Since the parton model was introduced by Feynman more than 50 years ago, much has been learned about the partonic structure of the proton through a large body of high-energy experimental data and dedicated global fits. However, limited progress has been made in calculating partonic observables such as the parton distribution function (PDFs) from the fundamental theory of strong interactions, quantum chromodynamics (QCD). Recently some advocated for a formalism, large-momentum effective theory (LaMET), through which one can extract parton physics from the properties of the proton traveling at a moderate boost factor such as $\gamma \sim 2–5$. The key observation behind this approach is that Lorentz symmetry allows the standard formalism of partons in terms of light-front operators to be replaced by an equivalent one with large-momentum states and time-independent operators of a universality class. With LaMET, the PDFs, generalized PDFs or generalized parton distributions, transverse-momentum-dependent PDFs, and light-front wave functions can all be extracted in principle from lattice simulations of QCD (or other nonperturbative methods) through standard effective field theory matching and running. Future lattice QCD calculations with exascale computational facilities could help one to understand the experimental data related to the hadronic structure, including those from the upcoming electron-ion colliders dedicated to exploring the partonic landscape of the proton. Here the progress made in the past few years in the development of the LaMET formalism and its applications is reviewed, with an emphasis on a demonstration of its effectiveness from initial lattice QCD simulations.

中文翻译：

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大动量有效理论

自从费曼在 50 多年前引入部分子模型以来，通过大量高能实验数据和专门的全局拟合，人们对质子的部分子结构有了很多了解。然而，从强相互作用的基本理论、量子色动力学 (QCD) 计算部分子可观察量如部分子分布函数 (PDF) 方面取得的进展有限。最近有人提倡一种形式主义的大动量有效理论（LaMET），通过它可以从质子以中等助推因子行进的特性中提取部分物理，例如$\gamma ～2\mathrm{——}5$. 这种方法背后的关键观察是，洛伦兹对称性允许根据光前算子的标准形式主义被替换为具有大动量状态和普遍性类的时间无关算子的等效形式。使用 LaMET，原则上可以从 QCD（或其他非微扰方法）的晶格模拟中提取 PDF、广义 PDF 或广义部分子分布、横向动量相关 PDF 和光前波函数，通过标准有效场理论匹配和跑步。未来使用百亿亿级计算设施进行的晶格 QCD 计算可以帮助人们理解与强子结构相关的实验数据，包括来自即将推出的致力于探索质子部分子景观的电子离子对撞机的数据。