reliance on these experiments, here we use ab initio quantum chromodynamics (QCD) and quantum electrodynamics simulations to compute the LO-HVP contribution. We reach sufficient precision to discriminate between the measurement of the anomalous magnetic moment of the muon and the predictions of dispersive methods. Our result favours the experimentally measured value over those obtained using the dispersion relation. Moreover, the methods used and developed in this work will enable further increased precision as more powerful computers become available.