Three-Body Amplitudes from Lattice QCD

George Washington University, Washington DC

Investigators

Abstract

Strong forces are responsible for the formation of known matter in the Universe, but the detailed mechanisms of how this happens remain a mystery. Strong forces bind nucleons (protons and neutrons) together in atomic nuclei, and the properties of the nucleons are studied at state-of-the-art accelerator facilities such as the Thomas Jefferson National Accelerator Facility. This project aims at closing the gap between experiment and theoretical calculations using lattice QCD. Due to current limitations of classical computers Lattice QCD calculations are performed in a small cubic volume instead of infinite space. This project provides the translation from the former to the latter, so that fundamental calculations of QCD can be compared to Nature. The PI and his students will focus on properties of systems involving three particles interacting with each other. To help develop a diverse, globally competitive STEM workforce, the outreach component is dedicated to developing material for computational aspects of quantum mechanics (QM) and animations of time-dependent QM problems. Finite-volume effects for the case of three particles are poorly understood. In this project, the PI and his students will develop and apply three-body methods to map lattice QCD results to the physical world and to help answer fundamental questions regarding QCD predictions for the properties of excited mesons and baryons. For this, the principle of unitarity is efficiently used as the guiding principle to construct three- or more particle amplitudes. A conceptual upgrade of previous work concerns the introduction of more coupled channels and extensions to half-integer spin. Three-body dynamics is not only difficult on the theory but also on the phenomenology side. Therefore, three-body amplitudes in infinite volume will be developed and compared to experiment in a complementary effort, such as the Roper resonance and its multi-channel three-body dynamics, or the various decay channels of the A1(1260) axial meson. An extended analysis of new lattice QCD results from the GW group at two different pion masses is planned, that will allow to map out the chiral trajectory of the A1(1260) axial meson. 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.