RUI: Three Dimensional Structure of the Nucleon in QCD

Exploration of the internal structure of the nucleon, the proton or neutron in the nucleus, is one of the main goals of modern nuclear physics. Our understanding of the nucleon as an interacting system of yet more fundamental particles, quarks and gluons, collectively called partons, is based on the theory of strong interactions, Quantum Chromo Dynamics (QCD). Partons are both confined and moving inside of the nucleon. The exploration of the nucleon structure that incorporates the motion of partons will allow us to gain new information on the three dimensional (3D) structure of the nucleon. Knowing how the constituent parts combine together is essential to understanding the properties of the nucleon that we observe. The PI will work towards an improved phenomenological description of the 3D structure of the nucleon and will develop a web interface server based at PSU Berks to make the results available to researchers and the general public. Undergraduate students will be trained and supported by this project.

The scientific goals of the project are to extract precisely the Transverse Momentum Dependent distribution and fragmentation functions (TMDs) that describe the 3D nucleon structure, from the existing experimental data. TMDs are intimately related to the correlations of parton motion and the spin of the parton and /or 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 in the studies. The results of the project will help with planning future experiments at Jefferson Lab 12, and a future Electron Ion Collider. The project will also lead to the extraction of fundamental charges of the nucleon, in particular, the nucleon's tensor charge, which is important for searches of Beyond Standard Model (BSM) physics and complements efforts of its calculation in Lattice QCD.