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arXiv 2209.01872nucl-thhep-ph
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NJL模型中磁场下$\phi$介子的质量劈裂与自旋排列

Mass splitting and spin alignment for $ϕ$ mesons in a magnetic field in NJL model

Xin-Li Sheng, Shu-Yun Yang, Yao-Lin Zou, Defu Hou

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12 pages, 15 figures
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AI总结：

本文基于NJL模型开发计算矢量介子自旋排列的框架，研究磁场中$\phi$介子的质量劈裂与自旋排列，发现沿磁场方向自旋排列大于1/3，与STAR数据定性一致，有助于理解手性相变中强子自旋结构的形成。

摘要：

基于Nambu-Jona-Lasinio（NJL）模型，我们开发了一个计算矢量介子自旋排列的框架，并将其应用于研究磁场中的$\phi$介子。我们计算了$\phi$介子的质量谱，并观察到纵向极化态与横向极化态之间存在质量劈裂。在热平衡系统中，$\phi$介子更倾向于占据自旋$\lambda=0$的态，而不是自旋$\lambda=\pm1$的态，因为前者的能量较小。因此，我们得出结论，如果沿着磁场方向进行测量，自旋排列将大于1/3，这与最近的STAR数据在定性上是一致的。在临界温度$T_{C}=150$ MeV附近，相对于1/3的正向偏离与磁场强度的平方成正比，这与非相对论合并模型的结果一致。引入夸克的反常磁矩会改变夸克的动力学质量，从而影响$\phi$介子的质量谱和自旋排列。在NJL模型中对自旋排列的讨论可能有助于我们更好地理解手性相变期间强子自旋结构的形成。

英文摘要：

Based on the Nambu-Jona-Lasinio (NJL) model, we develop a framework for calculating the spin alignment of vector mesons and applied it to study $ϕ$ mesons in a magnetic field. We calculate mass spectra for $ϕ$ mesons and observe mass splitting between the longitudinally polarized state and transversely polarized states. The $ϕ$ meson in a thermal equilibrium system is preferred to occupy the state with spin $λ=0$ than those with spin $λ=\pm1$, because the former state has a smaller energy. As a consequence, we conclude that the spin alignment will be larger than 1/3 if one measures along the direction of the magnetic field, which is qualitatively consistent with the recent STAR data. Around the critical temperature $T_{C}=150$ MeV, the positive deviation from 1/3 is proportional to the square of the magnetic field strength, which agrees with the result from the non-relativistic coalescence model. Including the anomalous magnetic moments for quarks will modify the dynamical masses of quarks and thus affect the mass spectra and spin alignment of $ϕ$ mesons. The discussion of spin alignment in the NJL model may help us better understand the formation of hadron's spin structure during the chiral phase transition.

机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。

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