Production and Elliptic Flow of Dileptons and Photons in the semi-Quark Gluon Plasma

TL;DR

This paper investigates how the semi-Quark-Gluon Plasma affects the production and flow of dileptons and photons in high-temperature QCD, revealing a mild increase in dileptons and a significant suppression of photons compared to the perturbative QGP.

Contribution

It introduces a semi-QGP model with suppressed color excitations and compares its dilepton and photon production to the perturbative QGP, highlighting new effects on electromagnetic signals in heavy ion collisions.

Findings

Mild enhancement of dileptons in semi-QGP

Significant suppression of hard photons in semi-QGP

Photon elliptic flow biased towards hadronic phase

Abstract

We consider the thermal production of dileptons and photons at temperatures above the critical temperature in QCD. We use a model where color excitations are suppressed by a small value of the Polyakov loop, the semi Quark-Gluon Plasma (QGP). Comparing the semi-QGP to the perturbative QGP, we find a mild enhancement of thermal dileptons. In contrast, to leading logarithmic order in weak coupling there are far fewer hard photons from the semi-QGP than the usual QGP. To illustrate the possible effects on photon and dileptons production in heavy ion collisions, we integrate the rate with a realistic hydrodynamic simulation. Dileptons uniformly exhibit a small flow, but the strong suppression of photons in the semi-QGP tends to bias the elliptical flow of photons to that generated in the hadronic phase.