AI 中文总结
研究利用相对论重离子碰撞，通过逐事件粘性流体动力学模拟超中心$^{238}$U+$^{238}$U碰撞，借助高阶集体流分离$\beta_4$贡献并测试相关性，揭示非线性QGP动力学可编码几何信息，确立$\beta_4$符号为相关特征。
AI 中文摘要
确定固有十六极形变（$\beta_4$）在核结构中的作用一直是个长期挑战。相对论重离子碰撞提供了独特机会，通过将初始核几何转化为夸克 - 胶子等离子体（QGP）的集体运动来解决此问题。利用$\sqrt{s_{NN}} = 193$ GeV下超中心$^{238}$U + $^{238}$U碰撞的逐事件粘性流体动力学模拟，研究高阶集体流能否分离$\beta_4$的贡献并测试$\beta_2 - \beta_4$相关性。结果表明$\beta_4$符号携带的信息在QGP演化中幸存并通过非线性流体动力学响应增强，非线性响应系数$\xi_{6,222}$能清晰区分$(\beta_2,\beta_4)$固有核拓扑。这些结果确立了$\beta_4$的符号作为偏离四极 - 十六极相关性的可实验获取特征，表明高阶集体流可直接探测核多极结构，并揭示非线性QGP动力学如何将微妙的高阶几何信息编码到末态可观测量中。
英文摘要
Determining the role of intrinsic hexadecapole deformation ($β_4$) in nuclear structure remains a long-standing challenge. Relativistic heavy-ion collisions provide a unique opportunity to address this problem by converting the initial nuclear geometry into the collective motion of the quark--gluon plasma (QGP). Using event-by-event viscous hydrodynamic simulations of ultra-central $^{238}$U+$^{238}$U collisions at $\sqrt{s_{NN}}=193$ GeV, we investigate whether higher-order collective flow can isolate the contribution of $β_4$ and test the $β_2-β_4$ correlation. We demonstrate that information carried by the sign of $β_4$ survives the QGP evolution and is enhanced through nonlinear hydrodynamic response: the fourth-order flow harmonic acquires its topology dependence predominantly from the linear response, whereas the sensitivity of the sixth-order harmonic originates almost entirely from nonlinear mode coupling. As a consequence, the nonlinear response coefficient $ξ_{6,222}$ cleanly separates the $(β_2,β_4)$ intrinsic nuclear topologies. These results establish the sign of $β_4$ as an experimentally accessible signature of deviations from the quadrupole--hexadecapole correlation, demonstrating that higher-order collective flow provides a direct probe of nuclear multipole structure while revealing how nonlinear QGP dynamics encode subtle higher-order geometric information into final-state observables.
Comments9 pages, 4 figures
