Charting QCD jet evolution in extreme conditions
PT-CERN Call 2022/2
José Guilherme Milhano
Instituto Superior Técnico (Universidade de Lisboa)
Laboratório de Instrumentação e Física Experimental de Partículas
This PhD program aims for a deeper understanding of the QCD building blocks across the different energy and density regimes and consistent QCD description ranging from perturbative to non-perturbative momentum scales. This will be done through the use of jets - spray of particles originated by the fragmentation of a high energy quark or gluon. These objects, massively created in current ultra-relativistic heavy-ion collisions performed at the LHC and RHIC, are the perfect laboratory for such studies. They hold in their substructure the effects of a multitude of QCD processes, ranging from the high-momentum perturbative emissions to the low-momentum, the non-perturbative phenomena such as the poorly known hadronization mechanisms that are responsible for confining partons at lower energy scales. In vacuum collisions, particle evolution can be understood via a momentum scale prescription that has been recently used to signal a transition between perturbative and non-perturbative QCD. Moreover, in heavy-ion collisions, the emergence of a strongly coupled QCD fluid, the Quark-Gluon Plasma (QGP), modifies QCD jets with the introduction of additional perturbative and non-perturbative effects. They also provide the unique opportunity of assigning a time prescription to QCD dynamics as the QCD medium dilutes simultaneously with the jet evolution. The purpose of this PhD is to achieve a consistent description of QCD processes by designing novel time-differential jet substructure observables, with different sensitivities to perturbative and non-perturbative momentum scales, successively complementing vacuum and heavy-ion studies with the insights from each collision system. Novel phenomenological approaches will be sought in a framework for a scale-differential study of fundamental physics. Altogether, this PhD’s output will provide the basis to quantify hadronization scales and QGP evolution through QCD jet probes.