Breakthrough Discovery Sheds Light on the First Moments of the Universe
Physicists have discovered quark-gluon plasma in oxygen-oxygen collisions at CERN’s LHC, revealing new insights into the universe’s earliest moments.
CMS detector at CERN’s Large Hadron Collider, where scientists observed quark-gluon plasma in lighter atomic nuclei for the first time.
In an unprecedented experiment, physicists witnessed the first direct evidence of quark-gluon plasma or QGP — the state of nuclear matter that could have existed immediately after the Big Bang — being formed in collisions involving small nuclei. This discovery represents a giant leap toward understanding how the cosmos came into being.
Hungarian researchers and students from ELTE Institute of Physics and Astronomy and HUN-REN Wigner Research Center for Physics contributed significantly to the international research conducted at the CMS (Compact Muon Solenoid) experiment of CERN's Large Hadron Collider.
What Is Quark-Gluon Plasma?
The quark-gluon plasma is said to be an extremely hot and extremely dense state of matter that comes into existence when an atomic nucleus collides with another at speeds close to that of light. It simulates the extreme conditions that prevailed in the universe a microsecond after the Big Bang. One of the hallmark symptoms of the formation of QGP is the so-called jet quenching: Jet quenching is the loss in the amount of energy of the particle beams (jets) when passing through the plasma, consequently saying less secondary particles.
Until now, scientists have noticed the absorption of such radiation only in very heavy nuclei collisions-provided that nuclei being collided were lead and xenon. Smaller systems, thus proton-lead collisions, provided otherwise, and that leaves one wondering: How large must a nucleus be for the QGP to be created?
Oxygen-Oxygen Collisions Confirm a QGP Also in Small Systems
This fresh data analysis from July 2025 yielded a baffling discovery. Researchers first witnessed jet quenching in oxygen-oxygen collisions, thus confirming that relatively small nuclei can create QGP. Such a breakthrough implies that the plasma state does not require extremely massive nuclei, thereby remapping all theories for the threshold concept for QGP formation.
They have now started analyzing neon-neon collisions in an effort to deepen their understanding of how the sizes of colliding nuclei influence radiation absorption. By comparing the behavior of oxygen, neon, and larger nuclei, physicists hope to eventually achieve a model-independent description of QGP formation.
Why This Matters
It has been claimed that this bridges the gap between small and large collision systems, giving fresh insights into the behaviors of matter in the universe at its earliest stage. Although blatant signatures of QGP had been hinted at during previous proton-lead collisions, an outright observation of radiation absorption was not seen.
Having reached this milestone is the CMS experiment. Being one of the largest scientific collaborations in history, the CMS experiment involves around 5,800 experts at 241 institutes across 54 countries.
Hungary's Key Role in the Discovery:
The Hungarian team of scientists and students from ELTE and the HUN-REN Wigner Research Center was at the core of the data collection, collision data analysis, and interpretation. They worked alongside key researchers from the University of Chicago and MIT in a nearly 20-member group.
"Research into hot, free quark matter at CERN is pushing the boundaries of physics and offering new windows into the origin of the universe," said the statement.
