Physicists at the ALICE experiment at CERN have uncovered new data regarding the behavior of gluons within atomic nuclei. Using the Large Hadron Collider, the research team analyzed incoherent J/ψ photonuclear production to map gluon distribution at unprecedented spatial scales. These measurements provide a clearer picture of how gluons fluctuate inside nuclei, offering a significant look at the components that provide the mass of visible matter.
The findings suggest that gluons begin to act collectively when packed into high-density regions. This behavior points toward gluon saturation, a phenomenon predicted by quantum chromodynamics. The experiment specifically tracked variations in gluon density at resolutions as small as one-quarter the size of a proton. By varying momentum transfer, researchers effectively adjusted the focus of their measurements to distinguish these structures from the surrounding nuclear matter.
This evidence challenges the long-standing model of nuclear shadowing. While nuclear shadowing explains earlier observations through the overlap of gluon layers, it fails to account for the suppression patterns detected in this latest study. The data shows that at extremely high densities, gluons interact strongly with one another, which limits the number of gluons that can occupy a specific space.
The study involved a collaboration between CERN and the University of Kansas. By measuring particle production across energy ranges from 20 to 633 billion electron volts, the team captured a detailed view of the strong force in action. These results represent a shift in how particle physics defines the internal structure of atomic nuclei and the fundamental nature of mass.