A Guide to Light-Cone PDFs from Lattice QCD: An Overview of Approaches, Techniques, and Results
A Guide to Light-Cone PDFs from Lattice QCD: An Overview of Approaches, Techniques, and Results
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DOI：
10.1155/2019/3036904
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发表时间：
2018-11
影响因子：
1.7
通讯作者：
K. Cichy;M. Constantinou
中科院分区：
文献类型：
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作者：
K. Cichy;M. Constantinou
在量子色动力学(QCD)理论中，强子丰富的结构可以用普遍的非微扰函数来定量描述，其中包括：部分子分布函数(PDF)、广义部分子分布(GPD)、动量相关的横向部分子分布(TMD)和分布振幅(DAs)。半个多世纪以来，为了获得这些部分子函数，人们进行了实验和理论的共同努力。然而，强相互作用的复杂性给这些分布带来了严重的限制，关于这些分布的第一原理信息主要是从它们在晶格QCD中计算的矩中提取出来的。最近，突破性的想法改变了格局，提出了几种在晶格上访问分布本身的方法。在这篇文章中，我们相当详细地回顾了与部元分布直接相关的方法。我们重点介绍了季羡林最近提出的一个关于提取准分布的想法，这一想法重新引起了整个领域的兴趣，并在晶格QCD中引发了大量的数值研究。我们讨论理论和实践的发展，包括必须克服的挑战，以及一些尚未处理的挑战。我们还回顾了数值结果，包括基于对基本概念的不断发展的理解以及理论和实践进展的讨论。特别注意了验证准分布方法的重要方面，如重整化、与光锥分布的匹配和晶格技术。除了对准分布的深入讨论外，我们还考虑了其他方法：强子张量、辅助夸克方法、伪分布、不含OPE的OPE和良好的晶格截面。在论文的最后部分，我们对该领域进行了总结和展望，重点讨论了获得具有可控不确定性的结果的必要条件。
Within the theory of Quantum Chromodynamics (QCD), the rich structure of hadrons can be quantitatively characterized, among others, using a basis of universal nonperturbative functions: parton distribution functions (PDFs), generalized parton distributions (GPDs), transverse momentum dependent parton distributions (TMDs), and distribution amplitudes (DAs). For more than half a century, there has been a joint experimental and theoretical effort to obtain these partonic functions. However, the complexity of the strong interactions has placed severe limitations, and first-principle information on these distributions was extracted mostly from their moments computed in Lattice QCD. Recently, breakthrough ideas changed the landscape and several approaches were proposed to access the distributions themselves on the lattice. In this paper, we review in considerable detail approaches directly related to partonic distributions. We highlight a recent idea proposed by X. Ji on extracting quasidistributions that spawned renewed interest in the whole field and sparked the largest amount of numerical studies within Lattice QCD. We discuss theoretical and practical developments, including challenges that had to be overcome, with some yet to be handled. We also review numerical results, including a discussion based on evolving understanding of the underlying concepts and the theoretical and practical progress. Particular attention is given to important aspects that validated the quasidistribution approach, such as renormalization, matching to light-cone distributions, and lattice techniques. In addition to a thorough discussion of quasidistributions, we consider other approaches: hadronic tensor, auxiliary quark methods, pseudodistributions, OPE without OPE, and good lattice cross-sections. In the last part of the paper, we provide a summary and prospects of the field, with emphasis on the necessary conditions to obtain results with controlled uncertainties.