RUI: The Three-Dimensional Momentum and Spin Structure of the Nucleon in QCD

The visible universe is made up of nucleons: protons and neutrons, and electrons. Nucleons themselves are interacting dynamical systems of partons, quarks and gluons, the degrees of freedom of the theory of strong interaction, Quantum Chromo Dynamics (QCD). Unfolding the QCD quark and gluon structure of nucleons is one of the highest priorities of nuclear physics. The main objective of this project is to advance theoretical and phenomenological studies of the three-dimensional (3D) momentum and spin structure of the nucleon in QCD and to map its internal landscape encoded in the Transverse Momentum Dependent parton distribution and fragmentation functions. The PI will contribute to the education of a diverse, globally-engaged workforce with world-class skills by providing and developing courses on modern statistics and nuclear physics, organizing and teaching summer schools for graduate students, and running annual workshops on the 3D structure of the nucleon.

The scientific goals of this project are to precisely extract the 3D nucleon structure and Transverse Momentum Dependent distribution and fragmentation functions from the existing experimental data. TMDs are intimately related to the correlations of parton spin and motion with the spin of the nucleon and generate Spin Asymmetries in scattering processes. The project is intended to unify existing formalisms of the description of the 3D nucleon structure, and ultimately explore the origin of the Spin Asymmetries in various processes. The data from past and existing facilities, such as HERMES (DESY), COMPASS (CERN), and Jefferson Lab, BELLE (KEK), BaBar (SLAC), BESIII (Beijing), RHIC (BNL), LHC (CERN), will be used. This study will be performed for constructing the global QCD fit of the data and unifying collinear and TMD physics. The PI will study TMD evolution, extract the non-perturbative input from the experimental data and use it for the description and prediction of future data. This project will expand the impact of the existing programs at Jefferson Lab and Brookhaven National Laboratory, and of the future Electron Ion Collider in the USA by performing phenomenological and theoretical studies, providing analysis, explanation of present data, and predictions for future measurements.

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.