Exploring the phase space of medium induced QCD radiation with jets in ALICE at the LHC

Jets are back to back cascades of particles produced in the hard scattering of quarks and gluons. The pattern of cascade as these recoiling partons separate is governed by the properties of Quantum Chromo-Dynamics (QCD), the field theory for the strong nuclear force that binds together the quarks and gluons that make up the atomic nucleus. Studying jets from their production to their fragmentation gives insight into various unanswered aspects of QCD. Additionally, studying their modification in the presence of a strongly interacting deconfined medium of quarks and gluons produced in heavy-ion collisions, known as the Quark-Gluon Plasma (QGP), can help us to understand the properties of the strong nuclear force under the most extreme conditions akin to those believed to exist at the earliest stages of the universe or in the core of neutron stars. In this thesis, novel approaches to studying jet substructure are presented. Measurements were performed using the ALICE detector at the CERN LHC on pp collisions with a centre-of- mass energy of $\sqrt{s}$ = 7 TeV and Pb-Pb collisions at $\sqrt{s_{NN}}$ = 2.76 TeV. The results from Pb--Pb collisions are compared to those from pp collisions where signicant differences in the momentum fraction between two subjets identified via grooming methods are observed. A dependence of this modication on the opening angle between the subjets is observed. Additionally, new measurements are performed on the number of splittings identied in jets using iterative declustering techniques.