Scaling of pre-equilibrium dilepton production in QCD kinetic theory
Oscar Garcia-Montero, Philip Plaschke, Sören Schlichting
Abstract
We use quantum chromodynamics (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 <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"> <a:mrow> <a:mi>η</a:mi> <a:mo>/</a:mo> <a:mi>s</a:mi> </a:mrow> </a:math> and entropy density <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" display="inline"> <c:mi>d</c:mi> <c:mi>S</c:mi> <c:mo>/</c:mo> <c:mi>d</c:mi> <c:mi>ζ</c:mi> <c:mo>∼</c:mo> <c:msubsup> <c:mrow> <c:mo stretchy="false">(</c:mo> <c:mi>T</c:mi> <c:msup> <c:mi>τ</c:mi> <c:mrow> <c:mn>1</c:mn> <c:mo>/</c:mo> <c:mn>3</c:mn> </c:mrow> </c:msup> <c:mo stretchy="false">)</c:mo> </c:mrow> <c:mi>∞</c:mi> <c:mrow> <c:mn>3</c:mn> <c:mo>/</c:mo> <c:mn>2</c:mn> </c:mrow> </c:msubsup> </c:math> , 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.