State-of-the-art hydrodynamic simulations of the quark-gluon plasma are unable to reproduce the elliptic flow of particles observed at the BNL Relativistic Heavy Ion Collider (RHIC) in relativistic ${}^{238}\mathrm{U}+{}^{238}\mathrm{U}$ collisions when they rely on information obtained from low-energy experiments for the implementation of deformation in the colliding ${}^{238}\mathrm{U}$ ions. We show that this is due to an inappropriate treatment of well-deformed nuclei in the modeling of the initial conditions of the quark-gluon plasma. Past studies have identified the deformation of the nuclear surface with that of the nuclear volume, though these are different concepts. In particular, a volume quadrupole moment can be generated by both a surface hexadecapole and a surface quadrupole moment. This feature was so far neglected in the modeling of heavy-ion collisions, and is particularly relevant for nuclei like ${}^{238}\mathrm{U}$, which is both quadrupole deformed and hexadecapole deformed. With rigorous input from Skyrme density functional calculations, we show that correcting for such effects in the implementation of nuclear deformations in hydrodynamic simulations restores agreement with BNL RHIC data. This brings consistency to the results of nuclear experiments across energy scales, and demonstrates the impact of the hexadecapole deformation of ${}^{238}\mathrm{U}$ on high-energy collisions.

中文翻译：

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相对论重离子对撞机中铀 238 中六极变形的证据

最先进的夸克-胶子等离子体流体动力学模拟无法再现 BNL 相对论重离子对撞机 (RHIC) 在相对论中观察到的椭圆粒子流${}^{238}\mathrm{ü}+{}^{238}\mathrm{ü}$当它们依赖于从低能实验中获得的信息来实现碰撞变形时的碰撞${}^{238}\mathrm{ü}$离子。我们表明，这是由于在夸克-胶子等离子体初始条件的建模中对变形良好的原子核进行了不适当的处理。过去的研究已经确定了核表面的变形与核体积的变形，尽管这些是不同的概念。特别地，体积四极矩可以由表面十六极矩和表面四极矩产生。到目前为止，这个特征在重离子碰撞的建模中被忽略了，并且与原子核特别相关${}^{238}\mathrm{ü}$，这是四极变形和六极变形。通过 Skyrme 密度泛函计算的严格输入，我们表明在流体动力学模拟中对核变形实施中的此类影响进行校正可以恢复与 BNL RHIC 数据的一致性。这为跨能量尺度的核实验结果带来了一致性，并证明了六极变形的影响${}^{238}\mathrm{ü}$关于高能碰撞。