有限密度等离子体中矢量介子的自旋排列
Spin alignment of vector mesons in a plasma at finite density
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中文总结 AI 辅助
在软墙全息模型中，研究有限密度下$J/\boldsymbol{\u03c8}$与$\boldsymbol{\u03c6}$介子的自旋排列，分析温度、化学势对其谱函数及自旋排列参数$\boldsymbol{\u03c1_{00}}$的影响，揭示介质中矢量介子的解离与熔解特性。
中文摘要 AI 辅助
我们在软墙全息模型框架下，研究有限密度下$J/\boldsymbol{\u03c8}$与$\boldsymbol{\u03c6}$介子的谱函数及自旋排列，该模型提供夸克-胶子等离子体背景，矢量介子由体矢量场描述。我们推导不同自旋道产生率与对应介质中谱函数的关系，并考察其对化学势、介子动量和温度的依赖。我们分析矢量介子相对于热浴运动诱导的自旋排列。在$\boldsymbol{T=0.15~\text{GeV}}$时，$\boldsymbol{J/\boldsymbol{\u03c8}}$的谱函数呈现清晰的共振峰，表明$\boldsymbol{c\bar{c}}$对仍可形成准稳定束缚态；随着化学势升高，该峰变低变宽，显示介质中解离增强。相同温度下的$\boldsymbol{\u03c6}$介子无明显峰，表明其显著熔解，因此其谱函数更能表征热环境中不稳定$\boldsymbol{s\bar{s}}$对的分布。在$\boldsymbol{T=0.15~\text{GeV}}$时，螺旋度框架自旋排列参数$\boldsymbol{\u03c1_{00}}$对$\boldsymbol{J/\boldsymbol{\u03c8}}$呈正偏离$\boldsymbol{1/3}$，对$\boldsymbol{\u03c6}$呈负偏离；有限化学势会改变这些偏离，使$\boldsymbol{J/\boldsymbol{\u03c8}}$的偏离幅度减小，$\boldsymbol{\u03c6}$的偏离幅度增大。
英文摘要
We study the spectral functions and spin alignment of $J/ψ$ and $ϕ$ mesons at finite density in a soft-wall holographic model. The quark-gluon plasma background is described by a charged black hole geometry, and the vector mesons are treated as probe bulk vector fields. The present analysis extends the zero-density study of Phys. Rev. D 110 (2024) 056047 (Ref.~\cite{XLS2024}) to finite density; in the zero-density limit our results reproduce the corresponding findings. We derive the relation between the production rates in different spin channels and the corresponding in-medium spectral functions, and examine their dependence on the chemical potential, meson momentum, and temperature. We analyze the spin alignment induced by the motion of the vector meson relative to the thermal bath. At $T=0.15~\mathrm{GeV}$, the $J/ψ$ spectral function exhibits a clear resonance peak, indicating that the $c\bar{c}$ pair can still form a quasistable bound state. As the chemical potential increases, this peak becomes lower and broader, signaling enhanced dissociation in the medium. For the $ϕ$ meson at the same temperature, no pronounced peak is observed, indicating substantial melting; its spectral function thus better characterizes the distribution of unstable $s\bar{s}$ pairs in the thermal environment. At $T=0.15~\mathrm{GeV}$, the helicity-frame spin alignment parameter $ρ_{00}$ shows a positive deviation from $1/3$ for the $J/ψ$ and a negative one for the $ϕ$ meson. A finite chemical potential alters these deviations, reducing the magnitude for the $J/ψ$ while increasing it for the $ϕ$ meson. The calculations are performed within a bottom-up soft-wall model; the results should be read as model-based estimates rather than model-independent predictions.
发表机构
- School of Mathematics and Physics, China University of Geosciences (Wuhan)（中国地质大学（武汉）数理学院）
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