Jet quenching parameter in QCD kinetic theory

We study the jet quenching parameter <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:mover accent="true"><a:mi>q</a:mi><a:mo stretchy="false">^</a:mo></a:mover></a:math> in a nonequilibrium plasma using the QCD effective kinetic theory. We discuss subleading terms at large jet momentum <e:math xmlns:e="http://www.w3.org/1998/Math/MathML" display="inline"><e:mi>p</e:mi></e:math>, show that our expression for <g:math xmlns:g="http://www.w3.org/1998/Math/MathML" display="inline"><g:mover accent="true"><g:mi>q</g:mi><g:mo stretchy="false">^</g:mo></g:mover></g:math> reproduces thermal results at small and large transverse momentum cutoffs for infinite <k:math xmlns:k="http://www.w3.org/1998/Math/MathML" display="inline"><k:mi>p</k:mi></k:math>, and construct an interpolation between these limits to be used in phenomenological applications. Using simple nonequilibrium distributions that model pertinent features of the bottom-up thermalization scenario, we analytically assess how anisotropy, underoccupation, or overoccupation affect the jet quenching parameter. Our work provides more details on the <m:math xmlns:m="http://www.w3.org/1998/Math/MathML" display="inline"><m:mover accent="true"><m:mi>q</m:mi><m:mo stretchy="false">^</m:mo></m:mover></m:math> formula used in our preceding work [ ] and sets the stage for further numerical studies of jet momentum broadening in the initial stages of heavy-ion collisions from QCD kinetic theory. Published by the American Physical Society 2024