Vorticity and Spin Polarization --- A Theoretical Perspective

Probing vorticity structure in heavy-ion collisions by local $Λ$ polarization

We study the local structure of the vorticity field and the $Λ$ polarization in Au+Au collisions in the energy range $\sqrt{s_{\mathrm{NN}}}=7.7$--$200$ GeV and Pb+Pb collisions at $\sqrt{s_{\mathrm{NN}}}=2760$ GeV using A Multi-Phase Transport (AMPT) model. We focus on the vorticity field arising from the non-uniform expansion of the fireball, which gives the circular structure of the transverse vorticity $\boldsymbolω_{\perp}=(ω_{x},ω_{y})$ around the $z$ direction as well as the quadrupole pattern of the longitudinal vorticity $ω_{z}$ in the transverse plane. As a consequence, the three com…

Vorticity and Particle Polarization in Relativistic Heavy-Ion Collisions

We review studies of vortical motion and the resulting global polarization of $Λ$ and $\barΛ$ hyperons in heavy-ion collisions, in particular, within 3FD model. 3FD predictions for the global midrapidity polarization in the FAIR-NICA energy range are presented. The 3FD simulations indicate that energy dependence of the observed global polarization of hyperons in the midrapidity region is a consequence of the decrease of the vorticity in the central region with the collision energy rise because of pushing out the vorticity field into the fragmentation regions. At high collision energies this pu…

Polarization and Vorticity in the Quark Gluon Plasma

The quark-gluon plasma produced by collisions between ultra-relativistic heavy nuclei is well described in the language of hydrodynamics. Non-central collisions are characterized by very large angular momentum, which in a fluid system manifests as flow vorticity. This rotational structure can lead to a spin polarization of the hadrons that eventually emerge from the plasma, providing experimental access to flow substructure at unprecedented detail. Recently, first observations of $Λ$ hyperon polarization along the direction of collisional angular momentum have been reported. These measurements…

Hydrodynamic helicity polarization in relativistic heavy ion collisions

We study helicity polarization through the (3+1) dimensional relativistic viscous hydrodynamic models at $\sqrt{s_{NN}}=200$GeV Au+Au collisions. Similar to the local spin polarization, we consider the helicity polarization beyond global equilibrium and investigate the contributions induced by thermal vorticity, shear viscous tensor, and the fluid acceleration. We find that the local helicity polarization induced by thermal vorticity dominates over other contributions. It also implies that in the low-energy collisions, the the fluid vorticity as part of thermal vorticity may play the crucial r…

Global hyperon polarization at local thermodynamic equilibrium with vorticity, magnetic field and feed-down

The system created in ultrarelativistic nuclear collisions is known to behave as an almost ideal liquid. In non-central collisions, due to the large orbital momentum, such a system might be the fluid with the highest vorticity ever created under laboratory conditions. Particles emerging from such a highly vorticous fluid are expected to be globally polarized with their spins on average pointing along the system angular momentum. Vorticity-induced polarization is the same for particles and antiparticles, but the intense magnetic field generated in these collisions may lead to the splitting in p…

Kinetic approach to polarization-vorticity coupling and hydrodynamics with spin

Recently introduced equilibrium Wigner functions for spin-one-half particles are used in the semiclassical kinetic equations to study the relation between spin polarization and vorticity. It is found, in particular, that such a framework does not necessarily imply that the thermal-vorticity and spin polarization tensors are equal. Subsequently, a procedure to formulate the hydrodynamic framework for particles with spin-one-half, based on the semiclassical expansion, is outlined.

