Physicists at CERN have generated the quark-gluon plasma (QGP) — the extremely hot, dense state of matter thought to have filled the universe in the first microseconds after the Big Bang — using far smaller particle collisions than previously achieved. Because this primordial substance no longer exists naturally, recreating it in miniature gives researchers a rare window into the conditions of the very early universe and how matter first formed. The findings, described as a "little big bang", push forward decades of work trying to establish just how small a collision can be while still producing this fluid-like plasma.

The international team, whose results appear in Physical Review Letters, produced the plasma by colliding oxygen-16 and neon-20 nuclei, both under a tenth the mass of lead, previously seen as the lightest element capable of generating QGP. Despite the reduced scale, the collisions yielded signals consistent with QGP behaviour, briefly expanding collectively like a fluid before cooling into ordinary particles. Study co-author You Zhou of the Niels Bohr Institute said the work clarifies the minimum conditions needed to trigger this transition and could help explain how the plasma evolved into the matter that makes up the universe today.