An international team working with the ALICE detector at the Large Hadron Collider has produced primordial quark-gluon plasma — matter last seen a millionth of a second after the Big Bang — by colliding light oxygen and neon nuclei instead of the heavy lead ions long thought necessary, while also using the collisions to map the geometric shape of the nuclei themselves.
For decades, recreating the extreme conditions of the universe’s first moments at CERN’s Large Hadron Collider has meant colliding heavy atomic nuclei — typically lead — at close to the speed of light. The resulting quark-gluon plasma, an ultra-hot state of matter in which protons and neutrons dissolve into their constituent quarks and gluons, is believed to have filled the universe during its first millionth of a second. Physicists had long assumed that only heavy nuclei carried enough mass and energy density to produce this state.
Researchers led by You Zhou, an associate professor recently of the Niels Bohr Institute at the University of Copenhagen, working within the international ALICE collaboration, have now shown that assumption was wrong. By colliding much lighter oxygen-16 and neon-20 nuclei, the team generated the same primordial quark-gluon plasma — “pushing the boundary for how small the atomic nuclei can be while still recreating this primordial matter,” in Zhou’s words. The results, drawing on roughly 3 billion oxygen-oxygen collisions and 400 million neon-neon collisions recorded by the ALICE detector, were published in Physical Review Letters.
A bonus: mapping nuclear shape through collision debris
Because quark-gluon plasma exists for only a minuscule fraction of a second before it cools and expands, it cannot be observed directly. Instead, physicists infer its properties from the pattern of particles that stream outward after a collision — and the new experiments revealed that this pattern also carries a geometric fingerprint of the colliding nuclei’s shape. The collision debris preserved distinguishable signatures of oxygen and neon’s differing nuclear geometries, giving physicists a new experimental tool for probing nuclear structure — how protons and neutrons are arranged inside small nuclei — through high-energy collision data rather than through traditional nuclear-structure techniques alone.
Why it matters
This is genuine, incremental progress on two fronts at once rather than a single headline discovery: it expands the range of experimental systems physicists can use to study the earliest moments of the universe, and it opens a new observational window into nuclear geometry using an existing, already-operating detector rather than new instrumentation. Neither result overturns existing physics, but both extend the boundaries of what CERN’s collision data can be used to investigate, with the light-ion technique likely to be applied to further systems and energy ranges in follow-up runs. For a facility whose headline discoveries — the Higgs boson chief among them — arrived over a decade ago, findings of this kind represent the more typical, cumulative texture of frontier particle physics: expanding what a known experimental apparatus can measure rather than a single transformative result.
Pradeep VS Kollipara
Key facts
- ALICE collaboration at CERN’s Large Hadron Collider produced quark-gluon plasma using light oxygen-16 and neon-20 nuclei, not the heavy lead ions previously thought necessary
- Analysis drew on ~3 billion oxygen-oxygen and ~400 million neon-neon collisions
- Collision debris patterns also revealed the differing geometric shapes of the colliding nuclei, offering a new tool to probe nuclear structure
- Published in Physical Review Letters; led by You Zhou, Niels Bohr Institute, University of Copenhagen
