CERN physicists have re-created a primordial state of matter using far smaller particle collisions than previously thought possible, offering a fresh way to study the universe’s earliest moments. Because no natural source of this ancient material still exists, these micro-scale “little big bangs” can help reveal what happened during the first few minutes after the cosmos formed.
The European Organization for Nuclear Research and an international team of collaborators demonstrated that quark-gluon plasma can emerge from collisions of very light atomic nuclei. The findings were published in the journal Physical Review Letters.
What Quark-Gluon Plasma Reveals
Quarks are the components of protons and neutrons, which in turn form the atoms that make up all matter. Gluons, as their name implies, bind quarks together. During the first microseconds after the universe began, quarks and gluons were not yet locked inside protons and neutrons. Instead, they existed as an extremely hot plasma. As the universe expanded and cooled, the quarks condensed into larger particles.
After decades of studying QGP through large nuclear collisions, physicists are now testing the limits of this unusual state of matter. A central question is how small a collision can be while still producing a group of particles that behaves like a drop of fluid.
Smaller Nuclei, Same Extreme State
According to the study, the team generated the substance using oxygen-16 and neon-20. Both weigh less than a tenth of a lead atom, which had previously been considered one of the lightest elements capable of producing quark-gluon plasma.
“We have pushed the boundary for how small the atomic nuclei can be while still re-creating this primordial matter—what you could call a ‘little big bang,'” said You Zhou, a researcher at the Niels Bohr Institute and a coauthor of the study. “We now know more about the fundamental conditions required for matter to transition into this extreme state.”
Despite the small size of the oxygen and neon nuclei, the collisions produced signals consistent with the behavior expected in QGP. For an instant, the resulting matter appeared to expand collectively like a fluid before cooling and reverting into particles.
Why the Discovery Matters
The experiment gives researchers a new tool for probing conditions that existed shortly after the universe formed. By scaling down the collisions, scientists can better map the boundaries at which ordinary matter transforms into this extreme plasma.
“Hopefully, this will help us better understand how the plasma behaved during the first moments of the universe—and how it later evolved into the forms of matter that everything around us is made of,” Zhou added.
