This award funds the research activities of Professor Carleton DeTar at the University of Utah.
With the rapid growth of computing power over the past couple of decades and equally important improvements in computer algorithms, physicists are now able, with the aid of high-performance computing, to solve quantum chromodynamics (QCD), the theory of interacting quarks and gluons, to high precision. This capability has revolutionized this subfield of theoretical high energy physics and brought such studies to the precision frontier, just as the Large Hadron Collider (LHC) in Europe is advancing the energy frontier. In this research project, Professor DeTar and students will be using computer simulations to extract the most precise values to date of key constants in the Standard Model of the fundamental interactions. The results to be obtained will be essential for analyzing experimental measurements at national accelerator laboratories and at the LHC, as well as for testing the internal consistency of the Standard Model. Professor DeTar and his students will also continue studies of the high-temperature phase transition between confined matter and the quark-gluon plasma, and they will study the charm quark content of the plasma. This novel plasma occurred in the evolution of the early universe and has been shown to be produced in the laboratory in collisions of heavy ions at the RHIC accelerator at Brookhaven National Laboratory and at the LHC.
This research also has broader impacts. Valuable data files and effective codes are disseminated widely and used by other researchers throughout the world. Graduate students are trained, not only in physics, but also in state-of-the-art methods for solving general problems using high-performance computers. Research results also figure into classroom instruction, both undergraduate and graduate. Finally, this research activity enhances the local computing infrastructure and expertise at the University of Utah.
Intellectual Merit The most fundamental particles and their interactions are described by the so-called "Standard Model". This model includes electrons and its cousins, photons, neutrinos, quarks, gluons, and, recently the Higgs boson. We know the model is incomplete. It doesn't explain dark matter or dark energy and gravity is not well included. An elementary Higgs boson creates some awkward complications, which would be solved if the Higgs boson were made of something more fundamental. So it is widely believed that more fundamental particles and processes are waiting to be discovered. This is the main goal of experiments at the Large Hadron Collider in Europe, where many hundreds of US scientists conduct international research. One way to search for clues for more fundamental particles and processes is to subject the Standard Model to exacting tests and look for discrepancies between its predictions and experimental measurements. Our research aims to do just that. We solve for the strong interactions of quarks and gluons. To do so requires large-scale high-performance computing. Our computations yield some of the most precise predictions of the Standard Model in the world. They are essential for making the most of experimental measurements. In this way they are needed in tests of the Standard Model. We have not yet found any convincing evidence for new physical phenomena, but we have pushed the limits much farther in this grant period. Indeed, there are some tantalizing disagreements between predictions and experiment, but they not large enough to declare victory. In the meantime, we have obtained the most precise values of some of the key parameters of the Standard Model, including the ratios of masses of the four lightest quarks and the constants that control transitions between the various quark types. Precise values are important for a wide variety of calculations. Our computer codes are made freely available to other scientists. Other important products, namely our valuable gluon field configuration files, are published for use by others in their physics research. Both our codes and collections of files are used by many dozens of researchers worldwide. Broader impacts: Our work trains graduate students and postdoctoral research associates (including a female postdoc) in high performance computing and statistical analysis. When they graduate and move on in their careers, they carry these skills with them into other disciplines, into industry, or to other universities and colleges. For example, a recent PhD student currently works for the National Institutes of Health modeling neural networks. This work makes use of his skills in high-performance computing. In one outreach project we contributed to an international competition in high performance computing that attracts teams of bright young aspiring computational scientists. They compete to squeeze the best performance from a variety of computing platforms. Such an experience is highly valuable career training.