Quark spin - thermal vorticity alignment and the Lambda, anti-Lambda polarization in heavy-ion collisions

It has been proposed that the $Λ$ and $\overlineΛ$ polarizations observed in heavy-ion collisions are due to the interaction between quark spin and thermal vorticity. In this work we report on a computation of the relaxation time required for this alignment to occur at finite temperature and baryon chemical potential, considering quarks with a finite mass. The calculation is performed after modelling the interaction by means of an effective vertex which couples the thermal gluons and quarks within the vortical medium. We show that the effect of the quark mass is to reduce the relaxation time a…

$Λ$ polarization in peripheral collisions at moderate relativistic energies

The polarization of $Λ$ hyperons from relativistic flow vorticity is studied in peripheral heavy ion reactions at FAIR and NICA energies, just above the threshold of the transition to the Quark-Gluon Plasma. Previous calculations at higher energies with larger initial angular momentum, predicted significant $Λ$ polarization based on the classical vorticity term in the polarization, while relativistic modifications decreased the polarization and changed its structure in the momentum space. At the lower energies studied here, we see the same effect namely that the relativistic modifications decr…

Vorticity and $Λ$ polarization in the microscopic transport model PACIAE

We study the behavior of four types of vorticities in non-central Au+Au collisions at energies $\sqrt{S_{NN}}$ = 5--200 GeV using a microscopic transport model PACIAE. The results show that the vorticities decay faster at lower energy and smaller impact parameter. The non-monotonic dependence of the initial vorticities on the collision energies is reconfirmed and the turning point is 10-15 GeV for different vorticities. The global $Λ$ polarization at energies $\sqrt{S_{NN}}$ = 7.7--200 GeV is reproduced by introducing an energy density freeze-out criterion.

Femto-cyclones and hyperon polarization in Heavy-Ion Collisions

We study the structure of vorticity and hydrodynamic helicity fields in peripheral heavy-ion collisions using the kinetic Quark-Gluon String Model. The angular momentum conservation within this model holds with a good accuracy. We observe the formation of specific toroidal structures of vorticity field (vortex sheets). Their existence is mirrored in the polarization of hyperons of the percent order.

Vorticity in the QGP liquid and hyperon polarization at the RHIC BES energies

We calculate the polarization of $Λ$ hyperons in Au-Au collisions at RHIC Beam Energy Scan range $\sqrt{s_{\rm NN}}=7.7, \dots, 200$ GeV in a state-of-the-art 3+1 dimensional cascade + viscous hydro model vHLLE+UrQMD. We find that the polarization of $Λ$ in the out-of-plane direction decreases substantially with collision energy. We explore the connection between the polarization signal and thermal vorticity and discuss the feed-down and hadronic rescattering effects on the mean polarization of all produced $Λ$ hyperons.

Vorticity and hyperon polarization at NICA energies

We study the formation of fluid vorticity and the hyperon polarization in heavy-ion collisions at NICA energies in the framework of the Parton-Hadron-String Dynamic Model, taking into account both hadronic and quark-gluonic (partonic) degrees of freedom. The vorticity properties in peripheral Au+Au collisions at $\sqrt{s_{NN}}=$7.7\,GeV are demonstrated and confronted with other models. The obtained result for the $Λ$ polarization is in agreement with the experimental data by the STAR collaboration, whereas the model is not able to explain the observed high values of the anti-hyperon $\barΛ$ p…

Generating spin polarization from vorticity through nonlocal collisions

We derive the collision term in the Boltzmann equation using the equation of motion for the Wigner function of massive spin-1/2 particles. To next-to-lowest order in $\hbar$ it contains a nonlocal contribution, which is responsible for the conversion of orbital into spin angular momentum. In a proper choice of pseudo-gauge the antisymmetric part of the energy-momentum tensor arises solely from this nonlocal contribution. We show that the collision term vanishes only in global equilibrium and that the spin potential is then equal to the thermal vorticity. In the nonrelativistic limit, the equat…

Vorticity and Polarization in Heavy Ion Collisions: Hydrodynamic Models

Fluid dynamic approach is a workhorse for modelling collective dynamics in relativistic heavy-ion collisions. The approach has been successful in describing various features of the momentum distributions of hadrons produced in the heavy-ion collisions, such as $p_T$ spectra, flow coefficients $v_n$ etc. As such, the description of the phenomenon of polarization of $Λ$ hyperons in heavy-ion collisions has to be incorporated into the hydrodynamic approach. We start this chapter by introducing different definitions of vorticity in relativistic fluid dynamics. Then we present a derivation of the p…

