格点量子色动力学与μ子的反常磁矩
Lattice QCD and the anomalous magnetic moment of the muon
摘要：
在BNL的E821实验上测量了μ子的反常磁矩a_μ，总精度为540 ppb。自2004年发表这一结果以来，一直存在与基于标准模型的理论预测a_mu的3.5标准偏差的持续紧张关系。后者的不确定性主要是由强相互作用的影响，特别是强子真空极化（HVP）和强子光的光（HLbL）散射的贡献，这是通常使用数据驱动的方法和强子模型，分别评估。鉴于理论和实验之间的差异是目前标准模型可能失败的最有趣的暗示之一，从第一原理确定HVP和HLbL的贡献是至关重要的。本文介绍了格点量子色动力学对高阶HVP和HLbL散射贡献a_mu^hvp和a_mu^hlbl的计算现状。在描述的形式主义，以表示一个_mu^hvp和一个_mu^hlbl的欧几里得关联函数，可以计算的晶格，我们专注于系统的影响，必须控制，以实现第一原则的决定占主导地位的强相互作用贡献一个_mu与所需的精度水平。我们还介绍了当前格点量子色动力学的a_mu^hvp和a_mu^hlbl结果的概述，以及相关的量，如过渡形状因子的pi 0-> gamma*gamma*。虽然目前的格点量子色动力学估计a_mu^hvp的总误差已经达到百分之几的水平，但它必须进一步减小到1/5才能与数据驱动的色散方法相竞争。同时，在确定a_mu^hlbl方面取得了良好进展，不确定度为10-15%。
英文摘要：
The anomalous magnetic moment of the muon, a_mu, has been measured with an overall precision of 540 ppb by the E821 experiment at BNL. Since the publication of this result in 2004 there has been a persistent tension of 3.5 standard deviations with the theoretical prediction of a_mu based on the Standard Model. The uncertainty of the latter is dominated by the effects of the strong interaction, notably the hadronic vacuum polarisation (HVP) and the hadronic light-by-light (HLbL) scattering contributions, which are commonly evaluated using a data-driven approach and hadronic models, respectively. Given that the discrepancy between theory and experiment is currently one of the most intriguing hints for a possible failure of the Standard Model, it is of paramount importance to determine both the HVP and HLbL contributions from first principles. In this review we present the status of lattice QCD calculations of the leading-order HVP and the HLbL scattering contributions, a_mu^hvp and a_mu^hlbl. After describing the formalism to express a_mu^hvp and a_mu^hlbl in terms of Euclidean correlation functions that can be computed on the lattice, we focus on the systematic effects that must be controlled to achieve a first-principles determination of the dominant strong interaction contributions to a_mu with the desired level of precision. We also present an overview of current lattice QCD results for a_mu^hvp and a_mu^hlbl, as well as related quantities such as the transition form factor for pi0 -> gamma*gamma*. While the total error of current lattice QCD estimates of a_mu^hvp has reached the few-percent level, it must be further reduced by a factor 5 to be competitive with the data-driven dispersive approach. At the same time, there has been good progress towards the determination of a_mu^hlbl with an uncertainty at the 10-15%-level.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
