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Comparison of inclusive and photon-tagged jet suppression in 5.02 TeV Pb+Pb collisions with ATLAS

Research output: Contribution to Journal/MagazineJournal articlepeer-review

  • ATLAS Collaboration
Article number138154
<mark>Journal publication date</mark>10/11/2023
<mark>Journal</mark>Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics
Publication StatusPublished
Early online date22/09/23
<mark>Original language</mark>English


Parton 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 s NN=5.02 TeV, with the ATLAS detector. The process pp →γ+jet+X and its analogue in Pb+Pb collisions is measured in events containing an isolated photon with transverse momentum (p T) above 50 GeV and reported as a function of jet p T. This selection results in a sample of jets with a steeply falling p T distribution that are mostly initiated by the showering of quarks. The pp and Pb+Pb measurements are used to report the nuclear modification factor, R AA, and the fractional energy loss, S loss, 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 R AA and S loss 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.