Speaker
Description
The theoretical interpretation of jet observables in heavy-ion collisions is a complex task due to the intricate interplay of perturbative and non-perturbative effects. One way to reduce this complexity is to groom away soft, wide-angle radiation so that perturbative dynamics dominates. Even in this simplified scenario, there are competing explanations for the physical origin of the measured medium-induced modifications.
We present a new approach to compute groomed sub-structure observables. The core idea is to treat medium effects as an effective energy shift of the hard, vacuum-like substructure. We first study a NLO-exact dijet configuration in vacuum and apply radiative energy-loss to the two subjets. The latter includes a gradual onset of colour decoherence depending on the opening angle of the two subjets. We find that this minimal setup already captures the narrowing trend of groomed observables but it’s not able to quantitatively describe the existing data. Next, we match the NLO matrix-element to a leading-logarithm accurate parton shower and perform a clustering algorithm to recover a two-prong system to which we again apply the energy-loss distribution. Despite its simplicity, the model results in a very good theory-to-data agreement (within 10%) for a broad range of observables including both ALICE and ATLAS kinematics.