Grant: Subatomic Physics Envelope - Individual

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. The aim of nuclear structure theory is to develop a unified first-principles, or ab initio, picture for all atomic nuclei starting from only the fundamental forces at work. This problem is particularly daunting, as we must first construct these forces consistent with the underlying symmetries of strong and electroweak interactions. Then we must develop methods to solve the nuclear many--body problem in a controlled and systematically improvable manner. At the same time we will incorporate advanced machine-learning and AI algorithms for rigorous uncertainty quantification in all topics to be treated within the scope of this Discovery Grant (DG). A number of landmark breakthroughs were achieved during my last DG, which significantly enhanced the profile of my research program and the standing of Canada in the global nuclear theory community. The valence-space in medium similarity renormalization group (VS-IMSRG) is currently world-leading in its capability to calculate essentially all properties of nuclei to the heavy 208Pb region. The central focus of this proposal is therefore a strong push to rapidly capitalize on our unique standing to provide first ab initio calculations worldwide directly impacting SIX of the "Eight Key Science Drivers" highlighted in the 2022--2026 Canadian Subatomic Physics Long--Range Plan (subatomicphysics.ca). The range of the VS-IMSRG is incredibly broad: applications to exotic nuclei and superheavy elements present some of the most exciting opportunities to understand how the structure of the most extreme nuclear systems emerge from only underlying forces. We will also generate first--principles input for r-process nucleosynthesis simulations, which model the formation of heavy elements in the universe. We will also attack the most critical questions in beyond-standard-model physics involving nuclei. The most prominent of these is the nuclear matrix element (NME) for neutrinoless double-beta (0vßß) decay, crucial to extract the absolute neutrino mass from a hypothetical discovery and guide strategic planning for next-generation searches. We will provide final ab initio NMEs for all candidate nuclei with rigorous systematic uncertainties from our machine-learning algorithms. For understanding the nature of dark matter, WIMP-nucleus scattering calculations are needed to interpret results of deep-underground direct-detection searches. We will provide first ab initio results for dark matter and neutrino scattering, as well as symmetry-violating moments to guide and interpret novel searches using radioactive molecules for understanding the origins of the abundance of matter over antimatter in our universe. All results will directly impact the hundreds of millions of dollars of Canadian investment into all such experimental efforts at TRIUMF and SNOLAB.