Global polarization of Λ, Ξ−, and Ω− hyperons in Au+Au collisions at RHIC BES-II energies
Abstract
We investigate the global spin polarization of Λ hyperons and the multi-strange hyperons Ξ− and Ω− in Au+Au collisions across the RHIC Beam Energy Scan II (BES-II) energy range, √(sNN)=7.7--$27$ GeV. The polarization is computed using the modified Cooper--Frye formula, which includes contributions from thermal vorticity, the thermal shear tensor, and the gradient of the baryon chemical potential, combined with the (3+1)-dimensional viscous hydrodynamic framework CLVisc with SMASH initial conditions. We present the global polarization as a function of collision energy, centrality, transverse momentum, and rapidity. We find that the global polarization of Ω− is systematically larger than those of Λ and Ξ− because of its larger spin quantum number, but it remains below the central value of the recent STAR measurement. This discrepancy may suggest that additional mechanisms, such as spin correlations among strange quarks inside the Ω−, could contribute to the observed Ω− polarization. We also find that the global-polarization splitting between hyperons and anti-hyperons increases toward lower collision energies and is dominated by the chemical-potential-gradient contribution.
Related
- Global polarization of Λ, Ξ, and Ω hyperons in Au+Au collisions from the RHIC Beam Energy Scan-II
- Differential measurement of global polarization of Λ, Ξ, and Ω hyperons in Au+Au collisions at √(sNN)=7.7--27 GeV from the RHIC Beam Energy Scan-II
- Measurements of local polarization of Λ hyperons with event shape engineering in Au+Au collisions at RHIC-STAR
- Deep Learning for Longitudinal Asymmetry in Heavy-Ion Collisions at RHIC Energies
- Measurement of transverse polarization of Λ and Λ ̅ hyperons inside jets in unpolarized proton-proton collisions at √s=200 GeV
BibTeX
@misc{li2026global,
title = {{Global polarization of $Λ$, $Ξ^-$, and $Ω^-$ hyperons in Au+Au collisions at RHIC BES-II energies}},
author = {Gen-Hui Li and Cong Yi and Xiang-Yu Wu and Shi Pu and Guang-You Qin},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2606.10341},
eprint = {2606.10341},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2606.10341},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Global polarization of Λ, Ξ^−, and Ω^− hyperons in Au+Au collisions at RHIC BES-II energies
AU - Gen-Hui Li
AU - Cong Yi
AU - Xiang-Yu Wu
AU - Shi Pu
AU - Guang-You Qin
PY - 2026
DA - 2026/10/20
PB - arXiv
DO - 10.48550/arxiv.2606.10341
UR - https://arxiv.org/abs/2606.10341
AB - We investigate the global spin polarization of Λ hyperons and the multi-strange hyperons Ξ^− and Ω^− in Au+Au collisions across the RHIC Beam Energy Scan II (BES-II) energy range, √(s_NN)=7.7--$27$ GeV. The polarization is computed using the modified Cooper--Frye formula, which includes contributions from thermal vorticity, the thermal shear tensor, and the gradient of the baryon chemical potential, combined with the (3+1)-dimensional viscous hydrodynamic framework CLVisc with SMASH initial conditions. We present the global polarization as a function of collision energy, centrality, transverse momentum, and rapidity. We find that the global polarization of Ω^− is systematically larger than those of Λ and Ξ^− because of its larger spin quantum number, but it remains below the central value of the recent STAR measurement. This discrepancy may suggest that additional mechanisms, such as spin correlations among strange quarks inside the Ω^−, could contribute to the observed Ω^− polarization. We also find that the global-polarization splitting between hyperons and anti-hyperons increases toward lower collision energies and is dominated by the chemical-potential-gradient contribution.
ER -