3D Parton Structure of the Nucleon

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The objective of this research is to advance the understanding of the internal structure of hadrons, which include protons, neutrons, and other subatomic particles described in terms of quarks and gluons. One of the central goals of modern nuclear physics research concerns the 3-dimensional imaging of the internal structure of the proton and atomic nuclei. To achieve the objective the investigator and his students will conduct theoretical and phenomenological projects which aim at revealing the 3-dimensional structure of protons, neutrons, and atomic nuclei in terms of quarks and gluons. This research will advance the development of the theory tools necessary to understand experiments which are in preparation at the Thomas Jefferson National Laboratory, the Brookhaven National Laboratory, and other facilities world-wide. The broader impacts of the research program include training of graduate students and offering research opportunities for undergraduate students, and include outreach activities at a wide variety of levels from K-12 to college level. Public lectures will be given to inform the population of the latest research in nuclear and particle physics, what physicists learn from that, and how the society will benefit from it.The theoretical tools to describe the internal structure of hadrons in terms of quarks and gluons, the degrees of freedom of quantum chromodynamics, are provided by parton distribution functions which can be accessed in high energy scattering experiments. In order to address 3-dimensional imaging two theoretical approaches are explored: transverse momentum dependent distributions (TMDs), and generalized parton distributions (GPDs). These complementary approaches provide powerful tools to access so far unexplored aspects of the nucleon structure, including spin-orbit correlations of partons and the mapping of strong forces exerted on partons inside the nucleon. The theoretical research will address the flavor asymmetry in the polarized quark sea, TMDs of valence and sea quarks, GPDs and studies of the energy-momentum tensor, and the exploration of chiral symmetry breaking effects for the partonic structure of the nucleon. The applications of this research include mapping of strong forces inside the nucleon, and the description of exotic tetra- and pentaquark hadronic states recently observed at LHC and other experiments. This research will support experimental programs at Jefferson, Brookhaven, and Fermi National Labs, and contribute to the planning of the Electron-Ion Collider, the next generation research facility envisioned by the U.S. nuclear physics community.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.