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在非对心相对论重离子碰撞中, 参与反应的系统具有巨大的轨道角动量, 从而使产生的夸克胶子等离子体具有极强涡旋场, 并通过自旋-轨道相互作用导致部分子的自旋极化, 经过强子化导致重子的自旋极化以及矢量介子的自旋排列等可观测效应. 矢量介子的自旋排列是指其自旋密度矩阵的00元素
$\rho_{00}$ 偏离 1/3. 在矢量介子衰变到两个赝标介子的过程中, 衰变产物的极角分布只与$\rho_{00}$ 有关, 以此可以对自旋排列进行测量. 理论研究表明, 重离子碰撞过程中, 重子的自旋极化反映了夸克自旋极化的时空平均效应, 而矢量介子自旋排列则反映了夸克反夸克自旋极化的局域相空间关联. 本文回顾了相对论重离子碰撞中矢量介子自旋排列的相关理论工作. 重点以非相对论夸克融合模型为例, 明确地计入夸克极化的相空间依赖性, 展示了矢量介子自旋排列与夸克反夸克自旋极化特别是它们之间相空间关联的关系. 本文还讨论了涡旋、电磁场、有效ϕ介子场以及它们的局域涨落对ϕ介子自旋排列的贡献, 结果显示强作用场的时空关联效应是导致ϕ介子自旋排列的主要因素. 矢量介子自旋排列为探索强相互作用物质和强相互作用场的性质提供了新途径.In non-central relativistic heavy-ion collisions, the large initial orbital angular momentum results in strong vorticity fields in the quark-gluon plasma, which polarize partons through the spin-orbit coupling. The global polarization of quark matter will be converted to the global polarization of baryons and the global spin alignment of vector mesons. The spin alignment refers to the$\rho_{00}$ element of the spin density matrix for vector mesons. When a vector meson decays to two pseudoscalar mesons, the polar angle distribution for the decay product depends on$\rho_{00}$ , through which the spin alignment can be measured. Theoretical studies show that the global spin polarization of baryons reflects the space-time average of the quark polarization, while the spin alignment of vector mesons reflects the local phase space correlation between the polarization of quark and antiquark. In this article, we review recent theoretical works about the spin alignment of vector mesons. We consider a non-relativistic quark coalescence model in spin and phase space. Within this model, the spin alignment of the vector meson can be described through the phase space correlation of quark's and antiquark's polarization. The contributions to the spin alignment of ϕ mesons from vorticity fields, electromagnetic fields, and effective ϕ meson fields are discussed. The spin alignment of vector mesons opens a new window for the properties of strong interaction fields in heavy-ion collisions.-
Keywords:
- global spin polarization /
- spin alignment of vector mesons /
- spin-orbit coupling /
- quark coalescence model /
- heavy ion collisions
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[26] Li F, Liu Y F S 2022 e-Print: 2206.11890
[27] Wanger D, Weickgenannt N, Speranza E 2022 e-Print: 2207.01111
[28] 孙旭, 周晨升, 陈金辉, 陈振宇, 马余刚, 唐爱洪, 徐庆华 2023 物理学报 72 072401
Sun X, Zhou C S, Chen J H, Chen Z Y, Ma Y G, Tang A H, Xu Q H 2023 Acta. Phys. Sin. 72 072401
[29] 寿齐烨, 赵杰, 徐浩洁, 李威, 王钢, 唐爱洪, 王福强 2023 物理学报 Accepted
Shou Q Y, Zhao J, Xu H J, Li W, Wang G, Tang A H, Wang F Q 2023 Acta. Phys. Sin. Accepted
[30] 侯德富, 黄梅, 马国亮 2023 物理学报 Accepted
Hou D F, Huang M, Ma G L 2023 Acta. Phys. Sin. Accepted
[31] 高建华, 盛欣力, 王群, 庄鹏飞 2023 物理学报 Accepted
Gao J H, Sheng X L, Wang Q, Zhuang P F 2023 Acta. Phys. Sin. Accepted
[32] 黄旭光, 浦实 2023 物理学报 72 071202
Huang X G, Pu S 2023 Acta. Phys. Sin. 72 071202
