相对论重离子对撞机中铀-238十六极形变的证据
Evidence of Hexadecapole Deformation in Uranium-238 at the Relativistic Heavy Ion Collider
AI总结：
本文指出流体力学模拟未能重现RHIC上$^{238}$U碰撞椭圆流数据的原因在于混淆了核表面形变与体积形变，通过Skyrme密度泛函计算修正核形变实现后恢复了与实验数据的一致性，从而揭示了$^{238}$U十六极形变对高能碰撞的重要影响。
摘要：
有强有力的证据表明，夸克-胶子等离子体（QGP）的流体力学模拟未能重现BNL相对论重离子对撞机（RHIC）上$^{238}$U核相对论碰撞中粒子椭圆流的数据。我们证明这一失败源于在流体力学框架中对诸如$^{238}$U这类显著形变离子的不当实现。过去的研究将核表面形变与核体积形变等同起来，尽管它们是不同的概念。特别是，体积四极矩既可以由表面十六极矩产生，也可以由表面四极矩产生。这一特征迄今为止在重离子碰撞建模中被忽略，而对于像$^{238}$U这样同时具有四极形变和十六极形变的原子核来说尤其重要。借助Skyrme密度泛函计算的严格输入，我们表明在流体力学模拟中修正核形变实现中的此类效应后，可以恢复与BNL RHIC数据的一致性。这使不同能量尺度下的核实验结果趋于一致，并证明了$^{238}$U的十六极形变对高能碰撞的影响。
英文摘要：
There is strong evidence of the failure of hydrodynamic simulations of the quark-gluon plasma (QGP) to reproduce data on the elliptic flow of particles in relativistic collisions of $^{238}$U nuclei at the BNL Relativistic Heavy Ion Collider (RHIC). We demonstrate that this failure is caused by an inappropriate implementation of well-deformed ions, such as $^{238}$U, in the hydrodynamic framework. 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 $^{238}$U, which is both quadrupole- 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 $^{238}$U on high-energy collisions.
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