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The quark-gluon plasma produced by collisions between ultra-relativistic heavy nuclei is well described in the language of hydrodynamics. Non-central collisions are characterized by very large angular momentum, which in a fluid system…

Nuclear Experiment · Physics 2020-03-10 Francesco Becattini , Michael Lisa

Fermions become polarized in a vortical fluid due to spin-vorticity coupling. The spin polarization density is proportional to the local fluid vorticity at the next-to-leading order of a gradient expansion in a quantum kinetic theory. Spin…

High Energy Physics - Phenomenology · Physics 2016-11-09 Long-Gang Pang , Hannah Petersen , Qun Wang , Xin-Nian Wang

Polarization of $\Lambda$ hyperons and their antiparticles is calculated in a 3+1 dimensional viscous hydrodynamic model with initial state from UrQMD hadron/string cascade. We find that, along with recent results from STAR, the mean…

Nuclear Theory · Physics 2018-03-14 Iu. Karpenko , F. Becattini

The equations of perfect spin hydrodynamics are solved for the first time using a realistic (3+1)-dimensional hydrodynamic background, calibrated to reproduce a comprehensive set of hadronic observables, including rapidity distributions,…

High Energy Physics - Phenomenology · Physics 2025-02-19 Sushant K. Singh , Radoslaw Ryblewski , Wojciech Florkowski

Large orbital angular momentum can be generated in non-central heavy-ion collisions, and part of it is expected to be converted into final particle's polarization due to the spin-orbit coupling. Within the framework of A Multi-Phase…

Nuclear Theory · Physics 2017-12-08 Xiao-Liang Xia , Hui Li , Qun Wang

We investigate the hydrodynamic helicity polarization of $\Lambda$ hyperons, defined as the projection of the spin polarization vector along the directions of particle momenta, at RHIC-BES energies by utilizing the relativistic (3+1)D…

High Energy Physics - Phenomenology · Physics 2023-04-19 Cong Yi , Xiang-Yu Wu , Di-Lun Yang , Jian-Hua Gao , Shi Pu , Guang-You Qin

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

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

The extreme temperatures and energy densities generated by ultra-relativistic collisions between heavy nuclei produce a state of matter with surprising fluid properties. Non-central collisions have angular momentum on the order of…

Nuclear Experiment · Physics 2017-08-29 STAR Collaboration

We calculate the contribution to the polarization of $\Lambda$ hyperons in relativistic nuclear collisions at high energy from the decays of $\Sigma^*(1385)$ and $\Sigma^0$, which are the predominant sources of $\Lambda$ production besides…

Nuclear Theory · Physics 2019-10-02 F. Becattini , Gaoqing Cao , Enrico Speranza

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 findings on the spin polarization of $\Lambda$, $\Xi$, and $\Omega$ hyperons and spin alignment of $K^{*0}$, $\phi$, and $D^{*+}$ mesons in relativistic heavy-ion collision experiments at the RHIC and LHC facilities propose the…

High Energy Physics - Phenomenology · Physics 2026-02-17 Bhagyarathi Sahoo , Captain R. Singh , Raghunath Sahoo

We calculate the polarization of $\Lambda$ hyperons in Au-Au collisions at RHIC Beam Energy Scan range $\sqrt{s_{\rm NN}}=7.7, \dots, 200$ GeV in a state-of-the-art 3+1 dimensional cascade + viscous hydro model vHLLE+UrQMD. We find that the…

Nuclear Theory · Physics 2017-03-08 Iu. Karpenko , F. Becattini

Polarization has opened a new physics chapter in relativistic heavy-ion collisions. Since the first prediction and experimental observation of global spin polarization, a lot of progress has been made in understanding its features, both at…

Nuclear Theory · Physics 2024-02-08 Francesco Becattini , Matteo Buzzegoli , Takafumi Niida , Shi Pu , Ai-Hong Tang , Qun Wang

With a Yang-Mills flux-tube initial state and a high resolution (3+1)D Particle-in-Cell Relativistic (PICR) hydrodynamics simulation, we calculate the $\Lambda$ polarization for different energies. The origination of polarization in high…

Nuclear Theory · Physics 2017-03-16 Yilong Xie , Dujuan Wang , László P. Csernai

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

STAR collaboration at RHIC has recently measured the polarization of $\Lambda$ hyperons in non-central heavy ion collisions in the RHIC Beam Energy Scan (BES) program. The magnitude of the polarization was found to decrease from few…

Nuclear Theory · Physics 2019-01-23 Iurii Karpenko , Francesco Becattini

Since the observation of $\Lambda$ global polarization at RHIC, indicating the most vortical fluid ever observed so far, many experimental and theoretical progresses have been made in understanding of vorticity and polarization phenomena in…

Nuclear Experiment · Physics 2022-11-30 Takafumi Niida

We study the directed flow of identified particles in Au+Au collisions at $\sqrt{s_\text{NN}}=7.7$ to 62.4 GeV. The Glauber model is extended to include both a tilted deformation of the QGP fireball with respect to the longitudinal…

Nuclear Theory · Physics 2023-03-10 Ze-Fang Jiang , Xiang-Yu Wu , Shanshan Cao , Ben-Wei Zhang

Global polarization of $\Lambda$ and $\bar{\Lambda}$ hyperons in Au+Au collisions at collision energies $\sqrt{s_{NN}}=$ 4-40 GeV in the midrapidity region and total polarization, i.e. averaged over all rapidities, are studied within the…

Nuclear Theory · Physics 2019-07-31 Yu. B. Ivanov , V. D. Toneev , A. A. Soldatov