Two particle correlations: a probe of the LHC QCD medium

TL;DR

This paper explores using gamma-jet pairs in heavy-ion collisions at the LHC to probe the quark-gluon plasma by analyzing medium modifications of jet properties through simulation and initial proton-proton data.

Contribution

It introduces a method to measure jet fragmentation and azimuthal correlations in heavy-ion collisions, demonstrating feasibility with simulation and initial ALICE data.

Findings

Method can approximate jet fragmentation and azimuthal alignment

Medium modifies jet structure compared to proton-proton collisions

Initial results suggest potential for medium property inference

Abstract

The properties of $\gamma$--jet pairs emitted in heavy-ion collisions provide an accurate mean to perform a tomographic measurement of the medium created in the collision through the study of the medium modified jet properties. The idea is to measure the distribution of hadrons emitted on the opposite side of the %oppositely by tagging the direct photon. The feasibility of such measurements is studied by applying the approach on the simulation data, we have demonstrated that this method allows us to measure, with a good approximation, both the jet fragmentation and the back-to-back azimuthal alignment of the direct photon and the jet. Comparing these two observables measured in pp collisions with the ones measured in AA collisions reveals the modifications induced by the medium on the jet structure and consequently allows us to infer the medium properties. In this contribution, we discuss a first attempt of such measurements applied to real proton-proton data from the ALICE experiment.