A Test of Color-Octet Heavy Quarkonium Production Mechanism

Using the scale evolution of nuclear parton distributions,the contribution of color-octet heavy quarkonium production mechanism to the P + Fe → J/ψ + γ + X process in calculated and discussed.Comparing our theoretical results with the future experimental data,the color-octet heavy quarkonium production mechanism can be examined.     

Nuclear PDFs at NLO – status report and review of the EPS09 results

We review the current status of the global DGLAP analysis of nuclear parton distribution functions, nPDFs, focusing on the recent EPS09 analysis [K.J. Eskola, H. Paukkunen, C.A. Salgado, JHEP 0904 (2009) 065. [arXiv:0902.4154 [hep-ph]]], whose output, EPS09NLO, is the best-constrained NLO nPDF set on the market. Collinear factorization is found to work very well in the kinematical region studied. With the error sets released in the EPS09 package one can compute how the nPDF-related uncertainties propagate into factorizable nuclear hard-process cross sections. A comparison with the other existing NLO nPDF sets is shown, and the BRAHMS forward-η hadron data from d+Au collisions are discussed in the light of the EPS09 nPDFs and their error sets.     

Associated J/ψ+γ Production Through Double Pomeron Exchange: the Nature of the Pomeron and Hard Diffractive Factorization Breaking

We present a study of associated J/ψ+γ production through double pomeron exchange at energies reached at the Fermilab Tevatron.and CERN LHC based on the Ingelman-Schlein model for hard difiactive scattering and the factorization formalism of nonrelativistic QCD for quarkonia production. We find that the process p+p→p +p + J/ψ+γ + X can be used to probe the gluon content of the pomeron and study the nature of hard difiactive factorization breaking.     

Small x phenomenology on gluon evolution through the BFKL equation in light of a constraint in multi-Regge kinematics

We investigate the impact of so-called kinematic constraint on gluon evolution at small x.Implanting the constraint on the real emission term of the gluon ladder diagram, we obtain an integro-differential form of the Balitsky-Fadin-Kuraev-Lipatov(BFKL) equation. Later we solve the equation analytically using the method of characteristics. We sketch the Bjorken x and transverse momentum k_t~2 dependence of our solution of unintegrated gluon distributions f (x,k_t~2) in the kinematic constraint supplemented BFKL equation and contrasted the same with the original BFKL equation. Then we extract the integrated gluon density xg(x, Q~2) from unintegrated gluon distributions f (x,k_t~2) and compared our theoretical prediction with that of global data fits, namely NNPDF3.1 sx and CT14. Finally we illustrate the phenomenological implication of our solution for unintegrated gluon distribution f (x,k_T~2) towards exploring high precision HERA DIS data by the theoretical prediction of proton structure functions(F_2 and F_L).     

An update on the evolution of double parton distributions

We consider double parton distributions in the general case in which the virtualities of the interacting partons are different. We elaborate the corresponding evolution equations and their extension to next-to-leading logarithmic accuracy.     

通过基矢光前量子化方法对π介子的研究

为研究介子的性质,通过基矢光前量子化方法获得介子的光前波函数。基失光前量子化是一种在哈密顿量体系下基于量子场论的非微扰方法。在哈密顿量中我们考虑了动能项、基于全息色动力学的横向禁闭势、与横向禁闭势互补的纵向禁闭势和基于QCD的夸克-胶子相互作用。我们的基矢空间包括最低阶的两个Fock空间,即领头阶■与次领头阶■。根据所得的光前波函数我们计算了介子衰变常数以及(基于领头Fock空间的)电磁半径,这些结果与粒子数据手册(PDG)上的结果相近。此外,我们计算了(基于领头Fock空间的)介子部分子分布,QCD演化后,与原先的结果相近(蓝江山等,Phys Rev Lett,2 019,122:172 001.),能够很好地描述费米国家实验室(FNAL)与欧洲核子中心(CERN)的实验数据。     

A New Effect in the QCD Fusion of Nuclear Partons

The parton fusion in nucleus at the leading order of recombination is investigated based on perturbative QCD. We compute various cut diagrams including the nuclear parton fusion, and find that the parton-fusion effects depend on the nuclear QCD structure.     

