Overcoming the Limitations of Quantum Chromodynamics with Nucleon Spin Structure Measurements

Our world, including humans and everything we interact with on a daily basis, is made up of tiny building blocks called nucleons, but how these nucleons are internally structured is still a mystery. This award aims to test the accuracy of the most successful theory for what this structure may look like, a theory known as Quantum Chromodynamics. Using a cutting edge US-based particle accelerator located at the Thomas Jefferson National Laboratory, the PI and two Ph.D. students will collect data that reveals more about how everything in the universe is shaped on a quantum level, and help turn Quantum Chromodynamics into a better theory about our world by bypassing some of its current limitations. The supported researchers will access unprecedented working efficiency by utilizing new artificial intelligence driven techniques to develop instruments and analyze the data. This project lays the groundwork for two brand-new large scale particle scattering experiments at Jefferson Lab, which will rely on the techniques and equipment developed by this project’s team. Working on these experiments will serve as unique professional training for the Ph.D. students involved in the project, preparing them with technical skills and Nuclear Physics expertise which will make them highly skilled members of the workforce. Some of the most successful tests of Quantum Chromodynamics (QCD) come from nucleon spin structure measurements, particularly of the spin structure functions g1 and g2, as well as transverse momentum dependent parton distribution functions (TMDs). To better understand how quarks and gluons combine to form individual nucleons (protons and neutrons) as well as composite nuclei, this project will collaboratively build a dynamic nuclear polarization target at Jefferson Lab along with other participating institutions which is capable of carrying out a broad and innovative program of nucleon spin structure measurements. The research team will also perform a study of the magnetic optics for part of this program, approved Jefferson Lab experiment E12-24-002, and will refine new machine learning tools to streamline the eventual analysis of the scattering data and NMR polarization measurements. The PI will also participate in building a brand new program to measure the never-before-extracted tensor TMDs of the deuteron, mentoring two Ph.D. students as they work to analyze a CLAS-Approved-Analysis (CAA) using Run Group C data from Jefferson Lab’s Hall B, in search of the world’s first look at these deuteron TMD quantities and the quality 3D map of nuclear structure that they provide. 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.