Speaker
Description
In ultra-relativistic heavy-ion collisions, jet yields are suppressed relative to proton–proton baselines due to partonic energy loss in the quark–gluon plasma. This phenomenon, known as jet quenching, reflects the interaction of hard-scattered partons with the hot and dense medium created in the early stages of the collision. This ATLAS contribution presents a set of measurements that go beyond inclusive observables by probing the connection between jet quenching and jet fragmentation using substructure techniques. The results include measurements of large-radius jet substructure using track and sub-jets, studies of jets recoiling against isolated photons, and measurements of b-jet suppression, providing sensitivity to the flavour dependence of partonic energy loss. Jet quenching is quantified via the nuclear modification factor, $R_{AA}$, measured as a function of centrality, jet transverse momentum, and a range of substructure observables. Together, these measurements offer complementary constraints on quark- and gluon-initiated jets and their modification in the medium.