能量损失效应引起的核Drell-Yan微分截面比的压低

核环境中夸克的能量损失可以通过高能核Drell-Yan过程的核依赖进行测量. 利用文献中给出的夸克能量损失公式和从轻子－原子核深度非弹性散射实验数 据得到的束缚核子中的部分子分布函数, 计算了FNAL E772 800GeV的质子打击不同原子核的Drell-Yan过程截面比, 发现考虑能量损失的计算结果与FNAL E772实验数据符合甚好. 建议在利用核Drell-Yan过程实验数据抽取束缚核子内部分子分布函数时应该考虑能量损失效应.     

Quark Energy Loss and Shadowing in Nuclear Drell-Yan Process

The energy loss effect in nuclear matter is another nuclear effect apart from the nuclear effects on the parton distribution as in deep inelastic scattering process. The quark energy loss can be measured best by the nuclear dependence of the high energy nuclear Drell-Yan process. By means of three kinds of quark energy loss parameterizations given in literature and the nuclear parton distribution extracted only with lepton-nucleus deep inelastic scattering experimental data, measured Drell-Yan production cross sections are analyzed for 800 GeV proton incident on a variety of nuclear targets from FNAL E866. It is shown that our results with considering the energy loss effect are much different from those of the FNAL E866, who analyzes the experimental data with the nuclear parton distribution functions obtained by using the deep inelastic IA collisions and pA nuclear Drell-Yan data. Considering the existence of energy loss effect in Drell-Yan lepton pairs production, we suggest that the extraction of nuclear parton distribution functions should not include Drell-Yan experimental data.     

Quark Energy Loss and Shadowing in Nuclear Drell-Yan Process

The energy loss effect in nuclear matter is another nuclear effect apart from the nuclear effects on the parton distribution as in deep inelastic scattering process. The quark energy loss can be measured best by the nuclear dependence of the high energy nuclear Dre11-Yan process. By means of three kinds of quark energy loss parameterizations given in literature and the nuclear parton distribution extracted only with lepton-nucleus deep inelastic scattering experimental data, measured Dre11-Yan production cross sections are analyzed for 800 GeV proton incident on a variety of nuclear targets from FNAL E866. It is shown that our results with considering the energy loss effect are much different from those of the FNAL E866, who analyzes the experimental data with the nuclear parton distribution functions obtained by using the deep inelastic IA collisions and pA nuclear Drell-Yan data. Considering the existence of energy loss effect in Drell-Yan lepton pairs production, we suggest that the extraction of nuclear parton distribution functions shoul““““d not include Dre11-Yan experimental data.     

核环境中部分子演化与重组效应下的核内胶子分布

在既考虑到泄漏在束缚核子外的海夸克与胶子间的重组,又考虑到仍束缚在核子内的部分子由于其禁闭空间的变化而发生的演化的基础上,给出了核内胶子分布函数的普遍形式,并具体计算了锡梭与碳核的胶子分布比,结果与NMC实验合作组的最新实验相一致.     

An Examination of Extended a-Rescaling Model

The extended x-rescaling model can explain the quark‘s nuclear effect very well. Weather it can also explain the gluon‘s nuclear effect should be investigated further. Associated J/ψ and γ production with large PT is a very clean channel to probe the gluon distribution in proton or nucleus. In this paper, using the extended x-rescaling model, the PT distribution of the nuclear effect factors of p Fe → J/Ψ γ X process is calculated and discussed. Comparing our theoretical results with the future experimental data, the extended x-rescaling model can be examined.``     

An Examination of Extended x-Rescaling Model

The extended x-rescaling model can explain the quark's nuclear effect very well. Weather it can also explain the gluon's nuclear effect should be investigated further. Associated J/ψ and γ production with large P_T is a very clean channel to probe the gluon distribution in proton or nucleus. In this paper, using the extended x-rescaling model, the P_T distribution of the nuclear effect factors of p+Fe→J/ψ+γ+X process is calculated and discussed. Comparing our theoretical results with the future experimental data, the extended x-rescaling model can be examined.     

