Initial temperature of the strongly interacting Quark Gluon Plasma created at RHIC

TL;DR

This paper models the evolution of the Quark-Gluon Plasma at RHIC using relativistic hydrodynamics, showing that photon momentum distributions can distinguish initial temperatures, with data supporting an initial temperature around 370 MeV.

Contribution

It introduces a 1+3D hydrodynamic model that links initial temperatures to observable photon spectra, highlighting the importance of photon data in determining initial conditions.

Findings

Photon momentum distribution can differentiate initial temperatures.

Model with initial temperature 370 MeV agrees with experimental data.

Multiple initial states produce similar hadronic observables.

Abstract

A 1+3 dimensional solution of relativistic hydrodynamics is analyzed in this paper. Momentum distribution and other observables are calculated from the solution and compared to hadronic measurements from the Relativistic Heavy Ion Collider (RHIC). The solution is compatible with the data, but only the freeze-out point of the evolution is determined. Many equation of states and initial states (initial temperatures) are valid with the same freeze-out distribution, thus the same hadronic observables. The observable that would distinguish between these initial temperatures is momentum distribution of photons, as photons are created throughout the evolution of the fireball created in RHIC collisions. The PHENIX experiment at RHIC measures such data via low invariant mass e+e- pairs. Average temperature from this data is T=221+-23+-18 MeV, while a model calculation with initial temperature 370 MeV agree with the data.