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.
Highlights
One of the challenges in developing a more complete picture of the dynamics of the many-body system generated at heavy-ion collision experiments is the lack of reliable information about the initial conditions of the system due to the strong interactions among the degrees of freedom, relevance of many effects at extreme conditions, and the loss of information in a pseudothermalized system
In order to calculate the yield and elliptic flow coefficient of real photons emitted from the quark-gluon plasma (QGP), we convolve the local rest frame (LRF) anisotropic photon production rate with the space-time evolution of the strongly interacting fluid provided by 3 þ 1d anisotropic hydrodynamics (aHydro) with a quasiparticle equation of state and smooth Glauber initial conditions [70,71]
We present the results for the yield and elliptic flow coefficient (v2) of real photons emitted from a momentum-anisotropic QGP with space-time evolution described by aHydro
Summary
One of the challenges in developing a more complete picture of the dynamics of the many-body system generated at heavy-ion collision experiments is the lack of reliable information about the initial conditions of the system due to the strong interactions among the degrees of freedom, relevance of many effects at extreme conditions, and the loss of information in a pseudothermalized system. One important feature of nonequilibrium quark-gluon plasma (QGP), as suggested by different microscopic models and successful phenomenological studies, is the anisotropy of the local rest frame (LRF) momentum distributions for partonic degrees of freedom [67]. For first time we include in the LRF photon rate calculation the momentum anisotropy in the transverse direction in the form of ellipsoidal deformation of isotropic distributions. This is done using an efficient method introduced in our previous paper [81] to calculate the quark self-energies in anisotropic medium. We investigate the uncertainties due to our approximations in using aHydro output for photon rate calculations
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