Quantum Transport and Hadronization in QCD Matter

在大爆炸后的最初几微秒内，宇宙充满了一种称为夸克胶子等离子体（QGP）的极热物质。令人着迷的是，大约140亿年后，QGP可以在实验室中通过以非常高的能量碰撞原子核来重建和研究。了解夸克和胶子如何过渡到称为强子的束缚态，如质子和中子，这是宇宙中可见物质的组成部分，约占其质量的98%，这是一个根本的兴趣。 然而，由于QGP在实验室中的寿命非常短，它的性质必须从大型探测器中观察到的数千个粒子中推断出来。到目前为止，观察到的粒子光谱表明，QGP的行为像一个非常强的耦合，接近完美的液体，其传输特性接近量子力学设定的普遍下限。在这个项目中，PI与他的研究生和本科生团队一起研究QGP的性质及其强子化是如何从强核力的基本理论--量子色动力学（QCD）中产生的。“强耦合QGP”（sQGP）的一个关键性质是其组分之间的相互作用速率非常大。这些相互作用率意味着一个非常大的量子力学的不确定性的粒子的能量，并被证明是密切相关的热QCD介质的输运性质的量子下限。PI采用严格的量子多体理论自洽地计算了QGP中的夸克和胶子以及强子介质中的复合强子的谱分布和散射振幅。他利用有效的理论，通过第一原理晶格QCD计算的信息来约束基本相互作用。 特别是，他开发了一个框架，使计算从夸克和胶子过渡到强子的基础上，他们在介质中的光谱特性。他的理论计算被应用于重粲和底夸克的输运模型，这使得布鲁克海文实验室的相对论重离子对撞机和欧洲的大型强子对撞机的实验数据可以进行比较和解释。他的项目培养了一个包容性的学术环境，包括本科生研究和对地区高中生的外展活动。该奖项反映了NSF的法定使命，并被认为值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估来支持。

In the first few microseconds after the Big Bang, the Universe was filled with an extremely hot substance called quark-gluon plasma (QGP). It is fascinating that about 14 billion years later, the QGP can be recreated and studied in the laboratory by colliding atomic nuclei at very high energies. It is of fundamental interest to understand how the quarks and gluons transition into bound states called hadrons, such as protons and neutrons, which are the building blocks of the visible matter in the Universe and make up about 98% of its mass. However, due to the very short lifetime of the QGP in the laboratory, its properties have to be inferred from the thousands of particles that are observed in large detectors. Thus far, the observed particle spectra indicate that the QGP behaves like a very strongly coupled, near-perfect liquid whose transport properties are close to universal lower bounds set by quantum mechanics. In this project the PI, together with his team of graduate and undergraduate students, investigates how the properties of the QGP and its hadronization emerge from the fundamental theory of the strong nuclear force, Quantum Chromodynamics (QCD).A key property of the "strongly-coupled QGP" (sQGP) are very large interaction rates between its constituents. These interaction rates imply a very large quantum-mechanical uncertainty in the energies of the particles, and are conjectured to be closely related to the quantum lower bounds in the transport properties of the hot QCD medium. The PI employs rigorous quantum many-body theory to self-consistently calculate the spectral distributions and scattering amplitudes of the medium particles, both for quarks and gluons in the QGP and for the composite hadrons in the hadronic medium. He utilizes effective theories to constrain the fundamental interactions through information from first-principles lattice-QCD computations. In particular, he develops a framework that enables calculation of the transition from quarks and gluons to hadrons based on their in-medium spectral properties. His theoretical calculations are applied in transport models for heavy charm and bottom quarks, which allow for comparisons to, and interpretations of, experimental data from the Relativistic Heavy-Ion Collider at Brookhaven Lab and the Large Hadron Collider in Europe. His program fosters an inclusive scholarly environment including undergraduate research and outreach activities to regional high-school students.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.