Lattice Gauge Theory at the Intensity Frontier

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This award funds the research activities of Professor Carleton DeTar at the University of Utah.Our current understanding of the most fundamental elementary particles and interactions in Nature is encapsulated in the so-called "Standard Model". Unfortunately, it is incomplete. For example, it can't explain the dark matter that permeates the Universe. Thus physicists almost universally believe that still more fundamental particles and interactions are yet to be discovered. A large experimental search is underway at accelerators, such as the European Large Hadron Collider, to find new particles. Even if the accelerator energy is not high enough to find them, such new particles will reveal their existence through discrepancies between careful measurements and precise theoretical predictions based on the Standard Model. Such comparisons are effective only if the residual uncertainties in the predicted quantities are reduced in tandem with improvements in the accuracy of experimental measurements. Professor DeTar and collaborators are using the most powerful computers and codes to make precise predictions that can be compared with results of experimental measurements, with particular attention to those cases where some tantalizing discrepancies have already been found. This work is in the national interest in that it furthers our understanding of the most fundamental laws of Nature. Its broader impacts include the training of students and postdoctoral research associates in programming and utilizing the highest-performance computers, in the management of large data sets, and in the statistical analysis and extraction of physically important information. Many of Professor DeTar's students and postdoctoral research associates have found jobs that utilize those skills in industrial as well as academic settings.More technically, this project will use methods of lattice quantum chromodynamics in a precision study of the hadronic environment of heavy-quark decays. The resulting hadronic decay constants and form factors are then combined with measurements of the decays of mesons containing those heavy quarks. The project will also involve the calculation of the strong-interaction contribution to the anomalous magnetic moment of the muon. The resulting value for the hadronic vacuum polarization will be compared with results of ongoing high-precision experimental measurements of the magnetic moment. Both comparisons provide stringent tests of the consistency of the Standard Model and constraints on theoretical models of new physics. These calculations are intended to be sufficiently precise that it is now necessary to include the effects of virtual photons. This project will therefore advance our ability to include them.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.