Aad G.Abbott B.Abeling K.Abicht N. J.Abidi S. H.Aboulhorma A.Abramowicz H.Abreu H.Abulaiti Y.Acharya B. S.Bourdarios C. AdamAdamczyk L.Addepalli S. V.Addison M. J.Adelman J.Adiguzel A.Adye T.Affolder A. A.Afik Y.Agaras M. N.Agarwala J.Aggarwal A.Agheorghiesei C.Ahmad A.Ahmadov F.Ahmed W. S.Ahuja S.Ai X.Aielli G.Aikot A.Tamlihat M. AitAitbenchikh B.Aizenberg I.Akbiyik M.Akesson T. P. A.Akimov A. V.Akiyama D.Akolkar N. N.Al Khoury K.Alberghi G. L.2025-05-192025-05-192023/11/100370-2693http://dx.doi.org/10.1016/j.physletb.2023.138154https://publicacionesabiertas.userena.cl/handle/123456789/292Parton energy loss in the quark-gluon plasma (QGP) is studied with a measurement of photon-tagged jet production in 1.7 nb-1 of Pb+Pb data and 260 pb-1 of pp data, both at root sNN = 5.02 TeV, with the ATLAS detector. The process pp -> gamma +jet+X and its analogue in Pb+Pb collisions is measured in events containing an isolated photon with transverse momentum (pT) above 50 GeV and reported as a function of jet pT. This selection results in a sample of jets with a steeply falling pT distribution that are mostly initiated by the showering of quarks. The pp and Pb+Pb measurements are used to report the nuclear modification factor, RAA, and the fractional energy loss, Sloss, for photon-tagged jets. In addition, the results are compared with the analogous ones for inclusive jets, which have a significantly smaller quark-initiated fraction. The RAA and Sloss values are found to be significantly different between those for photon-tagged jets and inclusive jets, demonstrating that energy loss in the QGP is sensitive to the colour-charge of the initiating parton. The results are also compared with a variety of theoretical models of colour-charge-dependent energy loss. (c) 2023 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons .org /licenses /by /4 .0/). Funded by SCOAP3.Article