Nuclear Structure and Reactions from Effective Field Theory

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The fundamental interactions in nuclear physics are described by the theory of Quantum Chromodynamics (QCD). At low energies, QCD is a strongly interacting theory that cannot be solved from first principles in a pencil-and-paper calculation. The effective field theory (EFT) formulation provides a complementary framework where nuclear properties at low energy can be systematically calculated. As such, EFT calculations can provide accurate input for astrophysical models of element synthesis that cannot be obtained in direct experimental measurements. In this project, the PI and his collaborators will use numerical methods defined on a space-time lattice to calculate properties of medium-light atomic nuclei (mass number up to around 40) using EFT. The PI will use Bayesian statistics to quantitatively compare competing EFT formulations. The latter is useful in constructing an accurate and systematic theory for low energy nuclear physics. Broader impacts of the research include training of graduate students in numerical and analytical work for an academic or industry career benefiting society.The current project builds on the lattice EFT pinhole algorithm that was previously introduced by the PI. This algorithm allows for the calculation of the charge and matter distribution (in the center-of-mass coordinate) in Monte Carlo simulations that is necessary to couple external electro-weak currents to atomic nuclei. The PI aims to calculate electromagnetic moments of light nuclei. The same method will be used to calculate neutrino-nucleus coherent scattering that is sensitive to the neutron matter distribution. This cross section serves as a background in dark matter search experiments. The PI will study also low energy nuclear reactions involving halo nuclei using Bayesian statistics. Halo nuclei are characterized as weakly bound quantum systems and play an important role in element synthesis in the Big Bang and stellar burning. Bayesian analysis provides a natural framework to incorporate EFT assumptions about naturalness of sizes of couplings in parameter estimation. It also allows quantitative comparison of competing theories and aids in model selection. This project will support the science programs at planned major U.S. investments in rare isotope beam experiments.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.