Understanding the internal structure of the proton and other strongly interacting particles is at the forefront of modern nuclear physics research. Generalized Parton Distribution Functions (GPDs) are a powerful tool to advance the understanding of hadron structure. In addition to the information about the one-dimensional collinear momentum distributions of partons (quarks, anti-quarks, and gluons) known from studies of high energy deep-inelastic reactions, GPDs also carry information on the distribution of partons in the transverse plane and allow us in this way to access the three-dimensional structure of the nucleon. GPDs can be studied in hard-exclusive reactions and contain information on the energy-momentum tensor form factors, allowing us to gain insights on quantities like pressure or angular momentum distribution inside the nucleon. In this talk, I will cover energy-momentum tensor form factors and densities, and all leading-twist GPDs in the bag model. This quark model provides a consistent theoretical framework to investigate many general concepts that have recently attracted interest, including the distribution of energy, angular momentum, pressure, and shear forces inside the nucleon. Another important aspect of this talk will be the relation between the monopole and quadrupole contributions to the angular momentum density. Finally, I will discuss the implementation of the Goloskokov-Kroll model description of pseudoscalar meson production in exclusive processes in the PARTONS framework, a software development project which will provide direct support for experiments at the Jefferson National Lab and the future Electron-Ion Collider.
Salvatore Fazio