Scaling of pre-equilibrium dilepton production in QCD Kinetic Theory

Abstract

We use QCD kinetic theory to compute dilepton production coming from the pre-equilibrium phase of the Quark-Gluon Plasma created in high-energy heavy-ion collisions. We demonstrate that the dilepton spectrum exhibits a simple scaling in terms of the specific shear viscosity $\eta/s$ and entropy density $dS/d\zeta \sim {\scriptstyle \left(T\tau^{1/3}\right)_\infty^{3/2}}$, which can be derived from dimensional analysis in the presence of a pre-equilibrium attractor. Based on this scaling we perform event-by-event calculations of in-medium dilepton production and determine the invariant mass range where the pre-equilibrium yield is the leading contribution.