RUI: Relativistic Heavy-Ion Theory

相对论核碰撞实验探索夸克和胶子之间的相互作用，这两种基本粒子能感受到强核力。由于强磁力比电磁力强得多，提高我们的理解可以推动未来的技术前沿。相对论重离子对撞机（RHIC）和大型强子对撞机（LHC）以接近光速的速度将原子核碰撞在一起，产生一种由夸克和胶子组成的热而稠密的汤，称为夸克-胶子等离子体（QGP）。确定QGP的特征性质，如其粘度或达到平衡所需的时间，是约束强作用力理论的重要方法。领先的理论计算假设强大的力会迅速推动QGP走向平衡，但如果在实验系统中不是这样，就会对测量到的特性产生误解。本项目重点研究QGP膨胀和冷却的理论建模方法，确定QGP是否达到平衡状态，并研究膨胀和平衡的相互作用如何影响测量。这个项目非常强调本科教育，由于大多数物理学本科生将在科学之外找到职业，他们将把这种教育应用于无数的社会角色中。许多关于核碰撞产生的介质是QGP的解释是由于流体力学模型与实验数据的一致性。随着实验测量的改进，理论需要包含更深入、更详细的物理。此外，流体力学模型使用从局部平衡物质的量子色动力学计算中出现的状态方程。如果介质实际上不处于局部平衡状态，那么由流体力学推断出的性质就不一定是QGP的性质。该项目将通过发展流体力学和动力学理论方法来解决这些问题，包括局部和非局部噪声和粒子射流的随机效应。目标包括(1)推导出突出部分平衡碰撞事件行为的两粒子相关观测的演化方程，(2)研究部分平衡对RHIC小系统和束流能量扫描碰撞事件的影响，(3)研究射流相互作用如何产生介质波动和最终状态相关性，这些波动和最终状态相关性与初始状态或热源所描述的不同。(4)研究新的可观测值，以区分不同物理相关源的影响。这项工作将建立劳伦斯理工大学有史以来第一个活跃的物理研究项目，并将这项研究活动纳入本科教育。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Relativistic nuclear collision experiments explore interactions of quarks and gluons, the elementary particles that feel the strong nuclear force. Since the strong force is much stronger than the electromagnetic force, improving our understanding could drive the future frontiers of technology. The Relativistic Heavy-Ion Collider (RHIC) and the Large Hadron Collider (LHC) collide nuclei together at nearly the speed of light to create a hot and dense soup of quarks and gluons called quark-gluon plasma (QGP). Determining characteristic properties of QGP, like its viscosity or the time it takes to reach equilibrium, is an important way to constrain theories of the strong force. The leading theoretical calculations assume that the strong force rapidly drives the QGP toward equilibrium, but if this is not true in the experimental systems there will be a misinterpretation of the measured characteristic properties. This project focuses on theoretical methods for modeling the expansion and cooling of QGP, determining if QGP reaches an equilibrium state, and investigating how the interplay of expansion and equilibration will effect measurements. This project has strong emphasis on undergraduate education, and since most physics undergraduates will find careers outside of science, they will apply this education in uncountably many roles in society.Much interpretation that the medium produced in nuclear collisions is QGP results from the agreement of hydrodynamic models with experimental data. As experimental measurements improve, theories need to include deeper and more detailed physics. Moreover, hydrodynamic models use equations of state emerging from Quantum Chromodynamics calculations of locally equilibrated matter. If the medium is not actually in local equilibrium, then the properties that are inferred by hydrodynamics are not necessarily those of QGP. This project will address these issues by developing theoretical methods of hydrodynamics and kinetic theory to include stochastic effects from local and non-local noise and particle jets. Objectives include (1) deriving evolution equations for two-particle correlation observables that highlight the behaviors of partially equilibrated collision events, (2) investigating the influence of partial equilibration on small systems and Beam Energy Scan collision events at RHIC, (3) investigating how jet interactions could produce medium fluctuations and final state correlations that are distinguishable from those described by initial state or thermal sources, and (4) investigating new observables that distinguish the effects of different physical sources of correlations. This work will establish the first ever active physics research program at Lawrence Technological University and integrate this research activity into undergraduate education.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.