Global polarization of Λ, Ξ, and Ω hyperons in Au+Au collisions from the RHIC Beam Energy Scan-II
Abstract
Global polarization of Λ, Ξ, and Ω hyperons is measured in Au+Au collisions at √(sNN)=7.7, 9.2, 11.5, 14.6, 17.3, 19.6, and 27~GeV using high-statistics data from the second phase of the RHIC Beam Energy Scan. No significant difference between the Λ and Λ̅ polarizations is observed over the measured collision-energy range, providing improved constraints on magnetic-field-induced contributions. The Λ polarization increases with the magnitude of rapidity, with the slope of the linear fit differing from zero by 4.8 standard deviations, providing the first evidence for a nonzero rapidity dependence of global polarization in this energy range. Global polarization of Ξ−+Ξ̅+ is observed for the first time at these energies at a significance exceeding 5 standard deviations, with a magnitude comparable to that of Λ+Λ̅ and an increase toward lower collision energies. Measurements of Ω−+Ω̅+ are compatible with a similar energy dependence and favor the decay parameter γΩ= +1 with high probability under the assumption of the global polarization picture. These measurements provide new constraints on the energy evolution, rapidity dependence, and species dependence of global polarization in heavy-ion collisions.
Related
- 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
- Global polarization of Λ, Ξ−, and Ω− hyperons in Au+Au collisions at RHIC BES-II energies
- Measurements of local polarization of Λ hyperons with event shape engineering in Au+Au collisions at RHIC-STAR
- Measurement of transverse polarization of Λ and Λ ̅ hyperons inside jets in unpolarized proton-proton collisions at √s=200 GeV
- Probing nuclear deformation through global Λ polarization in U+U collisions at HIAF
BibTeX
@misc{collaboration2026global,
title = {{Global polarization of $Λ$, $Ξ$, and $Ω$ hyperons in Au+Au collisions from the RHIC Beam Energy Scan-II}},
author = {STAR Collaboration},
howpublished = {arXiv},
year = {2026},
month = nov,
doi = {10.48550/arxiv.2611.03044},
eprint = {2611.03044},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2611.03044},
note = {CC BY-NC-ND 4.0},
}
RIS
TY - UNPB
TI - Global polarization of Λ, Ξ, and Ω hyperons in Au+Au collisions from the RHIC Beam Energy Scan-II
AU - STAR Collaboration
PY - 2026
DA - 2026/11/02
PB - arXiv
DO - 10.48550/arxiv.2611.03044
UR - https://arxiv.org/abs/2611.03044
AB - Global polarization of Λ, Ξ, and Ω hyperons is measured in Au+Au collisions at √(s_NN)=7.7, 9.2, 11.5, 14.6, 17.3, 19.6, and 27~GeV using high-statistics data from the second phase of the RHIC Beam Energy Scan. No significant difference between the Λ and Λ̅ polarizations is observed over the measured collision-energy range, providing improved constraints on magnetic-field-induced contributions. The Λ polarization increases with the magnitude of rapidity, with the slope of the linear fit differing from zero by 4.8 standard deviations, providing the first evidence for a nonzero rapidity dependence of global polarization in this energy range. Global polarization of Ξ^−+Ξ̅^+ is observed for the first time at these energies at a significance exceeding 5 standard deviations, with a magnitude comparable to that of Λ+Λ̅ and an increase toward lower collision energies. Measurements of Ω^−+Ω̅^+ are compatible with a similar energy dependence and favor the decay parameter γ_Ω= +1 with high probability under the assumption of the global polarization picture. These measurements provide new constraints on the energy evolution, rapidity dependence, and species dependence of global polarization in heavy-ion collisions.
ER -