Recently it has become apparent that event-by-event fluctuations in the initial state of hydrodynamical modelling of ultrarelativistic heavy-ion collisions are crucial in order to understand the full centrality dependence of the elliptic flow coefficient v_2. In particular, in central collisions the density fluctuations play a major role in generating the spatial eccentricity in the initial state. This raises the question to what degree high P_T physics, in particular leading-parton energy loss, which takes place in the background of an evolving medium, is sensitive to the presence of the event-by-event density fluctuations in the background. In this work, we report results for the effects of fluctuations on the nuclear modification factor R_AA in both central and noncentral sqrt(s_NN) = 200 GeV Au+Au collisions at RHIC. Two different types of energy-loss models, a radiative and an elastic, are considered. In particular, we study the dependence of the results on the assumed spatial size of the density fluctuations, and discuss the angular modulation of R_AA with respect to the event plane.
We compute bottomonium suppression and elliptic flow within the pNRQCD effective field theory using an open quantum systems approach. For the hydrodynamical background, we use 2+1D MUSIC second-order viscous hydrodynamics with IP-Glasma initial conditions and evolve bottom/antibottom quantum wave packets in real time in these backgrounds. We find that the impact of fluctuating initial conditions is small when compared to results obtained using smooth initial conditions. Including the effect of fluctuating initial conditions, we find that the Upsilon(1S) integrated elliptic flow is v_2[1S] = 0.…
Radiative jet energy loss in a three-dimensional hydrodynamical medium and high $p_T$ azimuthal asymmetry of $π_0$ suppression at mid and forward rapidity at RHIC
We constrain proton structure fluctuations at small-$x$ by comparing with the HERA diffractive vector meson production data, and find that large geometric fluctuations in the proton wave function are needed. Hydrodynamical simulations of proton-nucleus collisions including the fluctuating proton structure are found to be compatible with the momentum anisotropies measured at the LHC.
We constrain the amount of event-by-event fluctuations of the proton by comparing with the HERA coherent and incoherent diffractive $J/Ψ$ production data. We find that the HERA measurements prefer large geometric fluctuations. We then include the constrained fluctuating proton shapes in viscous hydrodynamical simulations of the proton-nucleus collisions at $\sqrt{s_{NN}}=5.02$ TeV, and find a good description of the mean transverse momentum and flow harmonics measured at the LHC.
In this paper, we give an account of the peripheral-tube model, which has been developed to give an intuitive and dynamical description of the so-called ridge effect in two-particle correlations in high-energy nuclear collisions. Starting from a realistic event-by-event fluctuating hydrodynamical model calculation, we first show the emergence of ridge + shoulders in the so-called two-particle long-range correlations, reproducing the data. In contrast to the commonly used geometric picture of the origin of the anisotropic flow, we can explain such a structure dynamically in terms of the presenc…
We show that high-$p_T$ $R_{AA}$ and $v_2$ are sensitive to the early expansion dynamics, and that the high-$p_T$ observables prefer delayed onset of energy loss and transverse expansion. To calculate high-$p_T$ $R_{AA}$ and $v_2$, we employ our newly developed DREENA-A framework, which combines state-of-the-art dynamical energy loss model with 3+1-dimensional hydrodynamical simulations. The model applies to both light and heavy flavor, and we predict a larger sensitivity of heavy flavor observables to the onset of transverse expansion. This presents the first time when bulk QGP behavior has b…
Initialization of hydrodynamics in relativistic heavy ion collisions with an energy-momentum transport model
相对论性重离子碰撞的流体动力学模拟的一个关键因素是热初始条件，这是一个尚未完全理解的前热动力学的结果。本文采用新近发展的前热阶段能量动量输运模型，研究了核-核碰撞中不同初始态对流体动力学起始时刻物质流动和能量密度分布的影响。特别是，各向同性和各向异性的初始状态的结果的依赖性进行了分析。结果表明，纵向压缩的初始动量分布在热化时刻横向流动较大，最大能量密度较高。结果还对弛豫时间参数、热化时的状态方程和初始能量密度分布的横向轮廓敏感：高斯近似，Glauber Monte Carlo轮廓等。此外，测试结果表明，基于能量-动量输运模型的数值程序能够为相对论核碰撞的流体动力学模拟提供平均和波动的初始条件。
