Mainz 2022 – wissenschaftliches Programm

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HK: Fachverband Physik der Hadronen und Kerne

HK 45: Heavy-Ion Collisions and QCD Phases IX

HK 45.4: Vortrag

Mittwoch, 30. März 2022, 17:00–17:15, HK-H1

Dielectron production in Pb–Pb collisions with ALICE — •Jerome Jung for the ALICE collaboration — IKF, Goethe University, Frankfurt, Germany

The study of dielectron production is an exceptional tool to disect the evolution of heavy-ion collisions. In peripheral collisions, a clear excess of dielectrons is observed which exceeds the hadronic decay background at low pair momenta. These soft dielectrons can be attributed to coherent interactions of photons originating from electromagnetic fields generated by the highly Lorentz-contracted colliding ions. In more central collisions, the energy densities are sufficient to create a hot and dense medium. Thermal radiation of this medium can be observed as an excess over the hadronic decay cocktail beyond the pion region. For invariant masses above 1.1 GeV/c², correlated heavy-flavour hadron decays are expected to dominate the dielectron yield. Their contribution is modified in the medium compared to elementary collisions to an unknown extend. Therefore, a topological separation based on the distance-of-closest approach (DCA) to the primary vertex can be applied to disentangle them from thermal dielectrons.

In this talk, ALICE measurements of dielectron production in Pb–Pb collisions at √s_NN=5.02 TeV, will be presented. In peripheral collisions, final results will be compared to theory and measurements at lower energies. In central collisions, the dielectron spectra will be compared to expectations from the hadronic decay cocktail. Finally, a outlook on a DCA analysis in Pb–Pb is given.