Phenix

PHENIX, short for Pioneering High Energy Nuclear Interaction eXperiment, was a major particle physics detector and international collaboration at the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory in the United States. It was designed to investigate the properties of hot, dense quantum chromodynamics matter created in high-energy nuclear collisions and to explore spin structure in polarized proton collisions.

PHENIX featured a set of specialized subsystems optimized for detecting photons, electrons, hadrons, and muons. Its apparatus included electromagnetic calorimetry, ring-imaging Cherenkov detectors, time-of-flight systems, and dedicated muon detectors, arranged in central and forward arms to cover a broad range of rapidities. This configuration enabled complementary measurements of jets, collective flow, heavy flavor production, and electromagnetic probes.

The physics program aimed to characterize the quark-gluon plasma and the spin structure of matter. PHENIX contributed to evidence that the quark-gluon plasma behaves as a strongly coupled, nearly perfect liquid, demonstrated jet quenching and significant high-pT particle suppression, and provided measurements of direct photons and dileptons as electromagnetic probes. It also studied quarkonia production and suppression patterns and explored spin-dependent phenomena in polarized proton collisions to constrain gluon polarization.

Operational history and status: construction and operation began in the early 2000s as part of RHIC’s program, with data-taking extending through the mid-2010s. The PHENIX detector was decommissioned in 2016, with its results published and preserved in scientific literature and archives.

Legacy: PHENIX’s multi-faceted measurements complemented other RHIC experiments, informing theoretical models of the quark-gluon plasma and spin physics, and influencing detector designs for future facilities.