Electromagnetic signals from Au+Au collisions at RHIC energy, $\sqrt{s_{NN}}$=200 GeV and Pb+Pb collisions at LHC energy, $\sqrt{s_{NN}}$=2.76 TeV

TL;DR

This paper analyzes experimental data on direct photon production from heavy-ion collisions at RHIC and LHC energies, comparing theoretical models with observations and justifying thermal photon production through spectral ratios.

Contribution

It provides a comparative analysis of photon spectra at different energies using a thermal model with specific initial conditions, validating the model against experimental data.

Findings

Theoretical predictions agree well with experimental data.

Thermal photon spectra are justified through spectral ratio analysis.

Initial temperatures and thermalization times are consistent with observed spectra.

Abstract

We analyse the recently available experimental data on direct photon productions from Au+Au collisions at $\sqrt{s_{NN}}$=200 GeV RHIC and from Pb+Pb collisions at $\sqrt{s_{NN}}$=2.76 TeV LHC energies. The transverse momentum ($p_T$) distributions have been evaluated with the assumption of an initial quark gluon plasma phase at temperatures $T_i$=404 and 546 MeV with initial thermalisation times $\tau_i$=0.2 and 0.1 fm/c respectively for RHIC and LHC energies. The theoretical evalutions agree reasonably well with the experimental observations. The thermal window for the LHC energy is justified through the ratio of the $p_T$ spectra of thermal photons to dileptons.