Ab initio theory for major questions in subatomic physics

点击翻译按钮获取中文摘要

Perhaps the most complicated quantum systems in the universe, the many facets of atomic nuclei are intertwined with some of the most profound questions in nature. Long considered a phenomenological discipline, modern nuclear theory now aims to confront these questions from the ground up: as a first-principles discipline capable of providing reliable predictions with quantified uncertainties. To do this we must first develop a consistent description of the forces which bind protons and neutrons into nuclei, as well as methods which solve the nuclear many-body problem starting only from those interactions.My previous Discovery Grant was crucial for establishing the valence-space in-medium similarity renormalization group (VS-IMSRG) as a powerful ab initio many-body tool. With the accuracy of large-space methods, but the versatility of the shell model, the VS-IMSRG is currently unique in its capability to calculate essentially all properties of all nuclei up to the mass 100 region. The central focus of this Discovery Grant will be a strong push to improve accuracy, estimate model uncertainty, and expand the physics reach to capitalize quickly on this progress. With sufficient support we will contribute directly to understanding five of the seven "Big Questions in Subatomic Physics", as laid out in the Canadian Subatomic Physics Long Range Plan.The range of the VS-IMSRG is broad, and applications to exotic nuclei present some of the most exciting possibilities to understand how the structure of nuclei emerges from nuclear forces. We will address major nuclear structure issues across the chart such as the limits of existence of nuclei (the proton and neutron driplines) in the light and medium-mass regions. Furthermore, we will predict the evolution of new magic numbers in unexplored regions to guide future experimental efforts. In the long term we will contribute first-principles data for r-process nucleosynthesis simulations modeling the formation of heavy elements in the universe.In addition we will address some of the most important questions related to nuclear-weak physics. The most prominent of these is the nuclear matrix element for neutrinoless double beta decay, which is necessary to extract the absolute neutrino mass scale from a potential experimental discovery. Ab initio calculations are underway for the light candidates 48Ca 76Ge and 82Se and will reach 130Te and 136Xe. Similarly for understanding the nature of dark matter, WIMP-nucleus cross sections are needed to interpret results of large-scale direct-detection searches. We will provide the first ab initio calculations of WIMP-nucleus elastic-scattering structure factors, where calculations for light candidates are underway, and will be extended to 129,131Xe. Finally for understanding physics at the electroweak scale, we will provide ab initio input to extract Gv and the up-down component of the CKM quark-mixing matrix.