2024/09/19 by ALICE Collaboration
#FOS: Physical sciences #High Energy Physics - Experiment (hep-ex) #Nuclear Experiment (nucl-ex)
paper · doi:10.48550/arxiv.2409.12641
The ALICE Collaboration at the CERN LHC has measured the inclusive production cross section of isolated photons at midrapidity as a function of the photon transverse momentum (p\rm Tγ), in Pb-Pb collisions in different centrality intervals, and in pp collisions, at centre-of-momentum energy per nucleon pair of √s\rm NN=5.02 TeV. The photon transverse momentum range is between 10-14 and 40-140 GeV/c, depending on the collision system and on the Pb-Pb centrality class. The result extends to lower p\rm Tγ than previously published results by the ATLAS and CMS experiments at the same collision energy. The covered pseudorapidity range is |ηγ| <0.67. The isolation selection is based on a charged particle isolation momentum threshold p\rm T\rm iso,~ch = 1.5 GeV/c within a cone of radii R=0.2 and 0.4. The nuclear modification factor is calculated and found to be consistent with unity in all centrality classes, and also consistent with the HG-PYTHIA model, which describes the event selection and geometry biases that affect the centrality determination in peripheral Pb-Pb collisions. The measurement is compared to next-to-leading order perturbative QCD calculations and to the measurements of isolated photons and Z0 bosons from the CMS experiment, which are all found to be in agreement.