标题： 质子与Pb原子核在$\sqrt{s_{NN}}=8.16$ TeV能级碰撞时，$Λ$超子沿束流方向的自旋极化，使用流体动力学方法研究 显示英文标题

标题： Spin polarization of $Λ$ hyperons along beam direction in p+Pb collisions at $\sqrt{s_{NN}}=8.16$ TeV using hydrodynamic approaches

摘要： 我们采用 TRENTO-3D 初始条件实现了三维 CLVisc 氢系统流模型，以研究质子与 Pb 原子核碰撞中沿束流方向的 $\Lambda$ 超子自旋极化情况，碰撞能量为 $\sqrt{s_{NN}} = 8.16$ TeV。 遵循我们之前基于量子动力学理论的框架，我们考虑了三种不同的场景：$\Lambda$ 平衡、$s$ 夸克平衡和等温平衡场景。 我们在三种场景下计算了沿束流方向的自旋极化第二正弦傅里叶系数，记为 $\left\langle P_{z} \sin 2(\phi_{p} - \Psi_{2}) \right\rangle$，其中 $\phi_{p} - \Psi_{2}$ 是相对于二阶事件平面 $\Psi_{2}$ 的方位角，作为多重性、横向动量和伪快度的函数。 此外，我们还计算了沿束流方向的自旋极化$P_{z}$随方位角的变化。 我们发现，由热涡度诱导的自旋极化总是与 p+Pb 碰撞中的剪切诱导极化提供相反的贡献。 由当前流体力学模型计算出的总自旋极化与 LHC-CMS 实验测量的数据不一致。 我们的研究结果表明，其他非流效应可能在 p+Pb 碰撞中起着关键作用。 显示英文摘要

摘要： We have implemented the 3+1 dimensional CLVisc hydrodynamics model with TRENTO-3D initial conditions to investigate the spin polarization of $\Lambda$ hyperons along the beam direction in p+Pb collisions at $\sqrt{s_{NN}} = 8.16$ TeV. Following our previous theoretical framework based on quantum kinetic theory, we consider three different scenarios: $\Lambda$ equilibrium, $s$ quark equilibrium, and iso-thermal equilibrium scenarios. We have computed the second Fourier sine coefficients of spin polarization along the beam direction, denoted as $\left\langle P_{z} \sin 2(\phi_{p} - \Psi_{2}) \right\rangle$, with $\phi_{p} - \Psi_{2}$ being the azimuthal angle relative to the second-order event plane $\Psi_{2}$, as functions of multiplicity, transverse momentum and pseudo-rapidity in the three scenarios. Additionally, we have also computed the spin polarization along the beam direction, $P_{z}$, as a function of the azimuthal angle. We find that the spin polarization induced by thermal vorticity always provides an opposite contribution compared to the shear-induced polarization in p+Pb collisions. The total spin polarization computed by the current hydrodynamic model disagrees with the data measured by LHC-CMS experiments. Our findings imply that other non-flow effects may play a crucial role in p+Pb collisions.