Heavy Quarkonia as Thermometer of Quark-Gluon Plasma

强作用力是自然界中最基本的力之一，被称为量子色动力学（QCD）的量子场论所描述。这种力负责将称为夸克的基本粒子结合成质子和中子，而后者又结合成原子核。在我们日常世界的正常条件下，夸克总是被束缚成复合物体，而孤立的夸克从未被观察到。然而，当强烈相互作用的物质被加热到极端温度（太阳核心温度的一百万倍以上）时，一种称为夸克-胶子等离子体（QGP）的物质新阶段出现，在那里复合物体熔化，夸克成为定义的基本自由度。PI将对重夸克的复合态（称为重夸克子）在QGP中的行为进行第一性原理研究。它们的性质和熔化模式的理论知识提供了关于QGP的信息，并使我们能够研究QGP的显微镜，夸克约束的性质和一般的强作用力。该项目的研究对于解释在布鲁克海文国家实验室的相对论重离子对撞机和欧洲核研究组织的大型强子对撞机上进行的相对论重离子碰撞实验项目的发现具有重要意义。该项目旨在实现重夸克谱函数的第一性原理，无参数预测，从基本QCD拉格朗日量开始编码有关夸克态的所有信息。PI将开发新的理论和计算方法，用于各向异性高度改进的交错夸克（aHISQ）作用下的蒙特卡罗晶格规范理论计算。重夸克将被纳入非相对论性QCD （NRQCD）框架。PI还将开发贝叶斯推理技术，用于解决从晶格QCD数据重建谱函数时出现的逆问题。我们将探索这些新方法，用可用的晶格数据进行测试，并在开源代码库中实现。主要目标是在具有充分评估的统计和系统不确定性的谱函数上获得预测结果。PI将指导参与研究的博士生，并参与公共宣传活动。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。

The strong force is one of the fundamental forces in nature, described by a quantum field theory called Quantum Chromodynamics (QCD). This force is responsible for binding elementary particles, called quarks, into protons and neutrons, and the latter into atomic nuclei. Under normal conditions in our everyday world quarks are always bound into composite objects and isolated quarks are never observed. However, when strongly interacting matter is heated to extreme temperatures (a million times the temperature in the core of the sun and above) a novel phase of matter, called a Quark-Gluon Plasma (QGP), appears where composite objects melt and quarks become the deconfined fundamental degrees of freedom. The PI will perform a first-principle study of how composite states of heavy quarks, referred to as heavy quarkonia, behave in a QGP. Theoretical knowledge of their properties and melting patterns provides information about QGP and allows us to study the microscopy of QGP, the nature of quark confinement and the strong force in general. The investigations in this project are of great relevance for explaining the findings of the experimental program of relativistic heavy-ion collisions, performed at the Relativistic Heavy-Ion Collider at Brookhaven National Laboratory and the Large Hadron Collider at the European Organization for Nuclear Research.This project seeks to carry out first-principle, parameter-free predictions of heavy quarkonia spectral functions that encode all information about the quarkonia states, from the fundamental QCD Lagrangian. The PI will develop novel theoretical and computational methods for performing Monte Carlo lattice gauge theory computations with anisotropic Highly Improved Staggered Quarks (aHISQ) action. The heavy quarks will be included in the framework of Non-Relativistic QCD (NRQCD). The PI will also develop Bayesian inference techniques for solving the inverse problem that arises when reconstructing the spectral functions from the lattice QCD data. These new methods will be explored, tested with the available lattice data, and implemented in an open-source codebase. The main goal is to achieve predictive results on the spectral functions with fully assessed statistical and systematic uncertainties. The PI will mentor doctorate students involved in the research as well as engage in public outreach activities.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.