Speaker
Description
While a variety of jet substructure measurements have been performed in heavy-ion collisions, a unified understanding of how the QGP affects the angular and momentum structure of jets remains an open question. One of the prominent puzzles is that measurements indicate no significant modification of the jet mass in heavy-ion collisions relative to proton-proton collisions, but significant narrowing of the jet girth. In order to shed light on this puzzle, we present new systematic measurements of a flexible and perturbatively calculable class of jet substructure observables known as the jet angularities. We report angularities spanning a wide range of angular regimes, mapping the transition from girth to mass and beyond. In order to further study the momentum structure of jets, we present the first measurements of the momentum fraction carried by sub-jets reclustered from primary jet constituents. These measurements extend to higher $z$ than hadron fragmentation measurements, enabling access to a quark-dominated sample of jets and exposing new insights about soft medium-induced radiation. We compare both the jet angularity and sub-jet fragmentation distributions to a variety of theoretical implementations of jet quenching, providing critical information on the medium modifications of jets as a function of their angular and momentum structure.
