A team of physicists at the U.S. Department of Energy’s Thomas Jefferson National Accelerator Facility has been studying the interactions of partons, which are the components of hadrons found in the nucleus of atoms. These partons, made up of quarks and gluons, are bound together by the strong force, one of the fundamental forces of nature. By using a mathematical approach called lattice quantum chromodynamics (QCD), the team aims to understand how these partons interact to form hadrons such as protons and neutrons.
The team, known as the HadStruc Collaboration, has developed a three-dimensional approach to understanding the structure of hadrons through the lens of QCD. This approach, based on generalized parton distributions (GPDs), offers theoretical advantages over previous one-dimensional parton distribution functions (PDFs). By studying the distribution of quarks and gluons within the proton, the team hopes to shed light on how spin and momentum are distributed among these particles.
One of the key questions the collaboration is trying to answer is how the proton’s spin arises, as experimental measurements have shown that the spin of quarks contributes to less than half of the overall spin of the proton. By studying GPDs, the team aims to better understand the role of gluons and the motion of partons in determining the proton’s spin. Additionally, the team hopes to address concepts such as the energy momentum tensor, which reveals how energy and momentum are distributed inside the proton.
To access this information, the team conducted 65,000 simulations of the theory and its assumptions, testing their 3D approach on supercomputers at various facilities. These simulations involved running processors for millions of hours to analyze the interactions of protons with different momenta and collections of gluons. The results of these simulations confirmed the validity of the 3D approach developed by the team, marking an important milestone for the Quark-Gluon Tomography (QGT) Topical Collaboration.
Looking ahead, the HadStruc Collaboration plans to apply their GPD theory to experiments conducted at high-energy facilities such as the Electron-Ion Collider (EIC) at DOE’s Brookhaven National Laboratory. By comparing their calculations with experimental data, the team hopes to refine their understanding of hadronic structure and potentially make predictions beyond what current instruments can achieve. The collaboration is also exploring additional experimental applications of their QCD theory work to advance the field of nuclear physics.