Progress towards a precise ab initio determination of parton structure of hadrons

这一建议是我们长期合作的一部分，以大大提高强子结构物理格点QCD的有用性。格点QCD要求解析地将时间延续到虚时间。这具有令人不快的结果，即只有在时间上是局部的场激励器才能被直接评估。这些都是由运营商的产品扩展到夸克和胶子分布函数的时刻。不幸的是，在实践中，由于数值噪声和算子混合，只能确定前几个时刻，这不足以满足LHC（CERN，瑞士），BNL（美国）的EIC以及中国计划的CEPC和EicC的高亮度实验的需要。几年前，人们提出了几种替代方法，这些方法有可能从根本上改变这种情况，首先是季教授提出的LaMET。过去已经提出了相关建议，但没有实际后果。现在情况已经改变了。在“Lattice Parton协作”（LPC）中，我们系统地测试和改进了LaMET，并扩展了其适用性。到目前为止，这主要发生在德国方面的SFB/TRR-55“强子物理学从晶格QCD”，将于2020年6月30日结束。这个建议的目的是在一个仔细的确定使用CLS配置和两个回路的匹配函数，我们计划得到的核子和介子DA的扭曲-2 PDF的系统不确定性。

This proposal is part of a long term effort of our collaboration to substantially improved the usefulness of Lattice QCD for hadron structure physics. Lattice QCD requires to analytically continue time to imaginary time. This has the unpleasant consequence that only field correlators which are local in time can be straightforwardly evaluated. These are related by operator product expansion to moments of quark and gluon distribution functions. Unfortunately, in practice only the leading few moments can be determined due to numerical noise and operator mixing, which is insufficient for the needs of high luminsity experiments as performed/planned at LHC (CERN, Switzerland), the EIC at BNL (USA), as well as the CEPC and EicC planned in China. A few years ago several alternative approaches have been suggested, which have the potential to change this situation fundamentally, starting with LaMET suggested by Prof. Ji. Related suggestions were already made in the past but without practical consequences. This has changed now. Within the "Lattice Parton Collaboration" (LPC) we systematically test and improve LaMET and expand its applicability. So far this happened on the German side primarily within SFB/TRR-55 "Hadron Physics from Lattice QCD" which will end June,30 2020. This proposal aims at a careful determination of the systematic uncertainties for twist-2 pdfs of the nucleon and meson DAs using CLS configurations and two-loop matching functions which we plan to derive.