Gottfried sum rule from maximum entropy method quark distributions with DGLAP evolution and with DGLAP evolution with GLR-MQ-ZRS corrections

A new method to test the valence quark distribution of nucleons obtained from the maximum entropy method using the Gottfried sum rule by performing the DGLAP equations with GLR-MQ-ZRS corrections and the original leading-order/next-to-leading-order （LO/NLO） DGLAP equations is outlined. The test relies on knowledge of the unpolarized electron proton structure function F2^ep and the electron neutron structure function F2^en and the assumption that Bjorken scaling is satisfied. In this work, the original Gottfried summation value obtained by the integrals of the structure function at different Q2 is in accordance with the theoretical value of 1/3 under the premise of light-quark flavor symmetry of the nucleon sea, whether it results from dynamical evolution equations or from global quantum chromodynamics fits of PDFs. Finally, we present the summation value of the LO/NLO DGLAP global fits of PDFs under the premise of light-quark flavor asymmetry of the nucleon sea. According to analysis of the original Gottfried summation value with two evolution equations at different Q2 we find that the valence quark distributions of nucleons obtained by using the maximum entropy method are effective and reliable.

K介子部分子分布函数的研究

核子和介子中的部分子分布函数是描述其性质的基本物理量,但不同研究小组给出的分布函数并不一致.从最简单的价夸克模型出发,提出了在某一低动量标度(Q^2)下,K介子完全由价夸克组成,胶子和海夸克都是通过量子色动力学(Quantum Chromodynamics,QCD)辐射产生.根据一个考虑了部分子间重组效应的演化方程一Modified DokshitzerGribov-Lipatov-Altarelli-Parisi(MD-DGLAP)方程和相应的实验数据,给出了K介子的初始价夸克分布函数,对高动量标度下的部分子分布进行了预言,并与其他模型进行了比较分析.

退耦近似在重味夸克分布函数标度演化中的应用

核子中存在非微扰的intrinsic重味夸克FOCK态是量子色动力学的一个严格理论预言,对这个预言的研究是当前重味夸克物理中的一个重要课题.采用退耦近似,忽略intrinsic重味夸克与轻味夸克及胶子的混合贡献,可把异常复杂的重整化群演化方程近似处理为通常的胶子、轻味夸克、extrinsic重味夸克演化方程及intrinsic重味夸克非单态演化方程.详细分析intrinsic粲夸克概率为1%,3.5%情况下退耦近似演化的计算结果,对退耦近似的可信度进行详细分析,给出退耦近似下任意概率粲夸克分布.

Calculation of Gluon Distribution Functions in Leading Order by Regge-like Behavior at Low-x

An approximate analytical form of the gluon distribution function from the derivative F2 proton structure function data at low-x assuming the Regge-like behavior of the gluon distribution function at this limit is presented. In this method, we calculate λ and C parameters for each low-x value at several Q^2 values using the scaling violation of the F2 proton structure function. For low-x, A is found to be independent of x within the experimental accuracy. We make use of the leading order Altarelli-Parisi （A-P） evolution equations in our analysis. To test the validity of our new determined gluon distribution functions, we compare them with the QCD parton distribution functions at low-x region.

Analysis of the gluon distribution with next-to-leading order splitting function at small-x^(*)

An approximated solution for the gluon distribution from DGLAP evolution equations with the NLO splitting function in the small-x limit is presented.We first obtain simplified forms of the LO and NLO splitting functions in the small-x limit.With these approximated splitting functions,we obtain the analytical gluon distribution using the Mellin transform.The free parameters in the boundary conditions are obtained by fitting the CJ15 gluon distribution data.We find that the asymptotic behavior of the gluon distribution is consistent with the CJ15 data;however,the NLO results considering the"ladder"structure of gluon emission are slightly better than the LO results.These results indicate that the corrections from NLO have a significant influence on the behavior of the gluon distribution in the small-x region.In addition,we investigate the DGLAP evolution of the proton structure function using the analytical solution of the gluon distribution.The differential structure function reveals that our results have a similar tendency to the CJ15 data at small-x.

动力学部分子模型在核子和冷核物质中的应用

本工作研究了自由核子和冷原子核物质的动力学产生的海夸克和胶子分布。在动力学部分子模型中,所有的海夸克和胶子纯粹来自DGLAP方程描述的QCD涨落过程,而较少的固有海夸克成分忽略不计。在Q_(0)^(2)~0.1 GeV^(2)标度,选择最大熵方法估计的三价夸克分布作为非微扰输入。使用了在低Q^(2)(<1 GeV^(2))下饱和的跑动强耦合常数。关于原子核效应,考虑了核子变胖和部分子-部分子重组增强的影响。核子及冷核物质的动力学部分子分布均符合实验观测。应用预言的原子核部分子分布抽取得到部分子在穿过冷核物质时的能量损失。

An Analysis of the Proton Structure Function and the Gluon Distributions at Small x

Recently, we reported an analysis of Proton structure function at small x based on Taylor approximated DGLAP equations assuming a plausible relationship between the singlet and the gluon distributions. In this paper, we report a generalised version of the previous work. A corresponding study of the suggested gluon distribution is also made.The present generalised version of the model for the structure function results in a wider x range of phenomenological validity than the earlier one. A comparison of both the models of the proton structure function and the gluon distribution is made with exact result as well as with the Froissart saturated models of Block, Durand and Mckay.

Relativistic correction to gluon fragmentation function into pseudoscalar quarkonium

Inspired by the recent measurements of the ηc meson production at LHC experiments, we investigate the relativistic correction effect for the fragmentation functions of gluon/charm quark fragmenting into ηc, which constitute the crucial nonperturbative element for the ηc production at high pT. Employing three distinct methods,we calculate the next-to-leading-order（NLO） relativistic correction to g →ηc fragmentation function in the NRQCD factorization framework, as well as verifying the existing NLO result for the c →ηc fragmentation function. We also study the evolution behavior of these fragmentation functions with the aid of the DGLAP equation.