Photon production and elliptic flow from momentum-anisotropic quark-gluon plasma

TL;DR

This paper calculates photon emission rates from a momentum-anisotropic quark-gluon plasma, incorporating both hard and soft contributions, and applies anisotropic hydrodynamics to predict photon yield and elliptic flow in heavy-ion collisions.

Contribution

It introduces a parametrization of nonequilibrium photon emission rates and combines them with 3+1d anisotropic hydrodynamics for realistic yield and flow predictions.

Findings

Photon yield and elliptic flow are sensitive to initial momentum anisotropy.

The anisotropic photon production rate is successfully integrated with hydrodynamic evolution.

Results provide insights into the QGP properties at LHC and RHIC energies.

Abstract

The emission of real photons from a momentum-anisotropic quark-gluon plasma (QGP) is affected by both the collective flow of the radiating medium and the modification of local rest frame emission rate due to the anisotropic momentum distribution of partonic degrees of freedom. In this paper, we first calculate the photon production rate from an ellipsoidally momentum-anisotropic QGP including hard contributions from Compton scattering and quark pair annihilation and soft contribution calculated using the hard thermal loop (HTL) approximation. We introduce a parametrization of the nonequilibrium rate in order to facilitate its further application in yield and flow calculations. We convolve the anisotropic photon rate with the space-time evolution of QGP provided by 3+1d anisotropic hydrodynamics (aHydro) to obtain the yield and the elliptic flow coefficient $v_2$ of photons from QGP generated at Pb-Pb collisions at LHC at 2.76 TeV and Au-Au collisions at RHIC at 200 GeV. We investigate the effects of various parameters on the results. In particular we analyze the sensitivity of results to initial momentum anisotropy.