CERN's ALICE detector explains how light nuclei form in LHC collisions

The ALICE Collaboration at CERN has resolved a longstanding puzzle about how fragile light nuclei, specifically deuterons, form and survive in the extreme conditions created by proton collisions at the Large Hadron Collider (LHC). Despite the collisions generating energies around 100 MeV per particle—far exceeding the 2.23 MeV binding energy of deuterons—these nuclei not only form but remain intact. Using precision particle tracking and deuteron-pion femtoscopy, ALICE demonstrated that approximately 89% of antideuterons do not form immediately in the initial high-energy fireball. Instead, they assemble later from protons and neutrons released by short-lived resonances at much lower energies (~20 MeV), where stable binding becomes possible. This finding has significant implications beyond collider physics, impacting cosmic ray experiments and dark matter detection efforts that rely on accurate models of antideuteron production. The breakthrough was enabled by advances in detector technology and data analysis at ALICE, which is