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| Main Authors: | , , |
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| Format: | Preprint |
| Published: |
2023
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| Subjects: | |
| Online Access: | https://arxiv.org/abs/2312.16900 |
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| _version_ | 1866911817671901184 |
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| author | Kumar, Avdhesh Gubler, Philipp Yang, Di-Lun |
| author_facet | Kumar, Avdhesh Gubler, Philipp Yang, Di-Lun |
| contents | Starting with the polarization dependent Wigner function of vector mesons, we derive an expression for the 00-component ($ρ_{00}$) of spin density matrix in terms of the second order gradients of the vector meson distribution functions. We further apply a thermal model to analyze the transverse momentum and the azimuthal angle dependence of $ρ_{00}$ for $ϕ$ and $K^{*0}$ mesons resulting from distribution gradients in Au-Au collisions with $\sqrt{s_{NN}}=130$ GeV at mid-rapidity. Our results for the transverse momentum dependence indicate that the deviations of $ρ_{00}$ from $1/3$ as the signal for spin alignment are greatly enhanced at large transverse momenta and have a strong centrality dependence while analysis of the azimuthal angle ($ϕ_q$) dependence suggest that such deviations have a $\cos(2ϕ_q)$ structure with opposite sign for $ϕ$ and $K^{*0}$. Our finding may be considered as a baseline for probing spin-alignment mechanisms beyond hydrodynamic gradients. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2312_16900 |
| institution | arXiv |
| publishDate | 2023 |
| record_format | arxiv |
| spellingShingle | Spin alignment of vector mesons by second-order hydrodynamic gradients Kumar, Avdhesh Gubler, Philipp Yang, Di-Lun Nuclear Theory High Energy Physics - Phenomenology Starting with the polarization dependent Wigner function of vector mesons, we derive an expression for the 00-component ($ρ_{00}$) of spin density matrix in terms of the second order gradients of the vector meson distribution functions. We further apply a thermal model to analyze the transverse momentum and the azimuthal angle dependence of $ρ_{00}$ for $ϕ$ and $K^{*0}$ mesons resulting from distribution gradients in Au-Au collisions with $\sqrt{s_{NN}}=130$ GeV at mid-rapidity. Our results for the transverse momentum dependence indicate that the deviations of $ρ_{00}$ from $1/3$ as the signal for spin alignment are greatly enhanced at large transverse momenta and have a strong centrality dependence while analysis of the azimuthal angle ($ϕ_q$) dependence suggest that such deviations have a $\cos(2ϕ_q)$ structure with opposite sign for $ϕ$ and $K^{*0}$. Our finding may be considered as a baseline for probing spin-alignment mechanisms beyond hydrodynamic gradients. |
| title | Spin alignment of vector mesons by second-order hydrodynamic gradients |
| topic | Nuclear Theory High Energy Physics - Phenomenology |
| url | https://arxiv.org/abs/2312.16900 |