Research in Low-Energy Nuclear Theory

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The strong interaction is responsible for the binding of protons and neutrons into atomic nuclei. Improved quantitative understanding of how this happens is essential not only for fundamental nuclear research at US experimental facilities but for progress in astrophysics, for experiments on the nature of neutrinos, and for applications to energy and homeland security. This project enables in part a new era of precision calculations of nuclear structure and reactions. Activities include extending the range and capabilities of statistical methods for assessing theoretical uncertainties and for physics discovery, developing and testing a novel systematic approach to heavier nuclei, and improving the extraction of information from experiment that minimally depends on model assumptions. The training received by undergraduates, graduate students, and postdoctoral research associates in carrying out these activities contributes directly to the building of a diverse scientific workforce. The mix of analytical and numerical computation the students and postdocs must employ is excellent preparation for both academic and industrial research, which is validated by the strong track record of past members of the group. Projects are in three major categories: Bayesian statistical methods for effective field theory (EFT) uncertainty quantification, EFT for finite density nuclear systems, and calculation/extraction of process-independent quantities. The Bayesian methods will be applied to inter-nucleon interactions, few- and many-body systems, and electroweak probes. They will address EFT truncation errors, parameter estimation, model selection, and model mixing. Recent studies of the density matrix expansion and phase-space contributions to many-body calculations will be the basis for further work on finite-density power counting and a renewed study of EFT for nuclear density functional theory. Finally, The PI and his collaborators will build on recent progress in understanding knock-out reactions from a renormalization group perspective, which highlights scale and scheme dependence in these interactions and raises questions about how to best analyze experiments that rely on factorization assumptions. Applications range from optical potentials to alternative treatments of short-range-correlation physics. These projects all contribute to the goal of microscopic, model-independent calculations of nuclei with quantified uncertainties. They will impact forefront problems in low-energy nuclear physics as outlined in the Long Range Plan, such as structure and reactions for the physics of nuclei far from stability, which is relevant for astrophysics and to the future Facility for Rare Isotope Beams (FRIB).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.