New Results on Hard Probes in Heavy-Ion Collisions with ALICE

TL;DR

This paper presents new experimental results on high-momentum particle production and jet substructure in heavy-ion collisions, providing insights into the properties of the Quark-Gluon Plasma and medium-induced modifications of jets.

Contribution

It offers novel measurements of charged particle suppression and jet grooming techniques in heavy-ion collisions, advancing understanding of jet quenching phenomena.

Findings

Observation of charged particle suppression in various collision systems

Evidence of medium modifications in jet sub-structure

Analysis of peripheral collision effects on jet quenching

Abstract

Hard probes - final state particles related to an interaction with large momentum transfer or mass scale - play a distinguished role in the discovery and the study of the Quark-Gluon Plasma (QGP), a phase of deconfined quarks and gluons reached at high temperatures in heavy ion collisions. In heavy ion collisions, parton scatterings with a large momentum transfer ($1/Q \ll 1$ fm/$c$) occur prior to QGP formation and thus provide a source of coloured probe particles for the QGP created in the later stage of the reaction. The hard scattered partons and the subsequent parton shower interact strongly with the QGP and its constituents via elastic and radiative processes before hadronization into jets of observable particles. Thus, the comparison to jet and high-$p_T$ observables in pp (vacuum) potentially probes their modification due to medium effects. One of the key observables in the discovery and investigation of these jet modifications has been the nuclear modification factor $R_{AA}$, for which new results on charged particle production in different colliding systems are presented and the question of apparant suppression in peripheral Pb-Pb collisions is addressed. Fore more differential studies of the jet sub-structure and hence the parton shower evolution in the medium, recent results on jet grooming in heavy ion colisions are presented.