低能重离子碰撞中的全局$\Lambda$超子极化——无涡旋情景

Global $Λ$ hyperon polarization in low-energy heavy ion collisions -- a scenario without vorticity

提出重离子碰撞中$\Lambda$超子全局极化与无极化碰撞系统中长期存在的横向极化之间的直接联系，通过定向流驱动的$\Lambda$产生平面与反应平面对齐，将横向极化转化为全局极化信号。

Polarization Rotation of Chiral Fermions in Vortical Fluid

The rotation of polarization occurs for light interacting with chiral materials. It requires the light states with opposite chiralities interact differently with the materials. We demonstrate analogous rotation of polarization also exists for chiral fermions interacting with quantum electrodynamics plasma with vorticity using chiral kinetic theory. We find that the rotation of polarization is perpendicular both to vorticity and fermion momentum. The effect also exists for chiral fermions in quantum chromodynamics plasma with vorticity. It could lead to generation of a vector current when the p…

Thermodynamic versus kinetic approach to polarization-vorticity coupling

We critically compare thermodynamic and kinetic approaches, that have been recently used to study relations between the spin polarization and fluid vorticity in systems consisting of spin-one-half particles. The thermodynamic approach refers to general properties of global thermal equilibrium with a rigid-like rotation and demonstrates that the spin-polarization and thermal-vorticity tensors are equal. On the other hand, the kinetic approach uses the concept of the Wigner function and its semi-classical expansion. In most of the works done so far, the Wigner functions satisfy kinetic equations…

Longitudinal spin polarization in a thermal model

We use a thermal model with single freeze-out to determine longitudinal polarization of $Λ$ hyperons emitted from a hot and rotating hadronic medium. We consider the top RHIC energies and use the model parameters determined in the previous analyses of particle spectra and elliptic flow. Using a direct connection between the spin polarization tensor and thermal vorticity, we reproduce earlier results which indicate a quadrupole structure of the longitudinal component of the polarization three-vector with an opposite sign compared to that found in the experiment. We further use only the spatial …

热涡度和热剪切诱导的重离子碰撞中的自旋极化

Spin polarization in heavy-ion collisions induced by thermal vorticity and thermal shear

该研究利用局域热力学平衡流体的统计量子场论，建立费米子平均自旋与热涡度、热剪切等流体动力学量的关联，指出自旋可作为研究QCD性质的新工具。

Study of Lambda polarization at RHIC BES and LHC energies

In hydrodynamic approach to relativistic heavy ion collisions, hadrons with nonzero spin, produced out of the hydrodynamic medium, can acquire polarization via spin-vorticity thermodynamic coupling mechanism. The hydrodynamical quantity steering the polarization is the thermal vorticity, that is minus the antisymmetric part of the gradient of four-temperature field. Based on this mechanism there have been several calculations in hydrodynamic and non-hydrodynamic models for non-central heavy ion collisions in the RHIC Beam Energy Scan energy range, showing that the amount of polarization of pro…

Fluid Dynamics Study of the $Λ$ Polarization for Au+Au Collisions at $\sqrt{s_{NN}}=200$ GeV

With a Yang-Mills field, stratified shear flow initial state and a high resolution (3+1)D Particle-in-Cell Relativistic (PICR) hydrodynamic model, we calculate the $Λ$ polarization for peripheral Au+Au collisions at RHIC energy of $\sqrt{S_{NN}}=200$ GeV. The obtained longitudinal polarization in our model agrees with the experimental signature and the quadrupole structure on transverse momentum plane. It is found that the relativistic correction (2nd term), arising from expansion and from the time component of the thermal vorticity, plays a crucial role in our results. This term is changing t…

