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arXiv · 2403.07468

Holographic spin alignment of $J/\psi$ meson in magnetized plasma

Yan-Qing Zhao·Xin-Li Sheng·Si-Wen Li·Defu Hou
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Abstract

We study the mass spectra and spin alignment of vector meson $J/\psi$ in a thermal magnetized background using a generalized theoretical framework based on gauge/gravity duality. Utilizing a soft wall model for the QGP background and a massive vector field for the $J/\psi$ meson, we delve into the meson's spectral function and spin parameters $(\lambda_{\theta},\, \lambda_\varphi,\,\lambda_{\theta\varphi})$ for different cases, assessing their response to variations in magnetic field strength, momentum, and temperature. We initially examine scenarios where a meson's momentum aligns parallel to the magnetic field in helicity frame. Our results reveal a magnetic field-induced positive $\lambda_\theta^\text{H}$ for low meson momentum, transitioning to negative with increased momentum. As a comparison, we also study the case of momentum perpendicular to the magnetic field and find the direction of magnetic field does not affect the qualitative behavior for the $eB$-dependence of $\lambda_\theta^\text{H}$. Moreover, we apply our model to real heavy-ion collisions for three different spin quantization directions. Further comparisons with experimental data show qualitative agreement for spin parameters $\lambda_{\theta}$ and $\lambda_\varphi$ in the helicity and Collins-Soper frames.

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Yan-Qing Zhao, Xin-Li Sheng, Si-Wen Li, Defu Hou. 2024-03-12. Holographic spin alignment of $J/\psi$ meson in magnetized plasma. https://arxiv.org/abs/2403.07468

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