STAR finds 20% jet suppression in oxygen collisions, evidence of quark-gluon plasma
The STAR experiment at the US Relativistic Heavy Ion Collider found that high-energy particles and jets were suppressed by about 20% in oxygen collisions at 200 GeV, compared with lower-activity collisions. The collaboration’s results, published in Physical Review Letters, provide strong evidence that these small collisions produce quark-gluon plasma, matter thought to have filled the early universe.
Bottom line — The STAR result sets a lower-energy benchmark for studying quark-gluon plasma in small collision systems.
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STAR analysed oxygen–oxygen collision data collected at RHIC in 2021.
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The measured suppression corresponds to a 0.70 GeV/c shift in the momentum of large-radius jets, with statistical and systematic uncertainties reported by the collaboration.
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Each oxygen nucleus contains eight protons and eight neutrons, making the collision system smaller than the gold nuclei also studied at RHIC.
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Brookhaven National Laboratory says the Large Hadron Collider has also observed jet quenching in oxygen collisions, at collision energies above 5,000 GeV.
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Brookhaven says further oxygen-collision data were collected by STAR and sPHENIX during RHIC’s final run, which ended on 6 February 2026.