Emergence of collectivity in QCD
PT-CERN Call 2022/2
José Guilherme Milhano
Instituto Superior Técnico (Universidade de Lisboa)
Laboratório de Instrumentação e Física Experimental de Partículas
The key signature of Heavy ion Collisions is the formation of a complex, hot and dense state of matter, referred to as the Quark-Gluon Plasma (QGP). Crucially, the QGP, in the first instances after the collision occurs, is in a stage of non-equilibrium, evolving from there to a medium which flows collectively and accordingly with the laws of relativistic hydrodynamics. The question of how the QGP comes into being, from the simple interaction rules in QCD remains a challenge. A path to be explored to answer this question is by looking at “jet quenching” phenomena, where jets’ sub-structure properties are altered, resulting from their interaction with the medium they transverse. After all, both the jet and the medium response it induces, will be in an out-of-equilibrium state, and so will experience a process of thermalization with the medium. The focus of this work will be the recoiling medium partons, as they will most likely end up being reconstructed with the original jet, turning the jet into a laboratory associated with partons which are at a wide range of thermalization scales. The main objective of this PhD thesis is therefore to use the dynamics of such perturbations as a pathway to understand the emergence of collectivity in QCD. To achieve that, an effective kinetic theory model, which has the great advantage of being valid in- and out-of-equilibrium, will be used and numerically incorporated into a MC event generator (e.g. JEWEL) to describe the distribution of the recoiling partons. Afterwards, a search for jet observables sensitive to the kinetic description of the response’s evolution will be conducted, in the hopes of opening up a door into a first principle understanding of the emergence of collectivity in QCD. Moreover, my work will aim to produce open access computational tools to be used to extract relevant information from LHC data on heavy-ion collisions.