Dissipation, Collective Flow and Mach Cones at RHIC

Collective Flow and Mach Cones with Parton Transport

Fast thermalization and a strong build up of elliptic flow of QCD matter were investigated within the pQCD based 3+1 dimensional parton transport model BAMPS including bremsstrahlung $2 \leftrightarrow 3$ processes. Within the same framework quenching of gluonic jets in Au+Au collisions at RHIC can be understood. The development of conical structure by gluonic jets is investigated in a static box for the regimes of small and large dissipation. Furthermore we demonstrate two different approaches to extract the shear viscosity coefficient $η$ from a microscopical picture.

（3+1）d理想流体力学中的射流传播与马赫锥

Jet Propagation and Mach Cones in (3+1)d Ideal Hydrodynamics

在RHIC上对喷流淬灭和相关的远离侧马赫锥相关性的观察为A+A反应中产生的sQGP提供了强有力的“外部”探测，但同时也提出了喷流能量沉积在何处的问题。通过椭圆流观察到的近乎完美的整体流动性表明，马赫锥-类似的相关性也可能是由于快速的局部平衡后穿透射流。多粒子相关性进一步支持了这种可能性。然而，需要对能量沉积和流体响应进行综合研究。我们数值求解三维理想流体动力学方程，计算各种可能的能量-动量沉积模型产生的流动相关模式。马赫锥相关性的关键取决于能量和动量沉积机制。它们只适用于一类特殊的有限能量--动量损失模型，该模型假定纵向动量损失明显小于单位长度的能量损失。我们的结论是，正确的解释远离侧射流相关性将需要改进的理解和独立的实验约束射流能量-动量损失流体耦合。

射流与介质的相互作用

Focus talk on interactions between jets and medium

在核介质演化过程中，硬部分子在热密物质中传播所损失的能量和动量必须重新分配。除了加热介质，还有可能激发集体模式，导致马赫锥或切伦科夫辐射的出现。最近在RHIC上由STAR \cite{Wang:2004kf}和PHENIX \cite{Adler:2005ee}进行的两粒子关联测量表明，这种现象可能在理解喷流-介质相互作用中发挥重要作用。可能的集体模式进行了讨论，它表明，无色或有色的声音所创建的马赫锥是一个可能的解释的硬二粒子相关数据。

Elliptic flow of heavy flavors

The propagation of charm and bottom quarks through an ellipsoidal domain of quark gluon plasma has been studied within the ambit of non-equilibrium statistical mechanics. Energy dissipation of heavy quarks by both radiative and collisional processes are taken in to account. The experimental data on the elliptic flow of the non-photonic electrons resulting from the semi-leptonic decays of hadrons containing heavy flavours has been reproduced with the same formalism that has been used earlier to reproduce the nuclear suppression factors. The elliptic flow of the non-photonic electron from heavy …

微扰QCD中喷注淬火的物理学

The Physics of Jet Quenching in Perturbative QCD

本文综述微扰QCD框架下喷注淬火的理论进展，系统介绍介质诱导辐射、输运系数重整化、颜色退相干和非线性演化，并讨论其与RHIC及LHC实验数据的结合。

Mach Cones in Viscous Matter

Employing a microscopic transport model we investigate the evolution of high energetic jets moving through a viscous medium. For the scenario of an unstoppable jet we observe a clearly strong collective behavior for a low dissipative system $η/s \approx 0.005$, leading to the observation of cone-like structures. Increasing the dissipation of the system to $η/s \approx 0.32$ the Mach Cone structure vanishes. Furthermore, we investigate jet-associated particle correlations. A double-peak structure, as observed in experimental data, is even for low-dissipative systems not supported, because of th…

Estimating Elliptic Flow Coefficient in Heavy Ion Collisions using Deep Learning

Machine Learning (ML) techniques have been employed for the high energy physics (HEP) community since the early 80s to deal with a broad spectrum of problems. This work explores the prospects of using Deep Learning techniques to estimate elliptic flow ($v_2$) in heavy-ion collisions at the RHIC and LHC energies. A novel method is developed to process the input observables from particle kinematic information. The proposed DNN model is trained with Pb-Pb collisions at $\sqrt{s_{\rm NN}} = 5.02$ TeV minimum bias events simulated with AMPT model. The predictions from the ML technique are compared …