发表机构
University of Chinese Academy of Sciences; Charmo University; Hangzhou Normal University（中国科学院大学; 查莫大学; 杭州师范大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究利用四味软墙全息框架探究相对论重离子碰撞中矢量介子自旋排列的介质效应，发现轻重矢量介子低横动量下自旋排列行为相反，建立了跨味区平衡全息基线。
AI 中文摘要
理解相对论重离子碰撞中矢量介子的自旋排列，需要对其自旋相关的介质内性质进行非微扰描述。我们在一个统一的四味软墙全息框架下研究该问题，该框架结合了有限温度、重子化学势和角速度下的各向异性Einstein--Maxwell--dilaton背景。自旋排列通过瞬时冻出方案，由介质诱导的自旋分辨矢量流谱函数劈裂确定。我们系统研究了奇异和粲矢量介子$K^{*}$、$ϕ$、$D^{*}$、$D_s^{*}$和$J/ψ$，以及它们的自旋排列对横动量、快度、温度、重子化学势和角速度的依赖关系。我们发现，重粲矢量介子$D^{*}$、$D_s^{*}$和$J/ψ$在低横动量下表现为$ρ_{00}>1/3$，而轻奇异矢量介子$K^{*}$和$ϕ$表现出相反的低动量行为，角分布满足$ρ_{00}<1/3$。我们将这种味依赖的差异归因于真空质量壳相对于热移动的纵向和横向谱峰的位置不同。该结果定性重现了低横动量和中间横动量下观测到的若干趋势。自旋排列对重子化学势不敏感，仅受角速度的微弱影响。这些结果为跨味区的矢量介子自旋排列建立了平衡全息基线，并有助于界定非平衡演化、涨落和硬产生等额外机制发挥重要作用的区域。
英文摘要
Understanding the spin alignment of vector mesons in relativistic heavy-ion collisions requires a nonperturbative description of their spin-dependent in-medium properties. We investigate this problem within a unified four-flavor soft-wall holographic framework that combines an anisotropic Einstein--Maxwell--dilaton background at finite temperature, baryon chemical potential, and angular velocity. Spin alignment is determined from the medium-induced splitting of the spin-resolved vector-current spectral functions through an instantaneous freeze-out prescription. We systematically study the strange and charm vector mesons $K^{*}$, $ϕ$, $D^{*}$, $D_s^{*}$, and $J/ψ$ and the dependence of their spin alignment on transverse momentum, rapidity, temperature, baryon chemical potential, and angular velocity. We find that the heavy charm vector mesons $D^{*}$, $D_s^{*}$, and $J/ψ$ mesons exhibit $ρ_{00}>1/3$ at low transverse momentum, whereas the light strange vector mesons $K^{*}$ and $ϕ$ exhibit the opposite low-momentum behavior and angular distributions with $ρ_{00}<1/3$. We trace this flavor-dependent separation to the different locations of the vacuum mass shell relative to the thermally shifted longitudinal and transverse spectral peaks. The results qualitatively reproduce several trends observed at low and intermediate transverse momentum. Spin alignment is insensitive to baryon chemical potential and only weakly affected by angular velocity. These results establish an equilibrium holographic baseline for vector-meson spin alignment across flavor sectors and help delineate the regimes in which additional mechanisms, such as nonequilibrium evolution, fluctuations, and hard production, become important.
Comments21 pages, 14 figures, 3 tables
