### Imaging the proton through generalized parton distributions:

Generalized parton distributions (GPDs) provide an important theoretical tool to visualize the proton. In the early days, physicists study the internal structure through form factors (or structure factors), which can be measured through diffractive scattering of the electrons. However, this only provides the static information without understanding of the dynamics. A dynamical information is provided by the momentum distributions of constituents, which give us the snapshots of the proton in momentum space. GPDs are a type of “phase-space” distributions which interpolate between the form factors and momentum distributions, providing the simultaneous pictures of where the constituents are and how much momentum they carry.

### Precision Studies for QCD at the Electron Ion Collider:

For over half a century we have known that nucleons are composed of quarks and gluons. We also know that global properties of nucleons and nuclei, such as their mass and spin, and interactions are the consequences of the underlying physics of quarks and gluons, governed by the theory of strong interaction, Quantum-Chromo-Dynamics (QCD). Yet we still do not understand how the properties of nucleons emerge from the fundamental interaction. The US Electron Ion Collider in its low-to-medium center-of-mass energy implementation enables a program of exploration that extends the kinematic reach much beyond the valence quark domain to include the sea of quarks, anti-quarks and gluons. The EIC in its full range of 28 to 140 GeV center-of-mass energy and featuring high luminosity operation will be a powerful facility for the exploration of the most intricate secrets of the strong interaction, and the potential discovery of phenomena not observed before.

PSQ@EIC Final (11/8) White Paper can be found here!

PSQ@EIC Draft (9/19) White Paper can be found here!

### High-energy probes of the nuclear femto-structure

A new type of nuclear structure probe is called deeply virtual exclusive processes (DVEPs). One important example of DVEPs is called deeply virtual Compton scattering (DVCS), in which a highly virtual photon scatters on a nuclear system (proton, neutron etc),which then recoils after radiating a high-energy photon. When the real photon is replaced by mesons, we have other DVEPs. In DVEPs, the quark and gluon degrees of freedom in the target are directly responsible for the scattering, which in turn allow for probes of the quark and gluon dynamics in nuclear systems. The recently upgraded 12 GeV Continuous Electron Beam Accelerator Facility at Jefferson Lab and the future Electron-Ion Collider will study the proton and other nuclear systems through this powerful new process.

### Large-scale QCD simulations of the proton structure:

Quantum Chromodynamics (QCD) is the fundamental theory of strong interactions. It is a field theory that can be approximated on a four-dimensional Euclidean lattice, allowing researchers to use supercomputers to calculate this theory in lattice QCD. Although many properties of the proton, such as mass and charge distribution can be readily calculated in lattice QCD, its structure as probed by high-energy electron beams cannot be computed on the lattice in a straightforward way. It must be approximated through an additional theoretical formalism, called large-momentum effective theory.

### Machine Learning/Artificial Intelligence in Femtography

In Nuclear Femtography, many intermediate steps involve large amounts of data. Using ML/AI techniques in those steps will allow nuclear physicists to obtain results in a timely and resource-saving manner. From simulations of deeply virtual Compton scattering events, to the storage and retrieval of experimental data, to solving the inverse problem of extracting the generalized parton distributions from experiments, to large-scale lattice quantum chromodynamics simulations, ML/AI will provide much needed help.

## Projects

**2021-2022**

### Next-Generation Imaging Filters and Mesh-Based Data Representation for Phase-Space Calculations in Nuclear Femtography

PIs: Nikos Chrisochoides (ODU CS), Charles Hyde (ODU Physics) co-I: Christian Weiss (JLab), Gagik Gavaliain (JLab)

Students: CHristos Tsolakis (CS), Mitch Kerver (Physics), Spiros Tsolakis (CS), Angelos Angelopoulos (CS), Thomadakis Polykarpos (CS), Kevin Garner (CS), Joi Best (CS)

### Paths of Discovery: A Problem Oriented Approach to the CNF Ecosystem

PI: D. Heddle (CNU)

co-PIs: W. Briscoe (GWU), V.D. Burkert (JLab), L. Elouadrhiri (JLab), F.X. Girod (GWU), N. Polys (VPI).

Post-docs: Giovanni Angelini (GWU), Timothy Haywood (UConn/CNF)

Students: Audrey Lawton (CNU), Zach Meador (CNU), Cassie Villarreal (CNU), Mai Dahshan (VPI), Sheeban Mohd (VPI)

### Machine learning for QCD global analysis in the femto-science era

PIs: Yaohang Li (ODU), Nobuo Sato (JLab)

co-I: Wally Melnitchouk (JLab), Michelle Kuchera (Davidson), Raghu Ramanujan (Davidson)

Students: Manal Almaeen (ODU), Herambeshwar Pendyala (ODU), *Yasir Alanzzi (ODU), *Rida Shahid (Davidson), *Eleni Tsitinidi (Davidson), *Annabel Winters-McCabe (Davidson)

### Summer Institute on Wigner Imaging and Femtography/ Femtonet

PI: Simonetta Liuti (UVA)

co-PIs: Peter Alonzi (UVA Data Science), Gordon Cates (UVA Physics), Dustin Keller (UVA Physics), Oliver Pfister (UVA Physics), Matthias Burkardt (NMSU Physics)

Students: Brandon Kriesten (UVA Physics), Tyler Horoho (UVA Physics), *Jake Grigsby (UVA CS/Math), *Grace Tong (UVA Math and French),* Philip Velie (UVA Physics), *Emma Yeats (UVA Physics), *Fernanda Yepez Lopez (UVA Math)

### Nucleon Structure from Lattice QCD

PI: Kostas Orginos (WM Physics)

co-PIs: C. Monahan (WM Physics), David Richards (JLab), A. Stathopoulos (WM CS)

Students: C. Egerer (WM), T. Khan (WM), D. Kovner (WM), T. Claringbold (WM), *J. O’Cain (WM), H.M. Switzer (WM CS)

* Undergraduate Student

### Projects Archive

## Publications

*Novel twist-3 transverse-spin sum rule for the proton and related generalized parton distributions, Yuxun Guo, Xiangdong Ji, Kyle Shiells, *https://arxiv.org/abs/2101.05243

*Why is LaMET an Effective Field Theory for Partonic Structure? *Xiangdong Ji, https://arxiv.org/abs/2007.06613

*Transverse Spin Sum Rule of the Proton,* Xiangdong Ji, Feng Yuan, https://arxiv.org/abs/2008.04349, PLB.

*Proton spin after 30 years: what we know and what we don't?, *Xiangdong Ji, Feng Yuan, Yong Zhao, https://arxiv.org/abs/2009.01291, Nature Review (to appear)

*Pion Valence Quark Distribution from Current-Current Correlation in Lattice QCD*, Raza Sabbir Sufian, Colin Egerer, Joseph Karpie, Robert G. Edwards, Bálint Joó, Yan-Qing Ma, Kostas Orginos, Jian-Wei Qiu, David G. Richards, arxiv.org:2001.04960, Phys. Rev. D (to appear).