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Physicists at CERN have produced evidence that some of the smallest atomic nuclei used in high-energy collisions can create quark-gluon plasma, an extreme state of matter believed to have filled the Universe during its first moments. The finding challenges the long-standing assumption that only collisions involving heavy nuclei could produce this primordial material.
Researchers from the University of Copenhagen’s Niels Bohr Institute and the international ALICE collaboration studied collisions involving oxygen-16 and neon-20 nuclei traveling at nearly the speed of light. The experiments produced tiny, short-lived droplets of matter resembling conditions that existed during the first millionth of a second after the Big Bang, according to the University of Copenhagen.
Quark-gluon plasma forms at extraordinary temperatures and pressures, when protons and neutrons break down into their fundamental components, quarks and gluons. Scientists have recreated this state at CERN for years using heavy nuclei such as lead, but the latest results show that much smaller collision systems can also display signatures associated with the primordial state.
“We have pushed the boundary for how small the atomic nuclei can be while still recreating this primordial matter,” said You Zhou, the associate professor who led the experiment.
The plasma exists for only a tiny fraction of a second before expanding and transforming into other particles. Researchers cannot observe the plasma directly, so they study the particles produced afterward to reconstruct what happened during the collision.
Those particles also revealed information about the shapes of the nuclei themselves. Oxygen-16 collisions produced patterns consistent with a more rounded nuclear structure, while neon-20 collisions generated patterns associated with an elongated, bowling-pin-like shape. CERN previously reported that light-nucleus collisions can reveal nuclear geometry through the collective movement of particles produced in the collision.
This gives physicists a new way to investigate nuclear structure while studying the conditions of the early Universe. Rather than relying solely on conventional measurements of how nuclei rotate or vibrate, researchers can examine the debris from high-energy collisions to infer their internal geometry.
The results also contribute to a broader shift in understanding how small a system can be while still producing quark-gluon plasma. CERN reported in July 2026 that ALICE, ATLAS, CMS and LHCb had all found signs of this extreme state in oxygen and neon collisions.
Future experiments could push the boundary even further by investigating lighter nuclei and smaller collision systems. The goal is to determine the minimum conditions required to create this primordial form of matter and better understand how the Universe transitioned from its earliest state into the matter that exists today.
