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arXiv · 2509.00380

Hydrodynamic effects on spin polarization along the beam direction in Au+Au and p+Pb collisions

Cong Yi·Xiang-Yu Wu·Jie Zhu·Shi Pu·Guang-You Qin
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Abstract

We investigate hydrodynamic effects on the spin polarization of $\Lambda$ hyperons in Au+Au collisions at $\sqrt{s_{NN}} = 200$ GeV and p+Pb collisions at $\sqrt{s_{NN}} = 8.16$ TeV using the CLVisc hydrodynamic framework. We present numerical results for the second Fourier sine coefficient of the longitudinal spin polarization, $\langle P_{z} \sin 2(\phi_{p} - \Psi_{2}) \rangle$, as a function of multiplicity (centrality) under three equilibrium scenarios: $\Lambda$ equilibrium, $s$-quark equilibrium, and isothermal equilibrium. We highlight the respective roles of thermal vorticity and the thermal-shear tensor in generating $\langle P_{z} \sin 2(\phi_{p} - \Psi_{2}) \rangle$ across collision systems and scenarios.

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Cong Yi, Xiang-Yu Wu, Jie Zhu, Shi Pu, Guang-You Qin. 2025-08-30. Hydrodynamic effects on spin polarization along the beam direction in Au+Au and p+Pb collisions. https://arxiv.org/abs/2509.00380

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