热涡度抑制作为QCD临界点的指示器

Suppression of thermal vorticity as an indicator of QCD critical point

研究QCD临界点对粘性QGP中Λ超子自旋极化的影响，发现热涡度导致的全局极化显著降低，且快度依赖性剧变可作为临界点信号。

Shear-induced spin polarization in heavy-ion collisions

We study the spin polarization generated by the hydrodynamic gradients. In addition to the widely studied thermal vorticity effects, we identify an undiscovered contribution from the fluid shear. This shear-induced polarization (SIP) can be viewed as the fluid analog of strain-induced polarization observed in elastic and nematic materials. We obtain the explicit expression for SIP using the quantum kinetic equation and linear response theory. Based on a realistic hydrodynamic model, we compute the differential spin polarization along both the beam direction $\hat{z}$ and the out-plane directio…

Global $Λ$ polarization in heavy-ion collisions from a transport model

The polarizations of $Λ$ and $\barΛ$ hyperons are important quantities in extracting the fluid vorticity of the strongly coupled quark gluon plasma and the magnitude of the magnetic field created in off-central heavy-ion collisions, through the spin-vorticity and spin-magnetic coupling. We computed the energy dependence of the global $Λ$ polarization in off-central Au+Au collisions in the energy range $\sqrt{s_{NN}}=7.7-200$ GeV using a multiphase transport model. The observed polarizations with two different impact parameters agree quantitatively with recent STAR measurements. The energy depe…

Λ超子在全球极化中的表现：在TeV能量下的热QCD物质

Global polarization of $Λ$ hyperons in hot QCD matter at TeV energies

研究Λ超子的自旋极化，探讨热QCD物质的角动量和涡旋结构，通过二阶相对论粘性流体动力学框架分析热涡旋和磁场的影响，与ALICE实验数据对比，揭示QCD物质的涡旋结构。

Is Hyperon Polarization in Relativistic Heavy Ion Collisions Connected to Axial U(1) Symmetry Breaking at High Temperature?

Experiments at the Relativistic Heavy Ion Collider (RHIC) have measured the net polarization of $Λ$ and $\barΛ$ hyperons and attributed it to a coupling between their spin and the vorticity of the fluid created in heavy ion collisions, but how the spin comes to equilibrium with vorticity is an open problem. Recently we found that vorticity fluctuations and helicity flip of strange quarks in quark-gluon plasma through perturbative QCD processes resulted in equilibration times far too long to be relevant. Here we consider the Nambu--Jona-Lasinio model with the inclusion of the six-quark Kobayash…

Global $Λ$ polarization in heavy-ion collisions at energies 2.4--7.7 GeV: Effect of Meson-Field Interaction

Based on the three-fluid model, the global $Λ$ polarization in Au+Au collisions at 2.4 $\leq\sqrt{s_{NN}}\leq$ 7.7 GeV is calculated, including its rapidity and centrality dependence. Contributions from the thermal vorticity and meson-field term (proposed by Csernai, Kapusta and Welle) to the global polarization are considered. The results are compared with data from recent and ongoing STAR and HADES experiments. It is predicted that the polarization maximum is reached at $\sqrt{s_{NN}}\approx$ 3 GeV, if the measurements are performed with the same acceptance. The value of the polarization is …

Vortical fluid and $Λ$ spin correlations in high-energy heavy-ion collisions

Fermions become polarized in a vortical fluid due to spin-vorticity coupling. The spin polarization density is proportional to the local fluid vorticity at the next-to-leading order of a gradient expansion in a quantum kinetic theory. Spin correlations of two $Λ$-hyperons can therefore reveal the vortical structure of the dense matter in high-energy heavy-ion collisions. We employ a (3+1)D viscous hydrodynamic model with event-by-event fluctuating initial conditions from A MultiPhase Transport (AMPT) model to calculate the vorticity distributions and $Λ$ spin correlations. The azimuthal correl…

Probing vorticity in heavy ion collision with dilepton production

We study the effect of vorticity present in heavy ion collisions (HICs) on the temperature evolution of hot quark-gluon plasma in the presence of spin-vorticity coupling. The initial global rotation entails a nontrivial dependence of the longitudinal flow velocity on the transverse coordinates and also develops a transverse velocity component that depends upon the longitudinal coordinate. Both of these velocities lead to a 2+1 dimensional expansion of the fireball. It is observed that with finite vorticity and spin-polarization the fireball cools faster as compared to the case without vorticit…

