Photons production in heavy-ion collisions as a signal of deconfinement phase

TL;DR

This paper investigates photon production in heavy-ion collisions as an indicator of deconfinement, showing that anisotropic electromagnetic fields catalyze gluon conversion into photons during deconfinement.

Contribution

It introduces a mean-field approach to QCD vacuum to distinguish confinement and deconfinement phases based on gluon-photon conversion probabilities.

Findings

Photon production is suppressed in the confinement phase.

Deconfinement leads to a nonzero probability of gluon conversion into photons.

Photon angular distribution becomes strongly anisotropic in the deconfined phase.

Abstract

The photon production due to conversion of two gluons into a photon, $gg\rightarrow\gamma$, in the presence of the background gauge fields is studied within the specific mean-field approach to QCD vacuum. In this approach, mean field in the confinement phase is represented by the statistical ensemble of almost everywhere homogeneous abelian (anti-)self-dual gluon configurations, while the deconfined phase can be characterized by the purely chromomagnetic fields. The probability of gluon conversion of two gluons into a photon vanishes in the confinement phase due to the randomness of the background field configurations. The anisotropic strong electromagnetic field, generated in the collision of relativistic heavy ions, serves as a catalyst for deconfinement with the appearance of an anisotropic purely chromomagnetic mean field. Respectively, deconfined phase is characterized by nonzero probability of the conversion of two gluons into a photon with strongly anisotropic angular distribution.