A phenomenological quasiparticle model, featuring dynamically generated self-energies of excitation modes, successfully describes lattice QCD results relevant for the QCD equation of state and related quantities both at zero and non-zero net baryon density. Here, this model is extended to study bulk and shear viscosities of the gluon-plasma within an effective kinetic theory approach. In this way, the compatibility of the employed quasiparticle ansatz with the apparent low viscosities of the strongly coupled deconfined gluonic medium is shown.
Shear and Bulk Viscosities of a Gluon Plasma in Perturbative QCD: Comparison of Different Treatments for the gg<->ggg Process
在微扰QCD中,胶子等离子体的剪切和体粘滞系数η和η的首阶贡献包括gg -> gg(22)过程、gg <->ggg(23)过程和称为Landau-Pomeranchuk-Migdal(LPM)效应的多重散射过程。Arnold,Moore and Yaffe(AMY)和Arnold,Dogan and Moore(ADM)分别对η和η进行了完整的首阶计算,其中非弹性过程由有效的<->ggg胶子分裂计算。我们研究了如何互补计算与22和23过程和一个简单的处理来模拟LPM效应比较AMY和ADM的结果,我们发现,我们的结果与他们的误差范围内同意。通过研究23过程对η的贡献,我们发现在流体局域静止系中末态胶子间的最小夹角θ在θ \sim \sqrt{α_{s}}处有一个峰值分布,类似于AMY和ADM所断言的近共线分裂,但θ的平均值远大于其峰值,因为它的分布是倾斜的,有一个长尾.在质心系中,如果把23矩阵元取到软胶子韧致辐射极限,也可以看到同样的θ行为。这表明CM框架中的软胶子韧致辐射在流体局域静止框架中仍然具有某些近似共线的行为。我们还将结果推广到一般的SU(N_c)纯规范理论,并总结了目前QCD中粘滞系数的计算。
In recent years, there has been a significant effort to extract the temperature-dependent shear ($η/s$) and bulk ($ζ/s$) viscosity over entropy ratios of the quark-gluon plasma from a global comparison of heavy-ion data with results of hydrodynamic simulations. However, anisotropic flow, which is arguably the most sensitive probe of viscosity, is only sensitive to an {\it effective\/} viscosity over entropy ratio, which is obtained by taking a weighted average over the temperature, and summing the contributions of shear and bulk. We estimate this effective viscosity using existing first-princi…
Harish-Chandra Research Institute, A CI of Homi Bhabha National Institute(哈里什-昌德拉研究所,霍米·巴哈国家学院下属机构);Instituto de Fisica Gleb Wataghin, University of Campinas(坎皮纳斯大学格列布·瓦塔金物理研究所);Department of Physics and Astronomy, University of Alabama(阿拉巴马大学物理与天文学系);Institute for Theoretical Physics and Astrophysics, Julius-Maximilians Universität Würzburg(维尔茨堡朱利叶斯-马克西米利安大学理论与天体物理研究所);Shanghai Institute for Mathematics and Interdisciplinary Sciences (SIMIS)(上海数学与交叉学科研究院)
We give the alternative formulation of quasiparticle model of quark gluon plasma with medium dependent dispersion relation. The model is thermodynamically consistent provided the medium dependent contribution to the energy density is taken in to account. We establish the connection of our model with other variants of quasiparticle models which are thermodynamically consistent. We test the model by comparing the equation of state with the lattice gauge theory simulations of SU(3) pure gluodynamics .
Thermodynamical analysis of QGP using effective PNJL model with Quasiparticle approach
Hansraj College, University of Delhi(德里大学汉斯拉吉学院);Sri Aurobindo College, University of Delhi(德里大学圣奥罗宾多学院);Netaji Subhas University of Technology(内塔吉·苏巴斯技术大学);University of Lucknow(勒克瑙大学)
Dilepton production by dynamical quasiparticles in the strongly interacting quark gluon plasma
讨论了强相互作用夸克胶子等离子体(sQGP)组分产生双轻子的问题。为了在较低的等离子体温度(O(T_c))、较低的双轻子质量(O(1GeV))和较强的耦合(α S =0.5-1)下进行定量预测,我们不仅考虑了高阶pQCD反应机制,而且考虑了夸克、反夸克和胶子的非微扰谱函数(离壳)和自能,从而超出了主导扭转。为此,我们的计算利用了匹配的动力学准粒子模型(DQPM)提供的夸克和胶子非微扰传播子的参数化来重现晶格数据。DQPM用单粒子格林函数描述QCD性质(在两粒子不可约方法的意义上),并导致sQGP的成分是有效准粒子的概念,这些准粒子是大质量的,具有宽谱函数(由于大的相互作用速率)。本文导出了反应q+qbar->l^+l^-中双轻子产生的离壳层截面。(Drell-Yan机理),q+qbar->g+l^+l^-(夸克湮灭与末态的胶子韧致辐射),q(qbar)+g->q(qbar)+l^+l^-通过用夸克和胶子的DQPM传播子修饰微扰图中的夸克和胶子线,得到了sQGP中g->q+qbar+l ^+l^-和q(qbar)->q(qbar)+g+l^+l^-(虚胶子衰变,虚夸克衰变)的关系.
We investigate the suppression of $π^0$-spectrum in a wide range of $p_\perp$ up 60 GeV/c which is caused by the energy loss of the gluon and quark jets in quark-gluon plasma. The physical characteristics of initial and mixed phases were found in the effective quasiparticle model by analogy with previous work \cite{5}. The PHENIX data up 10 GeV/c within the limits of precision are described by quasiparticle model with decrease of the thermal gluon mass and effective coupling in the region of phase transitin (at $T\to T_c$ from above). We also take into account the intrinsic transverse momentum…
A bottom-up Einstein-Maxwell-Dilaton holographic model is used to compute, for the first time, the behavior of several transport coefficients of the hot and baryon-rich strongly coupled quark-gluon plasma at the critical point and also across the first-order phase transition line in the phase diagram. The observables under study are of the shear and bulk viscosities, baryon diffusion, thermal conductivity, the jet quenching parameter $\hat{q}$, as well as the heavy-quark drag force and Langevin diffusion coefficients. These calculations provide a phenomenologically promising estimate for these…