A report from Cadena 3 says results from four LHC collaborations, ALICE, ATLAS, CMS and LHCb, contain multiple signatures associated with quark–gluon plasma (QGP) in small oxygen and neon collisions. Together, the signals point to possible QGP-like conditions; they do not establish that every collision forms plasma.
QGP is a state of matter associated with the universe’s earliest moments. LHC experiments investigate it by studying particle collisions.
Different experiments probe different signals
In Cadena 3’s account, ATLAS measured energy differences between paired jets in oxygen–oxygen and neon–neon collisions, with a stronger effect in more central collisions. CMS reported suppressed charged-particle production in oxygen–oxygen and neon–neon collisions relative to proton–proton collisions. The account also describes variable suppression of upsilon mesons and preliminary ALICE observations of different anisotropic-flow patterns for baryons and mesons in oxygen–oxygen collisions.
Why ALICE compares oxygen with proton collisions
ALICE compares neutral-pion production in oxygen–oxygen and proton–oxygen collisions. The CERN Indico abstract describes a double ratio designed to constrain and largely cancel cold-nuclear-matter effects. That comparison provides a way to test for parton energy loss in oxygen–oxygen collisions.
What LHCb measured
The LHCb collaboration’s study gives the D⁰-meson production ratio in neon–neon versus oxygen–oxygen collisions at 5.36 TeV per nucleon pair. This specific charm-particle measurement adds a different observable to the broader set of reported signals.
Why suppression alone is not enough
Suppression means that fewer particles are produced relative to a reference collision system. Cadena 3 notes that other physical processes can also cause suppression, so the charged-particle result alone does not establish parton energy loss.
