My primary research interest is understanding the nature of matter in terms of its underlying quark and gluon structure. Matter is made up of nuclei; nuclei are in turn made up of protons and neutrons; and these protons and neutrons are composed of quarks and gluons.

We have a good understanding of how protons and neutrons bind to form nuclei, and how their longitudinal momentum is carried by different quark and gluon flavors. However, there are still significant mysteries that we hope to resolve in the coming decades. Our goal is to build a complete picture of how quarks and gluons are arranged and move inside protons and neutrons.

For example, protons and neutrons have a fixed quantum mechanical property called spin, which is closely related to their intrinsic magnetism. Yet we still do not fully understand how the spins and orbital motion of quarks and gluons combine to produce the final spin of the proton and neutron.
We study this structure by colliding high-energy particles with protons, or with neutrons inside nuclei, and observing how they scatter. Depending on the experiment, we may use electrons, protons, or other particles as probes. These measurements allow us to infer the internal quark and gluon structure of matter. I conduct this research at several Department of Energy facilities, including the Relativistic Heavy Ion Collider, Jefferson Laboratory, and the future Electron-Ion Collider.