Jet thermalization in QCD kinetic theory

Abstract

We perform numerical studies in the framework of QCD kinetic theory to investigate the energy and angular profiles of a high energy parton — as a proxy for a jet produced in heavy ion collisions — passing through a Quark-Gluon Plasma (QGP). We find that the fast parton loses energy to the plasma mainly via a radiative turbulent quark and gluon cascade that transports energy locally from the jet down to the temperature scale where dissipation takes place. In this first stage of the system time evolution, the angular structure of the turbulent cascade is found to be relatively collimated. However, when the lost energy reaches the plasma temperature it is rapidly transported to large angles w.r.t. the jet axis and thermalizes. We investigate the contribution of the soft jet constituents to the total jet energy. We show that for jet opening angles of about 0.3 rad or smaller, the effect is negligible. Conversely, larger opening angles become more and more sensitive to the thermal component of the jet and thus to medium response. Our result showcases the importance of the jet cone size in mitigating or enhancing the details of dissipation in jet quenching observables.

Jet polarisation in an anisotropic medium

“…Alternatively, and perhaps more efficiently, one could use the Monte-Carlo formulation of the in-medium partonic cascades, as developed in [43,[82][83][84]; that would also permit to include the vacuum-like parton branchings (those resulting from parton virtualities). Yet another approach would be to solve the linearized kinetic equations describing the evolution of the jet partonic distributions via both elastic and inelastic collisions [85]. In such an approach, the jet quenching parameters are dynamically generated.…”

“…In such an approach, the jet quenching parameters are dynamically generated. Yet, for the present purposes, the equations in [85] must be extended to a non-equilibrium background distribution, which is anisotropic.…”