Lattice Gauge Theory at the University of the Pacific 2016-2019

该奖项资助太平洋大学詹姆斯·赫特里克教授和基兰·霍兰德教授的研究活动。2012年，随着希格斯玻色子的发现，大型强子对撞机(LHC)的实验计划开启了粒子物理学的新纪元。通过在受控环境中以有史以来最高的能量碰撞质子，我们正在了解自然界的对称性是如何被打破的，以及宇宙是如何从大爆炸后的最早时刻进化到数十亿年后的现在状态的。粒子物理学的目标是了解基本粒子，如电子和夸克，如何相互作用，以及它们的集体动力学如何塑造宇宙的基本规律。大型强子对撞机提供的实验结果是整理所有可能描述宇宙的模型的基本成分，并专注于那些让我们更深入、更好地理解我们观察到的东西的模型。除了大型强子对撞机，布鲁克海文国家实验室相对论重离子对撞机(RHIC)的实验项目还探索了夸克和胶子在宇宙早期的行为，它们在宇宙膨胀时冷却之前形成了热而密集的等离子体，导致质子、中子的产生，进而产生原子和分子。在这里，需要量子色动力学(QCD)的相关理论以更高的精度来预测这种转变是如何发生的。作为该项目的一部分，赫特里克和霍兰德教授将研究新的物理模型，这些模型可能会阐明希格斯玻色子的性质，其相对较轻的质量是一个无法解释的谜团。他们还将研究QCD和类似的模型，利用计算机模拟更好地洞察强相互作用系统。因此，这项工作符合国家利益，因为它加强了美国基础科学的进步。这项工作还产生了重大的更广泛的影响，使太平洋大学的本科生有机会从事现代研究，例如学习数值模拟技术。从技术上讲，霍兰德教授将研究强相互作用的复合希格斯模型，该模型假设了一种类似于QCD的新规范力。在这样的理论中，希格斯玻色子以束缚态的形式出现，很像是通过夸克的强束缚形成的介子。这样的模型可以解释为什么如果新的规范理论具有近乎保角的行为，希格斯玻色子就相对较轻。这导致了在大型强子对撞机上应该观察到的额外束缚态的预测，这些束缚态现在已经达到了被检测到或排除的水平。与QCD一样，这类模型需要在超级计算机上进行数值格子模拟，才能做出可靠的预测。赫特里克教授将致力于另一种想法，即希格斯玻色子的性质通过Hosotani机制从高维理论中显现出来，在这种机制中，特殊的边界条件打破了对称性。同样，需要数值计算来测试这些理论，并将它们与当前的实验结果进行比较。霍兰德教授和赫特里克教授还将研究QCD的性质，例如该理论如何随着对称性的增加而简化，以及为国际研究界共享数值资源提供技术支持。

This award funds the research activities of Professors James Hetrick and Kieran Holland at the University of the Pacific. The experimental program at the Large Hadron Collider (LHC) has ushered in a new era in particle physics with the discovery of the Higgs boson in 2012. By colliding protons at the highest-ever energy in a controlled environment, we are learning how symmetries are broken in nature and how the universe evolved from the earliest moments after the Big Bang to the present state billions of years later. The goal of particle physics is to understand the basic laws of how fundamental particles, like electrons and quarks, interact with one another and how their collective dynamics shape the universe. Experimental results provided by the LHC are the essential ingredient to sort through all the possible models that could describe the universe and focus on those which give us a deeper and better understanding of what we observe. In addition to the LHC, the experimental program at the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory probes the early-universe behavior of quarks and gluons, which formed a hot dense plasma before cooling as the universe expanded, leading to the creation of protons, neutrons and in turn atoms and molecules. Here, the relevant theory of quantum chromodynamics (QCD) is needed with ever-higher precision to predict how this transition occurred. As part of this project, Professors Hetrick and Holland will investigate new physics models which potentially elucidate the properties of the Higgs boson, whose relatively light mass is an unexplained mystery. They will also study QCD and similar models, using computer simulations for better insight into strongly-interacting systems. This work is therefore aligned with the national interest in that it reinforces the progress of fundamental science in the United States. This work also has a significant broader impact, giving undergraduate students at the University of the Pacific an opportunity to work on modern-day research, such as learning numerical simulation techniques. More technically, Professor Holland will be studying strongly-interacting composite Higgs models, which postulate a new gauge force analogous to QCD. In such theories, the Higgs boson emerges as a bound state, much like a pion forms via the strong binding of quarks. Such models could explain why the Higgs boson is relatively light if the new gauge theory has near-conformal behavior. This leads to predictions of additional bound states that should be observed at the LHC, which are now reaching to the level of being detected or ruled out. Like QCD, such models require numerical lattice simulations on supercomputers in order to make reliable predictions. Professor Hetrick will be working on an alternate idea in which the properties of the Higgs boson emerge from a higher-dimensional theory via the Hosotani mechanism, where particular boundary conditions break the symmetry. Again, numerical computations are needed to test such theories and compare them against current experimental results. Both Professors Holland and Hetrick will also be studying properties of QCD as well, such as how the theory simplifies as the symmetry is increased, as well as providing technical support for the sharing of numerical resources across the international research community.