Search for the quark-gluon plasma diffusion wake via measurements of jet-hadron correlations in photon-jet events in Pb+Pb and pp collisions at sqrt(s_NN) = 5.02 TeV with the ATLAS detector

This note describes the measurement of jet-hadron correlations in photon-jet events, using 1.73 nb−1 of Pb+Pb data and 260 pb−1 of pp data, both taken at sqrt(s_{NN}) = 5.02 TeV with the ATLAS detector in 2018 and 2017, respectively. The angular correlation is reported in different Pb+Pb centrality categories as a function of relative pseudorapidity \Delta\eta(jet, hadron) between jets with p_{T} > 40 GeV and charged hadrons with p_{T} =1-2 GeV in opposite azimuthal hemispheres |\Delta\phi(jet, hadron)| > \pi/2 is measured in high-p_{T} photon (90 − 180 GeV) events, where the photon and jet are back-to-back, |\Delta\phi(jet,\gamma)| > 3𝜋/4. These correlations are predicted to be sensitive to the diffusion wake in the quark-gluon plasma resulting from the lost energy of high-p_{T} partons traversing the plasma.