Seminar in Hadronic Physics

Photon emission from quark-gluon plasma out of equilibrium

Sigtryggur Hauksson

Nuclear Theory Group
McGill University

The quark-gluon plasma (QGP) produced in heavy-ion collisions has very low transport coefficients, including the lowest ratio of shear viscosity to entropy density of any known material. More accurate values of these transport coefficients could be obtained through experimental probes like jets and photons which are sensitive to the whole evolution of the QGP. This requires a study of these probes in a QGP medium out of thermal equilibrium. In this talk we present the first field-theoretical study of the Landau-Pomeranchuk-Migdal (LPM) effect for photons in a non-equilibrium QGP. The LPM effect describes how photon emission rates are reduced significantly because the emitting quark scatters repeatedly and coherently off the medium. We derive an integral equation that captures this effect and discuss its range of validity. In the special case of an isotropic plasma the equation only depends on three non-equilibrium constants.