Elliptic flow of thermal photons in heavy-ion collisions at Relativistic Heavy Ion Collider and Large Hadron Collider

TL;DR

This paper models the thermal photon spectra and elliptic flow in heavy-ion collisions at RHIC and LHC energies using hydrodynamics constrained by hadron data, analyzing sensitivities and making predictions.

Contribution

It provides a hydrodynamical calculation of thermal photon spectra and elliptic flow at RHIC and LHC, including sensitivity analysis and predictions for LHC collisions.

Findings

Photon $v_2$ is discussed in relation to measured spectra.

Sensitivity of results to QCD equation of state and emission rates analyzed.

Predictions made for LHC thermal photon spectra and elliptic flow.

Abstract

We calculate the thermal photon transverse momentum spectra and elliptic flow in $\sqrt{s_{NN}} = 200$ GeV Au+Au collisions at RHIC and in $\sqrt{s_{NN}} = 2.76$ TeV Pb+Pb collisions at the LHC, using an ideal-hydrodynamical framework which is constrained by the measured hadron spectra at RHIC and LHC. The sensitivity of the results to the QCD-matter equation of state and to the photon emission rates is studied, and the photon $v_2$ is discussed in the light of the photonic $p_T$ spectrum measured by the PHENIX Collaboration. In particular, we make a prediction for the thermal photon $p_T$ spectra and elliptic flow for the current LHC Pb+Pb collisions.