Topics in Strong Force

Arizona State University, Scottsdale AZ

Investigators

Abstract

Understanding the internal structure of nucleons -- protons and neutrons, the building blocks of matter that is most familiar to us -- is one of the fundamental challenges in nuclear physics. This project will contribute new understanding to Quantum Chromodynamics (QCD), the theory describing the strong force between the quarks and gluons making up the nucleon. The PI will apply theoretical methods to build phenomenological models used to understand experimental data obtained at the Thomas Jefferson National Accelerator Facility (JLab) from experiments focused on measurements of nucleon properties. The recent 12 GeV upgrade at JLab will allow scientists to study the properties of QCD with an unprecedented level of precision. The educational component represents an important aspect of this project. The training and mentoring of graduate and undergraduate students will prepare junior researchers for future careers in industry or academia. The PI's outreach activities will increase public awareness of nuclear-particle physics through popular science presentations, as well as by mentoring and guidance of high school students. The two research areas of this project are related to the physics of the strong force and are based on phenomenological and theoretical approaches to the problem of quark confinement, broadly defined. The first thrust of the project is focused on understanding of higher twist/order corrections to processes sensitive to quasiprobability distributions, known as Generalized Parton Distributions (GPDs), and will be indispensable for proper analysis of experimental data. The PI and his students will develop a separation technique to disentangle GPDs from data by providing analytical formulas for azimuthal moments of differential cross sections of photon electroproduction cross sections. The second thrust is centered around maximally supersymmetric Yang-Mills theory, which took on the status of the harmonic oscillator of Yang-Mills theories and is central in attempts to solving QCD at strong coupling. Understanding gauge scattering amplitudes, which possess very similar perturbative expansions in the two theories, is the focus of the currently pursued analytical approach to gauge dynamics. A crucial step in establishing a formalism that allows one to address scattering amplitudes nonperturbatively is their dual description in terms of Wilson loops on null polygonal contours that are amenable to analytical techniques.