At short distances, the proton consists of weakly interacting point-like quarks and gluons, aka partons. At high energy this picture of the proton is expected to break down before confining forces take over when soft enough gluons, that are abundantly present inside the proton, interact in a non-linear fashion. This regime of Quantum Chromodynamics (QCD) is known as the saturation regime and is best described by strong classical gauge fields. The transition between these two regimes of QCD, yet to be fully understood, is crucial if we aim for a comprehensive description of the 3D structure of the proton particularly as it will be tested at colliders like the upcoming Electron-Ion Collider (EIC).
In this talk I will present a proposal to unify these two seemingly different descriptions, akin to the wave/particle duality, and discuss a novel 3D gluon distribution that smoothly interpolates between the strong classical field picture at high energy and the partonic picture. This distribution can be investigated at the upcoming EIC and/or through lattice simulations to gain valuable insights into the emergent phenomenon of gluon saturation, which may play a significant role in our understanding of proton structure.