格点量子色动力学光锥极限下色偶极的胶子结构函数
Gluon Structure Function of a Color Dipole in the Light-Cone Limit of Lattice QCD
摘要：
我们计算了近光锥SU（2）格点量子色动力学中色偶极子的胶子结构函数作为$x_B$的函数。夸克和反夸克是外部的非动力学自由度，它们作为定义偶极的胶子弦组态的来源。计算了沿光锥方向分离的横向色电和色磁场算符的色偶极矩阵元，其傅里叶变换为胶子结构函数.对于纯胶区的真空态，我们采用了近光锥哈密顿量的变分基态。我们导出了格点上胶子结构函数的一个类似于微扰的DGln方程的递推关系。它取决于组装偶极子的施温格弦的横向链接的数量。将胶子的平均动量分数固定为质子中的“实验值”，将我们的四链偶极态胶子结构函数与NLO \emph{MRST} 2002和$Q^2=1.5 \mathrm{GeV}^2$的\emph{CTEQAB-0}参数化进行了比较.在系统的不确定性，我们发现相当不错的协议。我们还讨论了模型计算中胶子结构函数的低$x_B$行为。
英文摘要：
We calculate the gluon structure function of a color dipole in near-light-cone SU(2) lattice QCD as a function of $x_B$. The quark and antiquark are external non-dynamical degrees of freedom which act as sources of the gluon string configuration defining the dipole. We compute the color dipole matrix element of transversal chromo-electric and chromo-magnetic field operators separated along a direction close to the light cone, the Fourier transform of which is the gluon structure function. As vacuum state in the pure glue sector, we use a variational ground state of the near-light-cone Hamiltonian. We derive a recursion relation for the gluon structure function on the lattice similar to the perturbative DGLAP equation. It depends on the number of transversal links assembling the Schwinger string of the dipole. Fixing the mean momentum fraction of the gluons to the "experimental value" in a proton, we compare our gluon structure function for a dipole state with four links with the NLO \emph{MRST} 2002 and the \emph{CTEQAB-0} parameterizations at $Q^2=1.5 \mathrm{GeV}^2$. Within the systematic uncertainty we find rather good agreement. We also discuss the low $x_B$ behavior of the gluon structure function in our model calculation.
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