- Researchers have recreated a little version of the universe’s possible post-Big Bang state by colliding two of the smallest atoms, oxygen-16 and neon-20, at nearly the speed of light.
- The collision creates a tiny blob of quark-gluon plasma, the same super-hot soup thought to have filled the universe right after the Big Bang.
- ALICE Collaboration analyzed oxygen-oxygen collisions and found direct evidence of parton energy loss (jet quenching), extending the evidence to the smallest nuclear system studied so far.
- The measured neutral pions across a range of transverse momenta showed suppressed production in oxygen-oxygen collisions relative to a proton-proton reference, with a pattern resembling the suppression seen in lead-lead collisions.
- Proton-oxygen collisions from the same 2025 run served as a control; the result was compatible with no suppression, while the oxygen-oxygen suppression remained significant at 4.9 standard deviations relative to models without parton energy loss.
- The analysis describes the result as establishing parton energy loss in oxygen-oxygen collisions, making it the smallest nuclear system with direct jet-quenching evidence.
- The plasma droplet expands and cools too fast to observe directly, so scientists studied the particles it leaves behind, which revealed something unexpected.
- When two oxygen atoms collided, particles sprayed out in a rounded pattern, but when two neon atoms collided, particles came out shaped more like a bowling pin, matching the true geometry of a neon nucleus.
- This gave researchers an unexpected way to see the shape of an atom with the naked human eye that they could never actually observe directly.
- “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 who led the study.
- “We now know more about the fundamental conditions required for matter to transition into this extreme state,” Zhou explained.
- “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,” said Zhou.
CERN's ALICE Collaboration has made a groundbreaking discovery by recreating a 'little Big Bang' through collisions of oxygen nuclei, marking the smallest nuclear system to reveal quark-gluon plasma. This experiment, conducted in July 2025, involved colliding oxygen-16 and neon-20 nuclei at a centre-of-mass energy of 5.36 teraelectronvolts per nucleon pair.12345910
The analysis indicates that energetic quarks and gluons experienced parton energy loss during their passage through the medium, a phenomenon known as jet quenching. The results showed a suppression of neutral pions in oxygen-oxygen collisions compared to proton-proton collisions, with a statistical significance of 4.9 sigma, establishing parton energy loss in this context.6
Researchers noted that the collision produced a droplet of quark-gluon plasma, which expands and cools rapidly, leaving behind particles that reveal the underlying dynamics. The study highlighted that when two oxygen atoms collided, the particles exhibited a rounded pattern, while neon collisions produced a shape resembling a bowling pin, reflecting the geometry of the neon nucleus.
Lead researcher You Zhou stated, “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.’” This research enhances our understanding of the conditions necessary for matter to transition into this extreme state, potentially shedding light on the early universe's evolution.
The findings not only extend the knowledge of jet quenching but also provide insights into the fundamental properties of matter in extreme conditions, paving the way for future explorations in high-energy physics.
“The ALICE Collaboration's analysis of oxygen-oxygen collisions showed neutral pion suppression resembling lead-lead patterns, while proton-oxygen control collisions showed no suppression. Lead researcher You Zhou said the work pushes the boundary for how small nuclei can be while still recreating primordial matter.”
Space Daily
