Heavy Quarkonia in Lattice QCD with Anisotropic Highly Improved Staggered Quarks

强力将称为夸克的基本粒子束缚成质子和中子，后者束缚成原子核，原子核是在所有尺度上观察到的宇宙中物质的基本组成部分。世纪发展起来的量子色动力学（QCD）成功地描述了这些基本组分之间的强相互作用。QCD的预言已经以惊人的实验精度得到了验证。在正常情况下，孤立的夸克是观察不到的--它们被限制在像质子和中子这样的复合物体中。然而，当强烈相互作用的物质被加热到非常高的温度（大约是太阳核心温度的百万倍）或压缩到非常高的密度（可能在中子星星的核心实现）时，一种称为夸克-胶子等离子体（QGP）的新物质相形成。本项目将从第一原理QCD计算研究QGP的性质，特别是重夸克的复合态如何响应QGP介质以及强作用力如何在非常短的距离尺度上表现（QGP的显微镜）。这些研究将为布鲁克海文国家实验室的相对论重离子对撞机和欧洲核子研究组织的大型强子对撞机的实验结果提供理论上的理解和解释。格点QCD模拟是通过蒙特卡罗方法在四维时空网格上对基本场的最可能组态进行采样并计算其上的物理观测量来进行的。关于重夸克束缚态的物理信息被编码在它们的谱函数中。为了从欧几里得晶格相关函数中可靠地提取谱函数，PI将开发各向异性高度改进交错夸克（aHISQ）的形式，其中时空网格是各向异性的，在时间方向上具有更高的分辨率。该项目将开发必要的算法和计算机代码，用于使用动态aHISQ夸克进行格点QCD模拟，并将生成一个公开可用的库，其中包含各种格点间距和各向异性下的场配置的高质量aHISQ系综，专门用于重夸克偶素谱函数重建。重夸克将被纳入非相对论QCD（NRQCD）的框架。非常高的各向异性结合动力学aHISQ夸克将铺平道路，以充分评估的统计和系统的不确定性的谱函数的可靠提取。 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NSF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 binds elementary particles called quarks into protons and neutrons and the latter into atomic nuclei that are the fundamental building blocks of the matter observed in the Universe at all scales. These strong interactions of the elementary constituents are successfully described by Quantum Chromodynamics (QCD) - a quantum field theory developed in the course of 20th century. Predictions of QCD have been verified with amazing experimental precision. Under normal conditions isolated quarks are not observed - they are confined in composite objects like protons and neutrons. However, when strongly interacting matter is heated up to very high temperatures (about million times the temperature in the core of the Sun) or compressed to very high densities (the ones presumably achieved at the core of a neutron star), a novel phase of matter called Quark-Gluon Plasma (QGP) is formed. This project will study from first-principle QCD calculations the properties of QGP, in particular, how composite states of heavy quarks respond to the QGP medium and how the strong force behaves at very short distance scales (microscopy of QGP). These investigations will provide theoretical understanding and interpretation of the experimental results from the Relativistic Heavy-Ion Collider at Brookhaven National Laboratory and Large Hadron Collider at the European Organization for Nuclear Research.Lattice QCD simulations are performed by Monte Carlo sampling the most probable configurations of fundamental fields on the four-dimensional space-time grid and computing physical observables on them. The physical information about heavy-quark bound states is encoded in their spectral functions. For reliable extraction of the spectral functions from Euclidean lattice correlation functions, the PI will develop a formalism of anisotropic Highly Improved Staggered Quarks (aHISQ), where the space-time grid is anisotropic with higher resolution in the temporal direction. The project will develop necessary algorithms and computer codes for lattice QCD simulations with dynamical aHISQ quarks and will generate a publicly available library of high-quality aHISQ ensembles of field configurations at various lattice spacings and anisotropies specifically for heavy quarkonia spectral function reconstruction. The heavy quarks will be included in the framework of Non-Relativistic QCD (NRQCD). Very high anisotropies combined with dynamical aHISQ quarks will pave the way to reliable extraction of 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.