Speaker
Description
We present a theoretical study of global and azimuthal-angle-dependent $\Lambda$ hyperon polarization in isobaric $^{96}_{40}$Zr+$^{96}_{40}$Zr collisions at $\sqrt{s_{NN}}=200$ GeV using the TRENTo-3D initial condition model coupled to (3+1)-D viscous hydrodynamic model CLVisc. A longitudinal flow velocity gradient, controlled by $f_v$, is introduced into \trento\ for the first time, providing an essential source of initial vorticity in this symmetric isobaric system. Within the isothermal polarization framework, the model achieves the first satisfactory description of STAR measurements of the global polarization $-P^{y}$ (centrality, $p_T$, and $\eta$ dependences) and the azimuthal modulation coefficients $P_{y,\mathrm{c0}}$ and $P_{y,\mathrm{c2}}$. The $p_T$ dependence reveals a non-monotonic structure from the competition between thermal vorticity and shear contributions, with $P_{y,\mathrm{c2}}$ dominantly shear-driven and proposed as a clean probe of shear-induced polarization. Scans of $f_v$, $k_T$, nuclear structure, and bulk viscosity demonstrate complementary constraints on the initial state; the five isobar parametrizations yield nearly indistinguishable polarization. For $P_z$, the isothermal scenario captures the azimuthal modulation but overpredicts its $p_T$ dependence, and the comparison with the standard thermal treatment reveals that neither scenario achieves a unified description.
| 请选择分会 | 高能重离子物理 |
|---|
