Hydrodynamic description of D meson production in high-energy heavy-ion collisions *
Hydrodynamic description of D meson production in high-energy heavy-ion collisions *
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DOI：
10.1088/1674-1137/abf645
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发表时间：
2021-01
影响因子：
3.6
通讯作者：
Chi Ding;W. Ke;L. Pang;Xin-Nian Wang
中科院分区：
文献类型：
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作者：
Chi Ding;W. Ke;L. Pang;Xin-Nian Wang
低$p_T$ $D$介子椭圆流的大值和组成-夸克数（NCQ）标度表明，在高能重离子碰撞中，最初通过硬过程产生的粲夸克可能通过与夸克-胶子等离子体（QGP）的强相互作用而部分热化。为了量化低$p_T$粲夸克的热化程度，我们将流体动力学模型的$D^0$介子谱和椭圆流与实验数据以及输运模型模拟进行了比较。我们使用冻结温度下的有效粲化学势来解释硬过程产生的初始粲夸克，并假设它们在冻结前在介质的局部运动框架中被加热。从由事件-事件（3+1）D粘性流体力学模型CLVisc描述的膨胀QGP的冻结超表面统计地采样了$D^0$介子。流体力学模型和输运模型都可以描述D^0介子在p_t_2 $ GeV/$c$下的椭圆流动。输运模型中的扩散机制和部分子能量损失机制可以在理论不确定度范围内较好地描述实测光谱。我们的比较研究表明，即使粲夸克在小和中$p_T$处获得与轻夸克强子相当的椭圆流，它们也只能在小$p_T$处接近局部热平衡。
The large values and the constituent-quark-number (NCQ) scaling of the elliptic flow of low-$p_T$ $D$ mesons imply that charm quarks, initially produced through hard processes, might be partially thermalized through the strong interactions with the quark-gluon plasma (QGP) in high-energy heavy-ion collisions. To quantify the degree of thermalization of low-$p_T$ charm quarks, we compare the $D^0$ meson spectra and elliptic flow from a hydrodynamic model to the experimental data as well as transport model simulations. We use an effective charm chemical potential at the freeze-out temperature to account for the initial charm quark production from hard processes and assume that they are thermalized in local comoving frame of the medium before freeze-out. $D^0$ mesons are sampled statistically from the freeze-out hyper-surface of the expanding QGP as described by the event-by-event (3+1)D viscous hydrodynamic model CLVisc. Both hydrodynamic and transport model can describe the elliptic flow of $D^0$ mesons at $p_T 2$ GeV/$c$. The diffusion and parton energy loss mechanisms in the transport model can describe the measured spectra reasonably well within the theoretical uncertainty. Our comparative study indicates that charm quarks only approach to local thermal equilibrium at small $p_T$ even though they acquire sizable elliptic flow that is comparable to light-quark hadrons at both small and intermediate $p_T$.