Hadron-Hadron Interactions and Exotic States using Lattice QCD with the Stochastic LapH Method

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Protons and neutrons, which make up atomic nuclei, are comprised of fundamental particles known as quarks and gluons, whose interactions are described by quantum chromodynamics (QCD). This theory suggests that many other types of composite particles, known as hadrons, should exist in Nature as unstable resonances. As such, this project will make possible a study of the properties of excited hadronic resonances as predicted by QCD, using large-scale computing resources. Understanding such resonances will help us gain insight into the key physical mechanisms at work inside hadrons and nuclei. The proposed research lends support to current experiments, such as the GlueX experiment in Hall D at the Thomas Jefferson National Accelerator Facility (JLab). Scattering involving one particular hadron known as a Delta baryon will be another focus. Detailed determinations of how the Delta baryon interacts with other particles will be crucial for experiments studying neutrinos, an important elementary particle that permeates the universe. The PI will mentor a graduate student engaged in this research, and the graduate student will also receive training in the use of state-of-the-art parallel computing resources. The physics of excited hadrons and hadron-hadron interactions will be studied using Monte Carlo estimates of path integrals involving quark and gluon fields on a space-time lattice. Quantum operators designed to probe exotic states, such as glueballs, hadrons with excited gluons, and tetraquarks, will be used to explore the nature of the excited states in quantum chromodynamics. Pion-pion, kaon-pion, nucleon-pion, nucleon-nucleon, and nucleon-hyperon scattering phase shifts will also be computed, yielding important information on hadron structure. New computational techniques, such as the stochastic LapH method, have made possible such computations in lattice QCD, which involve estimating temporal correlation matrices of multi-hadron and excited-state operators. Form factors involving the Delta baryon will be a particular focus since they are crucial to accelerated-based neutrino experiments, such as the Deep Underground Neutrino Experiment (DUNE).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.