Bottom-up approach to describe groomed jet data in heavy-ion collisions

TL;DR

This paper introduces a minimal, effective energy shift model for groomed jet substructure in heavy-ion collisions, successfully describing experimental data and highlighting the importance of color decoherence effects.

Contribution

It proposes a simple yet effective approach to model medium effects as an energy shift, improving understanding of jet modifications in heavy-ion environments.

Findings

Model achieves within 10% agreement with data across multiple observables.

Groomed jet data can discriminate between different medium effects.

Energy loss depends on jet substructure and color decoherence effects.

Abstract

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. In this paper, we present a minimal approach to compute groomed substructure observables. The core idea is to treat medium effects as an effective energy shift of the hard, vacuum-like substructure. This energy shift includes a gradual onset of colour decoherence effects and thus depends on the jet substructure itself. We first study a NLO-exact dijet configuration in vacuum and apply radiative energy-loss to 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. We also examine the discriminating power of groomed jet data in terms of colour decoherence effects and find that substructure-dependent energy loss yields an overall better agreement.