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arXiv 2405.04414hep-lathep-ph
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从格点上的赝分布方法提取广义部分子分布

Generalized parton distributions from the pseudo-distribution approach on the lattice

Shohini Bhattacharya, Krzysztof Cichy, Martha Constantinou, Andreas Metz, Niilo Nurminen, Fernanda Steffens

AI总结:

本文首次在格点QCD中实现赝分布方法提取零偏度非极化夸克GPDs,利用更高核子boost和八倍统计量的数据,通过比值重整化、坐标空间光锥匹配及拟合重建$x$依赖,给出味非单态$H$和$E$ GPDs的$-t$依赖,并与准GPDs结果比较。

摘要:

广义部分子分布(GPDs)是描述强子三维结构的关键物理量,目前是强子物理各个领域——唯象学、实验和理论(包括格点量子色动力学)——的研究焦点。这些领域之间的协同合作对于精确量化和理解物质基本成分(尤其是核子)的结构是必要且不可或缺的。本文首次研究了赝分布方法在提取非极化夸克零偏度(zero-skewness)GPDs时的数值实现。赝分布是可在格点QCD中计算的欧几里得部分子关联函数,可以通过微扰匹配转换到所关注的光锥部分子分布。赝分布与准分布(quasi-distributions)密切相关,并且来源于相同的格点提取矩阵元,但它们受到的系统效应不同。我们使用了先前用于准GPDs的数据,并扩展了其他动量转移和核子boost,特别是增加了一个更高的boost($P_3=1.67$ GeV),其统计量是准分布所用最大boost($P_3=1.25$ GeV)的八倍。我们采用比值方案对矩阵元进行重整化,并将得到的Ioffe时间分布匹配到坐标空间中的光锥。随后利用拟合假设(fitting ansatz)从匹配后的分布重建$x$依赖关系。我们研究了与该过程相关的一些系统效应,并将结果与准GPDs框架下得到的结果进行了比较。最终结果给出了味非单态($u-d$)$H$和$E$ GPDs对不变四动量转移平方($-t$)的依赖关系。

英文摘要:

Generalized parton distributions (GPDs) are key quantities for the description of a hadron's three-dimensional structure. They are the current focus of all areas of hadronic physics -- phenomenological, experimental, and theoretical, including lattice QCD. Synergies between these areas are desirable and essential to achieve precise quantification and understanding of the structure of, particularly nucleons, as the basic ingredients of matter. In this paper, we investigate, for the first time, the numerical implementation of the pseudo-distribution approach for the extraction of zero-skewness GPDs for unpolarized quarks. Pseudo-distributions are Euclidean parton correlators computable in lattice QCD that can be perturbatively matched to the light-cone parton distributions of interest. Being closely related to the quasi-distributions and coming from the same lattice-extracted matrix elements, they are, however, subject to different systematic effects. We use the data previously utilized for quasi-GPDs and extend it with other momentum transfers and nucleon boosts, in particular a higher one ($P_3=1.67$ GeV) with eight-fold larger statistics than the largest one used for quasi-distributions ($P_3=1.25$ GeV). We renormalize the matrix elements with a ratio scheme and match the resulting Ioffe time distributions to the light cone in coordinate space. The matched distributions are then used to reconstruct the $x$-dependence with a fitting ansatz.We investigate some systematic effects related to this procedure, and we also compare the results with the ones obtained in the framework of quasi-GPDs. Our final results involve the invariant four-momentum transfer squared ($-t$) dependence of the flavor non-singlet ($u-d$) $H$ and $E$ GPDs.

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