Jet Substrucure Measurements in Heavy-Ion Collisions at the LHC with ATLAS*

Measurements of jet substructure in heavy-ion collisions provide critical insights into the mechanisms of jet interactions with the hot and dense Quark-Gluon Plasma (QGP) created during these collisions. This talk presents jet substructure measurements from the ATLAS Collaboration in lead-lead (Pb+Pb) and proton-proton (pp) collisions at a center-of-mass collision energy of 5.02 TeV. These precision measurements utilize various jet constituents, including charged particles and novel objects reconstructed from tracker and calorimeter data. Jet suppression is quantified with the nuclear modification factor (R_AA) and is presented as a function of jet transverse momentum, the opening angle of the hardest internal splitting r_g, and the corresponding transverse momentum scale d₁₂. These results, when compared with theoretical models, enhance our understanding of jet energy loss in the QCD medium, provide new insights into the medium's properties, and test the theoretical understanding of QCD dynamics in heavy-ion collisions.