Electromagnetic emission from hot medium measured by the PHENIX experiment at RHIC

TL;DR

This paper reports on measurements of electromagnetic radiation, specifically photons, from heavy ion collisions at RHIC, revealing insights into the early collision stages and highlighting unexpected results in photon flow that challenge existing models.

Contribution

It provides new photon measurement data from the PHENIX experiment that reflect the thermodynamic properties of the hot medium created in heavy ion collisions.

Findings

Large positive elliptic flow for direct photons observed

Photon measurements indicate properties of the early collision medium

Current models cannot explain the observed photon flow

Abstract

Electromagnetic radiation has been of interest in heavy ion collisions because they shed light on early stages of the collisions where hadronic probes do not provide direct information since hadronization and hadronic interactions occur later. The latest results on photon measurement from the PHENIX experiment at RHIC reflect thermodynamic properties of the matter produced in the heavy ion collisions. An unexpectedly large positive elliptic flow measured for direct photons can not be explained by any of the current models.