Search for the jet-induced diffusion wake in the quark-gluon plasma via measurements of jet-track correlations in photon-jet events in Pb+Pb collisions at √sNN = 5.02 TeV with the ATLAS detector

Abstract

This paper presents a measurement of jet-track correlations in photon-jet events, using 1.72 nb-1 of Pb+Pbdata at SQUARE ROOTsNN = 5.02 TeV recorded with the ATLAS detector at the LHC. Events with energetic photon-jet pairsare selected, where the photon and jet are approximately back-to-back in azimuth. The angular correlationbetween jets and charged-particle tracks with transverse momentum (pT) in the range 0.5-2.0 GeV in thehemisphere opposite to the jet, |φ(jet,track)| > π/2, is measured as a function of their relative pseudorapiditydifference, |η(jet,track)|. In central Pb+Pb collisions, these correlations are predicted to be sensitive to thediffusion wake in the quark-gluon plasma resulting from the lost energy of high-pT partons traversing the plasma,with a characteristic modification as a function of |η(jet,track)|. The correlations are examined with differentselections on the jet-to-photon pT ratio to select events with different degrees of energy loss. No diffusion wakesignal is observed within the current sensitivity and upper limits at 95% confidence level on the diffusion wakeamplitude are reported.