All four LHC experiments report quark-gluon plasma signs in oxygen and neon collisions

All four major Large Hadron Collider experiments, ALICE, ATLAS, CMS and LHCb, have reported signs of quark-gluon plasma in collisions of relatively light oxygen and neon nuclei, according to SciTechDaily. Quark-gluon plasma forms under extreme pressure at temperatures more than 100,000 times hotter than the center of the Sun, when composite particles break into quarks and gluons. Physicists associate that state with the first millionths of a second after the Big Bang and have long recreated it mainly with heavy ions such as lead. SciTechDaily said the experiments, one year after the collider's first oxygen runs, identified several signals consistent with plasma formation in oxygen-oxygen and neon-neon collisions. ATLAS reported an imbalance between pairs of particle jets that grew stronger in more head-on collisions, a pattern tied to parton energy loss in a hot, dense medium. Preliminary ATLAS measurements of charged particles recoiling from photons showed a similar centrality dependence. CMS observed suppressed charged-particle production in oxygen-oxygen and neon-neon collisions compared with proton-proton collisions. LHCb found particles containing one charm quark and one light quark more strongly suppressed in neon-neon than in oxygen-oxygen collisions, matching expectations for a larger plasma volume in the heavier system. ALICE reported unambiguous evidence of parton energy loss in oxygen-oxygen data using neutral pions and also saw anisotropic flow in which baryons showed stronger directional emission than mesons. The report said researchers once thought plasma required very heavy ions, an assumption weakened by earlier light-system and proton-collision results. Work continues on the light-ion dataset as the LHC moves toward a High-Luminosity upgrade. Light-ion runs expand the experimental map of when collective quark matter appears, sharpening models used to interpret the early universe and heavy-ion programs.