ATLAS Experiment at CERN Observes New Aspect of Nuclear Structure

The ATLAS Collaboration at CERN has reported the first observation that nucleons (protons and neutrons) near the edge of an atomic nucleus possess different parton distribution functions (PDFs) compared to those at its center. This discovery, made by studying ultra-peripheral collisions of lead ions at the Large Hadron Collider, adds crucial information to understanding how nuclear PDF modifications occur, a long-standing puzzle in nuclear physics.