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

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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.