初始状态对$\u221a s_{NN}=5.36$ TeV Pb--Pb碰撞中纵向$\Lambda$极化的涡度--剪切竞争的调控

Initial-state control of vorticity--shear competition in longitudinal $Λ$ polarization in Pb--Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.36\,\mathrm{TeV}$

本研究通过理想流体动力学模拟，发现初始能量密度分布可调控纵向Λ极化的涡度-剪切竞争，并解释了ALICE观测到的正谐波。

高能重离子碰撞中的相对论流体动力学与涡度动力学：集体流视角

Relativistic Hydrodynamics and Vorticity Dynamics in High-Energy Heavy-Ion Collisions: A Collective Flow Perspective

研究用相对论流体力学描述夸克-胶子等离子体集体演化，通过映射空间偏心率到方位角动量分布，利用相关技术剖析涨落并求解涡度输运方程，探讨涡线守恒及不同预平衡机制对自旋排列可观测量的影响。

通过螺旋度极化探测RHIC-BES能区重离子碰撞中的涡旋结构

Probing vortical structures in heavy-ion collisions at RHIC-BES energies through helicity polarization

本文利用CLVisc流体力学与SMASH初始条件研究RHIC-BES能区Λ超子螺旋度极化，发现中低能下动涡量贡献主导，为实验探测局域涡旋精细结构提供理论预测。

Effect of thermal shear on longitudinal spin polarization in a thermal model

By including the recently introduced thermal shear term that contributes to the spin polarization vector at local equilibrium, we determine longitudinal polarization of $Λ$ hyperons emitted from a hot and rotating hadronic medium using the thermal model with single freeze-out. In our analysis, we consider the RHIC top energies and use the model parameters which were determined in the earlier analyses of particle spectra and elliptic flow. We confirm that, unlike the previous calculations done by using only the thermal vorticity, the thermal shear term alone leads to the correct sign of the qua…

Anomalous chiral transports and spin polarization in heavy-ion collisions

Relativistic heavy-ion collisions create hot quark-gluon plasma as well as very strong electromagnetic (EM) and fluid vortical fields. The strong EM field and vorticity can induce intriguing macroscopic quantum phenomena such as chiral magnetic, chiral separation, chiral electric separation, and chiral vortical effects as well as the spin polarization of hadrons. These phenomena provide us with experimentally feasible means to study the nontrivial topological sector of quantum chromodynamics, the possible parity violation of strong interaction at high temperature, and the subatomic spintronics…

Local and global $Λ$ polarization in a vortical fluid

We compute the fermion spin distribution in the vortical fluid created in off-central high-energy heavy-ion collisions. We employ the event-by-event (3+1)D viscous hydrodynamic model. The spin polarization density is proportional to the local fluid vorticity in quantum kinetic theory. As a result of strong collectivity, the spatial distribution of the local vorticity on the freeze-out hyper-surface strongly correlates to the rapidity and azimuthal angle distribution of fermion spins. We investigate the sensitivity of the local polarization to the initial fluid velocity in the hydrodynamic mode…

全局平衡下相对论流体中有质量和无质量粒子的精确自旋极化

Exact spin polarization of massive and massless particles in relativistic fluids at global equilibrium

本研究拓展了相对论流体中粒子自旋极化的线性阶表达式，通过解析延拓与级数求和得到任意自旋、有质量及无质量自由粒子的精确自旋极化形式，并探讨了其在相对论重离子碰撞Λ超子极化中的现象学意义。

