广义部分子分布函数及相关硬遍举过程的研究

Generalized parton distribution function is a powerful tool which was developed to describe the hadron structure in recent years. It unifies the conventional notions of parton density, form factor and distribution amplitude, which are widely used in the study of hadron structure. It is also a key approach toward a precision three-dimensional imaging of partons inside the hadron. In this project, we will start from the field-theoretical point of view, together with the phenomenological models, to study systematically the leading-twist generalized parton distributions. Besides the detailed investigation on the generalized parton distributions of valence quarks, in particular, we will also quantitatively calculate the generalized parton distributions of sea quarks and flavor off-diagonal type, and provide theoretical constraints on them. Secondly, We plan to study the deeply virtual Compton scattering and hard exclusive meson production processes of which the generalized parton distrubtions enter into the factorized description. We consider the kinematics at the lepton-nucleon experimental facilities that will run in the very near future, such as JLab 12 GeV and COMPASS II, to study the interference of virtual Compton scattering and the Bethe-Heitler process, as well as to investigate comprehensively the hard exclusive production of pseudoscalar meson, vector meson and lepton pair. We will present the prediction on the experimental observables, study the scheme that can be applied to extract generalized parton distributions from experimental data. Combining the theoretical and phenomenological analysis, we aim to obtain the generalized parton distributions for various kind of partons in details, therefore we can reveal a precise image of partons distributed in the one dimensional momentum space plus two dimensional coordinate space in the valence and sea region.

广义分布函数是近年来发展起来的用以描述强子结构的有力工具。它统一了部分子密度、形状因子和分布振幅等被广泛运用的传统概念，是通向精确刻画强子中部分子三维分布图像的关键途径。本项目将从理论场的方法出发，结合唯像模型对领头扭度的广义分布函数进行系统研究。除了对价夸克分布进行详尽的分析外，特别的，我们将定量计算海夸克以及味道非对角的广义分布，并对其提供理论约束。其次，项目将研究深度虚康普顿散射和介子的硬遍举产生等广义分布函数进入因子化描述的过程。我们将考虑即将运行的实验装置的运动学区域，分析虚康普顿散射和BH过程的干涉项，对赝标介子、矢量介子和轻子对的硬遍举产生进行细致研究。项目将预言实验可观测量，提出可行的参数化模型，研究从实验数据中提取广义分布函数的方案。结合理论和唯像分析，我们将获得各种部分子的广义分布的详尽信息，从而揭示出价区域和海区域部分子在一维动量+二维坐标空间分布的精确图像。

广义分布函数因为对部分子分布函数、形状因子、分布振幅等描述强子结构的各种非常重要的物理量提供了一个统一的描述，近年来在QCD和强子物理界获得了广泛的关注。本项目从理论和唯像学的角度出发，对广义分布函数及相关物理量进行了重点研究。首先，项目对强子的Wigner分布做了研究。作为一种准几率分布，Wigner分布和广义分布紧密联系，在横向动量为零的极限下，Wigner分布对应于广义分布函数的傅立叶变换，特别的，对于pion介子中夸克Wigner分布的模型计算，揭示了不同于质子分布的信息。其次，项目研究了超子的电磁形状因子。各种广义分布函数的一阶矩（对x进行积分）对应于不同的形状因子，因此对形状因子的研究亦可以获得广义分布函数的信息。第三，对quasi广义分布函数以及quasi部分子分别函数进行了理论计算。第四，研究了分布函数以及它们在高能过程中的效应。研究了碎裂函数以及它们在高能过程中的效应。项目期间共发表和项目相关的SCI论文20篇，会议论文4篇，在投论文两篇。参加国际会议6人次；培养毕业了3名博士生和两名硕士生。