Measurement of isolated photon plus multi-jet correlations in Pb+Pb and $pp$ collisions at 5.02 TeV with ATLAS

This note presents a measurement of isolated photon plus multi-jet correlations in $1.72$ nb$^{-1}$ of Pb+Pb data and $260$ pb$^{-1}$ of $pp$ data, both at $5.02$ TeV, with the ATLAS detector. Events containing a photon with transverse momentum ($p_\mathrm{T}$) in the range 90-180 GeV and at least two $R=0.2$ jets with $p_\mathrm{T} > 30$ GeV are selected for study. The medium-induced modification of the multi-jet system is explored with three new observables describing the kinematic relationship between a photon and a jet pair in the opposite azimuthal direction. The distributions are reported in $pp$ collisions and in Pb+Pb collisions with different centrality intervals, along with their ratios between Pb+Pb and $pp$ collisions. The results are compared to the predictions from a theoretical model of jet quenching.