重离子碰撞中的极化现象

Polarization phenomenon in heavy-ion collisions

本文综述重离子碰撞中涡度诱导粒子极化的实验进展，比较测量与理论计算，并讨论实验方法、探测器修正及未来测量对开放理论问题的意义。

Hyperon polarization in Heavy-Ion Collisions and gravity-related anomaly

We study the energy dependence of global polarization of $Λ$ hyperons in peripheral $Au-Au$ collisions. We combine the calculation of vorticity and strange chemical potential in the framework of kinetic Quark-Gluon String Model with the anomalous mechanism related to axial vortical effect. The earlier found effect of helicity separation implies the quadrupole structure of longitudinal vorticity. We pay special attention to the temperature dependent contribution related to gravitational anomaly and found that the preliminary RHIC data are compatible with its suppression discovered earlier in la…

物质中重夸克的自旋极化：来自有效场论的预测

Spin polarization of heavy quarks in matter: predictions from effective field theories

本研究利用两种有效场论分析LHC重离子碰撞中重夸克自旋极化，发现仅需一个与涡度相关的自由参数即可预测小到中等p_T区间的极化结果，且粲夸克与底夸克的该参数差异不大。

Evolution of $Λ$ polarization in the hadronic phase of heavy-ion collisions

Using the AMPT + MUSIC+UrQMD hybrid model, we study the global and local spin polarizations of $Λ$ hyperons as functions of the freeze-out temperature of the spin degree of freedom in the hadronic phase of Au+Au collisions at $\sqrt{s_{NN}}=19.6$ GeV. Including contributions from both the thermal vorticity and thermal shear of the hadronic matter, we find that, with the spin freeze-out temperature dropping from the hadronization temperature of 160 MeV to 110 MeV at the kinetic freeze-out, both the global and local spin polarizations of $Λ$ hyperons due to the thermal vorticity decrease by a fa…

利用流体动力学和输运模型估算相对论能量下 $Λ$ 和 $\barΛ$ 超子的纵向极化

Estimating Longitudinal Polarization of $Λ$ and $\barΛ$ Hyperons at Relativistic Energies using Hydrodynamic and Transport models

本研究利用流体动力学和输运模型，推导了纵向平均自旋向量与各向异性流系数的关联，探讨了重离子碰撞中Λ超子的纵向自旋极化对方位角、中心度和横动量的依赖性，预测了极化最大值出现的条件，支持了热介质的存在。

各向异性古布瑟流中的局域自旋极化：抑制机制与公式依赖性

Local Spin Polarization in Anisotropic Gubser Flow: Suppression Mechanism and Formulation Dependence

本文通过解析研究相对论重离子碰撞中的纵向自旋极化，揭示了热涡度与热剪切对自旋极化的抵消机制，以及参考单位矢量的选择会影响自旋极化符号的公式依赖性。

通过全局涡度探测夸克胶子等离子体的旋转动力学

Probing Rotational Dynamics of Quark Gluon Plasma via Global Vorticity

该研究通过从强子横向动量谱提取量化全局涡度场，利用Au+Au和Pb+Pb碰撞多能量及中心度数据，研究自旋 - 涡度耦合，发现涡度大小与理论相符，且对粒子种类、碰撞中心度和束流能量有依赖性，为QCD物质旋转性质提供新约束。

Au+Au碰撞中$Λ$与$\overlineΛ$的冻结分布及整体极化

$Λ$ and $\overlineΛ$ Freeze-Out Distributions and Global Polarizations in Au+Au Collisions

该研究利用PHSD输运模型结合流化与涡度计算，解释Au+Au碰撞中$Λ$和$\overlineΛ$整体极化的能量及中心度依赖，并与STAR数据比较。

Reexamination of local spin polarization beyond global equilibrium in relativistic heavy ion collisions

We study local spin polarization in the relativistic hydrodynamic model. Generalizing the Wigner functions previously obtained from chiral kinetic theory by Y. Hidaka et al. [Phys. Rev. D 97, 016004 (2018)] to the massive case, we present the possible contributions up to the order of $\hbar$ from thermal vorticity, shear viscous tensor, other terms associated with the temperature and chemical-potential gradients, and electromagnetic fields to the local spin polarization. We then implement the (3+1)-dimensional viscous hydrodynamic model to study the spin polarizations from these sources with a…

