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| Auteurs principaux: | , |
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| Format: | Preprint |
| Publié: |
2025
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| Accès en ligne: | https://arxiv.org/abs/2509.20200 |
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| _version_ | 1866915511539859456 |
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| author | Zhang, Zhong-Hua Huang, Xu-Guang |
| author_facet | Zhang, Zhong-Hua Huang, Xu-Guang |
| contents | We investigate how the curvature of the freeze-out hypersurface polarizes massive vector bosons in relativistic heavy-ion collisions. Starting from the Proca Lagrangian and using the Wigner function formalism, we perform a systematic gradient expansion to obtain a covariant spin-polarization tensor expressed in terms of hydrodynamic fields and the curvature tensor of the freeze-out hypersurface. Analytic results for Bjorken and Gubser flows show that curvature anisotropy generates a non-zero tensor polarization. For $ϕ$ meson, we estimate the curvature contribution to its spin alignment as $ δΘ_{yy} \sim -10^{-4} $ to $ -10^{-3} $. We also find that the curvature contribution grows as the system size decreases, suggesting that spin polarization measurements in small systems may provide a clean probe of this geometric effect. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2509_20200 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Tensor Spin Polarization Induced by Curved Freeze-Out Hypersurface Zhang, Zhong-Hua Huang, Xu-Guang High Energy Physics - Phenomenology Nuclear Theory We investigate how the curvature of the freeze-out hypersurface polarizes massive vector bosons in relativistic heavy-ion collisions. Starting from the Proca Lagrangian and using the Wigner function formalism, we perform a systematic gradient expansion to obtain a covariant spin-polarization tensor expressed in terms of hydrodynamic fields and the curvature tensor of the freeze-out hypersurface. Analytic results for Bjorken and Gubser flows show that curvature anisotropy generates a non-zero tensor polarization. For $ϕ$ meson, we estimate the curvature contribution to its spin alignment as $ δΘ_{yy} \sim -10^{-4} $ to $ -10^{-3} $. We also find that the curvature contribution grows as the system size decreases, suggesting that spin polarization measurements in small systems may provide a clean probe of this geometric effect. |
| title | Tensor Spin Polarization Induced by Curved Freeze-Out Hypersurface |
| topic | High Energy Physics - Phenomenology Nuclear Theory |
| url | https://arxiv.org/abs/2509.20200 |