2025/11/26 by Vendulka Humlova, Humlova, Vendulka
Physics and Astronomy · #FOS: Physical sciences #High-Energy Particle Collisions Research #Nuclear Experiment (nucl-ex) #Particle physics theoretical and experimental studies #Quantum Chromodynamics and Particle Interactions
paper · pdf · doi:10.48550/arxiv.2511.21239
openalex publication_date 2025/11/26 · openalex created_date 2025/11/28 · openalex updated_date 2026/07/28
A new phenomenon, gluon saturation, is expected to emerge in quantum chromodynamics (QCD) at high energies, when gluon splitting and recombination processes reach a dynamic equilibrium. In heavy nuclei, this balance is expected to be achieved at lower energies than in protons, making lead-lead collisions at the LHC an ideal environment to probe the onset of saturation. The diffractive photoproduction of the J/ψ vector meson provides an excellent tool to study this regime since it directly probes the gluon distribution in the target. ALICE offers unique kinematic coverage of the photon-nucleon centre-of-mass energy, spanning from 20 to 800 GeV, corresponding to three orders of magnitude in Bjorken-x from about 10-2 down to 10-5. This contribution presents the latest ALICE results on the energy dependence of coherent J/ψ production, which is sensitive to the average gluon density, and on the energy and Mandelstam-t dependence of incoherent production, which probes fluctuations of the gluon field at different spatial scales. These measurements provide unprecedented constraints on models of QCD in the high-energy limit and mark a milestone in studying the gluonic structure of nuclei.