PoS - Proceedings of Science
Volume 449 - The European Physical Society Conference on High Energy Physics (EPS-HEP2023) - T05 Ultra-Relativistic Nuclear Collisions
Electromagnetic radiation in pp and Pb--Pb collisions with dielectrons in ALICE
H.ย MuraKami* ย on behalf of the ALICE collaboration
Full text: pdf
Pre-published on: December 18, 2023
Published on: March 21, 2024
The latest ALICE results on low $๐‘_{{\rm T}}$ direct photon measurements via the virtual photon method are presented. Direct photons are measured in Pbโ€“Pb collisions at $\sqrt{s}_{{\rm NN}}$ = 5.02 TeV, and in minimum-bias (MB) and high-multiplicity pp collisions at $\sqrt{s}$ = 13 TeV with LHC Run 2 data. The virtual direct-photon signal is extracted from the dielectron mass spectra. Direct photon spectrum in Pbโ€“Pb collisions is measured in the range 1 < $๐‘_{{\rm T}}$ < 5 GeV/$๐‘$ and compared with theoretical predictions. In pp collisions, such measurement in minimum-bias events serves as a baseline for Pbโ€“Pb collisions and a fundamental test for perturbative QCD (pQCD) calculations, while studies in high charged-particle multiplicity events allow one to search for thermal radiation in small colliding systems. Direct photon spectra in pp collisions for both event multiplicity classes are measured in the range 1 < $๐‘_{{\rm T}}$ < 6 GeV/$๐‘$. The MB result was compared with NLO pQCD calculations and the viscous hydrodynamical model. Finally, the first result with the Run 3 pp data at $\sqrt{s}$ = 13.6 TeV, using the upgraded ALICE detector to disentangle the different dielectron sources, is reported.
DOI: https://doi.org/10.22323/1.449.0207
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