Speaker
Description
Non-central relativistic heavy-ion collisions generate extreme angular velocities leading to significant global vorticity. While the magnetic field from spectator protons has been extensively studied, the magnetization induced by the coupling between spin and rotation, classically known as the Barnett effect, has remained unexplored in the context of quantum chromodynamic matter. Here, we present the first theoretical investigation of Barnett magnetization in the hot, dense hadronic phase produced in heavy-ion collisions. Using a rotating hadron resonance gas model, we compute the Barnett magnetization $M_{\text{Barnett}}$ as a function of temperature $T$, baryochemical potential $\mu_B$, and angular velocity $\omega$. We demonstrate that $M_{\text{Barnett}}$ increases monotonically with all three parameters, leading to an induced magnetic field $B_{\text{ind}}$ that is comparable to the external magnetic field $B_{\text{ext}}$ at low center-of-mass energies ($\sqrt{s_{\text{NN}}} < 20$~GeV). This result establishes the Barnett effect as a previously overlooked but significant source of magnetization in heavy-ion collisions. It provides an explanation for the observed splitting between $\Lambda$ and $\bar{\Lambda}$ hyperon polarizations ($P_\Lambda < P_{\bar{\Lambda}}$), stemming from their opposite magnetic moments. Our findings suggest that Barnett-induced fields may dominate the spin dynamics at kinetic freeze-out, offering a new perspective on the interplay between rotation, magnetization, and spin transport in QCD matter.
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