论文标题
纯Gluon等离子体中的运输系数$ \ hat {q} $的晶格计算（2+1）-Fravor QCD等离子体
Lattice calculation of transport coefficient $\hat{q}$ in pure gluon plasma and (2+1)-flavor QCD plasma
论文作者
论文摘要
运输系数$ \ hat {q} $是一个领先的系数，它控制着跨越QGP的硬顿的修改，因此负责抑制高横向动量（横向到横梁方向）在重合离子碰撞中带电的hadrons。在本文中，我们介绍了$ \ hat {q} $的第一个未取消的晶格QCD计算。使用（2+1）的夸克味进行计算，使用高度改进的交错夸克动作（HISQ）和树级Symanzik改进的量规动作。该计算在多种温度下进行，范围从200 meV $ <t <$ 800 meV使用MILC代码软件包。我们考虑了一个领先的过程，其中硬顿通过交换glauber gluon（其横向动量大于其纵向成分），从而散布了热QCD培养基的胶场。与喷气区相关的硬尺度允许在扰动理论中对Gluon与该Parton的耦合。 Gluon与培养基的偶联是非扰动的。这种非扰动部分是根据非本地（两点）野外强度实场算子产物表示的，该算子可以在分析延续到深欧几里得区域后扩展。这样的扩展使我们能够用一系列本地运营商来编写$ \ hat {q} $，这些操作员被硬顿能量的因素所抑制。计算出的$ \ hat {q} $及其温度依赖性表明了与喷气机协作进行的现象学提取的合理一致。
The transport coefficient $\hat{q}$ is a leading coefficient that controls the modification of the hard parton traversing QGP, and hence, responsible for the suppression of the high transverse momentum (transverse to the beam direction) charged-hadrons in heavy-ion collisions. In this article, we present the first unquenched lattice QCD calculation of $\hat{q}$. The calculation is carried out using (2+1)-flavor of quarks, using the highly improved staggered quark action (HISQ) and tree-level Symanzik improved gauge action. The calculation is performed in a wide range of temperatures, ranging from 200 MeV $<T<$ 800 MeV using MILC code package. We considered a leading-order process where a hard parton scatters off the glue field of a thermal QCD medium by exchanging a Glauber gluon (whose transverse momentum is larger than its longitudinal components). The hard scale associated with the jet parton allows the coupling of the gluon to that parton to be treated in perturbation theory. The coupling of the gluon to the medium is treated non-perturbatively. This non-perturbative part is expressed in terms of a non-local (two-point) field-strength-field-strength operator product which can be Taylor expanded after analytic continuation to the deep Euclidean region. Such an expansion allows us to write $\hat{q}$ in terms of a series of local operators, which are suppressed by factors of the hard parton energy. The calculated $\hat{q}$ and its temperature dependence demonstrates reasonable agreement with the phenomenological extraction carried out by the JET collaboration.