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[1] Liang Z T, Wang X N 2005 Phys. Rev. Lett. 94 102301Google Scholar
[2] Becattini F, Piccinini F, Rizzo J 2008 Phys. Rev. C 77 024906Google Scholar
[3] Betz B, Gyulassy M, Torrieri G 2007 Phys. Rev. C 76 044901
[4] Gao J H, Chen S W, Deng W T, Liang Z T, Wang Q, Wang X N 2008 Phys. Rev. C 77 044902Google Scholar
[5] Zhang J J, Fang R H, Wang Q, Wang X N 2019 Phys. Rev. C 100 064904Google Scholar
[6] Wang Q 2017 Nucl. Phys. A 967 225Google Scholar
[7] Gao J H, Liang Z T, Wang Q, Wang X N 2021 Lect. Notes Phys. 987 195
[8] Huang X G, Liao J, Wang Q, Xia X L 2021 Lect. Notes Phys. 987 281
[9] Gao J H, Ma G L, Pu S, Wang Q 2020 Nucl. Sci. Technol. 31 90Google Scholar
[10] 高建华, 黄旭光, 梁作堂, 王群, 王新年 2023 物理学报 72 072501
Gao J H, Huang X G, Liang Z T, Wang Q, Wang X N 2023 Acta. Phys. Sin. 72 072501
[11] Liang Z T, Wang X N 2005 Phys. Lett. B 629 20Google Scholar
[12] Yang Y G, Fang R H, Wang Q, Wang X N 2018 Phys. Rev. C 97 034917Google Scholar
[13] Adamczyk L, Adkins J K, Agakishiev G, et al. 2017 Nature 548 62Google Scholar
[14] Adam J, Adamczyk L, Adams J R, et al. 2018 Phys. Rev. C 98 014910Google Scholar
[15] Adam J, Adamczyk L, Adams J R, et al. 2021 Phys. Rev. Lett. 126 162301Google Scholar
[16] Abou Yassine R, Adamczewski-Musch J, Asal C, et al. 2022 Phys. Lett. B 835 137506Google Scholar
[17] Acharya S, Adamova D, Adler A, et al. 2020 Phys. Rev. Lett. 125 012301Google Scholar
[18] Abdallah M S, Aboona B E, Adam J, et al. 2022 Nature 614 355
[19] Sheng X L, Oliva L, Wang Q 2020 Phys. Rev. D 101 096005Google Scholar
[20] Sheng X L, Wang Q, Wang X N 2020 Phys. Rev. D 102 056013Google Scholar
[21] Xia X L, Li H, Huang X G, Huang H Z 2021 Phys. Lett. B 817 136325Google Scholar
[22] Gao J H 2021 Phys. Rev. D 104 076016Google Scholar
[23] Mueller B, Yang D L 2022 Phys. Rev. D 105 1
[24] Sheng X L, Oliva L, Liang Z T, Wang Q, Wang X N 2022 e-Print: 2205.15689
[25] Sheng X L, Oliva L, Liang Z T, Wang Q, Wang X N 2022 e-Print: 2206.05868
[26] Li F, Liu Y F S 2022 e-Print: 2206.11890
[27] Wanger D, Weickgenannt N, Speranza E 2022 e-Print: 2207.01111
[28] 孙旭, 周晨升, 陈金辉, 陈振宇, 马余刚, 唐爱洪, 徐庆华 2023 物理学报 72 072401
Sun X, Zhou C S, Chen J H, Chen Z Y, Ma Y G, Tang A H, Xu Q H 2023 Acta. Phys. Sin. 72 072401
[29] 寿齐烨, 赵杰, 徐浩洁, 李威, 王钢, 唐爱洪, 王福强 2023 物理学报 Accepted
Shou Q Y, Zhao J, Xu H J, Li W, Wang G, Tang A H, Wang F Q 2023 Acta. Phys. Sin. Accepted
[30] 侯德富, 黄梅, 马国亮 2023 物理学报 Accepted
Hou D F, Huang M, Ma G L 2023 Acta. Phys. Sin. Accepted
[31] 高建华, 盛欣力, 王群, 庄鹏飞 2023 物理学报 Accepted
Gao J H, Sheng X L, Wang Q, Zhuang P F 2023 Acta. Phys. Sin. Accepted
[32] 黄旭光, 浦实 2023 物理学报 72 071202
Huang X G, Pu S 2023 Acta. Phys. Sin. 72 071202
[33] Bacchetta A, Mulders P J 2000 Phys. Rev. D 62 114004Google Scholar
[34] Faccioli P, Lourenco C, Seixas J, Wohri H K 2010 Eur. Phys. J. C 69 657Google Scholar
[35] Li Z, Zha W, Tang Z 2022 Phys. Rev. C 106 064908Google Scholar
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