Gießen 2024 – wissenschaftliches Programm
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HK: Fachverband Physik der Hadronen und Kerne
HK 46: Heavy-Ion Collisions and QCD Phases XI
HK 46.2: Vortrag
Mittwoch, 13. März 2024, 16:00–16:15, HBR 62: EG 18
Dielectron production in Pb–Pb collisions with ALICE — •Jerome Jung for the ALICE Germany collaboration — Goethe University Frankfurt
Dielectrons are an exceptional tool for studying the evolution of the medium created in heavy-ion collisions as they are produced at all stages of the collision with negligible final-state interactions. In central collisions, the energy densities are sufficient to create a quark-gluon plasma (QGP). Thermal e+e− pairs radiating from this medium can be observed as an excess over the hadronic decay cocktail beyond the pion region.
For invariant masses above 1.2 GeV/c2, correlated heavy-flavour (HF) hadron decays are expected to dominate the dielectron yield. Their contribution is modified in the medium compared to elementary collisions to an unknown extent, leading to large uncertainties in the subtraction of known hadronic sources.
To control this contribution, a topological separation based on the distance-of-closest approach (DCA) to the primary vertex is crucial to disentangle the thermal dielectron from HF contributions based on their characteristic proper decay lengths.
In this talk, the final results on dielectron production in central Pb–Pb collisions at √sNN=5.02 TeV with ALICE in Run 2 will be presented. The measurements are compared to expectations from hadronic decays and calculations from theory. Finally, the topological separation of e+e− pairs is applied to extract a prompt thermal contribution in the intermediate-mass region.
Keywords: Dielectrons; ALICE; Pb-Pb; Run 2