Energy Loss Effect in High-Energy Drell-Yan Dimuon Process

By means of the nuclear parton distribution obtained from DGLAP equation,measured Drell-Yan production cross sections for 800 GeV proton incident on a variety of nuclear targets are analyzed within Glauber framework with takes into account energy loss of the beam proton.It is shown that the theoretical results are in good agreement with the FNAL E866．     

Nuclear Effect Study Under K Factor‘s Nonconstancy

A consistent approach to estimating nuclear effect functions RA RvA (x2) and RSA(x2) based on numerical iteration technique is presented in the quark-parton model when taking into account the nonconstancy of quantum chromodynamics correction factor K. ARv (x2) and RsA(x2) correspond respectively to the valence quark distributions for one bound nucleon within the nucleus and to the sea quark ones. Related numerical analysis is given for nuclei 6 12C,20 40Ca, and 26 56Fe. As the basis, it adopts both experimental data of the high energy proton-nucleus Drell-Yan process and of the high energy lepton-nucleus deep inelastic scattering.     

Regularization dependence of pion generalized parton distributions

Pion generalized parton distributions are calculated within the framework of the Nambu–Jona-Lasinio model using different regularization schemes, including the proper time regularization scheme, the three-dimensional (3D) momentum cutoff scheme, the four-dimensional momentum cutoff scheme, and the Pauli-Villars regularization scheme. Furthermore, we check the theoretical constraints of pion generalized parton distributions required by the symmetries of quantum chromodynamics in different regularization schemes. The diagrams of pion parton distribution functions are plotted, in addition, we evaluate the Mellin moments of generalized parton distributions, which are related to the electromagnetic and gravitational form factors of pion. Pion generalized parton distributions are continuous but not differential at begin{document}$ x=pm ,xi $end{document}, when considering the effect of the contact contribution term, generalized parton distributions become not continuous at begin{document}$ x=pm ,xi $end{document} in all the four regularization schemes. Generalized parton distributions in impact parameter space are considered, the width distribution of u quark in the pion and the mean-squared begin{document}$ langle {boldsymbol{b}}_{bot}^2rangle_{pi}^u $end{document} are calculated. The light-front transverse-spin distributions are studied when quark polarized in the light-front-transverse begin{document}$ +,x $end{document} direction, the transverse-spin density is no longer symmetric around begin{document}$ (b_x=0,b_y=0) $end{document}, the peaks shift to begin{document}$ (b_x=0,b_y>0) $end{document}, we compare the average transverse shift begin{document}$ langle b_{bot}^yrangle_1^u $end{document} and begin{document}$ langle b_{bot}^yrangle_2^u $end{document} in different regularization schemes. The light-cone energy radius begin{document}$ r_{E,LC} $end{document} and the light-cone charge radius begin{document}$ r_{c,LC} $end{document} are also evaluated, we found that in the proper time regularization scheme the values of these quantities were the largest, in the 3D momentum cutoff scheme they were the smallest.     

Nuclear Effect Study Under K Factor's Nonconstancy

A consistent approach to estimating nuclear effect functions R_v^A(x₂) and R_s^A(x₂) based on numerical iteration technique is presented in the quark-parton model when taking into account the nonconstancy of quantum chromodynamics correction factor K. R_v^A(x₂) and R_s^A(x₂) correspond respectively to the valence quark distributions for one bound nucleon within the nucleus and to the sea quark ones. Related numerical analysis is given for nuclei ₆C¹², ₂₀Ca⁴⁰, and ₂₆Fe⁵⁶. As the basis, it adopts both experimental data of the high energy proton-nucleus Drell-Yan process and of the high energy lepton-nucleus deep inelastic scattering.     

Analysis of Vector Meson Transitions Among Heavy Quarkonium States

In this article,we study the vector meson transitions among the charmonium and bottomonium states with the heavy quark effective theory in a systematic way,and make predictions for the ratios among the vector meson decay widths of a special multiplet to another multiplet.The predictions can be confronted with the experimental data in the future.