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The hot and dense matter generated in heavy-ion collisions contains intricate vortical structure in which the local fluid vorticity can be very large. Such vorticity can polarize the spin of the produced particles. We study the…

Nuclear Theory · Physics 2019-01-23 De-Xian Wei , Wei-Tian Deng , Xu-Guang Huang

The global spin alignment of vector mesons has been observed by the STAR collaboration at the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory (BNL). It provides a unique opportunity to probe the correlation between…

High Energy Physics - Phenomenology · Physics 2025-02-27 Jin-Hui Chen , Zuo-Tang Liang , Yu-Gang Ma , Xin-Li Sheng , Qun Wang

In these proceedings I discuss the recent progress in the theory of spin polarization in relativistic fluids. To date, a number of studies have begun to examine the impact of the shear tensor on the local spin polarization and whether this…

Nuclear Theory · Physics 2023-03-22 Matteo Buzzegoli

We predict the polarization of Lambda and antiLambda hyperons in peripheral heavy ion collisions at ultrarelativistic energy, based on the assumption of local thermodynamical equilibrium at freeze-out. The polarization vector is…

Nuclear Theory · Physics 2013-11-21 F. Becattini , L. Csernai , D. J. Wang

We report the measurements of global spin polarization of hyperons ($P_{\Lambda}$) from FAIR, RHIC and LHC energies. The $P_{\Lambda}$ continue to follow an increasing trend at $\sqrt{s_{\mathrm NN}}$ < 7.7 GeV indicating that enormous…

Nuclear Experiment · Physics 2023-03-22 Subhash Singha

We present the measurements related to global polarization of $\Lambda$ hyperons and spin alignment of $\mathrm{K^{*0}}~$ vector mesons at mid-rapidity for Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}~$= 2.76 TeV using the ALICE detector at…

Nuclear Experiment · Physics 2019-08-21 Bedangadas Mohanty

We argue that spin alignment of the vector mesons observed in unpolarized hadron-hadron collisions is closely related to the single spin left-right asymmetry observed in transversely polarized hadron-hadron collisions. We present the…

High Energy Physics - Phenomenology · Physics 2009-11-10 Qing-hua Xu , Zuo-tang Liang

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…

Nuclear Theory · Physics 2018-03-14 Iurii Karpenko , Francesco Becattini

We derive expressions for the vector and tensor components of the spin polarization of massive vector bosons at local thermodynamic equilibrium up to second order in the space-time gradients of the thermodynamic fields pertaining to the…

High Energy Physics - Phenomenology · Physics 2025-07-24 Zhong-Hua Zhang , Xu-Guang Huang , Francesco Becattini , Xin-Li Sheng

Since its discovery, global polarization of the $\Lambda$ hyperon in heavy-ion collisions has been firmly established and is widely attributed to the large vorticity generated in the rotating quark-gluon plasma. In contrast, nearly fifty…

High Energy Physics - Phenomenology · Physics 2026-03-23 Feng Liu , Zhoudunming Tu

The first evidence of spin alignment of vector mesons ($K^{*0}$ and $\phi$) in heavy-ion collisions at the Large Hadron Collider (LHC) is reported. The spin density matrix element $\rho_{00}$ is measured at midrapidity ($|y| <$ 0.5) in…

Nuclear Experiment · Physics 2022-01-14 ALICE Collaboration

We study the longitudinal polarization of hyperons and anti-hyperons at forward pseudorapidity, $2.5<\eta<4$, in singly polarized $pp$ collisions at RHIC energies by using different parameterizations of the polarized parton densities and…

High Energy Physics - Phenomenology · Physics 2010-04-06 Wei Zhou , Shan-shan Zhou , Qing-hua Xu

The global spin polarization of hyperons in heavy-ion collisions have been investigated by including spin correlation effects among their constituent quarks. The available data on global spin polarizations of hyperons and spin alignments of…

High Energy Physics - Phenomenology · Physics 2026-03-12 Lucia Oliva , Qun Wang , Xin-Nian Wang

In the 1970s, an unexpected transverse $\Lambda$ polarization in unpolarized proton-Beryllium collisions was discovered, which initiated extensive studies on spin phenomena in high-energy physics. Over the past five decades, similar…

High Energy Physics - Phenomenology · Physics 2024-06-06 Zhoudunming Tu

The significant global spin alignment observed for $\phi$ mesons in heavy-ion collisions has sparked intense discussions about its origin and implications. One explanation suggests that fluctuations in the strong force field may introduce…

Nuclear Theory · Physics 2024-08-01 Diyu Shen , Jinhui Chen , Aihong Tang

We analyze the spin alignment of vector mesons stemming from spin correlation of the quark and antiquark induced by background color fields in relativistic heavy ion collisions. The quark-coalescence equation relating the collision kernel…

Nuclear Theory · Physics 2025-03-11 Di-Lun Yang

We study the longitudinal spin polarization of a relativistic fluid of massive spin-1/2 particles undergoing a boost-invariant expansion in the longitudinal direction and rotating in the transverse plane. We express the polarization vector…

Nuclear Theory · Physics 2025-03-18 Nora Weickgenannt , Jean-Paul Blaizot

Unexpectedly large and puzzling spin alignment, and thus tensor polarization, of vector mesons has been observed in heavy-ion collisions. Given that tensor polarization represents a fluctuation of spin, we derive, for the first time, a…

Nuclear Theory · Physics 2025-11-18 Feng Li , Shuai Y. F. Liu

We perform a systematic study of the spin polarization of hyperons in heavy-ion collisions using the MUSIC hydrodynamic model with A Multi-Phase Transport (AMPT) pre-equilibrium dynamics. Our model calculations nicely describe the measured…

Nuclear Theory · Physics 2021-02-10 Baochi Fu , Kai Xu , Xu-Guang Huang , Huichao Song

We perform a systematic study on the local and global spin polarization of $\Lambda$ and $\overline{\Lambda}$ hyperons in relativistic heavy-ion collisions at beam energy scan energies via the (3+1)-dimensional CLVisc hydrodynamics model…

High Energy Physics - Phenomenology · Physics 2022-06-28 Xiang-Yu Wu , Cong Yi , Guang-You Qin , Shi Pu