Recent Results from PHENIX Experiment at RHIC: Exploring the QCD Medium

TL;DR

This paper reviews key findings from the PHENIX experiment at RHIC, highlighting evidence of quark-gluon plasma formation, parton energy loss, and collective behavior in high-energy nuclear collisions.

Contribution

It provides comprehensive measurements of particle suppression, flow, and energy loss, demonstrating the properties of the QCD medium created in heavy-ion collisions.

Findings

Large suppression of high-pT hadrons indicates significant parton energy loss.

Elliptic flow measurements suggest collective behavior of the quark-gluon plasma.

Results support the interpretation of the medium as a nearly perfect fluid.

Abstract

We review some important results from the PHENIX experiment at RHIC. They were obtained in a unique environment for studying QCD bulk matter at temperatures and densities that sur- pass the limits where hadrons exist as individual entities, so raising to prominence the quark- gluon degrees of freedom. We present measurements of nuclear modification factors for neutral pions, light favors (strange hadrons), direct-photons and non-photonic electrons from decays of particles carrying charm or beauty quarks. We interpret the large suppression of hadron produc- tion at high transverse momenta as resulting from a large energy loss by the precursor parton on its path through the dense matter, primarily driven by gluon radiation. This dense QCD matter responds to energy loss in a pattern consistent with that expected from a hydrodynamic fluid. Further, its elliptic flow measurements suggest that the hadronization of bulk partonic matter exhibits collectivity with effective partonic degrees of freedom. The results are shown as a function of transverse momentum, centrality in different collision systems and energies.