This award funds the research activities of Professor Carleton DeTar of the Department of Physics and Astronomy at the University of Utah. These activities are carried out in collaboration with scientists at several US universities and government laboratories. The research addresses fundamental questions in high energy and nuclear physics, and is directly related to major experimental programs in these fields. The principal goal of this research is to discover evidence for new fundamental physical processes and particles. This is done by comparing precise predictions of the presently agreed upon models with results of precise experiments. Secondary projects include a study of exotic states consisting of heavy quarks and a study of the properties of matter at extreme temperatures, such as may have occurred in the very early universe. The methods the PI will develop and the calculational products and software are used widely around the world for related studies. Algorithmic ideas developed in this project will almost certainly have applications in other computational fields. The supported activity promotes the development of young scientists.
In more technical terms, Professor DeTar is carrying out a broad research program in Quantum Chromodynamics (QCD), the theory of interacting quarks and gluons, in which he has been engaged for a number of years. He does this using numerical calculations on high performance computers. These numerical calculations are done on a grid of space-time points (lattice). During the last several years he has generated a library of gluon configuration ensembles with up, down, strange and charm quarks, using the Highly Improved Staggered Quark (HISQ) action. They can be thought of as "snapshots" of the QCD vacuum. They are the basis for a wide variety of calculations of physical interest. These ensembles have significantly smaller lattice artifacts than those previously generated with the improved staggered (asqtad) action. Moreover, the PI has reached an important milestone by, for the first time, generating configurations in which the four lightest quarks are all included with masses at or very close to their physical values. For these reasons the HISQ ensembles are enabling major improvements in the calculation of a variety of physical quantities of importance in high energy physics. Under this project the PI will use them to extend studies of the leptonic decay constants of the pi, K, D, Ds, B and Bs mesons, the semileptonic form factors of D and B mesons, and the mixing of neutral B and Bs mesons with their antiparticles. These calculations will enable him to significantly improve the precision of the determinations of the Cabibbo-Kobayashi-Maskawa (CKM) matrix elements V_us, V_ub, V_cd, V_cs, and V_cb, as well as the masses of the up, down, strange, charm and bottom quarks. The calculations of the CKM matrix elements will enable more stringent tests of current theories of the fundamental interactions of physics, while the determination of related hadronic weak interaction matrix elements can shed light on theories that have been proposed to study physics that goes beyond our current theories. In addition, the PI will extend the study of QCD at high temperatures with the HISQ action that for the first time includes the effects of charm sea quarks. Finally, he will continue the effort to improve the precision of the determination of lattice spacings through use of the gradient flow.