Relaxation time for quark spin and thermal vorticity alignment in heavy-ion collisions

We compute the relaxation time for quark/antiquark spin and thermal vorticity alignment in a quark-gluon plasma at finite temperature and quark chemical potential. We model the interaction of quark/antiquark spin with thermal vorticity as driven by a phenomenological modification of the elementary quark interaction with gluons. We find that in a scenario where the angular velocity of the quark-gluon plasma produced in a peripheral heavy-ion collision is small, quarks/antiquarks take a long time to align their spin with the vorticity. However, when the angular velocity created in the reaction i…

全局平衡下任意自旋粒子的精确极化

Exact Polarization of Particles of Any Spin at Global Equilibrium

针对夸克-胶子等离子体中Λ粒子极化计算仅含热涡度线性项的局限，本文给出全局平衡下任意自旋有质量粒子的全阶精确解析结果，并扩展至局部平衡及3+1流体模拟评估。

石墨烯中电子的自旋流体力学及热涡度导致的磁化

Spin-hydrodynamics of electrons in graphene and magnetization due to thermal vorticity

本文在石墨烯电子流体力学中建立(2+1)维费米子自旋流体力学模型，证明热涡度满足全局平衡方程，并提出可在实验中观测的热涡致磁化新现象。

Azimuthal angle dependence of the longitudinal spin polarization in relativistic heavy ion collisions

The azimuthal angle dependence of quark spin polarization in the longitudinal beam direction of non-central relativistic heavy ion collisions is studied in the chiral kinetic approach. Contrary to the prediction from models based on the assumption of thermal equilibrium of spin degrees of freedom that the quark spin polarization always points along the direction of local vorticity field, we find the two can have opposite directions due to the effect from the transversal component of vorticity field, which can lead to a redistribution of axial charges in the produced matter. Our finding is cons…

高能核碰撞中初始态驱动的自旋关联

Initial-state-driven spin correlations in high-energy nuclear collisions

本文针对重离子碰撞自旋极化研究中末态效应的传统假设，提出初始态核子碰撞产生横向自旋密度诱导火球净极化的新机制，估计Λ重子净极化在中心/非中心碰撞中达1%/超10%，并设计双粒子关联观测量，其发现将推动核结构与相对论流体力学自旋研究。

重访热涡度诱导的自旋效应

Revisit spin effects induced by thermal vorticity

本文直接从自旋依赖分布函数重算热涡度诱导的自旋效应，给出自旋1/2粒子一阶极化并与自旋矢量结果比较，发现自旋1粒子一阶无自旋排列，二阶有贡献，且自旋方向与动量关联时存在额外贡献。

Spin-thermal shear coupling in a relativistic fluid

We show that spin polarization of a fermion in a relativistic fluid at local thermodynamic equilibrium can be generated by the symmetric derivative of the four-temperature vector, defined as thermal shear. As a consequence, besides vorticity, acceleration and temperature gradient, also the shear tensor contributes to the polarization of particles in a fluid. This contribution to the spin polarization vector, which is entirely non-dissipative, adds to the well known term proportional to thermal vorticity and may thus have important consequences for the solution of the local polarization puzzles…

相对论重离子碰撞中 $J/ψ$ 的极化

$J/ψ$ polarization in relativistic heavy ion collisions

本文研究相对论重离子碰撞中 $J/ψ$ 在不同中心度、横动量及三种参考系下的产额与极化，发现高 $p_T$ 区极化与 $pp$ 碰撞相似，低 $p_T$ 区由旋转 QGP 中极化粲夸克主导，为后续电磁场与涡旋场效应研究提供基准。

具有耗散修正的热模型中的纵向自旋极化

Longitudinal spin polarization in a thermal model with dissipative corrections

本文结合含自旋自由度的相对论动理学理论与冻结参数化，将热剪切和热涡度梯度导致的耗散修正纳入Pauli-Lubanski矢量，以解释重离子碰撞中Λ超子的纵向自旋极化，并估计自旋弛豫时间τ_s约为5 fm/c。