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arXiv · 2503.09937

Spin density matrix for neutral $\rho$ mesons in a pion gas in linear response theory

Yi-Liang Yin·Wen-Bo Dong·Cong Yi·Qun Wang
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Abstract

We calculate the spin density matrix for neutral $\rho$ mesons from the spectral function and thermal shear tensor by Kubo formula in the linear response theory, which contributes to the $\gamma$ correlator for the CME search. We derive the spectral function of neutral $\rho$ mesons with $\rho\pi\pi$ and $\rho\rho\pi\pi$ interactions using the Dyson-Schwinger equation. The thermal shear tensor contribution is obtained from the Kubo formula in the linear response theory. We numerically calculate $\rho_{00}-1/3$ and $\mathrm{Re}\rho_{-1,1}$ using the simulation results for the thermal shear tensor by the hydrodynamical model, which are of the order $10^{-3}\sim10^{-2}$.

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Yi-Liang Yin, Wen-Bo Dong, Cong Yi, Qun Wang. 2025-03-13. Spin density matrix for neutral $\rho$ mesons in a pion gas in linear response theory. https://arxiv.org/abs/2503.09937

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